一、前言：
我手机从来不装这些东西，不过，有次看到同事的android手机上，有个QQ管家在桌面上浮着，同事拖动管家时，管家就变成一只鸟，桌面下方还有个弹弓，桌面顶部有只乌鸦，把管家也就是鸟拖动到弹弓那，然后，松手，鸟就飞出去。这个过程是动画过程，做的事，实际上是清楚内存。

二：原理：
其实，没什么原理，用到的就是WindowManager以及WindowManager.LayoutParams，对这个LayoutParams做文章，当设置为属性后，然后，创建一个View，将这个View添加到WindowManager中就行。
代码如下：

package com.chris.floats.window;
import android.os.Bundle;
import android.util.DisplayMetrics;
import android.view.Gravity;
import android.view.WindowManager;
import android.app.Activity;
import android.content.Context;
public class MainActivity extends Activity {
private static WindowManager mWindowMgr = null;
private WindowManager.LayoutParams mWindowMgrParams = null;
private static FloatsWindowView mFloatsWindowView = null;

@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
}
/*
* 显示应用主界面时，去除悬浮层
*/
@Override
public void onWindowFocusChanged(boolean hasFocus) {
if(hasFocus){
if(mFloatsWindowView != null){
mWindowMgr.removeView(mFloatsWindowView);
mFloatsWindowView = null;
}
}else{
getWindowLayout();
}
}
private void initParams(){
DisplayMetrics dm = getResources().getDisplayMetrics();
mWindowMgrParams.x = dm.widthPixels - 136;
mWindowMgrParams.y = 300;
mWindowMgrParams.width = 136;
mWindowMgrParams.height = 136;
}
private void getWindowLayout(){
if(mFloatsWindowView == null){
mWindowMgr = (WindowManager)getBaseContext().getSystemService(Context.WINDOW_SERVICE);
mWindowMgrParams = new WindowManager.LayoutParams();

/*
* 2003 在指悬浮在所有界面之上
* (4.0+系统中，在下拉菜单下面，而在2.3中，在上拉菜单之上)
*/
mWindowMgrParams.type = 2003;
mWindowMgrParams.format = 1;

/*
* 代码实际是wmParams.flags |= FLAG_NOT_FOCUSABLE;
* 40的由来是wmParams的默认属性（32）+ FLAG_NOT_FOCUSABLE（8）
*/
mWindowMgrParams.flags = 40;
mWindowMgrParams.gravity = Gravity.LEFT | Gravity.TOP;
initParams();

mFloatsWindowView = new FloatsWindowView(this);
mWindowMgr.addView(mFloatsWindowView, mWindowMgrParams);
}
}
}

上面代码，主要在getWindowLayout函数中，最后两行就是创建一个View，并加入到WindowManager中。
继承View的悬浮View：
代码如下：

package com.chris.floats.window;
import android.content.Context;
import android.content.Intent;
import android.graphics.drawable.AnimationDrawable;
import android.util.AttributeSet;
import android.util.DisplayMetrics;
import android.view.Gravity;
import android.view.MotionEvent;
import android.view.View;
import android.view.ViewTreeObserver.OnPreDrawListener;
import android.view.WindowManager;
public class FloatsWindowView extends View {
private Context mContext = null;
private WindowManager mWindowMgr = null;
private WindowManager.LayoutParams mWindowMgrParams = null;
private AnimationDrawable mAnimationDrawable = null;

private int iPosX = 0;
private int iPosY = 0;
private int iLastPosX = 0;
private int iLastPosY = 0;
private boolean bMoved = false;

public FloatsWindowView(Context context) {
this(context, null, 0);
}
public FloatsWindowView(Context context, AttributeSet attrs) {
this(context, attrs, 0);
}
public FloatsWindowView(Context context, AttributeSet attrs, int defStyle) {
super(context, attrs, defStyle);

mContext = context;
mWindowMgr = (WindowManager)getContext().getApplicationContext().getSystemService("window");
mWindowMgrParams = new WindowManager.LayoutParams();
initParams();

mAnimationDrawable = new AnimationDrawable();
for(int i = 0; i < 4; i++){
int id = getResources().getIdentifier("a"+ i, "drawable", mContext.getPackageName());
mAnimationDrawable.addFrame(getResources().getDrawable(id), 100);
}
mAnimationDrawable.setOneShot(false);
this.setBackgroundDrawable(mAnimationDrawable);

OnPreDrawListener listener = new OnPreDrawListener(){
@Override
public boolean onPreDraw() {
mAnimationDrawable.start();
return true;
}
};
this.getViewTreeObserver().addOnPreDrawListener(listener);
}

private void initParams(){
DisplayMetrics dm = getResources().getDisplayMetrics();
mWindowMgrParams.x = dm.widthPixels - 136;
mWindowMgrParams.y = 300;
mWindowMgrParams.width = 136;
mWindowMgrParams.height = 136;
}

@Override
public boolean onTouchEvent(MotionEvent event) {

switch(event.getAction()){
case MotionEvent.ACTION_DOWN:
iPosX = (int)event.getX();
iPosY = (int)event.getY();
bMoved = false;
break;

case MotionEvent.ACTION_MOVE:
bMoved = true;
iLastPosX = (int)event.getX();
iLastPosY = (int)event.getY();
updatePostion(iLastPosX - iPosX, iLastPosY - iPosY);
break;

case MotionEvent.ACTION_UP:
if(!bMoved){
Intent it=new Intent(mContext, MainActivity.class);
mContext.startActivity(it);
}
break;

default:
break;
}
return true;
}
private void updatePostion(int x, int y){
mWindowMgrParams.type = 2003;
mWindowMgrParams.format = 1;
mWindowMgrParams.flags = 40;
mWindowMgrParams.gravity = Gravity.LEFT | Gravity.TOP;
mWindowMgrParams.x += x;
mWindowMgrParams.y += y;
mWindowMgr.updateViewLayout(this, mWindowMgrParams);
}
}

之所以将updatePosition中的参数与Activity中设置一样，是为了确保在MOVE时，造成相对位置的不一样，而导致闪砾，大家要是不理解，可以实验下。

三、小结：
这篇文章实现了简单的悬浮窗口动画效果，如果要想做成像360,QQ管家那样，还需要一些其它的操作：
1. 比如启动一个后台服务来监控系统信息；
2. ACTION_DOWN时，修改悬浮窗口上的图片；
3. ACTION_MOVE时窗口跟随；
4. ACTION_UP时，创建一个线程，来完成释放后，向上运动的动画过程等；