java - Android:使用简单的警报对话框处理 AsyncTask 中的 SocketTimeoutException

Question

我在我的 Android 应用程序中使用 AsyncTask 从服务器获取一些数据。为了建立连接，我使用了超时为 10 秒的 HttpURLConnection 类。现在，我想在(如果)该时间到期时显示一个简单的 AlertDialog，并带有一个将用户带回 Main Activity 的 OK 按钮。现在，这就是我的应用程序 (DoorActivity) 的相关部分的样子:

    protected String doInBackground(String... params) {

        try {

            URL url = new URL(params[0]);
            urlConnection = (HttpURLConnection) url.openConnection();
            urlConnection.setConnectTimeout(10000);
            urlConnection.setRequestMethod("GET");
            if (urlConnection.getResponseCode() != 200) {
                throw new IOException(urlConnection.getResponseMessage());
            }

            BufferedReader read = new BufferedReader(new InputStreamReader(urlConnection.getInputStream()));
            jsonString = read.readLine().toString();

        } catch (MalformedURLException malformedUrlException) {
            System.out.println(malformedUrlException.getMessage());
            malformedUrlException.printStackTrace();

        } catch (SocketTimeoutException connTimeout) {
            showTimeoutAlert();

showTimeoutAlert() 方法位于 DoorActivity 的根类中，如下所示:

protected void showTimeoutAlert(){
    TextView timeoutWarning = new TextView(this);
    AlertDialog.Builder builder = new AlertDialog.Builder(this);
    AlertDialog alertDialog;
    timeoutWarning.setText(R.string.conn_timeout_warning);
    builder.setView(timeoutWarning);
    builder.setPositiveButton("OK", new DialogInterface.OnClickListener() {

        @Override
        public void onClick(DialogInterface dialog, int which) {
            Intent intent = new Intent(DoorActivity.this, MainActivity.class);
            startActivity(intent);
        }
    });
    alertDialog = builder.create();
    alertDialog.show();
}

现在，当我运行这个应用程序时，服务器故意脱机，我得到以下异常:

java.lang.RuntimeException: 执行 doInBackground() 时发生错误

Caused by: java.lang.RuntimeException: Can't create handler inside thread that has not called Looper.prepare()

Answer 1

showTimeoutAlert(); 不应在 doInBackground() 中调用。任何与 UI 相关的代码都应该放在 onPostExecute() 中。

例如:

private boolean socketTimedOut = false;

@Override
protected String doInBackground(String... params) {
    try {
        ...
    } catch (SocketTimeoutException connTimeout) {
        this.socketTimedOut = true;
    }
}


@Override
protected void onPostExecute(String result) {
    if(this.socketTimedOut){
        showTimeoutAlert();
    }
}

---

替代方案(不推荐):

@Override
protected String doInBackground(String... params) {
    try {
        ...
    } catch (SocketTimeoutException connTimeout) {
        runOnUiThread(new Runnable() {
            public void run() {
                showTimeoutAlert();
            }
        });
    }
}