Question

美好的一天，对于我现在遇到的问题，我的asynctask适用于SDK 24或更高版本，但当我把它放在SDK 21,22,23模拟器和真实设备上时，它不起作用。

奇怪的是： 1.）我的第一个活动和片段上的Asynctasks正在工作，但第二个活动的asysntask不起作用，错误代码：400，异常java.lang.IllegalStateException：myURL。

我使用doInBackGround代码进行异步操作：

        @Override
        protected String doInBackground(Void... voids) {
                try {
                    //creating a URL
                    URL url = new URL(urlWebService);
                    //Opening the URL using HttpURLConnection
                    HttpURLConnection con = (HttpURLConnection) url.openConnection();

                    //StringBuilder object to read the string from the service
                    StringBuilder sb = new StringBuilder();

                    //We will use a buffered reader to read the string from service
                    BufferedReader bufferedReader = new BufferedReader(new InputStreamReader(con.getInputStream()));

                    //A simple string to read values from each line
                    String json;

                    while ((json = bufferedReader.readLine()) != null) {
                        if (!json.contains("<br")) {
                            sb.append(json + "\n");
                        }
                    }

                    //finally returning the read string
                    return sb.toString().trim();

                } catch (Exception e) {
                    System.out.println("Error in http connection " + e.toString());
                    return null;
                }
        }
    }

对于此代码，适用于SDK 24,25,26。它会在con.getInputStream（）中抛出异常。我不确定是什么问题。是线程还是其他什么问题？感谢。

IOExeption
10-27 02:28:29.453 16954-17698/com.example.reonyx.tracking5 W/System.err: java.io.FileNotFoundException:mrURL
10-27 02:28:29.453 16954-17698/com.example.reonyx.tracking5 W/System.err:     at com.android.okhttp.internal.http.HttpURLConnectionImpl.getInputStream(HttpURLConnectionImpl.java:197)
10-27 02:28:29.453 16954-17698/com.example.reonyx.tracking5 W/System.err:     at com.example.reonyx.tracking5.PlayBackActivity$1GetJSON.doInBackground(PlayBackActivity.java:1206)
10-27 02:28:29.453 16954-17698/com.example.reonyx.tracking5 W/System.err:     at com.example.reonyx.tracking5.PlayBackActivity$1GetJSON.doInBackground(PlayBackActivity.java:964)
10-27 02:28:29.453 16954-17698/com.example.reonyx.tracking5 W/System.err:     at android.os.AsyncTask$2.call(AsyncTask.java:288)
10-27 02:28:29.453 16954-17698/com.example.reonyx.tracking5 W/System.err:     at java.util.concurrent.FutureTask.run(FutureTask.java:237)
10-27 02:28:29.454 16954-17698/com.example.reonyx.tracking5 W/System.err:     at android.os.AsyncTask$SerialExecutor$1.run(AsyncTask.java:231)
10-27 02:28:29.454 16954-17698/com.example.reonyx.tracking5 W/System.err:     at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1112)
10-27 02:28:29.454 16954-17698/com.example.reonyx.tracking5 W/System.err:     at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:587)
10-27 02:28:29.454 16954-17698/com.example.reonyx.tracking5 W/System.err:     at java.lang.Thread.run(Thread.java:818)

Answer 1

是否aynctask无法正常工作或HttpURLConnection无法按预期工作？我可以理解，根据代码，您使用get url来检索数据。

我可以建议使用getResponseCode方法等待响应，然后尝试使用getInputStream方法。

@Override
protected String doInBackground(String... strings) {

    URL url;
    HttpURLConnection urlConnection = null;

    try {
        url = new URL(strings[0]);
        urlConnection = (HttpURLConnection) url.openConnection();

        int responseCode = urlConnection.getResponseCode();

        if(responseCode == HttpURLConnection.HTTP_OK) {

          // use bufferreder to get the data from input stream.

        }

    } catch (MalformedURLException e) {
        e.printStackTrace();
    } catch (IOException e) {
        e.printStackTrace();
    } finally {
       if(urlConnection!=null)
         urlConnection.disconnect();
    } 

    return null;
}

Asynctask不支持SDK 23或更早版本

1 个答案: