將投擲手勢添加到ImageView

Question

我正在嘗試將投擲手勢添加到imageview。 Im使用此代碼

public class MyActivity extends Activity { 
private void onCreate() { 
    final GestureDetector gdt = new GestureDetector(new GestureListener()); 
    final ImageView imageView = (ImageView) findViewById(R.id.image_view); 
    imageView.setOnTouchListener(new OnTouchListener() { 
     @Override 
     public boolean onTouch(final View view, final MotionEvent event) { 
      gdt.onTouchEvent(event); 
      return true; 
     } 
    }); 
}    

private static final int SWIPE_MIN_DISTANCE = 120; 
private static final int SWIPE_THRESHOLD_VELOCITY = 200; 

private class GestureListener extends SimpleOnGestureListener { 
    @Override 
    public boolean onFling(MotionEvent e1, MotionEvent e2, float velocityX, float velocityY) { 
     if(e1.getX() - e2.getX() > SWIPE_MIN_DISTANCE && Math.abs(velocityX) > SWIPE_THRESHOLD_VELOCITY) { 
      return false; // Right to left 
     } else if (e2.getX() - e1.getX() > SWIPE_MIN_DISTANCE && Math.abs(velocityX) > SWIPE_THRESHOLD_VELOCITY) { 
      return false; // Left to right 
     } 

     if(e1.getY() - e2.getY() > SWIPE_MIN_DISTANCE && Math.abs(velocityY) > SWIPE_THRESHOLD_VELOCITY) { 
      return false; // Bottom to top 
     } else if (e2.getY() - e1.getY() > SWIPE_MIN_DISTANCE && Math.abs(velocityY) > SWIPE_THRESHOLD_VELOCITY) { 
      return false; // Top to bottom 
     } 
     return false; 
    } 
} 
} 

但它只是不起作用。日誌說nullpointerexception，它是指這條線imageView.setOnTouchListener(new OnTouchListener() {

我的錯誤在哪裏？我錯過了什麼嗎？

Answer 1

您的ImageView得到ImageView的