我们实现这样的效果,废话不多说,先看东西.

hea3c-a23d9.gif

1 自定义属性

就这几个形状的颜色.

1.1 定义自定义属性

<?xml version="1.0" encoding="utf-8"?>
<resources>
    <declare-styleable name="ShapeView">
        <!--圆形的颜色-->
        <attr name="circleColor" format="color" />
        <!--正方形的颜色-->
        <attr name="squareColor" format="color" />
        <!--三角形的颜色-->
        <attr name="triangleColor" format="color" />
    </declare-styleable>

</resources>

1.2 取出自定义属性

    public ShapeView(Context context, @Nullable AttributeSet attrs, int defStyleAttr) {
        super(context, attrs, defStyleAttr);
        //自定义属性,圆的颜色,正方形的颜色,三角形的颜色
        //获取自定义属性
        TypedArray typedArray = context.obtainStyledAttributes(attrs, R.styleable.ShapeView);

        mCircleColor = typedArray.getColor(R.styleable.ShapeView_circleColor, mCircleColor);
        mSquareColor = typedArray.getColor(R.styleable.ShapeView_squareColor, mSquareColor);
        mTriangleColor = typedArray.getColor(R.styleable.ShapeView_triangleColor, mTriangleColor);
        //回收
        typedArray.recycle();
    }

2 onMeasure

确保是正方形即可.没有做特别处理.

    @Override
    protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {
        //之确保是正方形即可
        setMeasuredDimension(Math.min(MeasureSpec.getSize(widthMeasureSpec), MeasureSpec.getSize(heightMeasureSpec))
                , Math.min(MeasureSpec.getSize(widthMeasureSpec), MeasureSpec.getSize(heightMeasureSpec)));
    }

3 onDraw()

 @SuppressLint("DrawAllocation")
    @Override
    protected void onDraw(Canvas canvas) {
        //判断当前的是什么形状就绘制什么形状
        switch (mCurrentShape) {
            case CIRCLE:
                //绘制圆形
                float cx = getWidth() / 2;
                float cy = getWidth() / 2;
                float radius = getWidth() / 2;
                canvas.drawCircle(cx, cy, radius, mCirclePaint);
                break;
            case SQUARE:
                //绘制正方形
                if (mRect == null) {
                    mRect = new Rect(0, 0, getWidth(), getHeight());
                }
                canvas.drawRect(mRect, mSquarePaint);
                break;

            case TRIANGLE:
                //绘制三角形,canvas没有直接绘制三角形的方法.只能通过绘制路径
                if (mPath == null) {
                    mPath = new Path();
                    //等腰三角形
//                    mPath.moveTo(getWidth() / 2, 0);
//                    mPath.lineTo(0, getWidth());
//                    mPath.lineTo(getWidth(), getWidth());
//                    mPath.lineTo(getWidth() / 2, 0);
                    //改成等边三角形
                    mPath.moveTo(getWidth() / 2, 0);
                    mPath.lineTo(0, (float) (getWidth() / 2 * Math.sqrt(3)));
                    mPath.lineTo(getWidth(), (float) (getWidth() / 2 * Math.sqrt(3)));
                    mPath.close();//闭合路径
                }
                canvas.drawPath(mPath, mTrianglePaint);
                break;
            default:
                break;
        }
    }

绘制圆形和正方形没有可说了.
绘制三角形,Canvas没有方法绘制三角形的.只能通过绘制路径来绘制三角形.

等腰三角形

等边三角形

完整代码:shapeview