Android可移动的Button

关键

 package com.example.administrator.mystudent.ButtonMove;

 import android.app.Activity;
 import android.os.Bundle;
 import android.util.DisplayMetrics;
 import android.util.Log;
 import android.view.MotionEvent;
 import android.view.View;
 import android.widget.Button;
 import android.widget.Toast;

 import com.example.administrator.mystudent.R;

 public class ButtonMoveActivity extends Activity {

     private Button btn1;
     private int screenWidth;
     private int screenHeight;

     @Override
     protected void onCreate(Bundle savedInstanceState) {
         super.onCreate(savedInstanceState);
         setContentView(R.layout.activity_button_move);

         //DisplayMetrics取屏幕大小分辨率
         DisplayMetrics dm=getResources().getDisplayMetrics();
         screenWidth=dm.widthPixels;
         screenHeight=dm.heightPixels-50;

         btn1 = (Button) findViewById(R.id.btn1);
         btn1.setOnTouchListener(new MyOnTouchListener());

     }

     class MyOnTouchListener implements View.OnTouchListener {
         int lastX,lastY;

         @Override
         public boolean onTouch(View v, MotionEvent event) {
             int ea=event.getAction();
             Log.i("TAG", "Touch:"+ea);

             switch(ea){
                 case MotionEvent.ACTION_DOWN:

                     lastX=(int)event.getRawX();//获取触摸事件触摸位置的原始X坐标
                     lastY=(int)event.getRawY();
                     break;

                 case MotionEvent.ACTION_MOVE:
                     int dx=(int)event.getRawX()-lastX;
                     int dy=(int)event.getRawY()-lastY;

                     int l=v.getLeft()+dx;
                     int b=v.getBottom()+dy;
                     int r=v.getRight()+dx;
                     int t=v.getTop()+dy;

                     //下面判断移动是否超出屏幕
                     if(l<0){
                         l=0;
                         r=l+v.getWidth();
                     }

                     if(t<0){
                         t=0;
                         b=t+v.getHeight();
                     }

                     if(r>screenWidth){
                         r=screenWidth;
                         l=r-v.getWidth();
                     }

                     if(b>screenHeight){
                         b=screenHeight;
                         t=b-v.getHeight();
                     }
                     v.layout(l, t, r, b);

                     lastX=(int)event.getRawX();
                     lastY=(int)event.getRawY();
                     Toast.makeText(getApplicationContext(),
                             "当前位置："+l+","+t+","+r+","+b,
                             Toast.LENGTH_SHORT).show();

                     //利用invalidate()刷新界面(加post多线程)
                     v.postInvalidate();
                     break;
                 case MotionEvent.ACTION_UP:
                     break;
             }
             return false;
         }
     }

 }