RecyclerView<第十九篇>：条目动画之自定义DefaultItemAnimator

为了让RecyclerView更加用户友好，可以给条目添加动画，RecyclerView可以设置条目动画

设置条目动画的代码是：

mRecyclerView.setItemAnimator(new DefaultItemAnimator());

可以给RecyclerView设置一个默认的动画，使用默认动画的话可以给条目设置动画时间

    DefaultItemAnimator defaultItemAnimator = new DefaultItemAnimator();
    defaultItemAnimator.setRemoveDuration(200);
    defaultItemAnimator.setAddDuration(200);
    defaultItemAnimator.setMoveDuration(200);
    defaultItemAnimator.setChangeDuration(200);
    mRecyclerView.setItemAnimator(defaultItemAnimator);

另外，还可以自定义一个动画，这样就需要深入研究DefaultItemAnimator类了。

DefaultItemAnimator的最终父类是ItemAnimator，该类是RecyclerView的内部抽象类，根据它抽象的特性，我们可以自定义ItemAnimator，当然，如果这样的话就比较复杂了，因此，就自定义DefaultItemAnimator了。

public class MyCustomItemAnimator extends DefaultItemAnimator {

    @Override
    public boolean animateRemove(RecyclerView.ViewHolder holder) {
        //删除条目动画实现
        return super.animateRemove(holder);
    }

    @Override
    public boolean animateAdd(RecyclerView.ViewHolder holder) {
        //添加条目动画实现
        return super.animateAdd(holder);
    }

    @Override
    public boolean animateMove(RecyclerView.ViewHolder holder, int fromX, int fromY, int toX, int toY) {
        //移动条目动画实现
        return super.animateMove(holder, fromX, fromY, toX, toY);
    }

    @Override
    public boolean animateChange(RecyclerView.ViewHolder oldHolder, RecyclerView.ViewHolder newHolder, int fromX, int fromY, int toX, int toY) {
        //改变条目动画实现
        return super.animateChange(oldHolder, newHolder, fromX, fromY, toX, toY);
    }
}

如上代码，动画的实现主要体现在animateRemove、animateAdd、animateMove、animateChange这四个方法。

在不做修改的情况下，条目动画都是默认的，想要学会自定义动画，那么首先需要研究下DefaultItemAnimator类的源码。

研究源码后发现，当触发添加条目动作时会执行

public boolean animateAdd(ViewHolder holder) {
    this.resetAnimation(holder);
    holder.itemView.setAlpha(0.0F);
    this.mPendingAdditions.add(holder);
    return true;
}

当触发条目移动动作时执行

public boolean animateMove(ViewHolder holder, int fromX, int fromY, int toX, int toY) {
    View view = holder.itemView;
    fromX += (int)holder.itemView.getTranslationX();
    fromY += (int)holder.itemView.getTranslationY();
    this.resetAnimation(holder);
    int deltaX = toX - fromX;
    int deltaY = toY - fromY;
    if (deltaX == 0 && deltaY == 0) {
        this.dispatchMoveFinished(holder);
        return false;
    } else {
        if (deltaX != 0) {
            view.setTranslationX((float)(-deltaX));
        }

        if (deltaY != 0) {
            view.setTranslationY((float)(-deltaY));
        }

        this.mPendingMoves.add(new DefaultItemAnimator.MoveInfo(holder, fromX, fromY, toX, toY));
        return true;
    }
}

当触发条目删除时执行

public boolean animateRemove(ViewHolder holder) {
    this.resetAnimation(holder);
    this.mPendingRemovals.add(holder);
    return true;
}

当条目状态改变时

public boolean animateChange(ViewHolder oldHolder, ViewHolder newHolder, int fromX, int fromY, int toX, int toY) {
    if (oldHolder == newHolder) {
        return this.animateMove(oldHolder, fromX, fromY, toX, toY);
    } else {
        float prevTranslationX = oldHolder.itemView.getTranslationX();
        float prevTranslationY = oldHolder.itemView.getTranslationY();
        float prevAlpha = oldHolder.itemView.getAlpha();
        this.resetAnimation(oldHolder);
        int deltaX = (int)((float)(toX - fromX) - prevTranslationX);
        int deltaY = (int)((float)(toY - fromY) - prevTranslationY);
        oldHolder.itemView.setTranslationX(prevTranslationX);
        oldHolder.itemView.setTranslationY(prevTranslationY);
        oldHolder.itemView.setAlpha(prevAlpha);
        if (newHolder != null) {
            this.resetAnimation(newHolder);
            newHolder.itemView.setTranslationX((float)(-deltaX));
            newHolder.itemView.setTranslationY((float)(-deltaY));
            newHolder.itemView.setAlpha(0.0F);
        }

        this.mPendingChanges.add(new DefaultItemAnimator.ChangeInfo(oldHolder, newHolder, fromX, fromY, toX, toY));
        return true;
    }
}

以上四个方法并不是为了执行动画，而是初始化动画的准备工作，它们的作用大致有两个：
【一】 设置ViewHolder的初始状态，比如：

newHolder.itemView.setAlpha(0.0F);

【二】 存储将要执行动画的ViewHolder，比如：

//存储将要执行动画的ViewHolder（移除Item）
this.mPendingRemovals.add(holder);

//存储将要执行动画的ViewHolder（Item状态改变）
this.mPendingChanges.add(new DefaultItemAnimator.ChangeInfo(oldHolder, newHolder, fromX, fromY, toX, toY));

//存储将要执行动画的ViewHolder（位移Item）
this.mPendingMoves.add(new DefaultItemAnimator.MoveInfo(holder, fromX, fromY, toX, toY));

//存储将要执行动画的ViewHolder（新增Item）
this.mPendingAdditions.add(holder);

当一切准备工作做好之后，开始执行runPendingAnimations方法

public void runPendingAnimations() {
    boolean removalsPending = !this.mPendingRemovals.isEmpty();
    boolean movesPending = !this.mPendingMoves.isEmpty();
    boolean changesPending = !this.mPendingChanges.isEmpty();
    boolean additionsPending = !this.mPendingAdditions.isEmpty();
    if (removalsPending || movesPending || additionsPending || changesPending) {
        Iterator var5 = this.mPendingRemovals.iterator();

        while(var5.hasNext()) {
            ViewHolder holder = (ViewHolder)var5.next();
            this.animateRemoveImpl(holder);
        }

        this.mPendingRemovals.clear();
        final ArrayList additions;
        Runnable adder;
        if (movesPending) {
            additions = new ArrayList();
            additions.addAll(this.mPendingMoves);
            this.mMovesList.add(additions);
            this.mPendingMoves.clear();
            adder = new Runnable() {
                public void run() {
                    Iterator var1 = additions.iterator();

                    while(var1.hasNext()) {
                        DefaultItemAnimator.MoveInfo moveInfo = (DefaultItemAnimator.MoveInfo)var1.next();
                        DefaultItemAnimator.this.animateMoveImpl(moveInfo.holder, moveInfo.fromX, moveInfo.fromY, moveInfo.toX, moveInfo.toY);
                    }

                    additions.clear();
                    DefaultItemAnimator.this.mMovesList.remove(additions);
                }
            };
            if (removalsPending) {
                View view = ((DefaultItemAnimator.MoveInfo)additions.get(0)).holder.itemView;
                ViewCompat.postOnAnimationDelayed(view, adder, this.getRemoveDuration());
            } else {
                adder.run();
            }
        }

        if (changesPending) {
            additions = new ArrayList();
            additions.addAll(this.mPendingChanges);
            this.mChangesList.add(additions);
            this.mPendingChanges.clear();
            adder = new Runnable() {
                public void run() {
                    Iterator var1 = additions.iterator();

                    while(var1.hasNext()) {
                        DefaultItemAnimator.ChangeInfo change = (DefaultItemAnimator.ChangeInfo)var1.next();
                        DefaultItemAnimator.this.animateChangeImpl(change);
                    }

                    additions.clear();
                    DefaultItemAnimator.this.mChangesList.remove(additions);
                }
            };
            if (removalsPending) {
                ViewHolder holder = ((DefaultItemAnimator.ChangeInfo)additions.get(0)).oldHolder;
                ViewCompat.postOnAnimationDelayed(holder.itemView, adder, this.getRemoveDuration());
            } else {
                adder.run();
            }
        }

        if (additionsPending) {
            additions = new ArrayList();
            additions.addAll(this.mPendingAdditions);
            this.mAdditionsList.add(additions);
            this.mPendingAdditions.clear();
            adder = new Runnable() {
                public void run() {
                    Iterator var1 = additions.iterator();

                    while(var1.hasNext()) {
                        ViewHolder holder = (ViewHolder)var1.next();
                        DefaultItemAnimator.this.animateAddImpl(holder);
                    }

                    additions.clear();
                    DefaultItemAnimator.this.mAdditionsList.remove(additions);
                }
            };
            if (!removalsPending && !movesPending && !changesPending) {
                adder.run();
            } else {
                long removeDuration = removalsPending ? this.getRemoveDuration() : 0L;
                long moveDuration = movesPending ? this.getMoveDuration() : 0L;
                long changeDuration = changesPending ? this.getChangeDuration() : 0L;
                long totalDelay = removeDuration + Math.max(moveDuration, changeDuration);
                View view = ((ViewHolder)additions.get(0)).itemView;
                ViewCompat.postOnAnimationDelayed(view, adder, totalDelay);
            }
        }

    }
}

runPendingAnimations方法中，有执行四种动画的方法，分别是：

【animateRemoveImpl】 删除动画
【animateChangeImpl】 状态改变动画
【animateAddImpl】 添加条目动画
【animateMoveImpl】 条目位移动画

所以，可以断定，runPendingAnimations方法的作用是执行所有集合中的动画。

RecyclerView条目动画执行流程

从源码分析，RecyclerView条目动画执行过程是：（很重要）

animateAdd-->runPendingAnimations-->animateAddImpl
animateMove-->runPendingAnimations-->animateMoveImpl
animateRemove-->runPendingAnimations-->animateRemoveImpl
animateChange-->runPendingAnimations-->animateChangeImpl

前面源码看不懂不要紧，但是条目动画基本执行流程必须要清楚，因为接下来开始一步一步的手写自定义DefaultItemAnimator。

【第一步】 新建DefaultItemAnimator类，继承DefaultItemAnimator

我们看一下DefaultItemAnimator类，它的回调方法都是从父类DefaultItemAnimator重写过来的

public class MyCustomItemAnimator extends DefaultItemAnimator {

    @Override
    public boolean canReuseUpdatedViewHolder(@NonNull RecyclerView.ViewHolder viewHolder, @NonNull List<Object> payloads) {
        return super.canReuseUpdatedViewHolder(viewHolder, payloads);
    }

    @Override
    public void runPendingAnimations() {
        super.runPendingAnimations();
    }

    @Override
    public boolean animateRemove(RecyclerView.ViewHolder holder) {
        return super.animateRemove(holder);
    }

    @Override
    public boolean animateAdd(RecyclerView.ViewHolder holder) {
        return super.animateAdd(holder);
    }

    @Override
    public boolean animateMove(RecyclerView.ViewHolder holder, int fromX, int fromY, int toX, int toY) {
        return super.animateMove(holder, fromX, fromY, toX, toY);
    }

    @Override
    public boolean animateChange(RecyclerView.ViewHolder oldHolder, RecyclerView.ViewHolder newHolder, int fromX, int fromY, int toX, int toY) {
        return super.animateChange(oldHolder, newHolder, fromX, fromY, toX, toY);
    }

    @Override
    public void endAnimation(RecyclerView.ViewHolder item) {
        super.endAnimation(item);
    }

    @Override
    public boolean isRunning() {
        return super.isRunning();
    }

    @Override
    public void endAnimations() {
        super.endAnimations();
    }
    
}

那些方法有什么用呢？（重点）

canReuseUpdatedViewHolder

RecyclerView的复用机制是否可用，这里一般默认即可，或者将这个返回值改成true，也就是说，默认复用机制可用。然而，决定RecyclerView是否可以复用不仅仅是根据canReuseUpdatedViewHolder方法的返回值，而且还需要看Adapter中的getItemViewType方法的返回值。

也就是说，当canReuseUpdatedViewHolder的返回值为true并且多个ViewHolder为同一个类型，说明可复用。

@Override
public int getItemViewType(int position) {
    //所有ViewHolder类型都是0，所有都可复用
    return 0;
}

@Override
public int getItemViewType(int position) {
    //所有ViewHolder类型都是不一样，所有都不可复用
    return position;
}

@Override
public int getItemViewType(int position) {
    //ViewHolder类型为0的可以相互复用，ViewHolder类型为1的可以相互复用，不同类型的不可相互复用
    if(a){
        return 0;
    }else{
        return 1;
    }
}

animateAdd

这个方法的作用是存储即将被添加的ViewHolder。
这个方法的执行是最为频繁的了。
当RecyclerView删除某一项时，删除项之后的项都要被重新添加；
当RecyclerView新增某项时，新增项之后的项都要被重新添加；
当RecyclerView指定两个项相互对换位移时，这两项需要被重新添加；

animateRemove

这个方法的作用是存储即将被删除的ViewHolder。
当删除某项时，会执行这个方法。

animateMove

这个方法的作用是存储即将被位移的ViewHolder。
当新增项、删除项、项状态改变时都会执行到这个回调。
需要说明的是，当交换某两项位置时，这里只会触发animateAdd方法，而不会执行animateMove方法。

animateChange

这个方法的作用是存储即将状态被改变的ViewHolder。
当项状态改变时，执行animateChange方法。

isRunning

判断当前动画是否正在执行。

runPendingAnimations

这个方法才是最终执行动画的地方，animateAdd、animateRemove、animateMove、animateChange这四个方法只是将将要执行动画的ViewHolder保存到集合里面，最终这四个集合会在runPendingAnimations方法里遍历，将所有的ViewHolder执行动画。

endAnimation

结束动画时调用。

endAnimations

结束动画时调用。

【第二步】 条目被添加、删除、位移、改变时会执行到哪些方法？

添加项

adapter.notifyItemInserted(position);

当在指定位置插入某项时，会执行animateMove和animateAdd方法存储ViewHolder，最后执行runPendingAnimations方法执行动画。

删除项

adapter.notifyItemRemoved(position);

当删除某项时，会执行animateRemove、animateAdd、animateMove这三个方法存储ViewHolder，最后执行runPendingAnimations方法执行动画。

位移项

adapter.notifyItemMoved(position, position + 1);

当两个项互相交换位置时，执行animateAdd方法存储ViewHolder，最后执行runPendingAnimations方法执行动画。

项状态改变

adapter.notifyItemChanged(position);

当项状态改变时，执行animateChange和animateMove方法存储ViewHolder，最后执行runPendingAnimations方法执行动画。

【第三步】 将DefaultItemAnimator类中的基本实现拷贝到MyCustomItemAnimator方法中，报错的地方可以自行修改。

以下贴出我整理之后的代码

public class MyCustomItemAnimator extends DefaultItemAnimator {

    //用于存储将要移动的MoveInfo对象
    private ArrayList<MyCustomItemAnimator.MoveInfo> mPendingMoves = new ArrayList();
    //MoveInfo的临时存储集合
    private ArrayList<ArrayList<MyCustomItemAnimator.MoveInfo>> mMovesList = new ArrayList();
    //用于存储正在执行移动动画的ViewHolder
    private ArrayList<RecyclerView.ViewHolder> mMoveAnimations = new ArrayList();
    //用于存储将要被添加的ViewHolder
    private ArrayList<RecyclerView.ViewHolder> mPendingAdditions = new ArrayList();
    //存储被添加的ViewHolder的临时集合
    private ArrayList<ArrayList<RecyclerView.ViewHolder>> mAdditionsList = new ArrayList();
    //用于存储正在执行添加动画的ViewHolder
    private ArrayList<RecyclerView.ViewHolder> mAddAnimations = new ArrayList();
    //用于存储将要删除的ViewHolder
    private ArrayList<RecyclerView.ViewHolder> mPendingRemovals = new ArrayList();
    //用于存储正在执行删除动画的ViewHolder
    private ArrayList<RecyclerView.ViewHolder> mRemoveAnimations = new ArrayList();
    //用于存储将要改变的ViewHolder
    private ArrayList<MyCustomItemAnimator.ChangeInfo> mPendingChanges = new ArrayList();
    //存储被改变的ViewHolder的临时集合
    private ArrayList<ArrayList<MyCustomItemAnimator.ChangeInfo>> mChangesList = new ArrayList();
    //用于存储正在执行改变动画的ViewHolder
    private ArrayList<RecyclerView.ViewHolder> mChangeAnimations = new ArrayList();

    //定义一个插值器：先向相反方向改变，再加速播放，会超出目标值
    private AnticipateOvershootInterpolator accelerateDecelerateInterpolator;

    @Override
    public boolean canReuseUpdatedViewHolder(@NonNull RecyclerView.ViewHolder viewHolder) {
        return true;
    }


    @Override
    public boolean animateAdd(RecyclerView.ViewHolder holder) {
        //添加条目动画实现

        //开始重置动画
        holder.itemView.animate().setInterpolator((new ValueAnimator()).getInterpolator());
        endAnimation(holder);

        //让被添加的条目初始完全透明
        holder.itemView.setAlpha(0.0f);

        //把即将被添加的ViewHolder暂时缓存到mPendingAdditions中
        mPendingAdditions.add(holder);
        return true;
    }


    @Override
    public boolean animateMove(RecyclerView.ViewHolder holder, int fromX, int fromY, int toX, int toY) {
        //移动条目动画实现

        View view = holder.itemView;
        fromX += (int)holder.itemView.getTranslationX();
        fromY += (int)holder.itemView.getTranslationY();

        //开始重置动画
        holder.itemView.animate().setInterpolator((new ValueAnimator()).getInterpolator());
        endAnimation(holder);

        int deltaX = toX - fromX;
        int deltaY = toY - fromY;
        if (deltaX == 0 && deltaY == 0) {
            dispatchMoveFinished(holder);
            return false;
        } else {
            if (deltaX != 0) {
                view.setTranslationX((float)(-deltaX));
            }

            if (deltaY != 0) {
                view.setTranslationY((float)(-deltaY));
            }

            mPendingMoves.add(new MyCustomItemAnimator.MoveInfo(holder, fromX, fromY, toX, toY));
            return true;
        }
    }

    @Override
    public boolean animateRemove(RecyclerView.ViewHolder holder) {
        //删除条目动画实现


        //开始重置动画
        holder.itemView.animate().setInterpolator((new ValueAnimator()).getInterpolator());
        endAnimation(holder);

        //把将要执行删除动画的ViewHolder放入mPendingRemovals集合
        mPendingRemovals.add(holder);
        return true;
    }

    @Override
    public boolean animateChange(RecyclerView.ViewHolder oldHolder, RecyclerView.ViewHolder newHolder, int fromX, int fromY, int toX, int toY) {
        //改变条目动画实现


        if (oldHolder == newHolder) {
            return this.animateMove(oldHolder, fromX, fromY, toX, toY);
        } else {
            float prevTranslationX = oldHolder.itemView.getTranslationX();
            float prevTranslationY = oldHolder.itemView.getTranslationY();
            float prevAlpha = oldHolder.itemView.getAlpha();

            //开始重置动画
            oldHolder.itemView.animate().setInterpolator((new ValueAnimator()).getInterpolator());
            endAnimation(oldHolder);

            int deltaX = (int)((float)(toX - fromX) - prevTranslationX);
            int deltaY = (int)((float)(toY - fromY) - prevTranslationY);
            oldHolder.itemView.setTranslationX(prevTranslationX);
            oldHolder.itemView.setTranslationY(prevTranslationY);
            oldHolder.itemView.setAlpha(prevAlpha);
            if (newHolder != null) {

                //开始重置动画
                newHolder.itemView.animate().setInterpolator((new ValueAnimator()).getInterpolator());
                endAnimation(newHolder);

                newHolder.itemView.setTranslationX((float)(-deltaX));
                newHolder.itemView.setTranslationY((float)(-deltaY));
                newHolder.itemView.setAlpha(0.0F);
            }

            this.mPendingChanges.add(new MyCustomItemAnimator.ChangeInfo(oldHolder, newHolder, fromX, fromY, toX, toY));
            return true;
        }
    }

    @Override
    public void runPendingAnimations() {
        boolean removalsPending = !mPendingRemovals.isEmpty();
        boolean movesPending = !mPendingMoves.isEmpty();
        boolean changesPending = !mPendingChanges.isEmpty();
        boolean additionsPending = !mPendingAdditions.isEmpty();
        if (removalsPending || movesPending || additionsPending || changesPending) {
            Iterator var5 = mPendingRemovals.iterator();

            while(var5.hasNext()) {
                RecyclerView.ViewHolder holder = (RecyclerView.ViewHolder)var5.next();
                this.animateRemoveImpl(holder);
            }

            mPendingRemovals.clear();
            ArrayList additions;
            Runnable adder;
            if (movesPending) {
                additions = new ArrayList();
                additions.addAll(this.mPendingMoves);
                this.mMovesList.add(additions);
                this.mPendingMoves.clear();
                final ArrayList finalAdditions2 = additions;
                adder = new Runnable() {
                    public void run() {
                        Iterator var1 = finalAdditions2.iterator();

                        while(var1.hasNext()) {
                            MyCustomItemAnimator.MoveInfo moveInfo = (MyCustomItemAnimator.MoveInfo)var1.next();
                            animateMoveImpl(moveInfo.holder, moveInfo.fromX, moveInfo.fromY, moveInfo.toX, moveInfo.toY);
                        }

                        finalAdditions2.clear();
                        mMovesList.remove(finalAdditions2);
                    }
                };
                if (removalsPending) {
                    View view = ((MyCustomItemAnimator.MoveInfo)additions.get(0)).holder.itemView;
                    ViewCompat.postOnAnimationDelayed(view, adder, this.getRemoveDuration());
                } else {
                    adder.run();
                }
            }

            if (changesPending) {
                additions = new ArrayList();
                additions.addAll(this.mPendingChanges);
                mChangesList.add(additions);
                this.mPendingChanges.clear();
                final ArrayList finalAdditions1 = additions;
                adder = new Runnable() {
                    public void run() {
                        Iterator var1 = finalAdditions1.iterator();

                        while(var1.hasNext()) {
                            MyCustomItemAnimator.ChangeInfo change = (MyCustomItemAnimator.ChangeInfo)var1.next();
                            animateChangeImpl(change);
                        }

                        finalAdditions1.clear();
                        mChangesList.remove(finalAdditions1);
                    }
                };
                if (removalsPending) {
                    RecyclerView.ViewHolder holder = ((MyCustomItemAnimator.ChangeInfo)additions.get(0)).oldHolder;
                    ViewCompat.postOnAnimationDelayed(holder.itemView, adder, this.getRemoveDuration());
                } else {
                    adder.run();
                }
            }

            if (additionsPending) {
                additions = new ArrayList();
                additions.addAll(this.mPendingAdditions);
                this.mAdditionsList.add(additions);
                this.mPendingAdditions.clear();
                final ArrayList finalAdditions = additions;
                adder = new Runnable() {
                    public void run() {
                        Iterator var1 = finalAdditions.iterator();

                        while(var1.hasNext()) {
                            RecyclerView.ViewHolder holder = (RecyclerView.ViewHolder)var1.next();
                            animateAddImpl(holder);
                        }

                        finalAdditions.clear();
                        mAdditionsList.remove(finalAdditions);
                    }
                };
                if (!removalsPending && !movesPending && !changesPending) {
                    adder.run();
                } else {
                    long removeDuration = removalsPending ? this.getRemoveDuration() : 0L;
                    long moveDuration = movesPending ? this.getMoveDuration() : 0L;
                    long changeDuration = changesPending ? this.getChangeDuration() : 0L;
                    long totalDelay = removeDuration + Math.max(moveDuration, changeDuration);
                    View view = ((RecyclerView.ViewHolder)additions.get(0)).itemView;
                    ViewCompat.postOnAnimationDelayed(view, adder, totalDelay);
                }
            }

        }
    }

    @Override
    public void endAnimation(RecyclerView.ViewHolder item) {
        super.endAnimation(item);
    }

    @Override
    public boolean isRunning() {
        //用于判断动画是否正在执行
        return super.isRunning();
    }

    @Override
    public void endAnimations() {
        super.endAnimations();
    }

    /**
     * Item状态改变时的动画
     * @param changeInfo
     */
    void animateChangeImpl(final MyCustomItemAnimator.ChangeInfo changeInfo) {
        RecyclerView.ViewHolder holder = changeInfo.oldHolder;
        final View view = holder == null ? null : holder.itemView;
        RecyclerView.ViewHolder newHolder = changeInfo.newHolder;
        final View newView = newHolder != null ? newHolder.itemView : null;
        ViewPropertyAnimator newViewAnimation;
        if (view != null) {
            newViewAnimation = view.animate().setDuration(this.getChangeDuration());
            mChangeAnimations.add(changeInfo.oldHolder);
            newViewAnimation.translationX((float)(changeInfo.toX - changeInfo.fromX));
            newViewAnimation.translationY((float)(changeInfo.toY - changeInfo.fromY));
            final ViewPropertyAnimator finalNewViewAnimation = newViewAnimation;
            newViewAnimation.alpha(0.0F).setListener(new AnimatorListenerAdapter() {
                public void onAnimationStart(Animator animator) {
                    dispatchChangeStarting(changeInfo.oldHolder, true);
                }

                public void onAnimationEnd(Animator animator) {
                    finalNewViewAnimation.setListener((Animator.AnimatorListener)null);
                    view.setAlpha(1.0F);
                    view.setTranslationX(0.0F);
                    view.setTranslationY(0.0F);
                    dispatchChangeFinished(changeInfo.oldHolder, true);
                    mChangeAnimations.remove(changeInfo.oldHolder);
                    if (!isRunning()) {
                        dispatchAnimationsFinished();
                    }
                }
            }).start();
        }

        if (newView != null) {
            newViewAnimation = newView.animate();
            this.mChangeAnimations.add(changeInfo.newHolder);
            final ViewPropertyAnimator finalNewViewAnimation1 = newViewAnimation;
            newViewAnimation.translationX(0.0F).translationY(0.0F).setDuration(this.getChangeDuration()).alpha(1.0F).setListener(new AnimatorListenerAdapter() {
                public void onAnimationStart(Animator animator) {
                    dispatchChangeStarting(changeInfo.newHolder, false);
                }

                public void onAnimationEnd(Animator animator) {
                    finalNewViewAnimation1.setListener((Animator.AnimatorListener)null);
                    newView.setAlpha(1.0F);
                    newView.setTranslationX(0.0F);
                    newView.setTranslationY(0.0F);
                    dispatchChangeFinished(changeInfo.newHolder, false);
                    mChangeAnimations.remove(changeInfo.newHolder);
                    if (!isRunning()) {
                        dispatchAnimationsFinished();
                    }
                }
            }).start();
        }

    }

    /**
     * Item移动实现
     * @param holder
     * @param fromX
     * @param fromY
     * @param toX
     * @param toY
     */
    void animateMoveImpl(final RecyclerView.ViewHolder holder, int fromX, int fromY, int toX, int toY) {
        final View view = holder.itemView;
        final int deltaX = toX - fromX;
        final int deltaY = toY - fromY;
        if (deltaX != 0) {
            view.animate().translationX(0.0F);
        }

        if (deltaY != 0) {
            view.animate().translationY(0.0F);
        }

        final ViewPropertyAnimator animation = view.animate();
        this.mMoveAnimations.add(holder);
        animation.setDuration(this.getMoveDuration()).setListener(new AnimatorListenerAdapter() {
            public void onAnimationStart(Animator animator) {
                dispatchMoveStarting(holder);
            }

            public void onAnimationCancel(Animator animator) {
                if (deltaX != 0) {
                    view.setTranslationX(0.0F);
                }

                if (deltaY != 0) {
                    view.setTranslationY(0.0F);
                }

            }

            public void onAnimationEnd(Animator animator) {
                animation.setListener((Animator.AnimatorListener)null);
                dispatchMoveFinished(holder);
                mMoveAnimations.remove(holder);
                if (!isRunning()) {
                    dispatchAnimationsFinished();
                }
            }
        }).start();
    }

    /**
     * 添加Item动画实现
     * @param holder
     */
    void animateAddImpl(final RecyclerView.ViewHolder holder) {
        final View view = holder.itemView;
        final ViewPropertyAnimator animation = view.animate();
        this.mAddAnimations.add(holder);
        animation.alpha(1.0F).setDuration(this.getAddDuration()).setListener(new AnimatorListenerAdapter() {
            public void onAnimationStart(Animator animator) {
                dispatchAddStarting(holder);
            }

            public void onAnimationCancel(Animator animator) {
                view.setAlpha(1.0F);
            }

            public void onAnimationEnd(Animator animator) {
                animation.setListener((Animator.AnimatorListener)null);
                dispatchAddFinished(holder);
                mAddAnimations.remove(holder);
                if (!isRunning()) {
                    dispatchAnimationsFinished();
                }
            }
        }).start();
    }

    /**
     * 移除Item动画实现
     * @param holder
     */
    private void animateRemoveImpl(final RecyclerView.ViewHolder holder) {
        final View view = holder.itemView;
        final ViewPropertyAnimator animation = view.animate();
        this.mRemoveAnimations.add(holder);
        animation.setDuration(this.getRemoveDuration()).alpha(0.0F).setListener(new AnimatorListenerAdapter() {
            public void onAnimationStart(Animator animator) {
                dispatchRemoveStarting(holder);
            }

            public void onAnimationEnd(Animator animator) {
                animation.setListener((Animator.AnimatorListener)null);
                view.setAlpha(1.0F);
                dispatchRemoveFinished(holder);
                mRemoveAnimations.remove(holder);
                if (!isRunning()) {
                    dispatchAnimationsFinished();
                }
            }
        }).start();
    }

    private static class MoveInfo {
        public RecyclerView.ViewHolder holder;
        public int fromX;
        public int fromY;
        public int toX;
        public int toY;

        MoveInfo(RecyclerView.ViewHolder holder, int fromX, int fromY, int toX, int toY) {
            this.holder = holder;
            this.fromX = fromX;
            this.fromY = fromY;
            this.toX = toX;
            this.toY = toY;
        }
    }

    private static class ChangeInfo {
        public RecyclerView.ViewHolder oldHolder;
        public RecyclerView.ViewHolder newHolder;
        public int fromX;
        public int fromY;
        public int toX;
        public int toY;

        private ChangeInfo(RecyclerView.ViewHolder oldHolder, RecyclerView.ViewHolder newHolder) {
            this.oldHolder = oldHolder;
            this.newHolder = newHolder;
        }

        ChangeInfo(RecyclerView.ViewHolder oldHolder, RecyclerView.ViewHolder newHolder, int fromX, int fromY, int toX, int toY) {
            this(oldHolder, newHolder);
            this.fromX = fromX;
            this.fromY = fromY;
            this.toX = toX;
            this.toY = toY;
        }

        public String toString() {
            return "ChangeInfo{oldHolder=" + this.oldHolder + ", newHolder=" + this.newHolder + ", fromX=" + this.fromX + ", fromY=" + this.fromY + ", toX=" + this.toX + ", toY=" + this.toY + '}';
        }
    }
}

以上代码算是照搬DefaultItemAnimator源码，接下来回基于已整理好的代码上修改动画。

【第四步】 修改添加条目动画

    @Override
    public boolean animateAdd(RecyclerView.ViewHolder holder) {
        //添加条目动画实现

        //开始重置动画
        holder.itemView.animate().setInterpolator((new ValueAnimator()).getInterpolator());
        endAnimation(holder);

        //让被添加的条目初始完全透明
        holder.itemView.setAlpha(0.0f);

        //把即将被添加的ViewHolder暂时缓存到mPendingAdditions中
        mPendingAdditions.add(holder);
        return true;
    }

这个方法的执行比较频繁，这里保持默认，先重置动画，再将Item完全透明，最后将ViewHolder添加到mPendingAdditions集合中。

    /**
     * 添加Item动画实现
     * @param holder
     */
    void animateAddImpl(final RecyclerView.ViewHolder holder) {
        final View view = holder.itemView;
        final ViewPropertyAnimator animation = view.animate();
        this.mAddAnimations.add(holder);
        animation.alpha(1.0F).setDuration(2000).setListener(new AnimatorListenerAdapter() {
            public void onAnimationStart(Animator animator) {
                dispatchAddStarting(holder);
            }

            public void onAnimationCancel(Animator animator) {
                view.setAlpha(1.0F);
            }

            public void onAnimationEnd(Animator animator) {
                animation.setListener((Animator.AnimatorListener)null);
                dispatchAddFinished(holder);
                mAddAnimations.remove(holder);
                if (!isRunning()) {
                    dispatchAnimationsFinished();
                }
            }
        }).start();
    }

animateAddImpl方法基本也没有变化，只是将动画时长改成2000ms。

当ViewHolder不可复用时，它的执行效果如下：

136.gif

当ViewHolder可复用时，它的执行效果如下：

138.gif

【第五步】 修改位移动画

位移动画本身就写的挺不错了，这里偷个懒就只将动画时间修改为1秒。

位移动画主要体现在新增条目和删除条目上。

效果如下：（由于添加动画被完全透明了，所以这里只展示ViewHolder被复用的情况）

139.gif

【第六步】 修改删除动画

修改之后的代码如下：

    /**
     * 移除Item动画实现
     * @param holder
     */
    private void animateRemoveImpl(final RecyclerView.ViewHolder holder) {
        final View view = holder.itemView;
        final ViewPropertyAnimator animation = view.animate();
        this.mRemoveAnimations.add(holder);
        animation.setDuration(1000)
                .translationX(holder.itemView.getWidth())
                .setInterpolator(new AnticipateOvershootInterpolator())
                .setListener(new AnimatorListenerAdapter() {
            public void onAnimationStart(Animator animator) {
                dispatchRemoveStarting(holder);
            }

            public void onAnimationEnd(Animator animator) {
                animation.setListener((Animator.AnimatorListener)null);
                view.setTranslationX(0);
                dispatchRemoveFinished(holder);
                mRemoveAnimations.remove(holder);
                if (!isRunning()) {
                    dispatchAnimationsFinished();
                }
            }
        }).start();
    }

ViewHolder不可被复用的效果如下：

141.gif

ViewHolder可被复用的效果如下：

140.gif

【第七步】 修改状态改变时的动画

修改后的代码如下：

    @Override
    public boolean animateChange(RecyclerView.ViewHolder oldHolder, RecyclerView.ViewHolder newHolder, int fromX, int fromY, int toX, int toY) {
        //改变条目动画实现

        float prevTranslationX = oldHolder.itemView.getTranslationX();
        float prevTranslationY = oldHolder.itemView.getTranslationY();
        float prevAlpha = oldHolder.itemView.getAlpha();

        //开始重置动画
        oldHolder.itemView.animate().setInterpolator((new ValueAnimator()).getInterpolator());
        endAnimation(oldHolder);

        int deltaX = (int)((float)(toX - fromX) - prevTranslationX);
        int deltaY = (int)((float)(toY - fromY) - prevTranslationY);
        oldHolder.itemView.setTranslationX(prevTranslationX);
        oldHolder.itemView.setTranslationY(prevTranslationY);
        oldHolder.itemView.setAlpha(prevAlpha);
        if (newHolder != null) {

            //开始重置动画
            newHolder.itemView.animate().setInterpolator((new ValueAnimator()).getInterpolator());
            endAnimation(newHolder);

            newHolder.itemView.setTranslationX((float)(-deltaX));
            newHolder.itemView.setTranslationY((float)(-deltaY));
            newHolder.itemView.setAlpha(0.0F);
        }

        this.mPendingChanges.add(new MyCustomItemAnimator.ChangeInfo(oldHolder, newHolder, fromX, fromY, toX, toY));
        return true;
    }

在初始化的时候，oldHolder的透明度保持不变，newHolder给它完全透明。

    /**
     * Item状态改变时的动画
     * @param changeInfo
     */
    void animateChangeImpl(final MyCustomItemAnimator.ChangeInfo changeInfo) {
        RecyclerView.ViewHolder holder = changeInfo.oldHolder;
        final View view = holder == null ? null : holder.itemView;
        RecyclerView.ViewHolder newHolder = changeInfo.newHolder;
        final View newView = newHolder != null ? newHolder.itemView : null;
        ViewPropertyAnimator newViewAnimation;
        if (view != null) {
            newViewAnimation = view.animate().setDuration(2000);
            mChangeAnimations.add(changeInfo.oldHolder);
            newViewAnimation.translationX((float)(changeInfo.toX - changeInfo.fromX));
            newViewAnimation.translationY((float)(changeInfo.toY - changeInfo.fromY));
            final ViewPropertyAnimator finalNewViewAnimation = newViewAnimation;
            newViewAnimation.alpha(0.0F).setListener(new AnimatorListenerAdapter() {
                public void onAnimationStart(Animator animator) {
                    dispatchChangeStarting(changeInfo.oldHolder, true);
                }

                public void onAnimationEnd(Animator animator) {
                    finalNewViewAnimation.setListener((Animator.AnimatorListener)null);
                    view.setAlpha(1.0F);
                    view.setTranslationX(0.0F);
                    view.setTranslationY(0.0F);
                    dispatchChangeFinished(changeInfo.oldHolder, true);
                    mChangeAnimations.remove(changeInfo.oldHolder);
                    if (!isRunning()) {
                        dispatchAnimationsFinished();
                    }
                }
            }).start();
        }

        if (newView != null) {
            newViewAnimation = newView.animate();
            this.mChangeAnimations.add(changeInfo.newHolder);
            final ViewPropertyAnimator finalNewViewAnimation1 = newViewAnimation;
            newViewAnimation
                    .setDuration(2000)
                    .alpha(1.0F)
                    .setListener(new AnimatorListenerAdapter() {
                public void onAnimationStart(Animator animator) {
                    dispatchChangeStarting(changeInfo.newHolder, false);
                }

                public void onAnimationEnd(Animator animator) {
                    finalNewViewAnimation1.setListener((Animator.AnimatorListener)null);
                    newView.setAlpha(1.0F);
                    newView.setTranslationX(0.0F);
                    newView.setTranslationY(0.0F);
                    dispatchChangeFinished(changeInfo.newHolder, false);
                    mChangeAnimations.remove(changeInfo.newHolder);
                    if (!isRunning()) {
                        dispatchAnimationsFinished();
                    }
                }
            }).start();
        }

oldHolder透明度从1到0的动画，newHolder透明度从0到1的动画，动画时长为2000ms，效果如下：

142.gif

最后，贴出MyCustomItemAnimator类的全部代码

public class MyCustomItemAnimator extends DefaultItemAnimator {

    //用于存储将要移动的MoveInfo对象
    private ArrayList<MyCustomItemAnimator.MoveInfo> mPendingMoves = new ArrayList();
    //MoveInfo的临时存储集合
    private ArrayList<ArrayList<MyCustomItemAnimator.MoveInfo>> mMovesList = new ArrayList();
    //用于存储正在执行移动动画的ViewHolder
    private ArrayList<RecyclerView.ViewHolder> mMoveAnimations = new ArrayList();
    //用于存储将要被添加的ViewHolder
    private ArrayList<RecyclerView.ViewHolder> mPendingAdditions = new ArrayList();
    //存储被添加的ViewHolder的临时集合
    private ArrayList<ArrayList<RecyclerView.ViewHolder>> mAdditionsList = new ArrayList();
    //用于存储正在执行添加动画的ViewHolder
    private ArrayList<RecyclerView.ViewHolder> mAddAnimations = new ArrayList();
    //用于存储将要删除的ViewHolder
    private ArrayList<RecyclerView.ViewHolder> mPendingRemovals = new ArrayList();
    //用于存储正在执行删除动画的ViewHolder
    private ArrayList<RecyclerView.ViewHolder> mRemoveAnimations = new ArrayList();
    //用于存储将要改变的ViewHolder
    private ArrayList<MyCustomItemAnimator.ChangeInfo> mPendingChanges = new ArrayList();
    //存储被改变的ViewHolder的临时集合
    private ArrayList<ArrayList<MyCustomItemAnimator.ChangeInfo>> mChangesList = new ArrayList();
    //用于存储正在执行改变动画的ViewHolder
    private ArrayList<RecyclerView.ViewHolder> mChangeAnimations = new ArrayList();

    //定义一个插值器：先向相反方向改变，再加速播放，会超出目标值
    private AnticipateOvershootInterpolator accelerateDecelerateInterpolator;

    @Override
    public boolean canReuseUpdatedViewHolder(@NonNull RecyclerView.ViewHolder viewHolder) {
        return true;
    }


    @Override
    public boolean animateAdd(RecyclerView.ViewHolder holder) {
        //添加条目动画实现

        //开始重置动画
        holder.itemView.animate().setInterpolator((new ValueAnimator()).getInterpolator());
        endAnimation(holder);

        //让被添加的条目初始完全透明
        holder.itemView.setAlpha(0.0f);

        //把即将被添加的ViewHolder暂时缓存到mPendingAdditions中
        mPendingAdditions.add(holder);
        return true;
    }


    @Override
    public boolean animateMove(RecyclerView.ViewHolder holder, int fromX, int fromY, int toX, int toY) {
        //移动条目动画实现

        View view = holder.itemView;
        fromX += (int)holder.itemView.getTranslationX();
        fromY += (int)holder.itemView.getTranslationY();

        //开始重置动画
        holder.itemView.animate().setInterpolator((new ValueAnimator()).getInterpolator());
        endAnimation(holder);

        int deltaX = toX - fromX;
        int deltaY = toY - fromY;
        if (deltaX == 0 && deltaY == 0) {
            dispatchMoveFinished(holder);
            return false;
        } else {
            if (deltaX != 0) {
                view.setTranslationX((float)(-deltaX));
            }

            if (deltaY != 0) {
                view.setTranslationY((float)(-deltaY));
            }

            mPendingMoves.add(new MyCustomItemAnimator.MoveInfo(holder, fromX, fromY, toX, toY));
            return true;
        }
    }

    @Override
    public boolean animateRemove(RecyclerView.ViewHolder holder) {
        //删除条目动画实现

        //开始重置动画
        holder.itemView.animate().setInterpolator((new ValueAnimator()).getInterpolator());
        endAnimation(holder);

        //把将要执行删除动画的ViewHolder放入mPendingRemovals集合
        mPendingRemovals.add(holder);
        return true;
    }

    @Override
    public boolean animateChange(RecyclerView.ViewHolder oldHolder, RecyclerView.ViewHolder newHolder, int fromX, int fromY, int toX, int toY) {
        //改变条目动画实现

        float prevTranslationX = oldHolder.itemView.getTranslationX();
        float prevTranslationY = oldHolder.itemView.getTranslationY();
        float prevAlpha = oldHolder.itemView.getAlpha();

        //开始重置动画
        oldHolder.itemView.animate().setInterpolator((new ValueAnimator()).getInterpolator());
        endAnimation(oldHolder);

        int deltaX = (int)((float)(toX - fromX) - prevTranslationX);
        int deltaY = (int)((float)(toY - fromY) - prevTranslationY);
        oldHolder.itemView.setTranslationX(prevTranslationX);
        oldHolder.itemView.setTranslationY(prevTranslationY);
        oldHolder.itemView.setAlpha(prevAlpha);
        if (newHolder != null) {

            //开始重置动画
            newHolder.itemView.animate().setInterpolator((new ValueAnimator()).getInterpolator());
            endAnimation(newHolder);

            newHolder.itemView.setTranslationX((float)(-deltaX));
            newHolder.itemView.setTranslationY((float)(-deltaY));
            newHolder.itemView.setAlpha(0.0F);
        }

        this.mPendingChanges.add(new MyCustomItemAnimator.ChangeInfo(oldHolder, newHolder, fromX, fromY, toX, toY));
        return true;
    }

    @Override
    public void runPendingAnimations() {
        boolean removalsPending = !mPendingRemovals.isEmpty();
        boolean movesPending = !mPendingMoves.isEmpty();
        boolean changesPending = !mPendingChanges.isEmpty();
        boolean additionsPending = !mPendingAdditions.isEmpty();
        if (removalsPending || movesPending || additionsPending || changesPending) {
            Iterator var5 = mPendingRemovals.iterator();

            while(var5.hasNext()) {
                RecyclerView.ViewHolder holder = (RecyclerView.ViewHolder)var5.next();
                this.animateRemoveImpl(holder);
            }

            mPendingRemovals.clear();
            ArrayList additions;
            Runnable adder;
            if (movesPending) {
                additions = new ArrayList();
                additions.addAll(this.mPendingMoves);
                this.mMovesList.add(additions);
                this.mPendingMoves.clear();
                final ArrayList finalAdditions2 = additions;
                adder = new Runnable() {
                    public void run() {
                        Iterator var1 = finalAdditions2.iterator();

                        while(var1.hasNext()) {
                            MyCustomItemAnimator.MoveInfo moveInfo = (MyCustomItemAnimator.MoveInfo)var1.next();
                            animateMoveImpl(moveInfo.holder, moveInfo.fromX, moveInfo.fromY, moveInfo.toX, moveInfo.toY);
                        }

                        finalAdditions2.clear();
                        mMovesList.remove(finalAdditions2);
                    }
                };
                if (removalsPending) {
                    View view = ((MyCustomItemAnimator.MoveInfo)additions.get(0)).holder.itemView;
                    ViewCompat.postOnAnimationDelayed(view, adder, this.getRemoveDuration());
                } else {
                    adder.run();
                }
            }

            if (changesPending) {
                additions = new ArrayList();
                additions.addAll(this.mPendingChanges);
                mChangesList.add(additions);
                this.mPendingChanges.clear();
                final ArrayList finalAdditions1 = additions;
                adder = new Runnable() {
                    public void run() {
                        Iterator var1 = finalAdditions1.iterator();

                        while(var1.hasNext()) {
                            MyCustomItemAnimator.ChangeInfo change = (MyCustomItemAnimator.ChangeInfo)var1.next();
                            animateChangeImpl(change);
                        }

                        finalAdditions1.clear();
                        mChangesList.remove(finalAdditions1);
                    }
                };
                if (removalsPending) {
                    RecyclerView.ViewHolder holder = ((MyCustomItemAnimator.ChangeInfo)additions.get(0)).oldHolder;
                    ViewCompat.postOnAnimationDelayed(holder.itemView, adder, this.getRemoveDuration());
                } else {
                    adder.run();
                }
            }

            if (additionsPending) {
                additions = new ArrayList();
                additions.addAll(this.mPendingAdditions);
                this.mAdditionsList.add(additions);
                this.mPendingAdditions.clear();
                final ArrayList finalAdditions = additions;
                adder = new Runnable() {
                    public void run() {
                        Iterator var1 = finalAdditions.iterator();

                        while(var1.hasNext()) {
                            RecyclerView.ViewHolder holder = (RecyclerView.ViewHolder)var1.next();
                            animateAddImpl(holder);
                        }

                        finalAdditions.clear();
                        mAdditionsList.remove(finalAdditions);
                    }
                };
                if (!removalsPending && !movesPending && !changesPending) {
                    adder.run();
                } else {
                    long removeDuration = removalsPending ? this.getRemoveDuration() : 0L;
                    long moveDuration = movesPending ? this.getMoveDuration() : 0L;
                    long changeDuration = changesPending ? this.getChangeDuration() : 0L;
                    long totalDelay = removeDuration + Math.max(moveDuration, changeDuration);
                    View view = ((RecyclerView.ViewHolder)additions.get(0)).itemView;
                    ViewCompat.postOnAnimationDelayed(view, adder, totalDelay);
                }
            }

        }
    }

    @Override
    public void endAnimation(RecyclerView.ViewHolder item) {
        super.endAnimation(item);
    }

    @Override
    public boolean isRunning() {
        //用于判断动画是否正在执行
        return super.isRunning();
    }

    @Override
    public void endAnimations() {
        super.endAnimations();
    }

    /**
     * Item状态改变时的动画
     * @param changeInfo
     */
    void animateChangeImpl(final MyCustomItemAnimator.ChangeInfo changeInfo) {
        RecyclerView.ViewHolder holder = changeInfo.oldHolder;
        final View view = holder == null ? null : holder.itemView;
        RecyclerView.ViewHolder newHolder = changeInfo.newHolder;
        final View newView = newHolder != null ? newHolder.itemView : null;
        ViewPropertyAnimator newViewAnimation;
        if (view != null) {
            newViewAnimation = view.animate().setDuration(2000);
            mChangeAnimations.add(changeInfo.oldHolder);
            newViewAnimation.translationX((float)(changeInfo.toX - changeInfo.fromX));
            newViewAnimation.translationY((float)(changeInfo.toY - changeInfo.fromY));
            final ViewPropertyAnimator finalNewViewAnimation = newViewAnimation;
            newViewAnimation.alpha(0.0F).setListener(new AnimatorListenerAdapter() {
                public void onAnimationStart(Animator animator) {
                    dispatchChangeStarting(changeInfo.oldHolder, true);
                }

                public void onAnimationEnd(Animator animator) {
                    finalNewViewAnimation.setListener((Animator.AnimatorListener)null);
                    view.setAlpha(1.0F);
                    view.setTranslationX(0.0F);
                    view.setTranslationY(0.0F);
                    dispatchChangeFinished(changeInfo.oldHolder, true);
                    mChangeAnimations.remove(changeInfo.oldHolder);
                    if (!isRunning()) {
                        dispatchAnimationsFinished();
                    }
                }
            }).start();
        }

        if (newView != null) {
            newViewAnimation = newView.animate();
            this.mChangeAnimations.add(changeInfo.newHolder);
            final ViewPropertyAnimator finalNewViewAnimation1 = newViewAnimation;
            newViewAnimation
                    .setDuration(2000)
                    .alpha(1.0F)
                    .setListener(new AnimatorListenerAdapter() {
                public void onAnimationStart(Animator animator) {
                    dispatchChangeStarting(changeInfo.newHolder, false);
                }

                public void onAnimationEnd(Animator animator) {
                    finalNewViewAnimation1.setListener((Animator.AnimatorListener)null);
                    newView.setAlpha(1.0F);
                    newView.setTranslationX(0.0F);
                    newView.setTranslationY(0.0F);
                    dispatchChangeFinished(changeInfo.newHolder, false);
                    mChangeAnimations.remove(changeInfo.newHolder);
                    if (!isRunning()) {
                        dispatchAnimationsFinished();
                    }
                }
            }).start();
        }

    }

    /**
     * Item移动实现
     * @param holder
     * @param fromX
     * @param fromY
     * @param toX
     * @param toY
     */
    void animateMoveImpl(final RecyclerView.ViewHolder holder, int fromX, int fromY, int toX, int toY) {
        final View view = holder.itemView;
        final int deltaX = toX - fromX;
        final int deltaY = toY - fromY;
        if (deltaX != 0) {
            view.animate().translationX(0.0F);
        }

        if (deltaY != 0) {
            view.animate().translationY(0.0F);
        }

        final ViewPropertyAnimator animation = view.animate();
        this.mMoveAnimations.add(holder);
        animation.setDuration(1000).setListener(new AnimatorListenerAdapter() {
            public void onAnimationStart(Animator animator) {
                dispatchMoveStarting(holder);
            }

            public void onAnimationCancel(Animator animator) {
                if (deltaX != 0) {
                    view.setTranslationX(0.0F);
                }

                if (deltaY != 0) {
                    view.setTranslationY(0.0F);
                }

            }

            public void onAnimationEnd(Animator animator) {
                animation.setListener((Animator.AnimatorListener)null);
                dispatchMoveFinished(holder);
                mMoveAnimations.remove(holder);
                if (!isRunning()) {
                    dispatchAnimationsFinished();
                }
            }
        }).start();
    }

    /**
     * 添加Item动画实现
     * @param holder
     */
    void animateAddImpl(final RecyclerView.ViewHolder holder) {
        final View view = holder.itemView;
        final ViewPropertyAnimator animation = view.animate();
        this.mAddAnimations.add(holder);
        animation.alpha(1.0F).setDuration(2000).setListener(new AnimatorListenerAdapter() {
            public void onAnimationStart(Animator animator) {
                dispatchAddStarting(holder);
            }

            public void onAnimationCancel(Animator animator) {
                view.setAlpha(1.0F);
            }

            public void onAnimationEnd(Animator animator) {
                animation.setListener((Animator.AnimatorListener)null);
                dispatchAddFinished(holder);
                mAddAnimations.remove(holder);
                if (!isRunning()) {
                    dispatchAnimationsFinished();
                }
            }
        }).start();
    }

    /**
     * 移除Item动画实现
     * @param holder
     */
    private void animateRemoveImpl(final RecyclerView.ViewHolder holder) {
        final View view = holder.itemView;
        final ViewPropertyAnimator animation = view.animate();
        this.mRemoveAnimations.add(holder);
        animation.setDuration(1000)
                .translationX(holder.itemView.getWidth())
                .setInterpolator(new AnticipateOvershootInterpolator())
                .setListener(new AnimatorListenerAdapter() {
            public void onAnimationStart(Animator animator) {
                dispatchRemoveStarting(holder);
            }

            public void onAnimationEnd(Animator animator) {
                animation.setListener((Animator.AnimatorListener)null);
                view.setTranslationX(0);
                dispatchRemoveFinished(holder);
                mRemoveAnimations.remove(holder);
                if (!isRunning()) {
                    dispatchAnimationsFinished();
                }
            }
        }).start();
    }

    private static class MoveInfo {
        public RecyclerView.ViewHolder holder;
        public int fromX;
        public int fromY;
        public int toX;
        public int toY;

        MoveInfo(RecyclerView.ViewHolder holder, int fromX, int fromY, int toX, int toY) {
            this.holder = holder;
            this.fromX = fromX;
            this.fromY = fromY;
            this.toX = toX;
            this.toY = toY;
        }
    }

    private static class ChangeInfo {
        public RecyclerView.ViewHolder oldHolder;
        public RecyclerView.ViewHolder newHolder;
        public int fromX;
        public int fromY;
        public int toX;
        public int toY;

        private ChangeInfo(RecyclerView.ViewHolder oldHolder, RecyclerView.ViewHolder newHolder) {
            this.oldHolder = oldHolder;
            this.newHolder = newHolder;
        }

        ChangeInfo(RecyclerView.ViewHolder oldHolder, RecyclerView.ViewHolder newHolder, int fromX, int fromY, int toX, int toY) {
            this(oldHolder, newHolder);
            this.fromX = fromX;
            this.fromY = fromY;
            this.toX = toX;
            this.toY = toY;
        }

        public String toString() {
            return "ChangeInfo{oldHolder=" + this.oldHolder + ", newHolder=" + this.newHolder + ", fromX=" + this.fromX + ", fromY=" + this.fromY + ", toX=" + this.toX + ", toY=" + this.toY + '}';
        }
    }
}

[本章完...]

最后编辑于：2019.10.23 16:12:43

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RecyclerView<第十九篇>：条目动画之自定义DefaultItemAnimator

RecyclerView条目动画执行流程

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