在android中使用最多的就是ListView，GridView，用到这两个控件那么肯定要用到适配器，那就是定义一个类继承BaseAdapter，让后覆写它里面的getCount(),getView()等方法，下面来写一个demo。
1.我们来实现一个普通的ListView的Demo
-
主布局文件:activity_main.xml
<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:paddingBottom="@dimen/activity_vertical_margin"
android:paddingLeft="@dimen/activity_horizontal_margin"
android:paddingRight="@dimen/activity_horizontal_margin"
android:paddingTop="@dimen/activity_vertical_margin"
tools:context="com.kejiang.yuandl.fastdev.MainActivity">
<ListView
android:id="@+id/listview"
android:layout_width="wrap_content"
android:layout_height="wrap_content" />
</RelativeLayout>
* ListView的item布局:item.xml
```xml
<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:orientation="vertical" android:layout_width="match_parent"
android:layout_height="match_parent">
<TextView
android:text="万能适配器测试"
android:layout_width="match_parent"
android:layout_height="100px"
android:gravity="center"
android:id="@+id/textView" />
</LinearLayout>
- ListView的适配器代码:MyAdapter.java
/**
* * Created by yuandl on 2016-10-14.
* *listView的适配器
*/
public class MyAdapter extends BaseAdapter {
private Context context;
private List<String> datas;
public MyAdapter(Context context, List<String> datas) {
this.context = context;
this.datas = datas;
}
@Override
public int getCount() {
return datas == null ? 0 : datas.size();
}
@Override
public String getItem(int position) {
return datas.get(position);
}
@Override
public long getItemId(int position) {
return position;
}
@Override
public View getView(int position, View convertView, ViewGroup parent) {
ViewHolder viewHolder;
if (convertView == null) {
convertView = LayoutInflater.from(context).inflate(R.layout.item, null);
viewHolder = new ViewHolder();
viewHolder.textView = (TextView) convertView.findViewById(R.id.textView);
convertView.setTag(viewHolder);
} else {
viewHolder = (ViewHolder) convertView.getTag();
}
String name = datas.get(position);
viewHolder.textView.setText(name);
return convertView;
}
private class ViewHolder {
public TextView textView;
}
}
- 使用：MainActivity.java
public class MainActivity extends Activity {
private WebView webView;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
myAdapterTest();
}
/**
* 普通适配器的方法
*/
private void myAdapterTest() {
setContentView(R.layout.activity_main);
ListView listView= (ListView) findViewById(R.id.listview);
List<String> datas=new ArrayList<>();
datas.add("普通适配器测试1");
datas.add("普通适配器测试2");
datas.add("普通适配器测试3");
datas.add("普通适配器测试4");
listView.setAdapter(new MyAdapter(context,datas));
}
}
- 看效果图
运行效果
2.打造万能适配器第一步，万能ViewHolder--CommonViewHolder
import android.util.SparseArray;
import android.view.View;
/**
* Created by yuandl on 2016-10-13.
* 万能的ViewHolder
*
* @author
*/
public class CommonViewHolder {
/**
* @param view 所有缓存View的根View
* @param id 缓存View的唯一标识
* @return
*/
public static <T extends View> T get(View view, int id) {
SparseArray<View> viewHolder = (SparseArray<View>) view.getTag();
//如果根view没有用来缓存View的集合
if (viewHolder == null) {
viewHolder = new SparseArray<View>();
view.setTag(viewHolder);//创建集合和根View关联
}
View chidlView = viewHolder.get(id);//获取根View储存在集合中的孩纸
if (chidlView == null) {//如果没有改孩纸
//找到该孩纸
chidlView = view.findViewById(id);
viewHolder.put(id, chidlView);//保存到集合
}
return (T) chidlView;
}
}
3.打造万能适配器的最后封装--CommonAdapter
import android.content.Context;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.BaseAdapter;
import java.util.List;
/**
* Created by yuandl on 2016-10-13.
* 万能适配器
*/
public abstract class CommonAdapter<T> extends BaseAdapter {
private Context context;
private List<T> datas;
private int layoutId;
public CommonAdapter(Context context, List<T> datas, int layoutId) {
this.context = context;
this.datas = datas;
this.layoutId = layoutId;
}
@Override
public int getCount() {
return datas == null ? 0 : datas.size();
}
@Override
public T getItem(int position) {
return datas.get(position);
}
@Override
public long getItemId(int position) {
return position;
}
@Override
public View getView(int position, View convertView, ViewGroup parent) {
if (convertView == null) {
convertView = LayoutInflater.from(context).inflate(layoutId, null);
}
T t = getItem(position);
convertView(convertView, t);
return convertView;
}
/**
* 需要去实现的对item中的view的设置操作
* @param item
* @param t
*/
protected abstract void convertView(View item, T t);
}
4.万能适配器CommonAdapter的超简洁用法
- 使用代码
public class MainActivity extends Activity {
private WebView webView;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
myAdapterTest();
}
/**
* 万能适配器的方法
*/
private void commonAdapterTest() {
setContentView(R.layout.activity_main);
ListView listView= (ListView) findViewById(R.id.listview);
List<String> datas=new ArrayList<>();
datas.add("万能适配器测试1");
datas.add("万能适配器测试2");
datas.add("万能适配器测试3");
datas.add("万能适配器测试4");
listView.setAdapter(new CommonAdapter<String>(context,datas,R.layout.item) {
@Override
protected void convertView(View item, String s) {
TextView textView= CommonViewHolder.get(item,R.id.textView);
textView.setText(s);
}
});
}
}
- 运行效果
这里写图片描述
