转换结果 java.io.IOException 时出错：尝试在关闭的流上读取？

Question

考虑到下面的代码，当我调用 foo1() 然后 foo2() 时，一切都很好。但是当我将它们一起调用时，我随机得到错误：

• 错误转换结果 java.io.IOException: 尝试读取已关闭的流。

错误有时与 foo1 有时与 foo2 有关。但是，在每个错误之后，相关方法会停止工作，但会在几秒钟后恢复。如何解决问题？

public class myActivity extends Activity {
//some code including onCreate method
private void foo1() {
    new Thread(new Runnable() {
        @Override
        public void run() {
            try{
            while (true){
                JSONParser jsonParser = new JSONParser(); 
                JSONObject jsonObject = jsonParser.getJSONFromUrlByGet(url1);
                myList.add(jsonObject);
                url1 = getNewUrl(url1);                                             
                if(!jsonObject.getJSONObject("pagination").has("next_url"))
                    break;                                                 
            }  catch (Exception exception) {
                exception.printStackTrace();
            }               
        }
    }).start();
}
private void foo2() {
    new Thread(new Runnable() {
        @Override
        public void run() {
            try{
            while (true){
                JSONParser jsonParser = new JSONParser(); 
                JSONObject jsonObject = jsonParser.getJSONFromUrlByGet(url2);
                myList.add(jsonObject);
                url2 = getNewUrl(url2);                         
                if(!jsonObject.getJSONObject("pagination").has("next_url"))
                    break;                                                 
            }  catch (Exception exception) {
                exception.printStackTrace();
            }               
        }
    }).start();
}
}

public class JSONParser {
static InputStream is = null;
public JSONObject getJSONFromUrlByGet(String url) {

    try {
        DefaultHttpClient httpClient = new DefaultHttpClient();
        HttpGet httpGet = new HttpGet(url);

        HttpResponse httpResponse = httpClient.execute(httpGet);
        HttpEntity httpEntity = httpResponse.getEntity();
        is = httpEntity.getContent();

    } catch (UnsupportedEncodingException e) {
        e.printStackTrace();
    } catch (ClientProtocolException e) {
        e.printStackTrace();
    } catch (IOException e) {
        e.printStackTrace();
    }

    try {
        BufferedReader reader = new BufferedReader(new InputStreamReader(
                is, "iso-8859-1"), 8);
        StringBuilder sb = new StringBuilder();
        String line = null;
        while ((line = reader.readLine()) != null) {
            sb.append(line + "\n");
        }
        is.close();
        json = sb.toString();
    } catch (Exception e) {
    }
    try {
        jObj = new JSONObject(json);
    } catch (JSONException e) {
    }
    return jObj;
}

这是日志：

12-27 11:48:46.076: I/System.out(20738): got foo1 first pack
12-27 11:48:46.201: I/System.out(20738): got foo1 second pack
12-27 11:48:46.771: I/System.out(20738): got foo1 third pack
12-27 11:48:47.386: I/System.out(20738): got foo2 first pack
12-27 11:48:47.391: I/System.out(20738): E/Buffer Error(6888): Error converting result java.io.IOException: Attempted read on closed stream.
12-27 11:48:47.681: I/System.out(20738): got foo2 second pack
12-27 11:48:47.731: I/System.out(20738): got foo1 fourth pack
12-27 11:48:48.651: I/System.out(20738): got foo1 fifth pack
12-27 11:48:48.656: I/System.out(20738): E/Buffer Error(6888): Error converting result java.io.IOException: Attempted read on closed stream.
12-27 11:48:50.826: I/System.out(20738): got foo2 third pack
12-27 11:48:50.836: I/System.out(20738): got foo2 fourth pack
12-27 11:48:50.856: I/System.out(20738): got foo2 fifth pack
12-27 11:48:50.891: I/System.out(20738): got foo2 sixth pack
12-27 11:48:50.891: I/System.out(20738): got foo2 seventh pack
12-27 11:48:52.686: I/System.out(20738): E/Buffer Error(6888): Error converting result java.io.IOException: Attempted read on closed stream.
12-27 11:48:52.696: I/System.out(20738): got foo1 sixth pack

Answer 1

所以问题是您正在使用线程，这些线程会随机执行，因此有时您会在 foo1 和其他时候在 foo2 中出错。

在你的 run() 方法中，你会因为while(true){}而不断循环

假设你的 foo1 开始执行，它进入 while 循环，并调用 getJSONFromUrlByGet()，它依次读取数据直到结束，然后关闭流。见is.close()

但是由于是静态实例，“is”在类的所有实例之间共享。因此，当再次调用 getJSONFromUrlByGet() 时，流已经关闭，因此出现异常。