NetworkOnMainThreadException when trying to read a json file - json

Question

Good morning together from Germany!
I am trying to read a little json file from a webserver. When I start the app, I got the error message: android.os.NetworkOnMainThreadException.
The Target should be, that logcat is showing my json content:
{"first":"one","second":"two"}
Web server is working. When I access: 127.0.0.1/index.php, the browser shows me the upper line.
This is my Main:
package com.example.u0017007.jsonclient;
import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
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.app.Activity;
import android.os.Bundle;
import android.util.Log;
public class MainActivity extends Activity {
/** Called when the activity is first created. */
#Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
HttpClient httpClient = new DefaultHttpClient();
HttpGet httpGet = new HttpGet("http://127.0.0.1:80/index.php");
StringBuilder stringBuilder = new StringBuilder();
try {
HttpResponse response = httpClient.execute(httpGet);
int statusCode = response.getStatusLine().getStatusCode();
if (statusCode == 200) {
BufferedReader reader = new BufferedReader(
new InputStreamReader(response.getEntity().getContent()));
String line;
while ((line = reader.readLine()) != null) {
stringBuilder.append(line);
}
Log.i(this.getClass().getSimpleName(), stringBuilder.toString());
} else {
Log.e(this.getClass().getSimpleName(), "Fehler");
}
} catch (ClientProtocolException e) {
Log.e(this.getClass().getSimpleName(), e.getMessage());
} catch (IOException e) {
Log.e(this.getClass().getSimpleName(), e.getMessage());
}
}
}
That is the error log
FATAL EXCEPTION: main
Process: com.example.u0017007.jsonclient, PID: 16115
java.lang.RuntimeException: Unable to start activity ComponentInfo{com.example.u0017007.jsonclient/com.example.u0017007.jsonclient.MainActivity}: android.os.NetworkOnMainThreadException
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2646)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2707)
at android.app.ActivityThread.-wrap12(ActivityThread.java)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1460)
at android.os.Handler.dispatchMessage(Handler.java:102)
at android.os.Looper.loop(Looper.java:154)
at android.app.ActivityThread.main(ActivityThread.java:6077)
at java.lang.reflect.Method.invoke(Native Method)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:866)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:756)
Caused by: android.os.NetworkOnMainThreadException
at android.os.StrictMode$AndroidBlockGuardPolicy.onNetwork(StrictMode.java:1303)
at java.net.AbstractPlainSocketImpl.doConnect(AbstractPlainSocketImpl.java:333)
at java.net.AbstractPlainSocketImpl.connectToAddress(AbstractPlainSocketImpl.java:196)
at java.net.AbstractPlainSocketImpl.connect(AbstractPlainSocketImpl.java:178)
at java.net.SocksSocketImpl.connect(SocksSocketImpl.java:356)
at java.net.Socket.connect(Socket.java:586)
at org.apache.http.conn.scheme.PlainSocketFactory.connectSocket(PlainSocketFactory.java:124)
at org.apache.http.impl.conn.DefaultClientConnectionOperator.openConnection(DefaultClientConnectionOperator.java:149)
at org.apache.http.impl.conn.AbstractPoolEntry.open(AbstractPoolEntry.java:169)
at org.apache.http.impl.conn.AbstractPooledConnAdapter.open(AbstractPooledConnAdapter.java:124)
at org.apache.http.impl.client.DefaultRequestDirector.execute(DefaultRequestDirector.java:366)
at org.apache.http.impl.client.AbstractHttpClient.execute(AbstractHttpClient.java:560)
at org.apache.http.impl.client.AbstractHttpClient.execute(AbstractHttpClient.java:492)
at org.apache.http.impl.client.AbstractHttpClient.execute(AbstractHttpClient.java:470)
at com.example.u0017007.jsonclient.MainActivity.onCreate(MainActivity.java:29)
at android.app.Activity.performCreate(Activity.java:6662)
at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1118)
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2599)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2707) 
at android.app.ActivityThread.-wrap12(ActivityThread.java) 
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1460) 
at android.os.Handler.dispatchMessage(Handler.java:102) 
at android.os.Looper.loop(Looper.java:154) 
at android.app.ActivityThread.main(ActivityThread.java:6077) 
at java.lang.reflect.Method.invoke(Native Method) 
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:866) 
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:756

Answer 1

There are related questions that you can find and make use of them, but to give you the gist of the solutions available - you can solve them using any of the approaches given below:
You can refrain writing any Network related calls in your Main UI thread but use an AsyncTask to achieve what you want to, in it.
You can add the following code into your Main file by adding the following import as well.
The import:
import android.os.StrictMode;
The code:
if (android.os.Build.VERSION.SDK_INT > 9) {
StrictMode.ThreadPolicy policy = new StrictMode.ThreadPolicy.Builder().permitAll().build();
StrictMode.setThreadPolicy(policy);
}