在Android 4上从互联网下载XML文件时出现异常(但适用于Android 2.3)
在Android 4上从互联网下载XML文件时出现异常(但适用于Android 2.3)
提问于 2012-08-16 01:09:54
我有一个问题，从互联网下载的XML文件在Android。我写了一些代码，它可以在Android2.3模拟器上运行。然而，它不能在Android4.03模拟器上工作，也不能在真正的Android4设备上工作。下面是我的代码：
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;
}我在线路上有错误：
HttpResponse httpResponse = httpClient.execute(httpPost);以下是来自LogCat的日志：
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我能用它来做什么？
回答 2
Stack Overflow用户
回答已采纳
发布于 2012-08-16 02:07:35
您正在主线程上执行一个(可能很慢的)网络操作。如果你的目标SDK是11 ( Honeycomb )或更高，这将在Honeycomb或更高的版本上抛出一个NetworkOnMainThreadException，因为这种行为会阻塞UI并导致应用程序没有响应。即使是在蜂巢设备之前的this behaviour is discouraged。
Stack Overflow用户
发布于 2012-08-16 01:26:50
您需要使用AsyncTask来完成此操作。因此，网络操作会引发异常。
页面原文内容由Stack Overflow提供。腾讯云小微IT领域专用引擎提供翻译支持
原文链接：
https://stackoverflow.com/questions/11973831
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