悬浮窗，在大多数应用中还是很少见的，目前我们接触到的悬浮窗，差不多都是一些系统级的应用软件，例如：360安全卫士，腾讯手机管家等；在某些服务行业如金融，餐饮等，也会在应用中添加悬浮窗，例如：美团的偷红包，博闻金融快捷联系等。但两种悬浮窗还是有区别的：

系统悬浮窗：所有界面都会展示，包括主屏、锁屏
应用悬浮窗：只在应用Activity中展示。

一、窗口Window

在了解悬浮窗之前，首先我们需要认识一下Android窗口Window。Android Framework将窗口分为三个类型：

应用窗口：所谓应用窗口指的就是该窗口对应一个Activity，因此，要创建应用窗口就必须在Activity中完成了。
子窗口：所谓子窗口指的是必须依附在某个父窗口之上，比如PopWindow，Dialog。
系统窗口：所谓系统窗口指的是由系统进程创建，不依赖于任何应用或者不依附在任何父窗口之上，如：Toast,来电窗口等。

Framework定义了三种窗口类型，这三种类型定义在WindowManager的内部类LayoutParams中，WindowManager将这三种类型进行了细化，把每一种类型都用一个int常量来表示，这些常量代表窗口所在的层，WindowManagerService在进行窗口叠加的时候，会按照常量的大小分配不同的层，常量值越大，代表位置越靠上面，所以我们可以猜想一下，应用程序Window的层值常量要小于子Window的层值常量，子Window的层值常量要小于系统Window的层值常量。Window的层级关系如下所示。

应用窗口：层级范围是1~99
子窗口：层级范围是1000~1999
系统窗口：层级范围是2000~2999

1.各级别type值在WindowManager中的定义分别为：

i.应用窗口（1~99）

   //第一个应用窗口
   public static final int FIRST_APPLICATION_WINDOW = 1; //所有程序窗口的base窗口，其他应用程序窗口都显示在它上面 public static final int TYPE_BASE_APPLICATION = 1; //所有Activity的窗口，只能配合Activity在当前APP使用 public static final int TYPE_APPLICATION = 2; //目标应用窗口未启动之前的那个窗口 public static final int TYPE_APPLICATION_STARTING = 3; //最后一个应用窗口 public static final int LAST_APPLICATION_WINDOW = 99;

ii.子窗口（1000~1999）

  //第一个子窗口
  public static final int FIRST_SUB_WINDOW = 1000; // 面板窗口，显示于宿主窗口的上层,只能配合Activity在当前APP使用 public static final int TYPE_APPLICATION_PANEL = FIRST_SUB_WINDOW; // 媒体窗口（例如视频），显示于宿主窗口下层 public static final int TYPE_APPLICATION_MEDIA = FIRST_SUB_WINDOW+1; // 应用程序窗口的子面板，只能配合Activity在当前APP使用(PopupWindow默认就是这个Type) public static final int TYPE_APPLICATION_SUB_PANEL = FIRST_SUB_WINDOW+2; //对话框窗口,只能配合Activity在当前APP使用 public static final int TYPE_APPLICATION_ATTACHED_DIALOG = FIRST_SUB_WINDOW+3; // public static final int TYPE_APPLICATION_MEDIA_OVERLAY = FIRST_SUB_WINDOW+4; //最后一个子窗口 public static final int LAST_SUB_WINDOW = 1999;

iii.系统窗口（2000~2999）

        //系统窗口，非应用程序创建
        public static final int FIRST_SYSTEM_WINDOW = 2000; //状态栏，只能有一个状态栏，位于屏幕顶端，其他窗口都位于它下方 public static final int TYPE_STATUS_BAR = FIRST_SYSTEM_WINDOW; //搜索栏，只能有一个搜索栏，位于屏幕上方 public static final int TYPE_SEARCH_BAR = FIRST_SYSTEM_WINDOW+1; // //电话窗口，它用于电话交互（特别是呼入），置于所有应用程序之上，状态栏之下,属于悬浮窗(并且给一个Activity的话按下HOME键会出现看不到桌面上的图标异常情况) public static final int TYPE_PHONE = FIRST_SYSTEM_WINDOW+2; // //系统警告提示窗口，出现在应用程序窗口之上,属于悬浮窗, 但是会被禁止 public static final int TYPE_SYSTEM_ALERT = FIRST_SYSTEM_WINDOW+3; // //信息窗口，用于显示Toast, 不属于悬浮窗, 但有悬浮窗的功能, 缺点是在Android2.3上无法接收点击事件 public static final int TYPE_TOAST = FIRST_SYSTEM_WINDOW+5; // public static final int TYPE_KEYGUARD = FIRST_SYSTEM_WINDOW+4; //锁屏窗口 public static final int TYPE_KEYGUARD = FIRST_SYSTEM_WINDOW+4; //系统顶层窗口，显示在其他一切内容之上，此窗口不能获得输入焦点，否则影响锁屏 public static final int TYPE_SYSTEM_OVERLAY = FIRST_SYSTEM_WINDOW+6; //电话优先，当锁屏时显示，此窗口不能获得输入焦点，否则影响锁屏 public static final int TYPE_PRIORITY_PHONE = FIRST_SYSTEM_WINDOW+7; //系统对话框窗口 public static final int TYPE_SYSTEM_DIALOG = FIRST_SYSTEM_WINDOW+8; //锁屏时显示的对话框 public static final int TYPE_KEYGUARD_DIALOG = FIRST_SYSTEM_WINDOW+9; //系统内部错误提示，显示在任何窗口之上 public static final int TYPE_SYSTEM_ERROR = FIRST_SYSTEM_WINDOW+10; //内部输入法窗口，显示于普通UI之上，应用程序可重新布局以免被此窗口覆盖 public static final int TYPE_INPUT_METHOD = FIRST_SYSTEM_WINDOW+11; //内部输入法对话框，显示于当前输入法窗口之上 public static final int TYPE_INPUT_METHOD_DIALOG= FIRST_SYSTEM_WINDOW+12; //墙纸窗口 public static final int TYPE_WALLPAPER = FIRST_SYSTEM_WINDOW+13; //状态栏的滑动面板 public static final int TYPE_STATUS_BAR_PANEL = FIRST_SYSTEM_WINDOW+14; //安全系统覆盖窗口，这些窗户必须不带输入焦点，否则会干扰键盘 public static final int TYPE_SECURE_SYSTEM_OVERLAY = FIRST_SYSTEM_WINDOW+15; //最后一个系统窗口 public static final int LAST_SYSTEM_WINDOW = 2999;

2.窗口flags显示属性在WindowManager中也有定义：

        //窗口特征标记
        public int flags;
        //当该window对用户可见的时候，允许锁屏
        public static final int FLAG_ALLOW_LOCK_WHILE_SCREEN_ON = 0x00000001; //窗口后面的所有内容都变暗 public static final int FLAG_DIM_BEHIND = 0x00000002; //Flag：窗口后面的所有内容都变模糊 public static final int FLAG_BLUR_BEHIND = 0x00000004; //窗口不能获得焦点 public static final int FLAG_NOT_FOCUSABLE = 0x00000008; //窗口不接受触摸屏事件 public static final int FLAG_NOT_TOUCHABLE = 0x00000010; //即使在该window在可获得焦点情况下，允许该窗口之外的点击事件传递到当前窗口后面的的窗口去 public static final int FLAG_NOT_TOUCH_MODAL = 0x00000020; //当手机处于睡眠状态时，如果屏幕被按下，那么该window将第一个收到触摸事件 public static final int FLAG_TOUCHABLE_WHEN_WAKING = 0x00000040; //当该window对用户可见时，屏幕出于常亮状态 public static final int FLAG_KEEP_SCREEN_ON = 0x00000080; //：让window占满整个手机屏幕，不留任何边界 public static final int FLAG_LAYOUT_IN_SCREEN = 0x00000100; //允许窗口超出整个手机屏幕 public static final int FLAG_LAYOUT_NO_LIMITS = 0x00000200; //window全屏显示 public static final int FLAG_FULLSCREEN = 0x00000400; //恢复window非全屏显示 public static final int FLAG_FORCE_NOT_FULLSCREEN = 0x00000800; //开启窗口抖动 public static final int FLAG_DITHER = 0x00001000; //安全内容窗口，该窗口显示时不允许截屏 public static final int FLAG_SECURE = 0x00002000; //锁屏时显示该窗口 public static final int FLAG_SHOW_WHEN_LOCKED = 0x00080000; //系统的墙纸显示在该窗口之后 public static final int FLAG_SHOW_WALLPAPER = 0x00100000; //当window被显示的时候，系统将把它当做一个用户活动事件，以点亮手机屏幕 public static final int FLAG_TURN_SCREEN_ON = 0x00200000; //该窗口显示，消失键盘 public static final int FLAG_DISMISS_KEYGUARD = 0x00400000; //当该window在可以接受触摸屏情况下，让因在该window之外，而发送到后面的window的触摸屏可以支持split touch public static final int FLAG_SPLIT_TOUCH = 0x00800000; //对该window进行硬件加速，该flag必须在Activity或Dialog的Content View之前进行设置 public static final int FLAG_HARDWARE_ACCELERATED = 0x01000000; //让window占满整个手机屏幕，不留任何边界 public static final int FLAG_LAYOUT_IN_OVERSCAN = 0x02000000; //透明状态栏 public static final int FLAG_TRANSLUCENT_STATUS = 0x04000000; //透明导航栏

3.添加View到Window的流程代码：


      contactView = new ContactView(mContext);
        if (layoutParams == null) www.yongshiyule178.com {
            layoutParams = new WindowManager.LayoutParams();
            layoutParams.width = contactView.width;
            layoutParams.height = contactView.height;
            layoutParams.x += ScreenSizeUtil.getScreenWidth(www.078881.cn );
            layoutParams.y += ScreenSizeUtil.getScreenHeight(www.345608.cn/) - ScreenSizeUtil.dp2px(150); layoutParams.gravity = www.taohuayuan178.com  Gravity.TOP | Gravity.LEFT; if (Build.VERSION.SDK_INT > 18 && Build.VERSION.SDK_INT < www.feifanyule.cn 23) { layoutParams.type = WindowManager.LayoutParams.TYPE_TOAST;//Type设置 } else { layoutParams.type = WindowManager.LayoutParams.TYPE_APPLICATION; } layoutParams.flags = WindowManager.LayoutParams.FLAG_NOT_FOCUSABLE | WindowManager.LayoutParams.FLAG_NOT_TOUCH_MODAL;//Flags设置,窗口属性 layoutParams.format = PixelFormat.RGBA_8888;

悬浮窗添加原理：View添加到Window源码解析

Window在Android系统中十分重要，其Activity，Dialog的创建都离不开Window.具体Activity，Dialog是怎么添加到Window上的，详情如：
Activity的加载流程;
Dialog加载绘制流程

二、两种悬浮窗

在前言中已说到，悬浮窗在app中，分为两种：系统级别和应用级别。其中系统级别可以在任何界面展示，包括主屏、锁屏（看需要），应用级别只在应用中展示。通过上面对Window的认识，我们可以知道实现方式：

系统级别可以通过type设置为：TYPE_TOAST、TYPE_PHONE、TYPE_SYSTEM_ALERT；
应用级别可以通过type设置为：TYPE_APPLICATION、TYPE_APPLICATION_ATTACHED_DIALOG；

悬浮窗添加流程：

WindowManager.addView -> ViewRootImpl.setView -> WindowSession.addToDisplay(AIDL进行IPC) -> WindowManagerService.addWindow() -> ViewRootImpl.setView

1.系统悬浮窗

对于系统级别的悬浮窗来说，不同的设置，不同的Android版本，需要权限和交互都不同。通过阅读源码android4.4知：

android 7.1.1的addWindow方法为：


   public int addWindow(Session session, IWindow client, int seq,
            WindowManager.LayoutParams attrs, int viewVisibility, int displayId, Rect outContentInsets, InputChannel outInputChannel) { int[] appOp = new int[1]; int res = mPolicy.checkAddPermission(attrs, appOp); if (res != WindowManagerGlobal.ADD_OKAY) { return res; } ...... final int type = attrs.type; ...... } else if (type == TYPE_TOAST) {//android 7.1.1 添加代码（其他版本无） // Apps targeting SDK above N MR1 cannot arbitrary add toast windows. addToastWindowRequiresToken = doesAddToastWindowRequireToken(attrs.packageName, callingUid, attachedWindow); if (addToastWindowRequiresToken && token.windowType != TYPE_TOAST) { Slog.w(TAG_WM, "Attempted to add a toast window with bad token " + attrs.token + ". Aborting."); return WindowManagerGlobal.ADD_BAD_APP_TOKEN; } }.... synchronized(mWindowMap) { ...... mPolicy.adjustWindowParamsLw(win.mAttrs);

权限检查checkAddPermission(www.tiaotiaoylzc.com)方法：


    //权限检查
    @Override
    public int checkAddPermission(WindowManager.www.chaoyueyule.com LayoutParams attrs, int[] outAppOp) { int type = attrs.type; outAppOp[0] = AppOpsManager.OP_NONE; if (type < WindowManager.LayoutParams.FIRST_SYSTEM_WINDOW || type > WindowManager.LayoutParams.LAST_SYSTEM_WINDOW) { return WindowManagerGlobal.ADD_OKAY; } String permission = null; switch (type) { case TYPE_TOAST: // XXX right now the app process has complete control over // this... should introduce www.00534.cn   a token to let the system // monitor/control what they are doing. break; case TYPE_DREAM: case TYPE_INPUT_METHOD: case TYPE_WALLPAPER: case TYPE_PRIVATE_PRESENTATION: // The window manager www.dongfan178.com will check these. break; case TYPE_PHONE: case TYPE_PRIORITY_PHONE: case TYPE_SYSTEM_ALERT: case TYPE_SYSTEM_ERROR: case TYPE_SYSTEM_OVERLAY: permission = android.Manifest.permission.SYSTEM_ALERT_WINDOW; outAppOp[0] = AppOpsManager.OP_SYSTEM_ALERT_WINDOW; break; default: permission = android.Manifest.permission.INTERNAL_SYSTEM_WINDOW; } if (permission != null) { if (mContext.checkCallingOrSelfPermission(permission) != PackageManager.PERMISSION_GRANTED) { return WindowManagerGlobal.ADD_PERMISSION_DENIED; } } return WindowManagerGlobal.ADD_OKAY;

window的flags属性添加adjustWindowParamsLw()方法

//window的flags属性添加
//Android 2.0 - 2.3.7 PhoneWindowManager
    public void adjustWindowParamsLw(WindowManager.LayoutParams attrs) { switch (attrs.type) { case TYPE_SYSTEM_OVERLAY: case TYPE_SECURE_SYSTEM_OVERLAY: case TYPE_TOAST: // These types of windows can't receive input events. attrs.flags |= WindowManager.LayoutParams.FLAG_NOT_FOCUSABLE | WindowManager.LayoutParams.FLAG_NOT_TOUCHABLE; break; } } //Android 4.0.1 - 4.3.1 PhoneWindowManager public void adjustWindowParamsLw(WindowManager.LayoutParams attrs) { switch (attrs.type) { case TYPE_SYSTEM_OVERLAY: case TYPE_SECURE_SYSTEM_OVERLAY: case TYPE_TOAST: // These types of windows can't receive input events. attrs.flags |= WindowManager.LayoutParams.FLAG_NOT_FOCUSABLE | WindowManager.LayoutParams.FLAG_NOT_TOUCHABLE; attrs.flags &= ~WindowManager.LayoutParams.FLAG_WATCH_OUTSIDE_TOUCH; break; } } //Android 4.4 PhoneWindowManager @Override public void adjustWindowParamsLw(WindowManager.LayoutParams attrs) { switch (attrs.type) { case TYPE_SYSTEM_OVERLAY: case TYPE_SECURE_SYSTEM_OVERLAY: // These types of windows can't receive input events. attrs.flags |= WindowManager.LayoutParams.FLAG_NOT_FOCUSABLE | WindowManager.LayoutParams.FLAG_NOT_TOUCHABLE; attrs.flags &= ~WindowManager.LayoutParams.FLAG_WATCH_OUTSIDE_TOUCH;

由上可知：

Type为TYPE_TOAST：版本低于android4.4的，不能接受触摸事件，无法操作；版本高于Android 7.1.1的无法添加悬浮窗
Type为TYPE_PHONE：所有android版本都需要权限，版本低于android6.0的manifest中添加权限android.Manifest.permission.SYSTEM_ALERT_WINDOW即可，高于andorid6.0的需要判断权限且手动添加。
Type为TYPE_SYSTEM_ALERT：同TYPE_PHONE

所以系统级别的悬浮窗，android不同版本需要特别处理。

2.应用悬浮窗

对于应用悬浮窗来说，android版本对其影响不大。

Type为TYPE_APPLICATION：只要Activity建立了，就可以添加。
Type为TYPE_APPLICATION_ATTACHED_DIALOG：需要在Activity获取焦点，并且用户可操作时才可添加。

三、悬浮窗的实现

悬浮窗添加比较简单,主要是由WindowManager接口的实现类WindowManagerImpl进行操作，WindowManager接口又继承至ViewManager,其中主要方法为：

    public void addView(View view, ViewGroup.LayoutParams params);//添加View到Window
    public void updateViewLayout(View view, ViewGroup.LayoutParams params);//更新View在Window中的位置 public void removeView(View view);//删除View

主要实现代码：


public class ContactWindowUtil {
    private ContactView contactView; private View dialogView; private WindowManager windowManager; private WindowManager.LayoutParams layoutParams; private WindowManager.LayoutParams dialogParams; private Context mContext; private ContactWindowListener mListener; private ValueAnimator valueAnimator; private int direction; private final int LEFT = 0; private final int RIGHT = 1; public interface ContactWindowListener { void onDataCallBack(String str); } public void setDialogListener(ContactWindowListener listener) { mListener = listener; } //私有化构造函数 public ContactWindowUtil(Context context) { mContext = context; windowManager = (WindowManager) mContext.getSystemService(Context.WINDOW_SERVICE); // windowManager = (WindowManager) FloatWindowApp.getAppContext().getSystemService(Context.WINDOW_SERVICE); } public void showContactView() { hideContactView(); contactView = new ContactView(mContext); if (layoutParams == null) { layoutParams = new WindowManager.LayoutParams(); layoutParams.width = contactView.width; layoutParams.height = contactView.height; layoutParams.x += ScreenSizeUtil.getScreenWidth(); layoutParams.y += ScreenSizeUtil.getScreenHeight() - ScreenSizeUtil.dp2px(150); layoutParams.gravity = Gravity.TOP | Gravity.LEFT; if (Build.VERSION.SDK_INT > 18 && Build.VERSION.SDK_INT < 23) { layoutParams.type = WindowManager.LayoutParams.TYPE_TOAST; } else { layoutParams.type = WindowManager.LayoutParams.TYPE_APPLICATION; } layoutParams.flags = WindowManager.LayoutParams.FLAG_NOT_FOCUSABLE | WindowManager.LayoutParams.FLAG_NOT_TOUCH_MODAL; layoutParams.format = PixelFormat.RGBA_8888; } contactView.setOnTouchListener(touchListener); contactView.setOnClickListener(new View.OnClickListener() { @Override public void onClick(View view) { showContactDialog(); } }); windowManager.addView(contactView, layoutParams); } /** * 显示联系弹框 */ private void showContactDialog() { hideDialogView(); if (dialogParams == null) { dialogParams = new WindowManager.LayoutParams(); dialogParams.width = WindowManager.LayoutParams.MATCH_PARENT; dialogParams.height = WindowManager.LayoutParams.MATCH_PARENT; dialogParams.gravity = Gravity.CENTER; if (Build.VERSION.SDK_INT > 18 && Build.VERSION.SDK_INT < 25){ dialogParams.type = WindowManager.LayoutParams.TYPE_TOAST; } else { dialogParams.type = WindowManager.LayoutParams.TYPE_APPLICATION_ATTACHED_DIALOG; } dialogParams.flags = WindowManager.LayoutParams.FLAG_LAYOUT_IN_SCREEN | WindowManager.LayoutParams.FLAG_FULLSCREEN; dialogParams.format = PixelFormat.RGBA_8888; } LayoutInflater layoutInflater = (LayoutInflater) mContext.getSystemService(Context.LAYOUT_INFLATER_SERVICE); dialogView = layoutInflater.inflate(R.layout.window_contact, null); TextView okTv = dialogView.findViewById(R.id.mOkTv); TextView cancleTv = dialogView.findViewById(R.id.mCancleTv); final TextView contentTv = dialogView.findViewById(R.id.mContentTv); contentTv.setText(String.format("您确认拨打%s客服电话吗", "4008-111-222")); cancleTv.setOnClickListener(new View.OnClickListener() { @Override public void onClick(View view) { hideDialogView(); } }); okTv.setOnClickListener(new View.OnClickListener() { @Override public void onClick(View view) { hideDialogView(); mListener.onDataCallBack(""); } }); dialogView.setOnClickListener(new View.OnClickListener() { @Override public void onClick(View view) { hideDialogView(); } }); windowManager.addView(dialogView, dialogParams); } public void hideAllView() { hideContactView(); hideDialogView(); } public void hideContactView() { if (contactView != null) { windowManager.removeView(contactView); contactView = null; stopAnim(); } } public void hideDialogView() { if (dialogView != null) { windowManager.removeView(dialogView); dialogView = null; } } View.OnTouchListener touchListener = new View.OnTouchListener() { float startX; float startY; float moveX; float moveY; @Override public boolean onTouch(View v, MotionEvent event) { switch (event.getAction()) { case MotionEvent.ACTION_DOWN: startX = event.getRawX(); startY = event.getRawY(); moveX = event.getRawX(); moveY = event.getRawY(); break; case MotionEvent.ACTION_MOVE: float x = event.getRawX() - moveX; float y = event.getRawY() - moveY; //计算偏移量，刷新视图 layoutParams.x += x; layoutParams.y += y; windowManager.updateViewLayout(contactView, layoutParams); moveX = event.getRawX(); moveY = event.getRawY(); break; case MotionEvent.ACTION_UP: //判断松手时View的横坐标是靠近屏幕哪一侧，将View移动到依靠屏幕 float endX = event.getRawX(); float endY = event.getRawY(); if (endX < ScreenSizeUtil.getScreenWidth() / 2) { direction = LEFT; endX = 0; } else { direction = RIGHT; endX = ScreenSizeUtil.getScreenWidth() - contactView.width; } if(moveX != startX){ starAnim((int) moveX, (int) endX,direction); } //如果初始落点与松手落点的坐标差值超过5个像素，则拦截该点击事件 //否则继续传递，将事件交给OnClickListener函数处理 if (Math.abs(startX - moveX) > 5) { return true; } break; } return false; } }; private void starAnim(int startX, int endX,final int direction) { if (valueAnimator != null) { valueAnimator.cancel(); valueAnimator = null; } valueAnimator = ValueAnimator.ofInt(startX, endX); valueAnimator.setDuration(500); valueAnimator.setRepeatCount(0); valueAnimator.addUpdateListener(new ValueAnimator.AnimatorUpdateListener() { @Override public void onAnimationUpdate(ValueAnimator animation) { if(direction == LEFT){ layoutParams.x = (int) animation.getAnimatedValue()-contactView.width/2; }else{ layoutParams.x = (int) animation.getAnimatedValue(); } if (contactView != null) { windowManager.updateViewLayout(contactView, layoutParams); } } }); valueAnimator.setInterpolator(new LinearInterpolator()); valueAnimator.start(); } private void stopAnim() { if (valueAnimator != null) { valueAnimator.cancel(); valueAnimator = null;

悬浮窗源码:https://github.com/awenzeng/FloatWindowDemo

四、注意

1.应用悬浮窗WindowManager的获取环境必须是Activity环境，系统悬浮窗可以Activity环境，也可以是全局的环境。如：

        windowManager = (WindowManager) mContext.getSystemService(Context.WINDOW_SERVICE);
//      windowManager = (WindowManager) FloatWindowApp.getAppContext().getSystemService(Context.WINDOW_SERVICE);

2.应用级别悬浮窗也可以通过系统级别的方式实现，主要控制一下显示与隐藏就好。但如果只在应用中展示悬浮窗，建议使用应用级别，那样会省去许多不必要的麻烦。

3.系统级别Type为TYPE_PHONE、TYPE_SYSTEM_ALERT是权限判断及设置代码：

 /** 
     * 请求用户给予悬浮窗的权限 
     */  
    public void askForPermission() {  
        if (!Settings.canDrawOverlays(this)) { Toast.makeText(TestFloatWinActivity.this, "当前无权限，请授权！", Toast.LENGTH_SHORT).show(); Intent intent = new Intent(Settings.ACTION_MANAGE_OVERLAY_PERMISSION, Uri.parse("package:" + getPackageName())); startActivityForResult(intent, OVERLAY_PERMISSION_REQ_CODE); } else { startService(floatWinIntent); } }

Android悬浮窗原理解析(Window)[源码]

一、窗口Window

二、两种悬浮窗

三、悬浮窗的实现

四、注意

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