更新提示框

 final AlertDialog.Builder builder = new AlertDialog.Builder(con);
        builder.setTitle("更新提醒");
        builder.setMessage(desc);
        // builder.setCancelable(false);
        builder.setOnCancelListener(new DialogInterface.OnCancelListener() {
            @Override
            public void onCancel(DialogInterface dialog) {

            }
        });
        builder.setNegativeButton("下次再说", new DialogInterface.OnClickListener() {
            @Override
            public void onClick(DialogInterface dialog, int which) {
            }
        });
        builder.setPositiveButton("立刻更新", new DialogInterface.OnClickListener() {
            @Override
            public void onClick(DialogInterface dialog, int which) {
                System.out.println("下载：" );
//                download(downloadurl);
            }

        });
        builder.show();