我正在尝试从this回答浪潮代码检查是否启用了权限.但即使从设置启用了权限,它也会返回false.

public static boolean canDrawOverlayViews(Context con){
    if(Build.VERSION.SDK_INT< Build.VERSION_CODES.LOLLIPOP){return true;}
    try {
        return Settings.canDrawOverlays(con);
    }
    catch(NoSuchMethodError e){
        return canDrawOverlaysUsingReflection(con);
    }
}


public static boolean canDrawOverlaysUsingReflection(Context context) {

    try {

        AppOpsManager manager = (AppOpsManager) context.getSystemService(Context.APP_OPS_SERVICE);
        Class clazz = AppOpsManager.class;
        Method dispatchMethod = clazz.getMethod("checkOp", new Class[] { int.class, int.class, String.class });
        //AppOpsManager.OP_SYSTEM_ALERT_WINDOW = 24
        int mode = (Integer) dispatchMethod.invoke(manager, new Object[] { 24, Binder.getCallingUid(), context.getApplicationContext().getPackageName() });

        return AppOpsManager.MODE_ALLOWED == mode;

    } catch (Exception e) {  return false;  }

}

解决方法:

最近我也遇到了同样的问题并得到了以下解决方法.
参考
https://code.google.com/p/android/issues/detail?id=198671#c7

public boolean getWindoOverLayAddedOrNot2() {

   String sClassName = "android.provider.Settings";
   try {
       Class classToInvestigate = Class.forName(sClassName);
       if (context == null)
           context = activity;
       Method method = classToInvestigate.getDeclaredMethod("isCallingPackageAllowedToDrawOverlays", Context.class, int.class, String.class, boolean.class);
       Object value = method.invoke(null, context, Process.myUid(), context.getPackageName(), false);

       Log.i("Tag", value.toString());
       // Dynamically do stuff with this class
       // List constructors, fields, methods, etc.

   } catch (ClassNotFoundException e) {
       // Class not found!
   } catch (Exception e) {
       // Unknown exception
       e.printStackTrace();
   }

   return false;
}