android – 为什么我的ProgressDialog在任何键(触摸)而不是后退按钮上进行侦听？

我有一个像这样实现的ProgressDialog：

// show progress dialog while date is loading
        progressDialog = ProgressDialog.show(XYActivity.this,getResources().getString(R.string.progress_dialog_please_wait),getResources().getString(R.string.progress_dialog_loading),true);
        progressDialog.setOnCancelListener(new DialogInterface.OnCancelListener() {
            @Override
            public void onCancel(DialogInterface dialog) {
                cancel(true);
                Log.w(LOGTAG,"loading cancelled via back button");
            }

        });
        progressDialog.setCancelable(true);

此ProgressDialog在AsyncTask(PreExecute)中实现,因此cancel(true)方法停止AsyncTask.一切正常.

问题是,我可以在屏幕上随机触摸取消ProgressDialog.我只想通过按下后退按钮来解除对话框.请帮我！感谢你们.

@Override
protected void onPreExecute() {
    progressDialog = ProgressDialog.show(context,"Title","Loading...",true,new OnCancelListener() {
        @Override
        public void onCancel(DialogInterface dialog) {
            cancel(true);
        }
    });
    progressDialog.setCanceledOnTouchOutside(false);
}