NetworkOnMainThreadException When reading from web

问题

When i try to read single line of text from website i get error (NetworkOnMainThreadException). I tryed few thing but nothing works so far. So here is code if anyone could help. In manifest i have permission for internet so thath shouldnt be problem.

import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;

import org.apache.http.HttpEntity;
import org.apache.http.HttpResponse;
import org.apache.http.client.ClientProtocolException;
import org.apache.http.client.HttpClient;
import org.apache.http.client.methods.HttpGet;
import org.apache.http.impl.client.DefaultHttpClient;

import android.os.Bundle;
import android.view.View;
import android.view.View.OnClickListener;
import android.widget.Button;
import android.widget.TextView;

public class Weather extends Activity {

    Button button;
    TextView t;
    String result;

    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState); 

        setContentView(R.layout.weather);

        t = (TextView)findViewById(R.id.textView1);

    }   

    public void myButtonClickHandler (View view) throws ClientProtocolException, IOException {
        result = getContentFromUrl("http://url.com");
        t.setText(result);
    }

    public static String getContentFromUrl(String url) throws ClientProtocolException, IOException {

        HttpClient httpClient = new DefaultHttpClient();
        HttpGet httpGet = new HttpGet(url);
        HttpResponse response;

        response = httpClient.execute(httpGet);
        HttpEntity entity = response.getEntity();

        if(entity != null) {

            InputStream inStream = entity.getContent();

            String result = Weather.convertStreamToString(inStream);
            inStream.close();

            return result;
        }

        return null;

    }

    private static String convertStreamToString(InputStream is) {
        BufferedReader reader = new BufferedReader(new InputStreamReader(is));
        StringBuilder sb = new StringBuilder();

        String line = null;

        try {
            while ((line = reader.readLine()) != null) {
                sb.append(line + "\n");
            }
        } catch (IOException e) {
            e.printStackTrace();
        } finally {
            try {
                is.close();
            } catch (IOException e) {
                e.printStackTrace();
            }
        }
        return sb.toString();
    }
}

回答1:

don't use network activities in main thread.This exception only thrown for applications targeting the Honeycomb SDK or higher. perform all the network related task in separate thread ( either use handler looper or runOnUiThread) . your problem will get solved.

回答2:

Either you can move it to background thread or if you just want to eliminate this error just add this in your onCreate() :

 StrictMode.ThreadPolicy policy = new StrictMode.ThreadPolicy.Builder().permitAll().build();

    StrictMode.setThreadPolicy(policy);

Do not forget to add internet permission in manifest:

<uses-permission android:name="android.permission.INTERNET"/>

回答3:

You might want to do all your downloading using a AsyncTask, http://developer.android.com/reference/android/os/AsyncTask.html

or if your on api 11+ a AsyncTaskLoader, http://developer.android.com/reference/android/content/AsyncTaskLoader.html

来源：https://stackoverflow.com/questions/9442527/networkonmainthreadexception-when-reading-from-web

标签

android

networkonmainthread