从创建AlertDialog发生crash的WindowManager$BadTokenException看Window和Surface

在service中，进行AlertDialog调用，如

void showDialog() {
        AlertDialog.Builder builder = new AlertDialog.Builder(this, R.style.Theme_MyApplication);
        builder.setTitle("Test");
        builder.setMessage("hello, ");
        builder.setNegativeButton("cancel1", new DialogInterface.OnClickListener() {
@Override
            public void onClick(DialogInterface dialogInterface, int i) {
                dialogInterface.dismiss();
            }
        });
        AlertDialog dialog = builder.create();
//加上这个setType和赋权悬浮窗口后，就没有问题了，这里注释掉，展现出问题
//        dialog.getWindow().setType(WindowManager.LayoutParams.TYPE_APPLICATION_OVERLAY);
        dialog.show();
    }

会导致crash，

     Caused by: android.view.WindowManager$BadTokenException: Unable to add window -- token null is not val