NetWork On主线程异常

Question

嗨，我尝试使用以下方法检查网络连接和Internet存在

check = new 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;
}

}

注意 ：

但这将返回NetworkOnMainThread异常，如下所示。任何人都建议我犯了什么错误.......

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。 所以它引发了异常。 您需要在AsyncTask或其他Thread中执行此操作。

Answer 2

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

如果您尝试在主UI线程中发出网络请求，则抛出NetworkOnMainThreadException 。 所以所有网络相关的操作都应该在后台线程上完成。

AsyncTask旨在成为Thread和Handler的辅助类，并不构成通用的线程框架。 理想情况下，AsyncTasks应该用于短操作（最多几秒钟。）如果需要保持线程长时间运行，强烈建议您使用java.util.concurrent pacakge提供的各种API，例如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
          } 

}

asynctask的替代品是Robospice。 可以制作多个香料请求。 通知ui线程。 https://github.com/octo-online/robospice

检查Netowrk连接。

在你的活动中

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;
        }

    }
}
}