一、无障碍服务开启

AccessibilityService是一个抽象类，应用需要创建Service来继承AccessibilityService并实现抽象方法。

1、创建HongBaoService.java

2、AndroidManifest.xml中声明并配置

<service
    android:name="com.yhao.floatwindow.HongBaoService"
    android:enabled="true"
    android:exported="true"
    android:permission="android.permission.BIND_ACCESSIBILITY_SERVICE">
    <intent-filter>
        <action android:name="android.accessibilityservice.AccessibilityService"/>
    </intent-filter>
    <meta-data
        android:name="android.accessibilityservice"
        android:resource="@xml/qianghongbao"/>
</service>

3、无障碍服务配置文件

android:resource="@xml/qianghongbao"是无障碍服务的配置文件，大概内容如下

<?xml version="1.0" encoding="utf-8"?>
<accessibility-service
    xmlns:android="http://schemas.android.com/apk/res/android"
    android:accessibilityEventTypes="typeAllMask"
    android:accessibilityFeedbackType="feedbackGeneric"
    android:accessibilityFlags="flagReportViewIds|flagRetrieveInteractiveWindows"
    android:canPerformGestures="true"
    android:canRetrieveWindowContent="true"
    android:description="@string/app_name"
    android:notificationTimeout="100"
    />

qianghongbao.xml可以放置在res/xml目录下

4、启动无障碍服务

public static void startService(Context mContext){
    LogUtil.e("startService shan,======"+HongBaoService.isStart());
    if (!HongBaoService.isStart()) {
        Intent intent=new Intent(Settings.ACTION_ACCESSIBILITY_SETTINGS);
        Intent intent2=new Intent(Settings.ACTION_SETTINGS);
        intent.setFlags(Intent.FLAG_ACTIVITY_NEW_TASK);
        intent2.setFlags(Intent.FLAG_ACTIVITY_NEW_TASK);
        try {
            mContext.startActivity(intent);
        } catch (Exception e) {
            mContext.startActivity(intent2);
            LogUtil.e("Exception e"+e.getMessage());
            e.printStackTrace();
        }
        return;
    }
}

二、悬浮框

可以通过WindowManager动态添加居于其他应用上面的悬浮框，TYPE_ACCESSIBILITY_OVERLAY类型悬浮窗可以在锁屏、安装应用状态保持显示，TYPE_APPLICATION_OVERLAY类型悬浮窗在锁屏、安装应用状态会隐藏。

FloatPhone(Context applicationContext, PermissionListener permissionListener) {
    mContext = applicationContext;
    mPermissionListener = permissionListener;
    mWindowManager = (WindowManager) applicationContext.getSystemService(Context.WINDOW_SERVICE);
    mLayoutParams = new WindowManager.LayoutParams();
    mLayoutParams.format = PixelFormat.RGBA_8888;
    mLayoutParams.flags = WindowManager.LayoutParams.FLAG_NOT_TOUCH_MODAL
            | WindowManager.LayoutParams.FLAG_NOT_FOCUSABLE
            | WindowManager.LayoutParams.FLAG_LAYOUT_NO_LIMITS;
    mLayoutParams.windowAnimations = 0;
}
if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.O) {
    mLayoutParams.type = WindowManager.LayoutParams.TYPE_ACCESSIBILITY_OVERLAY;
   // mLayoutParams.type = WindowManager.LayoutParams.TYPE_APPLICATION_OVERLAY;
} else {
    mLayoutParams.type = WindowManager.LayoutParams.TYPE_PHONE;
}

TYPE_ACCESSIBILITY_OVERLAY类型悬浮框创建时要使用无障碍服务的context，否则程序会挂掉，报错信息Unable to add window -- token null is not valid; is Activity Running