Android:永远不会调用 onTouch()？

Question

我正在玩 UI 事件处理，我发现了一些我无法从 Android Dev 中找到解释的东西:我有一个 ImageView 和一个 TextView，每当我触摸 ImageView 时，TextView 都会显示一条消息。但以下代码不起作用:

    public class ShowSomething extends Activity {
 private LinearLayout ll;

 public void onCreate(Bundle savedInstanceState) {
  super.onCreate(savedInstanceState);

  setContentView(R.layout.main);  

  LinearLayout ll = (LinearLayout)findViewById(R.id.linearLayout);
  final TextView textview = (TextView)findViewById(R.id.textview);
  MyImageView image = new MyImageView(this, textview);
  image.setImageResource(R.drawable.icon);
  ll.addView(image, 48, 48);

 }
}

和MyImageView.java

public class MyImageView extends ImageView implements OnTouchListener{


 private TextView textview;

 public MyImageView(Context context,TextView textview) {
  super(context);
  this.textview = textview;
 }

 @Override
 public boolean onTouch(View v, MotionEvent event) {
  textview.setText("Event captured !");
  return true;
 }
}

主.xml

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:id="@+id/linearLayout"
android:layout_width="fill_parent"
android:layout_height="fill_parent"
android:orientation="vertical"
>
<TextView
android:id="@+id/textview"
android:layout_width="fill_parent"
android:layout_height="wrap_content"
android:text="Holder"
/>
</LinearLayout>

但是当我像这样在 MyImageView 上附加一个 OnTouchListener 时，它确实有效:文件 ShowSomething.java

public class ShowSomething extends Activity {

 private LinearLayout ll;

 public void onCreate(Bundle savedInstanceState) {
  super.onCreate(savedInstanceState);

  setContentView(R.layout.main);  

  LinearLayout ll = (LinearLayout)findViewById(R.id.linearLayout);
  final TextView textview = (TextView)findViewById(R.id.textview);


  MyImageView image = new MyImageView(this,textview);
  image.setImageResource(R.drawable.icon);
  image.setOnTouchListener(new OnTouchListener() {  
     @Override
     public boolean onTouch(View v, MotionEvent event) {
      textview.setText("Event captured!");      
      return false;
     }
    });
  ll.addView(image, 48, 48);

 } 

}

和文件 MyImageView.java

public class MyImageView extends ImageView { 


 private TextView textview;

 public MyImageView(Context context,TextView textview) {
  super(context);
  this.textview = textview;
 }


}

但据我所知，2 的实现是相同的(实现一个事件监听器)——我有没有误解什么？

Answer 1

您的第一个实现忘记设置监听器...在 MyImageView 构造函数中调用 setOnTouchListener(this) 它应该可以工作。