网络上的主线程异常

Question

嗨，尝试通过使用下面的方法来检查网络连接及因特网本

校验=新ConnectionDetector（getApplicationContext（））;

conn = check.isConnectingToInternet（）;

public class ConnectionDetector { 

private Context _context; 

public ConnectionDetector(Context context){ 
    this._context = context; 
} 

/** 
* Checking for all possible internet providers 
* **/ 
/*public boolean isConnectingToInternet(){ 
    ConnectivityManager connectivity = (ConnectivityManager) _context.getSystemService(Context.CONNECTIVITY_SERVICE); 
     if (connectivity != null) 
     { 
      NetworkInfo[] info = connectivity.getAllNetworkInfo(); 
      if (info != null) 
       for (int i = 0; i < info.length; i++) 
        if (info[i].getState() == NetworkInfo.State.CONNECTED) 
        { 
         return true; 
        } 

     } 
     return false; 
}*/ 

public boolean isConnectingToInternet(){ 
    try{ 
     ConnectivityManager cm = (ConnectivityManager)_context.getSystemService 
                (Context.CONNECTIVITY_SERVICE); 
     NetworkInfo netInfo = cm.getActiveNetworkInfo(); 
     Log.d("NetInfo", String.valueOf(netInfo)); 
     if (netInfo != null && netInfo.isConnected()) 
     { 
      //Network is available but check if we can get access from the network. 
      URL url = new URL("http://www.Google.com/"); 
      HttpURLConnection urlc = (HttpURLConnection) url.openConnection(); 
      urlc.setRequestProperty("Connection", "close"); 
      urlc.setConnectTimeout(2000); // Timeout 2 seconds. 
      urlc.connect(); 
      Log.d("NetInfo Response Code", String.valueOf(urlc.getResponseCode())); 
      // Toast.makeText(getApplicationContext(), String.valueOf(urlc.getResponseCode()), Toast.LENGTH_LONG).show(); 
      if (urlc.getResponseCode() == 200) //Successful response. 
      { 
       return true; 
      } 
      else 
      { 
       Log.d("NO INTERNET", "NO INTERNET"); 
       return false; 
      } 
     } 
    } 
    catch(Exception e) 
    { 
     e.printStackTrace(); 
    } 
    return false; 
} 

}

注：

但是，这将返回NetworkOnMainThread异常喜欢follows.kindly任何一个建议我我做了什么错误.......

03-27 12:53:35.617: W/System.err(1095): android.os.NetworkOnMainThreadException 
03-27 12:53:35.627: W/System.err(1095):  at android.os.StrictMode$AndroidBlockGuardPolicy.onNetwork(StrictMode.java:1084) 
03-27 12:53:35.637: W/System.err(1095):  at java.net.InetAddress.lookupHostByName(InetAddress.java:391) 
03-27 12:53:35.637: W/System.err(1095):  at java.net.InetAddress.getAllByNameImpl(InetAddress.java:242) 
03-27 12:53:35.647: W/System.err(1095):  at java.net.InetAddress.getAllByName(InetAddress.java:220) 
03-27 12:53:35.647: W/System.err(1095):  at libcore.net.http.HttpConnection.<init>(HttpConnection.java:71) 
03-27 12:53:35.657: W/System.err(1095):  at libcore.net.http.HttpConnection.<init>(HttpConnection.java:50) 
03-27 12:53:35.668: W/System.err(1095):  at libcore.net.http.HttpConnection$Address.connect(HttpConnection.java:351) 
03-27 12:53:35.668: W/System.err(1095):  at libcore.net.http.HttpConnectionPool.get(HttpConnectionPool.java:86) 
03-27 12:53:35.677: W/System.err(1095):  at libcore.net.http.HttpConnection.connect(HttpConnection.java:128) 
03-27 12:53:35.687: W/System.err(1095):  at libcore.net.http.HttpEngine.openSocketConnection(HttpEngine.java:308) 
03-27 12:53:35.699: W/System.err(1095):  at libcore.net.http.HttpEngine.connect(HttpEngine.java:303) 
03-27 12:53:35.699: W/System.err(1095):  at libcore.net.http.HttpEngine.sendSocketRequest(HttpEngine.java:282) 
03-27 12:53:35.707: W/System.err(1095):  at libcore.net.http.HttpEngine.sendRequest(HttpEngine.java:232) 
03-27 12:53:35.718: W/System.err(1095):  at libcore.net.http.HttpURLConnectionImpl.connect(HttpURLConnectionImpl.java:80) 
03-27 12:53:35.727: W/System.err(1095):  at com.slet.routemytrips.beta.ConnectionDetector.isConnectingToInternet(ConnectionDetector.java:50) 
03-27 12:53:35.727: W/System.err(1095):  at com.slet.routemytrips.beta.Disclaimer$1.onClick(Disclaimer.java:178) 
03-27 12:53:35.738: W/System.err(1095):  at android.view.View.performClick(View.java:3480) 
03-27 12:53:35.738: W/System.err(1095):  at android.view.View$PerformClick.run(View.java:13983) 
03-27 12:53:35.748: W/System.err(1095):  at android.os.Handler.handleCallback(Handler.java:605) 
03-27 12:53:35.757: W/System.err(1095):  at android.os.Handler.dispatchMessage(Handler.java:92) 
03-27 12:53:35.757: W/System.err(1095):  at android.os.Looper.loop(Looper.java:137) 
03-27 12:53:35.767: W/System.err(1095):  at android.app.ActivityThread.main(ActivityThread.java:4340) 
03-27 12:53:35.777: W/System.err(1095):  at java.lang.reflect.Method.invokeNative(Native Method) 
03-27 12:53:35.777: W/System.err(1095):  at java.lang.reflect.Method.invoke(Method.java:511) 
03-27 12:53:35.787: W/System.err(1095):  at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:784) 
03-27 12:53:35.797: W/System.err(1095):  at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:551) 
03-27 12:53:35.807: W/System.err(1095):  at dalvik.system.NativeStart.main(Native Method) 
03-27 12:57:05.237: D/dalvikvm(90): GC_CONCURRENT freed 666K, 10% free 12624K/14023K, paused 6ms+10ms 

Answer 1

您无法在主线程上发出HTTP请求，这会导致UI冻结。所以它会抛出异常。您需要在AsyncTask或其他线程中执行此操作。如果试图使主UI线程的网络请求

Answer 2

http://developer.android.com/reference/android/os/NetworkOnMainThreadException.html

NetworkOnMainThreadException被抛出。所以所有与网络相关的操作都应该在后台线程上完成。

AsyncTask被设计成围绕线程和处理程序的助手类，并不构成通用线程框架。 AsyncTasks理想情况下应该用于短操作（最多几秒钟）。如果您需要让线程长时间运行，强烈建议您使用java.util.concurrent pacakge提供的各种API如Executor，ThreadPoolExecutor和FutureTask。

http://developer.android.com/reference/android/os/AsyncTask.html

class TheTask extends AsyncTask<Void,Void,Void> 
{ 
      protected void onPreExecute() 
      {   super.onPreExecute(); 
        //display progressdialog. 
      } 

      protected void doInBackground(Void ...params) 
      { 
       //http request. do not update ui here 

       return null; 
      } 

      protected void onPostExecute(Void result) 
      {  
        super.onPostExecute(result); 
        //dismiss progressdialog. 
        //update ui 
      } 

} 

一种替代的AsyncTask是Robospice。可以做出多个香料请求。在ui线程上通知。 https://github.com/octo-online/robospice

检查Netowrk连接。

在你的活动

public class MainActivity extends Activity { 

@Override 
public void onCreate(Bundle savedInstanceState) { 
    super.onCreate(savedInstanceState); 
    setContentView(R.layout.main); 
    if(CheckNetwork.isInternetAvailable(MainActivity.this)) 
    { 
     //call asyntask and make http request. 
    } 
} 

CheckNetwork类

public class CheckNetwork { 

private static final String TAG = CheckNetwork.class.getSimpleName(); 

public static boolean isInternetAvailable(Context context) 
{ 
    NetworkInfo info = (NetworkInfo) ((ConnectivityManager) 
    context.getSystemService(Context.CONNECTIVITY_SERVICE)).getActiveNetworkInfo(); 

    if (info == null) 
    { 
     Log.d(TAG,"no internet connection"); 
     return false; 
    } 
    else 
    { 
     if(info.isConnected()) 
     { 
      Log.d(TAG," internet connection available..."); 
      return true; 
     } 
     else 
     { 
      Log.d(TAG," internet connection"); 
      return true; 
     } 

    } 
} 
}