android之OnTouchListener只能监听到ACTION_DOWN—–onTouchListener的返回值问题

释放双眼,带上耳机,听听看~!

做这样一个效果,界面上显示一个紫色方块,任意拖动方块到指定位置都可以,

运行后结果发现方块怎么都拖不动,打印log只有ACTION_DOWN有反应,MOVE和UP都监听不到,

很是奇怪,先把整段代码都贴下面了

package jason.com.security.ui;
import jason.com.security.R;
import android.app.Activity;
import android.content.SharedPreferences;
import android.content.SharedPreferences.Editor;
import android.os.Bundle;
import android.util.Log;
import android.view.MotionEvent;
import android.view.View;
import android.view.View.OnTouchListener;
import android.view.Window;
import android.widget.ImageView;
import android.widget.RelativeLayout;
import android.widget.RelativeLayout.LayoutParams;
public class DragViewActivity extends Activity implements OnTouchListener {
String TAG = "DragViewActivity";
void log(String s) {
Log.d(TAG, s);
}
private ImageView iv_drag_location;
private SharedPreferences sp;
int startX;
int startY;
@Override
protected void onCreate(Bundle savedInstanceState) {
// TODO Auto-generated method stub
super.onCreate(savedInstanceState);
requestWindowFeature(Window.FEATURE_NO_TITLE);
setContentView(R.layout.drag_view);
sp = getSharedPreferences("config", MODE_PRIVATE);
iv_drag_location = (ImageView) findViewById(R.id.iv_drag_location);
iv_drag_location.setOnTouchListener(this);
}
@Override
protected void onResume() {
// TODO Auto-generated method stub
super.onResume();
int x = sp.getInt("lastX", 0);
int y = sp.getInt("lastY", 0);
log("last X is " + x + ",lastY is " + y);
RelativeLayout.LayoutParams params = (LayoutParams) iv_drag_location
.getLayoutParams();
params.leftMargin = x;
params.topMargin = y;
iv_drag_location.setLayoutParams(params);
}
@Override
public boolean onTouch(View v, MotionEvent event) {
// TODO Auto-generated method stub
switch (v.getId()) {
case R.id.iv_drag_location:
switch (event.getAction()) {
case MotionEvent.ACTION_DOWN:
startX = (int) event.getRawX();
startY = (int) event.getRawY();
log("ACTION_DOWN :" + startX + "-" + startY);
break;
case MotionEvent.ACTION_MOVE:
int dx = (int) (event.getRawX() - startX);
int dy = (int) (event.getRawY() - startY);
log("ACTION_MOVE :" + dx + "-" + dy);
int l = iv_drag_location.getLeft();
int r = iv_drag_location.getRight();
int t = iv_drag_location.getTop();
int b = iv_drag_location.getBottom();
iv_drag_location.layout(l + dx, t + dy, r + dx, b + dy);
startX = (int) event.getRawX();
startY = (int) event.getRawY();
break;
case MotionEvent.ACTION_UP:
int lastX = iv_drag_location.getLeft();
int lastY = iv_drag_location.getTop();
log("ACTION_UP :" + lastX + "-" + lastY);
Editor editor = sp.edit();
editor.putInt("lastX", lastX);
editor.putInt("lastY", lastY);
editor.commit();
break;
default:
break;
}
break;
default:
break;
}
return false;
}
}

检查了N遍,逻辑上实在没问题,

最后发现,最后的返回值是return false;

由于这个是编译器自动生成的,我也没改动过,就改成了return true试试

果然,就是这个的问题,改成return true之后就正常了,

文档中对该方法的返回值描述如下:True if the listener has consumed the event, false otherwise。

大概意思就是说,如果返回true,则表示监听器处理了该事件(我的理解就是不用继续向上传递该事件了,该事件的传递到此为止);

否则返回false。

这样一想,我觉得之前返回false,可能造成之后检测到的事件向上传递了,而没有在该监听函数中处理。

所以导致了错误。

 

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