Android onPostExecute中的AlertDialog未显示

我试图在AsyncTask的onPostExecute方法上显示一个对话框

@Override
protected void onPostExecute(HttpResponse response) {
if (response == null) {
            Log.d(TAG, "onPostExecute, response == null");
            AlertDialog.Builder builder = new AlertDialog.Builder(ConfirmPhoneNoCode.this);
            builder.setMessage("Are you sure you want to exit?").setCancelable(false)
                    .setPositiveButton("Yes", new DialogInterface.OnClickListener() {
                        public void onClick(DialogInterface dialog, int id) {
                            ConfirmPhoneNoCode.this.finish();
                        }
                    }).setNegativeButton("No", new DialogInterface.OnClickListener() {
                        public void onClick(DialogInterface dialog, int id) {
                            dialog.cancel();
                        }
                    });
            AlertDialog alert = builder.create();
        } else {
            int responseCode = response.getStatusLine().getStatusCode();
            String message = response.getStatusLine().getReasonPhrase();
            Log.d(TAG, "Response Code: " + String.valueOf(responseCode));
            Log.d(TAG, "Message: " + message);
        }
    }

我收到了日志消息

03-31 23:02:42.912: D/ConfirmPhoneCode(21966): onPostExecute, response == null

这意味着

if(response == null) is executed but AlertDialog box don't show-up.

如果有人能帮我，我将不胜感激

提前感谢。

alert.show（）我想你必须添加它

AlertDialog alert = builder.create();
alert.show();

我觉得还可以。您正在调用
alert.show（）