在Android中跟踪全局触摸事件

Question

我创建了一个用于在后台检测触摸事件的服务。我正在从主要活动中启动服务。问题是可以正确识别触摸，但是对于x和y位置，在使用其他应用程序（例如Google Maps）时，我总是得到0值。

如何对此进行更正，以便获得正确的x和y位置值？

GlobalTouchService.java的代码如下：

import android.app.Service;
import android.content.Intent;
import android.graphics.Color;
import android.graphics.PixelFormat;
import android.os.IBinder;
import android.util.Log;
import android.view.Gravity;
import android.view.MotionEvent;
import android.view.View;
import android.view.View.OnTouchListener;
import android.view.WindowManager;
import android.widget.LinearLayout;
import android.widget.LinearLayout.LayoutParams;

public class GlobalTouchService extends Service implements OnTouchListener{

    private String TAG = this.getClass().getSimpleName();
    private WindowManager mWindowManager;
    private LinearLayout touchLayout;

    @Override
    public IBinder onBind(Intent arg0) {
        return null;
    }

    @Override
    public void onCreate() {
        super.onCreate();
        touchLayout = new LinearLayout(this);
        LayoutParams lp = new LayoutParams(1, LayoutParams.MATCH_PARENT);
        touchLayout.setLayoutParams(lp);
        touchLayout.setOnTouchListener(this);

        mWindowManager = (WindowManager) getSystemService(WINDOW_SERVICE);
        WindowManager.LayoutParams mParams = new WindowManager.LayoutParams(
                1, /* width */
                1, /* height */
                WindowManager.LayoutParams.TYPE_PHONE,
                WindowManager.LayoutParams.FLAG_NOT_FOCUSABLE |
                        WindowManager.LayoutParams.FLAG_NOT_TOUCH_MODAL |
                        WindowManager.LayoutParams.FLAG_WATCH_OUTSIDE_TOUCH,
                PixelFormat.TRANSPARENT);
        mParams.gravity = Gravity.LEFT | Gravity.TOP;

        mWindowManager.addView(touchLayout, mParams);

    }


    @Override
    public void onDestroy() {
        if(mWindowManager != null) {
            if(touchLayout != null) mWindowManager.removeView(touchLayout);
        }
        super.onDestroy();
    }

    @Override
    public boolean onTouch(View v, MotionEvent event) {
        Log.i(TAG, "Action :" + event.getAction() + "\t X :" + event.getX() + "\t Y :"+ event.getY());

        return false;
    }
}

对于MainActivity.java

import android.app.Activity;
import android.content.Intent;
import android.os.Bundle;
import android.view.View;
import android.widget.Button;
import android.widget.Toast;

public class MainActivity extends Activity {
    Intent globalService;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        globalService = new Intent(this,GlobalTouchService.class);
    }


    public void buttonClicked(View v){
        if(v.getTag() == null){
            startService(globalService);
            v.setTag("on");
            ((Button)v).setText("Stop Service");
            Toast.makeText(this, "Start Service", Toast.LENGTH_SHORT).show();
        }
        else{
            stopService(globalService);
            v.setTag(null);
            ((Button)v).setText("Start Service");
            Toast.makeText(this, "Stop Service", Toast.LENGTH_SHORT).show();
        }

    }
}