MainActivity.java
package com.example.floatviewdemo;
import com.example.floatviewdemo.service.FloatViewService;
import android.app.Activity;
import android.content.Intent;
import android.os.Bundle;
public class MainActivity extends Activity {
  @Override
  protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);
  }
  @Override
 protected void onStart() {
  Intent intent = new Intent(MainActivity.this, FloatViewService.class); 
     //启动FloatViewService 
     startService(intent); 
 super.onStart();
 }
 
 @Override
 protected void onStop() {
 // 销毁悬浮窗
 Intent intent = new Intent(MainActivity.this, FloatViewService.class); 
    //终止FloatViewService 
    stopService(intent); 
    super.onStop();
 }
}

<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
  xmlns:tools="http://schemas.android.com/tools"
  android:layout_width="match_parent"
  android:layout_height="match_parent"
  android:background="#fff"
  android:paddingBottom="@dimen/activity_vertical_margin"
  android:paddingLeft="@dimen/activity_horizontal_margin"
  android:paddingRight="@dimen/activity_horizontal_margin"
  android:paddingTop="@dimen/activity_vertical_margin"
  tools:context="com.example.floatviewdemo.MainActivity" >
  <TextView
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:text="@string/hello_world" />
</RelativeLayout>

package com.example.floatviewdemo.service;
import com.example.floatviewdemo.R;
import android.annotation.SuppressLint;
import android.app.Service;
import android.content.Intent;
import android.graphics.PixelFormat;
import android.os.IBinder;
import android.util.Log;
import android.view.Gravity;
import android.view.LayoutInflater;
import android.view.MotionEvent;
import android.view.View;
import android.view.View.OnClickListener;
import android.view.View.OnTouchListener;
import android.view.WindowManager;
import android.view.WindowManager.LayoutParams;
import android.widget.ImageButton;
import android.widget.LinearLayout;
import android.widget.Toast;
public class FloatViewService extends Service  
{ 
 private static final String TAG = "FloatViewService"; 
  //定义浮动窗口布局 
  private LinearLayout mFloatLayout; 
  private WindowManager.LayoutParams wmParams; 
  //创建浮动窗口设置布局参数的对象 
  private WindowManager mWindowManager; 
  private ImageButton mFloatView; 
  @Override 
  public void onCreate()  
  { 
    super.onCreate(); 
    Log.i(TAG, "onCreate"); 
    createFloatView();    
  } 
  @SuppressWarnings("static-access")
 @SuppressLint("InflateParams") private void createFloatView() 
  { 
    wmParams = new WindowManager.LayoutParams(); 
    //通过getApplication获取的是WindowManagerImpl.CompatModeWrapper 
    mWindowManager = (WindowManager)getApplication().getSystemService(getApplication().WINDOW_SERVICE); 
    //设置window type 
    wmParams.type = LayoutParams.TYPE_PHONE;  
    //设置图片格式，效果为背景透明 
    wmParams.format = PixelFormat.RGBA_8888;  
    //设置浮动窗口不可聚焦（实现操作除浮动窗口外的其他可见窗口的操作） 
    wmParams.flags = LayoutParams.FLAG_NOT_FOCUSABLE;    
    //调整悬浮窗显示的停靠位置为左侧置顶 
    wmParams.gravity = Gravity.LEFT | Gravity.TOP;     
    // 以屏幕左上角为原点，设置x、y初始值，相对于gravity 
    wmParams.x = 0; 
    wmParams.y = 152; 
    //设置悬浮窗口长宽数据  
    wmParams.width = WindowManager.LayoutParams.WRAP_CONTENT; 
    wmParams.height = WindowManager.LayoutParams.WRAP_CONTENT; 
    LayoutInflater inflater = LayoutInflater.from(getApplication()); 
    //获取浮动窗口视图所在布局 
    mFloatLayout = (LinearLayout) inflater.inflate(R.layout.alert_window_menu, null); 
    //添加mFloatLayout 
    mWindowManager.addView(mFloatLayout, wmParams); 
    //浮动窗口按钮 
    mFloatView = (ImageButton) mFloatLayout.findViewById(R.id.alert_window_imagebtn);
    mFloatLayout.measure(View.MeasureSpec.makeMeasureSpec(0, 
        View.MeasureSpec.UNSPECIFIED), View.MeasureSpec 
        .makeMeasureSpec(0, View.MeasureSpec.UNSPECIFIED)); 
    //设置监听浮动窗口的触摸移动 
    mFloatView.setOnTouchListener(new OnTouchListener()  
    { 
     boolean isClick;
  @SuppressLint("ClickableViewAccessibility") @Override
  public boolean onTouch(View v, MotionEvent event) {
  switch (event.getAction()) {
  case MotionEvent.ACTION_DOWN:
   mFloatView.setBackgroundResource(R.drawable.circle_red);
   isClick = false;
   break;
  case MotionEvent.ACTION_MOVE:
   isClick = true;
   // getRawX是触摸位置相对于屏幕的坐标，getX是相对于按钮的坐标
   wmParams.x = (int) event.getRawX()
    - mFloatView.getMeasuredWidth() / 2;
   // 减25为状态栏的高度
   wmParams.y = (int) event.getRawY()
    - mFloatView.getMeasuredHeight() / 2 - 75;
   // 刷新
   mWindowManager.updateViewLayout(mFloatLayout, wmParams);
   return true;
  case MotionEvent.ACTION_UP:
   mFloatView.setBackgroundResource(R.drawable.circle_cyan);
   return isClick;// 此处返回false则属于移动事件，返回true则释放事件，可以出发点击否。
  default:
   break;
  }
  return false;
  }
    });  
    mFloatView.setOnClickListener(new OnClickListener()  
    { 
      @Override 
      public void onClick(View v)  
      { 
        Toast.makeText(FloatViewService.this, "一百块都不给我！", Toast.LENGTH_SHORT).show(); 
      } 
    }); 
  } 
  @Override 
  public void onDestroy()  
  { 
    super.onDestroy(); 
    if(mFloatLayout != null) 
    { 
      //移除悬浮窗口 
      mWindowManager.removeView(mFloatLayout); 
    } 
  }
 @Override
 public IBinder onBind(Intent intent) {
 return null;
 } 
}

alert_window_menu.xml
<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
  android:layout_width="wrap_content"
  android:layout_height="wrap_content"
  android:orientation="vertical" >
  <ImageButton
    android:id="@+id/alert_window_imagebtn" 
    android:layout_width="50dp"
    android:layout_height="50dp"
    android:background="@drawable/float_window_menu"
    android:contentDescription="@null"
    />
</LinearLayout>