請求HTTP失敗在android

Question

我試圖使用下面的代碼來獲取http請求。網址是：

String url =「http://vlm1.uta.edu/~zhangzhong/questions.json」;

當致電InputStream source = retrieveStream(url)時，它給我一個錯誤。順便說，我已經添加<uses-permission android:name="android.permission.INTERNET"/>

private InputStream retrieveStream(String url) { 

     DefaultHttpClient client = new DefaultHttpClient(); 

     HttpGet getRequest = new HttpGet(url); 

     try { 

      HttpResponse getResponse = client.execute(getRequest); 
      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 (IOException e) { 
      getRequest.abort(); 
      Log.w(getClass().getSimpleName(), "Error for URL " + url, e); 
     } 

     return null; 
    } 

以下是logcat的：

04-22 16：36：37.042：d/dalvikvm（3840）：調試程序已拆卸;對象註冊了427

entries 
04-22 16:36:37.042: I/dalvikvm(3840): ignoring registerObject request in thread=1 
04-22 16:36:37.042: I/dalvikvm(3840): ignoring registerObject request in thread=1 
04-22 16:36:37.042: D/AndroidRuntime(3840): Shutting down VM 
04-22 16:36:37.042: W/dalvikvm(3840): threadid=1: thread exiting with uncaught exception (group=0x41760930) 
04-22 16:36:37.072: E/AndroidRuntime(3840): FATAL EXCEPTION: main 
04-22 16:36:37.072: E/AndroidRuntime(3840): java.lang.RuntimeException: Unable to start activity ComponentInfo{com.example.flashcard/com.example.flashcard.MainActivity}: android.os.NetworkOnMainThreadException 
04-22 16:36:37.072: E/AndroidRuntime(3840):  at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2180) 
04-22 16:36:37.072: E/AndroidRuntime(3840):  at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2230) 
04-22 16:36:37.072: E/AndroidRuntime(3840):  at android.app.ActivityThread.access$600(ActivityThread.java:141) 
04-22 16:36:37.072: E/AndroidRuntime(3840):  at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1234) 
04-22 16:36:37.072: E/AndroidRuntime(3840):  at android.os.Handler.dispatchMessage(Handler.java:99) 
04-22 16:36:37.072: E/AndroidRuntime(3840):  at android.os.Looper.loop(Looper.java:137) 
04-22 16:36:37.072: E/AndroidRuntime(3840):  at android.app.ActivityThread.main(ActivityThread.java:5041) 
04-22 16:36:37.072: E/AndroidRuntime(3840):  at java.lang.reflect.Method.invokeNative(Native Method) 
04-22 16:36:37.072: E/AndroidRuntime(3840):  at java.lang.reflect.Method.invoke(Method.java:511) 
04-22 16:36:37.072: E/AndroidRuntime(3840):  at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:793) 
04-22 16:36:37.072: E/AndroidRuntime(3840):  at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:560) 
04-22 16:36:37.072: E/AndroidRuntime(3840):  at dalvik.system.NativeStart.main(Native Method) 
04-22 16:36:37.072: E/AndroidRuntime(3840): Caused by: android.os.NetworkOnMainThreadException 
04-22 16:36:37.072: E/AndroidRuntime(3840):  at android.os.StrictMode$AndroidBlockGuardPolicy.onNetwork(StrictMode.java:1117) 
04-22 16:36:37.072: E/AndroidRuntime(3840):  at java.net.InetAddress.lookupHostByName(InetAddress.java:385) 
04-22 16:36:37.072: E/AndroidRuntime(3840):  at java.net.InetAddress.getAllByNameImpl(InetAddress.java:236) 
04-22 16:36:37.072: E/AndroidRuntime(3840):  at java.net.InetAddress.getAllByName(InetAddress.java:214) 
04-22 16:36:37.072: E/AndroidRuntime(3840):  at org.apache.http.impl.conn.DefaultClientConnectionOperator.openConnection(DefaultClientConnectionOperator.java:137) 
04-22 16:36:37.072: E/AndroidRuntime(3840):  at org.apache.http.impl.conn.AbstractPoolEntry.open(AbstractPoolEntry.java:164) 
04-22 16:36:37.072: E/AndroidRuntime(3840):  at org.apache.http.impl.conn.AbstractPooledConnAdapter.open(AbstractPooledConnAdapter.java:119) 
04-22 16:36:37.072: E/AndroidRuntime(3840):  at org.apache.http.impl.client.DefaultRequestDirector.execute(DefaultRequestDirector.java:360) 
04-22 16:36:37.072: E/AndroidRuntime(3840):  at org.apache.http.impl.client.AbstractHttpClient.execute(AbstractHttpClient.java:555) 
04-22 16:36:37.072: E/AndroidRuntime(3840):  at org.apache.http.impl.client.AbstractHttpClient.execute(AbstractHttpClient.java:487) 
04-22 16:36:37.072: E/AndroidRuntime(3840):  at org.apache.http.impl.client.AbstractHttpClient.execute(AbstractHttpClient.java:465) 
04-22 16:36:37.072: E/AndroidRuntime(3840):  at com.example.flashcard.MainActivity.retrieveStream(MainActivity.java:63) 
04-22 16:36:37.072: E/AndroidRuntime(3840):  at com.example.flashcard.MainActivity.onCreate(MainActivity.java:37) 
04-22 16:36:37.072: E/AndroidRuntime(3840):  at android.app.Activity.performCreate(Activity.java:5104) 
04-22 16:36:37.072: E/AndroidRuntime(3840):  at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1080) 
04-22 16:36:37.072: E/AndroidRuntime(3840):  at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2144) 
04-22 16:36:37.072: E/AndroidRuntime(3840):  ... 11 more 
04-22 16:36:37.092: I/Process(3840): Sending signal. PID: 3840 SIG: 9 
04-22 16:37:37.727: D/AndroidRuntime(3957): Shutting down VM 
04-22 16:37:43.443: D/AndroidRuntime(4077): Shutting down VM 
04-22 16:37:43.443: W/dalvikvm(4077): threadid=1: thread exiting with uncaught exception (group=0x41760930) 
04-22 16:37:43.443: E/AndroidRuntime(4077): FATAL EXCEPTION: main 
04-22 16:37:43.443: E/AndroidRuntime(4077): java.lang.RuntimeException: Unable to start activity ComponentInfo{com.example.flashcard/com.example.flashcard.MainActivity}: android.os.NetworkOnMainThreadException 
04-22 16:37:43.443: E/AndroidRuntime(4077):  at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2180) 
04-22 16:37:43.443: E/AndroidRuntime(4077):  at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2230) 
04-22 16:37:43.443: E/AndroidRuntime(4077):  at android.app.ActivityThread.access$600(ActivityThread.java:141) 
04-22 16:37:43.443: E/AndroidRuntime(4077):  at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1234) 
04-22 16:37:43.443: E/AndroidRuntime(4077):  at android.os.Handler.dispatchMessage(Handler.java:99) 
04-22 16:37:43.443: E/AndroidRuntime(4077):  at android.os.Looper.loop(Looper.java:137) 
04-22 16:37:43.443: E/AndroidRuntime(4077):  at android.app.ActivityThread.main(ActivityThread.java:5041) 
04-22 16:37:43.443: E/AndroidRuntime(4077):  at java.lang.reflect.Method.invokeNative(Native Method) 
04-22 16:37:43.443: E/AndroidRuntime(4077):  at java.lang.reflect.Method.invoke(Method.java:511) 
04-22 16:37:43.443: E/AndroidRuntime(4077):  at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:793) 
04-22 16:37:43.443: E/AndroidRuntime(4077):  at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:560) 
04-22 16:37:43.443: E/AndroidRuntime(4077):  at dalvik.system.NativeStart.main(Native Method) 
04-22 16:37:43.443: E/AndroidRuntime(4077): Caused by: android.os.NetworkOnMainThreadException 
04-22 16:37:43.443: E/AndroidRuntime(4077):  at android.os.StrictMode$AndroidBlockGuardPolicy.onNetwork(StrictMode.java:1117) 
04-22 16:37:43.443: E/AndroidRuntime(4077):  at java.net.InetAddress.lookupHostByName(InetAddress.java:385) 
04-22 16:37:43.443: E/AndroidRuntime(4077):  at java.net.InetAddress.getAllByNameImpl(InetAddress.java:236) 
04-22 16:37:43.443: E/AndroidRuntime(4077):  at java.net.InetAddress.getAllByName(InetAddress.java:214) 
04-22 16:37:43.443: E/AndroidRuntime(4077):  at org.apache.http.impl.conn.DefaultClientConnectionOperator.openConnection(DefaultClientConnectionOperator.java:137) 
04-22 16:37:43.443: E/AndroidRuntime(4077):  at org.apache.http.impl.conn.AbstractPoolEntry.open(AbstractPoolEntry.java:164) 
04-22 16:37:43.443: E/AndroidRuntime(4077):  at org.apache.http.impl.conn.AbstractPooledConnAdapter.open(AbstractPooledConnAdapter.java:119) 
04-22 16:37:43.443: E/AndroidRuntime(4077):  at org.apache.http.impl.client.DefaultRequestDirector.execute(DefaultRequestDirector.java:360) 
04-22 16:37:43.443: E/AndroidRuntime(4077):  at org.apache.http.impl.client.AbstractHttpClient.execute(AbstractHttpClient.java:555) 
04-22 16:37:43.443: E/AndroidRuntime(4077):  at org.apache.http.impl.client.AbstractHttpClient.execute(AbstractHttpClient.java:487) 
04-22 16:37:43.443: E/AndroidRuntime(4077):  at org.apache.http.impl.client.AbstractHttpClient.execute(AbstractHttpClient.java:465) 
04-22 16:37:43.443: E/AndroidRuntime(4077):  at com.example.flashcard.MainActivity.retrieveStream(MainActivity.java:63) 
04-22 16:37:43.443: E/AndroidRuntime(4077):  at com.example.flashcard.MainActivity.onCreate(MainActivity.java:37) 
04-22 16:37:43.443: E/AndroidRuntime(4077):  at android.app.Activity.performCreate(Activity.java:5104) 
04-22 16:37:43.443: E/AndroidRuntime(4077):  at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1080) 
04-22 16:37:43.443: E/AndroidRuntime(4077):  at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2144) 
04-22 16:37:43.443: E/AndroidRuntime(4077):  ... 11 more 
04-22 16:37:44.865: I/Process(4077): Sending signal. PID: 4077 SIG: 9 

Answer 1

這裏發生的事情是常有的事，你想你的應用程序的主線程上執行一些長期運行的操作。

這是什麼意思，主線程負責更新用戶界面，強制執行順暢的體驗，如果android檢測到你正在做一些長時間運行的操作將被阻止，它會強制關閉應用程序，讓你知道這是不好的。

有很多替代解決方案，如AsynTask或IntentService。

IntentService是一種服務，當您發送意圖運行：

public class NetworkHandler extends IntentService { 
    @Override 
    protected void onHandleIntent(Intent intent) { 
     //Do your request here 
    } 
} 

要激活IntentService，簡單地做：

Intent intent = new Intent(mContext, NetworkHandler.class); 
startService(intent);