在Android 4上从互联网上下载XML文件时出现异常（但它适用于Android 2.3）

我在Android上从Internet下载XML文件时出现问题。我写了一些代码，它在Android 2.3模拟器上工作。但是，它不适用于Android 4.03模拟器，也不适用于真正的Android 4设备。这里是我的代码：在Android 4上从互联网上下载XML文件时出现异常（但它适用于Android 2.3）

public String getXmlFromUrl(String url) { 
    String xml = null; 

    try { 
     // defaultHttpClient 
     DefaultHttpClient httpClient = new DefaultHttpClient(); 
     HttpPost httpPost = new HttpPost(url); 

     HttpResponse httpResponse = httpClient.execute(httpPost); 
     HttpEntity httpEntity = httpResponse.getEntity(); 
     xml = EntityUtils.toString(httpEntity); 

    } catch (UnsupportedEncodingException e) { 
     e.printStackTrace(); 
    } catch (ClientProtocolException e) { 
     e.printStackTrace(); 
    } catch (IOException e) { 
     e.printStackTrace(); 
    } 
    // return XML 
    return xml; 
}

我对行错误：

HttpResponse httpResponse = httpClient.execute(httpPost);

这里是日志从logcat的：

08-15 16:59:32.436: E/AndroidRuntime(623): FATAL EXCEPTION: main 
08-15 16:59:32.436: E/AndroidRuntime(623): java.lang.RuntimeException: Unable to start activity ComponentInfo{com.example.testy/com.example.testy.MainActivity}: android.os.NetworkOnMainThreadException 
08-15 16:59:32.436: E/AndroidRuntime(623): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:1956) 
08-15 16:59:32.436: E/AndroidRuntime(623): at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:1981) 
08-15 16:59:32.436: E/AndroidRuntime(623): at android.app.ActivityThread.access$600(ActivityThread.java:123) 
08-15 16:59:32.436: E/AndroidRuntime(623): at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1147) 
08-15 16:59:32.436: E/AndroidRuntime(623): at android.os.Handler.dispatchMessage(Handler.java:99) 
08-15 16:59:32.436: E/AndroidRuntime(623): at android.os.Looper.loop(Looper.java:137) 
08-15 16:59:32.436: E/AndroidRuntime(623): at android.app.ActivityThread.main(ActivityThread.java:4424) 
08-15 16:59:32.436: E/AndroidRuntime(623): at java.lang.reflect.Method.invokeNative(Native Method) 
08-15 16:59:32.436: E/AndroidRuntime(623): at java.lang.reflect.Method.invoke(Method.java:511) 
08-15 16:59:32.436: E/AndroidRuntime(623): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:784) 
08-15 16:59:32.436: E/AndroidRuntime(623): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:551) 
08-15 16:59:32.436: E/AndroidRuntime(623): at dalvik.system.NativeStart.main(Native Method) 
08-15 16:59:32.436: E/AndroidRuntime(623): Caused by: android.os.NetworkOnMainThreadException 
08-15 16:59:32.436: E/AndroidRuntime(623): at android.os.StrictMode$AndroidBlockGuardPolicy.onNetwork(StrictMode.java:1099) 
08-15 16:59:32.436: E/AndroidRuntime(623): at java.net.InetAddress.lookupHostByName(InetAddress.java:391) 
08-15 16:59:32.436: E/AndroidRuntime(623): at java.net.InetAddress.getAllByNameImpl(InetAddress.java:242) 
08-15 16:59:32.436: E/AndroidRuntime(623): at java.net.InetAddress.getAllByName(InetAddress.java:220) 
08-15 16:59:32.436: E/AndroidRuntime(623): at org.apache.http.impl.conn.DefaultClientConnectionOperator.openConnection(DefaultClientConnectionOperator.java:137) 
08-15 16:59:32.436: E/AndroidRuntime(623): at org.apache.http.impl.conn.AbstractPoolEntry.open(AbstractPoolEntry.java:164) 
08-15 16:59:32.436: E/AndroidRuntime(623): at org.apache.http.impl.conn.AbstractPooledConnAdapter.open(AbstractPooledConnAdapter.java:119) 
08-15 16:59:32.436: E/AndroidRuntime(623): at org.apache.http.impl.client.DefaultRequestDirector.execute(DefaultRequestDirector.java:360) 
08-15 16:59:32.436: E/AndroidRuntime(623): at org.apache.http.impl.client.AbstractHttpClient.execute(AbstractHttpClient.java:555) 
08-15 16:59:32.436: E/AndroidRuntime(623): at org.apache.http.impl.client.AbstractHttpClient.execute(AbstractHttpClient.java:487) 
08-15 16:59:32.436: E/AndroidRuntime(623): at org.apache.http.impl.client.AbstractHttpClient.execute(AbstractHttpClient.java:465) 
08-15 16:59:32.436: E/AndroidRuntime(623): at com.example.testy.XMLParser.getXmlFromUrl(XMLParser.java:54) 
08-15 16:59:32.436: E/AndroidRuntime(623): at com.example.testy.MainActivity.onCreate(MainActivity.java:34) 
08-15 16:59:32.436: E/AndroidRuntime(623): at android.app.Activity.performCreate(Activity.java:4465) 
08-15 16:59:32.436: E/AndroidRuntime(623): at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1049) 
08-15 16:59:32.436: E/AndroidRuntime(623): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:1920) 
08-15 16:59:32.436: E/AndroidRuntime(623): ... 11 more

我能做些什么呢？

来源

2012-08-15 michalsol

您正在主线程上执行（可能较慢）的网络操作。如果您的目标SDK为11（Honeycomb）或更高，则会在Honeycomb或更高版本上抛出NetworkOnMainThreadException，因为此行为可能会阻止UI并导致应用程序无响应。即使在预蜂窝设备this behaviour is discouraged。

您可以使用AsyncTask解决此问题，将数据加载到doInBackground(..)中。

来源

2012-08-15 18:07:35 Ahmad

您正在主线程上使用网络功能。您需要使用AsyncTask来完成此操作。从蜂巢开始Strictmode检查默认启用。所以网络操作引发了一个例外。姜饼中没有启用Strictmode。因此它使用姜饼而不是ICS

来源

2012-08-15 17:26:50 nandeesh

在Android 4上从互联网上下载XML文件时出现异常（但它适用于Android 2.3）

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