case expressions must be constant expressions问题

private int DIALOG_ALERT_DISMISS = 0;
   
    private Handler mhandler = new Handler() {
        public void handleMessage(Message msg) {
            switch (msg.what) {
            case DIALOG_ALERT_DISMISS:

                alertDialog.dismiss();
               
                break;
            }

        }
    };

 

这样作有什么错呢，case那行报错了：case expressions must be constant expressions

 

好像是没把DIALOG_ALERT_DISMISS定义成final类型的，那么这是为什么呢？

 

希望高手帮我分析分析。