AlertDialog alertDialog = new AlertDialog.Builder(activity).create();
        alertDialog.getWindow().setBackgroundDrawable(new ColorDrawable());
        alertDialog.show();
        alertDialog.setContentView(R.layout.dialog_loading);
        alertDialog.setCanceledOnTouchOutside(false);

xml檔案中根節點的高最好是具體數值，比如250dp，然後背景顏色設為transparent即可。例如：

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    android:layout_width="match_parent"
    android:layout_height="250dp"
    android:background="@color/transparent">

    <com.wzkj.vzone.org.widget.progress.AVLoadingIndicatorView
 
        android:id="@+id/progressBar1"
        android:layout_width="50dp"
        android:layout_height="50dp"
        android:layout_centerInParent="true"
        app:indicator="BallSpinFadeLoader"
        app:indicator_color="@color/titlecolor" />
</RelativeLayout>