Question

我一直在研究一个Android项目，我想要一些API来获取信息。看起来这应该是非常基本的！

以下是我的代码的一般要点：

private InputStream retrieveStream2(String url)
{
    DefaultHttpClient client = new DefaultHttpClient();

    HttpGet getRequest = new HttpGet(url);
    System.out.println("getRequest == " + getRequest);
    try {


        HttpResponse getResponse = client.execute(getRequest);//here is teh problem
        final int statusCode = getResponse.getStatusLine().getStatusCode();


        if (statusCode != HttpStatus.SC_OK)
        {
            Log.w(getClass().getSimpleName(),
                    "Error " + statusCode + " for URL " + url);
            return null;
        }

        HttpEntity getResponseEntity = getResponse.getEntity();
        return getResponseEntity.getContent();

    }
    catch (Exception e)
    {
        getRequest.abort();
        Log.w(getClass().getSimpleName(), "Error for URL, YO " + url, e);
    }
    return null;
}

其中url变量是字符串“http://search.twitter.com/search.json?q=javacodegeeks”。

正如您所看到的，该网站上有一些不错的JSON信息;我的问题是，每次调用'client.execute（getRequest）;''时，程序都会抛出并捕获异常。没有用！

我听说过两件事：

1）您必须为模拟器/设备设置使用互联网的权限！ - 我想我已经覆盖了这个，但也许我做错了！在androidmanifest.xml中我添加了

< uses-permission android:name="android.permission.INTERNET" >< /uses-permission>

所以就是这样。

2）（我不太确定）你不能在'ui'线程中启动'网络'线程。我不完全确定这意味着什么，但我继续前进并遵循Android Threads，Handlers和AsyncTasks的一些教程。这里：请查看我遵循的AsyncTask教程下的代码：

http://www.vogella.de/articles/AndroidPerformance/article.html

在跟随AsyncTask教程之后，我发现我仍然遇到了同样的问题 -

行： HttpGet httpGet = new HttpGet（url）总是像以前一样抛出异常。

以下是我尝试上面的线程教程的logcat：

02-27 20:43:28.565: I/ActivityManager(92): START {cmp=com.Prometheus.R1/.JsonParsingActivity} from pid 574
02-27 20:43:28.565: W/WindowManager(92): Failure taking screenshot for (180x300) to layer 21010
02-27 20:43:28.896: I/System.out(574): pre execute
02-27 20:43:29.236: I/ActivityManager(92): Displayed com.Prometheus.R1/.JsonParsingActivity: +638ms
02-27 20:43:29.329: I/ARMAssembler(35): generated scanline__00000077:03010104_00008001_00000000 [ 89 ipp] (110 ins) at [0x40fad6a8:0x40fad860] in 7204915 ns
02-27 20:43:30.016: W/System.err(574): java.net.UnknownHostException: Unable to resolve host "search.twitter.com": No address associated with hostname
02-27 20:43:30.016: W/System.err(574):  at java.net.InetAddress.lookupHostByName(InetAddress.java:426)
02-27 20:43:30.026: W/System.err(574):  at java.net.InetAddress.getAllByNameImpl(InetAddress.java:242)
02-27 20:43:30.026: W/System.err(574):  at java.net.InetAddress.getAllByName(InetAddress.java:220)
02-27 20:43:30.026: W/System.err(574):  at org.apache.http.impl.conn.DefaultClientConnectionOperator.openConnection(DefaultClientConnectionOperator.java:137)
02-27 20:43:30.036: W/System.err(574):  at org.apache.http.impl.conn.AbstractPoolEntry.open(AbstractPoolEntry.java:164)
02-27 20:43:30.036: W/System.err(574):  at org.apache.http.impl.conn.AbstractPooledConnAdapter.open(AbstractPooledConnAdapter.java:119)
02-27 20:43:30.046: W/System.err(574):  at org.apache.http.impl.client.DefaultRequestDirector.execute(DefaultRequestDirector.java:360)
02-27 20:43:30.046: W/System.err(574):  at org.apache.http.impl.client.AbstractHttpClient.execute(AbstractHttpClient.java:555)
02-27 20:43:30.046: W/System.err(574):  at org.apache.http.impl.client.AbstractHttpClient.execute(AbstractHttpClient.java:487)
02-27 20:43:30.055: W/System.err(574):  at org.apache.http.impl.client.AbstractHttpClient.execute(AbstractHttpClient.java:465)
02-27 20:43:30.055: W/System.err(574):  at com.Prometheus.R1.JsonParsingActivity$DownloadWebPageTask.doInBackground(JsonParsingActivity.java:88)
02-27 20:43:30.055: W/System.err(574):  at com.Prometheus.R1.JsonParsingActivity$DownloadWebPageTask.doInBackground(JsonParsingActivity.java:1)
02-27 20:43:30.055: W/System.err(574):  at android.os.AsyncTask$2.call(AsyncTask.java:264)<br/>
02-27 20:43:30.066: W/System.err(574):  at java.util.concurrent.FutureTask$Sync.innerRun(FutureTask.java:305)
02-27 20:43:30.066: W/System.err(574):  at java.util.concurrent.FutureTask.run(FutureTask.java:137)<br/>
02-27 20:43:30.066: W/System.err(574):  at android.os.AsyncTask$SerialExecutor$1.run(AsyncTask.java:208)
02-27 20:43:30.076: W/System.err(574):  at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1076)
02-27 20:43:30.076: W/System.err(574):  at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:569)
02-27 20:43:30.087: W/System.err(574):  at java.lang.Thread.run(Thread.java:856)
02-27 20:43:30.108: W/System.err(574): Caused by: libcore.io.GaiException: getaddrinfo failed: EAI_NODATA (No address associated with hostname)
02-27 20:43:30.116: W/System.err(574):  at libcore.io.Posix.getaddrinfo(Native Method)
02-27 20:43:30.116: W/System.err(574):  at libcore.io.ForwardingOs.getaddrinfo(ForwardingOs.java:55)
02-27 20:43:30.126: W/System.err(574):  at java.net.InetAddress.lookupHostByName(InetAddress.java:411)
02-27 20:43:30.126: W/System.err(574):  ... 18 more
02-27 20:43:30.136: I/System.out(574): Except thrown by url http://search.twitter.com/search.json?q=javacodegeeks, .... 
02-27 20:43:30.136: I/System.out(574): response =

您可以看到异常是UnknownHostException：
“ava.net.UnknownHostException：无法解析主机”search.twitter.com“：没有与主机名关联的地址”
但我不认为该网站是不可接受的......

任何人都可以告诉我发生了什么以及我需要做些什么才能通过它？

Answer 1

检查清单的权限，确保添加了以下内容：

<uses-permission android:name="android.permission.ACCESS_NETWORK_STATE"/>
<uses-permission android:name="android.permission.ACCESS_WIFI_STATE"/>
<uses-permission android:name="android.permission.INTERNET"/>

Answer 2

想出来。显然我把AVD从“飞机模式”上移开了。

对于遇到与我相同问题的人，你可能正在使用无线技术。出于某种原因，andriod会查看您的LAN卡，因此请转到您的网络连接并右键单击LAN卡 - 禁用该功能！问题解决了。

Answer 3

我认为问题在于您在http请求或互联网连接中提供的网址，请查看以下链接，它会对您有所帮助Link

Answer 4

我也遇到了这个问题。在我的情况下，我使用HttpURLConnection来加载JSON。当我启用＆＃34;跟随重定向时，问题得到解决。＆＃34;这是一个有效的代码片段：

    HttpURLConnection connection = null;
    BufferedReader reader = null;
    String JSON_data = null;

    try {
        final int half_hour = 30 * 60;
        URL fetch = new URL(requestUrl);
        connection = (HttpURLConnection) fetch.openConnection();

        // FIXED: request to follow redirects - this seems to solve networking issues on older devices < API 21
        connection.setInstanceFollowRedirects(true);

        connection.setUseCaches(true);
        connection.setDefaultUseCaches(true);
        connection.setRequestMethod("GET");
        connection.addRequestProperty("Cache-Control", "max-age="+half_hour);
        connection.addRequestProperty("X-Auth-Token", getString(R.string.api_key));

        boolean redirect = false;
        int status = connection.getResponseCode();
        if (status != HttpURLConnection.HTTP_OK) {
            if (status == HttpURLConnection.HTTP_MOVED_TEMP
                    || status == HttpURLConnection.HTTP_MOVED_PERM
                    || status == HttpURLConnection.HTTP_SEE_OTHER)
                redirect = true;
        }
        Log.d(TAG, "===> HTTP STATUS CODE: " + status + ", redirect=" + redirect);

        connection.connect();

        // Read the input stream into a String
        InputStream inputStream = connection.getInputStream();
        if (inputStream == null) {
            return;
        }

        reader = new BufferedReader(new InputStreamReader(inputStream));

        StringBuilder buffer = new StringBuilder();
        String line;
        while ((line = reader.readLine()) != null) {
            buffer.append(line);
            buffer.append("\n");
        }
        if (buffer.length() == 0) {
            return;
        }
        JSON_data = buffer.toString();
        Log.d(TAG, "JSON_data=" + JSON_data);
    } catch (Exception e) {
        // possible UnknownHostException on older Android device?
        Log.e(TAG, "HttpURLConnection Exception - e=" + e.getMessage());
        e.printStackTrace();
    } finally {
        if (connection != null) {
            connection.disconnect();
        }
        if (reader != null) {
            try {
                reader.close();
            } catch (IOException e) {
                Log.e(TAG, "Error closing stream - e=" + e.getMessage());
            }
        }
    }

Answer 5

这并不意味着您对应用程序有疑问，这是因为您使用的是Wi-Fi互联网，因此，要解决此问题，请使您的笔记本电脑保持Wi-Fi连接并重新启动模拟器

对我有用

Answer 6

就我而言，我刚刚重新启动了包含模拟器的Android Studio，并且该软件没有错误。

Answer 7

有时候，我在分析系统中看到类似的日志。我认为服务器中存在问题。有时它没有响应（短时间）。或者，也许是用户连接较弱（例如，在地下或建筑物内部）。

Answer 8

您可以通过以下代码段在主线程中允许网络访问。在您的活动的onCreate（）方法的开头。

StrictMode.ThreadPolicy policy = new StrictMode.
ThreadPolicy.Builder().permitAll().build();
StrictMode.setThreadPolicy(policy);

HttpResponse使用android问题：执行总是导致异常？

8 个答案: