android面试题-Service中弹出Dialog

AlertDialog.Builder alertDialog = new AlertDialog.Builder(this);
            alertDialog.setMessage("有新消息，是否查看？");
            alertDialog.setPositiveButton("否",
                    new DialogInterface.OnClickListener()
                    {
                        public void onClick(DialogInterface dialog, int which)
                        {
                        }
                    });

            alertDialog.setNegativeButton("是",
                    new DialogInterface.OnClickListener()
                    {
                        public void onClick(DialogInterface dialog, int which)
                        {
                        }
                    });

            ad = alertDialog.create();

            ad.getWindow().setType(WindowManager.LayoutParams.TYPE_SYSTEM_ALERT);  
            ad.setCanceledOnTouchOutside(false);//点击外面区域不会让dialog消失                               
            ad.show();

添加权限

<uses-permission android:name="android.permission.SYSTEM_ALERT_WINDOW"/>

if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.M) {
    if (!Settings.canDrawOverlays(this)) {
        Intent intent = new Intent(Settings.ACTION_MANAGE_OVERLAY_PERMISSION,
                Uri.parse("package:" + getPackageName()));
        startActivityForResult(intent, 1);
    }
}

@Override
protected void onActivityResult(int requestCode, int resultCode, Intent data) {
    if (requestCode == 1) {
        if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.M) {
            if (!Settings.canDrawOverlays(this)) {
                // SYSTEM_ALERT_WINDOW permission not granted...
            }
        }
    }
}