關於Adapter中的View.setTag和getTag

View中的setTag（Onbect）表示給View添加一個格外的數據，以後可以用getTag()將這個數據取出來。

可以用在多個Button添加一個監聽器，每個Button都設置不同的setTag。這個監聽器就通過getTag來分辨是哪個Button 被按下。

    
    
import android.app.Activity;     
import android.os.Bundle;     
import android.view.View;     
import android.widget.Button;     
    
public class Main extends Activity {     
        
    @Override    
    public void onCreate(Bundle savedInstanceState) {     
        super.onCreate(savedInstanceState);     
        setContentView(R.layout.main);     
        Button button1 = (Button) findViewById(R.id.Button01);     
        Button button2 = (Button) findViewById(R.id.Button02);     
        Button button3 = (Button) findViewById(R.id.Button03);     
        Button button4 = (Button) findViewById(R.id.Button04);     
        MyListener listener = new MyListener();     
        button1.setTag(1);     
        button1.setOnClickListener(listener);     
        button2.setTag(2);     
        button2.setOnClickListener(listener);     
        button3.setTag(3);     
        button3.setOnClickListener(listener);     
        button4.setTag(4);     
        button4.setOnClickListener(listener);     
    }     
    
    public class MyListener implements View.OnClickListener {     
    
        @Override    
        public void onClick(View v) {     
            int tag = (Integer) v.getTag();     
            switch (tag) {     
            case 1:     
                System.out.println("button1 click");     
                break;     
            case 2:     
                System.out.println("button2 click");     
                break;     
            case 3:     
                System.out.println("button3 click");     
                break;     
            case 4:     
                System.out.println("button4 click");     
                break;     
            }     
        }     
    
    }     
}

Adapter 有個getView方法，可以使用setTag把查找的view緩存起來方便多次重用

public View getView(int position, View convertView, ViewGroup parent) {
       ViewHolder vh;

       if (convertView == null) {
               LayoutInflater inflater = (LayoutInflater) mWidgetsSwitchApp
                               .getSystemService(Context.LAYOUT_INFLATER_SERVICE);
               convertView = inflater.inflate(R.layout.app_gallery_item, null);
               vh = new ViewHolder();
               vh.view1 = (ImageView) convertView.findViewById(R.id.view1);
               vh.view2 = (ImageView) convertView.findViewById(R.id.view2);
               vh.view3= (ImageView) convertView.findViewById(R.id.view3);