Android basic example with URL

Question

I have basic android example and I am trying to extend it with following code to fetch content of website:

    try {
        URL u = new URL("http://seznam.cz");
        InputStream is = u.openStream();
        BufferedReader br = new BufferedReader(new
                InputStreamReader(is));
        String s = "";

    } catch (MalformedURLException murle) { murle.printStackTrace();
    } catch (IOException ioe) { ioe.printStackTrace();
    }

So the current code is (my code in basic example that works):

public class MainActivity extends AppCompatActivity {
    public final static String EXTRA_MESSAGE = "com.example.myfirstapp.MESSAGE";
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
    }

    /** Called when the user clicks the Send button */
    public void sendMessage(View view) {
        Intent intent = new Intent(this, DisplayMessageActivity.class);
        EditText editText = (EditText) findViewById(R.id.edit_message);
        String message = editText.getText().toString();
        intent.putExtra(EXTRA_MESSAGE, message);
        startActivity(intent);
        try {
            URL u = new URL("http://seznam.cz");
            InputStream is = u.openStream();
            BufferedReader br = new BufferedReader(new
                    InputStreamReader(is));
            String s = "";

        } catch (MalformedURLException murle) { murle.printStackTrace();
        } catch (IOException ioe) { ioe.printStackTrace();
    }
    }
}

And the xml file:

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout
    xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:orientation="horizontal">
    <EditText android:id="@+id/edit_message"
        android:layout_weight="1"
        android:layout_width="0dp"
        android:layout_height="wrap_content"
        android:hint="@string/edit_message" />
    <Button
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="@string/button_send"
        android:onClick="sendMessage" />
</LinearLayout>

When I run it, I am getting following error:

E/AndroidRuntime: FATAL EXCEPTION: main
              Process: com.example.lucinka.myfirstapp, PID: 2562
              java.lang.IllegalStateException: Could not execute method for android:onClick
                  at android.support.v7.app.AppCompatViewInflater$DeclaredOnClickListener.onClick(AppCompatViewInflater.java:293)
                  at android.view.View.performClick(View.java:5610)
                  at android.view.View$PerformClick.run(View.java:22265)
                  at android.os.Handler.handleCallback(Handler.java:751)
                  at android.os.Handler.dispatchMessage(Handler.java:95)
                  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$MethodAndArgsCaller.run(ZygoteInit.java:865)
                  at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:755)
               Caused by: java.lang.reflect.InvocationTargetException
                  at java.lang.reflect.Method.invoke(Native Method)
                  at android.support.v7.app.AppCompatViewInflater$DeclaredOnClickListener.onClick(AppCompatViewInflater.java:288)
                  at android.view.View.performClick(View.java:5610) 
                  at android.view.View$PerformClick.run(View.java:22265) 
                  at android.os.Handler.handleCallback(Handler.java:751) 
                  at android.os.Handler.dispatchMessage(Handler.java:95) 
                  at android.os.Looper.loop(Looper.java:154) 
                  at android.app.ActivityThread.main(ActivityThread.java:6077) 
                  at java.lang.reflect.Method.invoke(Native Method) 
                  at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:865) 
                  at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:755) 
               Caused by: android.os.NetworkOnMainThreadException
                  at android.os.StrictMode$AndroidBlockGuardPolicy.onNetwork(StrictMode.java:1303)
                  at java.net.Inet6AddressImpl.lookupHostByName(Inet6AddressImpl.java:86)
                  at java.net.Inet6AddressImpl.lookupAllHostAddr(Inet6AddressImpl.java:74)
                  at java.net.InetAddress.getAllByName(InetAddress.java:752)
                  at com.android.okhttp.internal.Network$1.resolveInetAddresses(Network.java:29)
                  at com.android.okhttp.internal.http.RouteSelector.resetNextInetSocketAddress(RouteSelector.java:187)
                  at com.android.okhttp.internal.http.RouteSelector.nextProxy(RouteSelector.java:156)
                  at com.android.okhttp.internal.http.RouteSelector.next(RouteSelector.java:98)
                  at com.android.okhttp.internal.http.HttpEngine.createNextConnection(HttpEngine.java:345)
                  at com.android.okhttp.internal.http.HttpEngine.connect(HttpEngine.java:328)
                  at com.android.okhttp.internal.http.HttpEngine.sendRequest(HttpEngine.java:246)
                  at com.android.okhttp.internal.huc.HttpURLConnectionImpl.execute(HttpURLConnectionImpl.java:457)
                  at com.android.okhttp.internal.huc.HttpURLConnectionImpl.getResponse(HttpURLConnectionImpl.java:405)
                  at com.android.okhttp.internal.huc.HttpURLConnectionImpl.getInputStream(HttpURLConnectionImpl.java:243)
                  at java.net.URL.openStream(URL.java:1057)
                  at com.example.lucinka.myfirstapp.MainActivity.sendMessage(MainActivity.java:37)
                  at java.lang.reflect.Method.invoke(Native Method) 
                  at android.support.v7.app.AppCompatViewInflater$DeclaredOnClickListener.onClick(AppCompatViewInflater.java:288) 
                  at android.view.View.performClick(View.java:5610) 
                  at android.view.View$PerformClick.run(View.java:22265) 
                  at android.os.Handler.handleCallback(Handler.java:751) 
                  at android.os.Handler.dispatchMessage(Handler.java:95) 
                  at android.os.Looper.loop(Looper.java:154) 
                  at android.app.ActivityThread.main(ActivityThread.java:6077) 
                  at java.lang.reflect.Method.invoke(Native Method) 
                  at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:865) 
                  at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:755)

What does it mean? Where is the error? Thank you for any hint.

`Caused by: android.os.NetworkOnMainThreadException`. Well Google for it! You are number #### who happens this. — greenapps, Mar 06 '17 at 11:42

score 0 · Answer 1 · answered Mar 06 '17 at 11:44

try {
            URL u = new URL("http://seznam.cz");
            InputStream is = u.openStream();
            BufferedReader br = new BufferedReader(new
                    InputStreamReader(is));
            String s = "";

        } catch (MalformedURLException murle) { murle.printStackTrace();
        } catch (IOException ioe) { ioe.printStackTrace();
    }

For above line of code you have to required Async Task Cause after android 3.0 android not allow any network operation on UI thread so you have to call on Async task

score 0 · Answer 2 · answered Mar 06 '17 at 11:45

0

The exception android.os.NetworkOnMainThreadException is relevant. You should use a worker thread to perform network operations.

Thread t = new Thread(new Runnable() { public void run() { 
  // your code goes here... 
}});
t.start();

answered Mar 06 '17 at 11:45

Daniel Stancu

52
2
8

Android basic example with URL

2 Answers2