making a Get request from android throws exception?

Question

I'm trying to access a Web API from my android app, I have the Url and it's supposed to return some XML file. I looked online and found some code but none of them works, I can access the url from VM browser but not application, and I set all necessary permissions for accessing internet.

basic code:

public class MainActivity extends Activity {
    private static final String URL = "http://192.168.15.12/api/values/2";
    protected static final String TAG = null;
    HttpResponse response3 = null;
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        Button btn = (Button) findViewById(R.id.button1);

        btn.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View arg0) {
                Log.i(TAG, "2");
                try {
                    Log.i(TAG, "7");
                    Log.i(TAG, "9");
                    HttpClient client = new DefaultHttpClient();
                    HttpGet request = new HttpGet();
                    request.setURI(new URI(URL));
                    response3 = client.execute(request);
                    Log.i(TAG, "10");

                } catch (UnsupportedEncodingException e) {
                    e.printStackTrace();
                } catch (ClientProtocolException e) {
                    e.printStackTrace();
                } catch (IOException e) {
                    e.printStackTrace();
                } catch (URISyntaxException e) {
                    // TODO Auto-generated catch block
                    e.printStackTrace();
                } 
                // return XML
                Log.i(TAG, "00");

            }
        });
    }
    @Override
    public boolean onCreateOptionsMenu(Menu menu) {
        // Inflate the menu; this adds items to the action bar if it is present.
        getMenuInflater().inflate(R.menu.main, menu);
        return true;
    }

}

exception:

05-21 14:34:51.462: I/(789): 2
05-21 14:34:51.462: I/(789): 7
05-21 14:34:51.462: I/(789): 9
05-21 14:34:51.552: D/AndroidRuntime(789): Shutting down VM
05-21 14:34:51.552: W/dalvikvm(789): threadid=1: thread exiting with uncaught exception (group=0x40a71930)
05-21 14:34:51.613: E/AndroidRuntime(789): FATAL EXCEPTION: main
05-21 14:34:51.613: E/AndroidRuntime(789): android.os.NetworkOnMainThreadException
05-21 14:34:51.613: E/AndroidRuntime(789):  at android.os.StrictMode$AndroidBlockGuardPolicy.onNetwork(StrictMode.java:1117)
05-21 14:34:51.613: E/AndroidRuntime(789):  at libcore.io.BlockGuardOs.connect(BlockGuardOs.java:84)
05-21 14:34:51.613: E/AndroidRuntime(789):  at libcore.io.IoBridge.connectErrno(IoBridge.java:127)
05-21 14:34:51.613: E/AndroidRuntime(789):  at libcore.io.IoBridge.connect(IoBridge.java:112)
05-21 14:34:51.613: E/AndroidRuntime(789):  at java.net.PlainSocketImpl.connect(PlainSocketImpl.java:192)
05-21 14:34:51.613: E/AndroidRuntime(789):  at java.net.PlainSocketImpl.connect(PlainSocketImpl.java:459)
05-21 14:34:51.613: E/AndroidRuntime(789):  at java.net.Socket.connect(Socket.java:842)
05-21 14:34:51.613: E/AndroidRuntime(789):  at org.apache.http.conn.scheme.PlainSocketFactory.connectSocket(PlainSocketFactory.java:119)
05-21 14:34:51.613: E/AndroidRuntime(789):  at org.apache.http.impl.conn.DefaultClientConnectionOperator.openConnection(DefaultClientConnectionOperator.java:144)
05-21 14:34:51.613: E/AndroidRuntime(789):  at org.apache.http.impl.conn.AbstractPoolEntry.open(AbstractPoolEntry.java:164)
05-21 14:34:51.613: E/AndroidRuntime(789):  at org.apache.http.impl.conn.AbstractPooledConnAdapter.open(AbstractPooledConnAdapter.java:119)
05-21 14:34:51.613: E/AndroidRuntime(789):  at org.apache.http.impl.client.DefaultRequestDirector.execute(DefaultRequestDirector.java:360)
05-21 14:34:51.613: E/AndroidRuntime(789):  at org.apache.http.impl.client.AbstractHttpClient.execute(AbstractHttpClient.java:555)
05-21 14:34:51.613: E/AndroidRuntime(789):  at org.apache.http.impl.client.AbstractHttpClient.execute(AbstractHttpClient.java:487)
05-21 14:34:51.613: E/AndroidRuntime(789):  at org.apache.http.impl.client.AbstractHttpClient.execute(AbstractHttpClient.java:465)
05-21 14:34:51.613: E/AndroidRuntime(789):  at com.example.sms4.MainActivity$1.onClick(MainActivity.java:70)
05-21 14:34:51.613: E/AndroidRuntime(789):  at android.view.View.performClick(View.java:4204)
05-21 14:34:51.613: E/AndroidRuntime(789):  at android.view.View$PerformClick.run(View.java:17355)
05-21 14:34:51.613: E/AndroidRuntime(789):  at android.os.Handler.handleCallback(Handler.java:725)
05-21 14:34:51.613: E/AndroidRuntime(789):  at android.os.Handler.dispatchMessage(Handler.java:92)
05-21 14:34:51.613: E/AndroidRuntime(789):  at android.os.Looper.loop(Looper.java:137)
05-21 14:34:51.613: E/AndroidRuntime(789):  at android.app.ActivityThread.main(ActivityThread.java:5041)
05-21 14:34:51.613: E/AndroidRuntime(789):  at java.lang.reflect.Method.invokeNative(Native Method)
05-21 14:34:51.613: E/AndroidRuntime(789):  at java.lang.reflect.Method.invoke(Method.java:511)
05-21 14:34:51.613: E/AndroidRuntime(789):  at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:793)
05-21 14:34:51.613: E/AndroidRuntime(789):  at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:560)
05-21 14:34:51.613: E/AndroidRuntime(789):  at dalvik.system.NativeStart.main(Native Method)

Answer 1

You are performin an HTTP request from the UI Thrad. That's is forbidden since Android 3.0+. Perform the request with an AsyncTask. Here a reference. All the blocking code has to be executed in a different thread. All the Http logic has to be executed inside the doInBackground method

Answer 2

You should execute network-related operations on a separate thread using AsyncTask and not on the main (UI) thread.