在dialog的构造方法中加入如下代码

 Window window = this.getWindow();
        WindowManager.LayoutParams wl = window.getAttributes();
        wl.x = 0;
        wl.y = ((Activity) context).getWindowManager().getDefaultDisplay().getHeight();
        // 以下这两句是为了保证按钮可以水平满屏
        wl.width = ViewGroup.LayoutParams.MATCH_PARENT;
        wl.height = ViewGroup.LayoutParams.MATCH_PARENT;
   
        this.onWindowAttributesChanged(wl);
        // 设置点击外围解散
        this.setCanceledOnTouchOutside(true);