Android: AlertDialog 改變其高度

AlertDialog alert = new AlertDialog.Builder(this).create();
alert.show();  
//
DisplayMetrics metrics = new DisplayMetrics();
getWindowManager().getDefaultDisplay().getMetrics(metrics);
int h90 = (int)(0.9f*((float)metrics.heightPixels)) ;   //高度設為90％
alert.getWindow().setLayout(ViewGroup.LayoutParams.WRAP_CONTENT, h90);
//