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。
作者：jason0539
微博：http://weibo.com/2553717707
博客：http://blog.csdn.net/jason0539（转载请说明出处）