calling localhost from android emulator

Question

SORRY BECAUSE IT'S BEEN ASKED MANY TIMES but really I can't find an answer, I'm running a web service on my local machine that runs at localhost:8080 and I want to call the service from an app running in the Android emulator, but it keeps crashing with this error message (Unfortunately app has stopped).

here's my code

public void HttpRequest(View view)throws Exception{
    BufferedReader reader = null;
    StringBuilder stringBuilder;
    URL url = new URL("http://10.0.2.2:8080");
    HttpURLConnection urlConnection = (HttpURLConnection) url.openConnection();
    reader = new BufferedReader(new InputStreamReader(urlConnection.getInputStream()));
    stringBuilder = new StringBuilder();
    String line = null;
    while ((line = reader.readLine()) != null)
    {
        stringBuilder.append(line + "\n");
    }
}

and here's the LogCat

06-22 08:57:11.733 2370-2370/com.example.ssalameh.myfirstapp I/art: Not late-enabling -Xcheck:jni (already on)
    06-22 08:57:11.785 2370-2370/com.example.ssalameh.myfirstapp W/System: ClassLoader referenced unknown path: /data/app/com.example.ssalameh.myfirstapp-3/lib/x86
    06-22 08:57:14.699 2370-2370/com.example.ssalameh.myfirstapp W/System: ClassLoader referenced unknown path: /data/app/com.example.ssalameh.myfirstapp-3/lib/x86
    06-22 08:57:15.294 2370-2380/com.example.ssalameh.myfirstapp W/art: Suspending all threads took: 42.728ms
    06-22 08:57:15.458 2370-2370/com.example.ssalameh.myfirstapp W/art: Before Android 4.1, method android.graphics.PorterDuffColorFilter android.support.graphics.drawable.VectorDrawableCompat.updateTintFilter(android.graphics.PorterDuffColorFilter, android.content.res.ColorStateList, android.graphics.PorterDuff$Mode) would have incorrectly overridden the package-private method in android.graphics.drawable.Drawable
    06-22 08:57:15.721 2370-2376/com.example.ssalameh.myfirstapp W/art: Suspending all threads took: 49.366ms
    06-22 08:57:15.909 2370-2526/com.example.ssalameh.myfirstapp D/OpenGLRenderer: Use EGL_SWAP_BEHAVIOR_PRESERVED: true

[ 06-22 08:57:15.912  2370: 2370 D/         ]
HostConnection::get() New Host Connection established 0xaff08410, tid 2370
06-22 08:57:15.985 2370-2526/com.example.ssalameh.myfirstapp I/OpenGLRenderer: Initialized EGL, version 1.4
06-22 08:57:16.320 2370-2370/com.example.ssalameh.myfirstapp D/item: Food
06-22 08:57:17.597 2370-2370/com.example.ssalameh.myfirstapp D/AndroidRuntime: Shutting down VM
06-22 08:57:17.619 2370-2370/com.example.ssalameh.myfirstapp E/AndroidRuntime: FATAL EXCEPTION: main
Process: com.example.ssalameh.myfirstapp, PID: 2370
java.lang.IllegalStateException: Could not execute method for android:onClick
at android.support.v7.app.AppCompatViewInflater$DeclaredOnClickListener.onClick(AppCompatViewInflater.java:293)
at android.view.View.performClick(View.java:5198)
at android.view.View$PerformClick.run(View.java:21147)
at android.os.Handler.handleCallback(Handler.java:739)
at android.os.Handler.dispatchMessage(Handler.java:95)
at android.os.Looper.loop(Looper.java:148)
at android.app.ActivityThread.main(ActivityThread.java:5417)
at java.lang.reflect.Method.invoke(Native Method)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:726)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:616)
Caused by: java.lang.reflect.InvocationTargetException
at java.lang.reflect.Method.invoke(Native Method)
at android.support.v7.app.AppCompatViewInflater$DeclaredOnClickListener.onClick(AppCompatViewInflater.java:288)
at android.view.View.performClick(View.java:5198) 
at android.view.View$PerformClick.run(View.java:21147) 
at android.os.Handler.handleCallback(Handler.java:739) 
at android.os.Handler.dispatchMessage(Handler.java:95) 
at android.os.Looper.loop(Looper.java:148) 
at android.app.ActivityThread.main(ActivityThread.java:5417) 
at java.lang.reflect.Method.invoke(Native Method) 
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:726) 
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:616) 
Caused by: android.os.NetworkOnMainThreadException
at android.os.StrictMode$AndroidBlockGuardPolicy.onNetwork(StrictMode.java:1273)
at libcore.io.BlockGuardOs.connect(BlockGuardOs.java:110)
at libcore.io.IoBridge.connectErrno(IoBridge.java:137)
at libcore.io.IoBridge.connect(IoBridge.java:122)
at java.net.PlainSocketImpl.connect(PlainSocketImpl.java:183)
at java.net.PlainSocketImpl.connect(PlainSocketImpl.java:452)
at java.net.Socket.connect(Socket.java:884)
at com.android.okhttp.internal.Platform.connectSocket(Platform.java:117)
at com.android.okhttp.internal.http.SocketConnector.connectRawSocket(SocketConnector.java:160)
at com.android.okhttp.internal.http.SocketConnector.connectCleartext(SocketConnector.java:67)
at com.android.okhttp.Connection.connect(Connection.java:152)
at com.android.okhttp.Connection.connectAndSetOwner(Connection.java:185)
at com.android.okhttp.OkHttpClient$1.connectAndSetOwner(OkHttpClient.java:128)
at com.android.okhttp.internal.http.HttpEngine.nextConnection(HttpEngine.java:341)
at com.android.okhttp.internal.http.HttpEngine.connect(HttpEngine.java:330)
at com.android.okhttp.internal.http.HttpEngine.sendRequest(HttpEngine.java:248)
at com.android.okhttp.internal.huc.HttpURLConnectionImpl.execute(HttpURLConnectionImpl.java:433)
at com.android.okhttp.internal.huc.HttpURLConnectionImpl.getResponse(HttpURLConnectionImpl.java:384)
at com.android.okhttp.internal.huc.HttpURLConnectionImpl.getInputStream(HttpURLConnectionImpl.java:231)
at com.example.ssalameh.myfirstapp.MainActivity.HttpRequest(MainActivity.java:55)
at java.lang.reflect.Method.invoke(Native Method) 
at android.support.v7.app.AppCompatViewInflater$DeclaredOnClickListener.onClick(AppCompatViewInflater.java:288) 
at android.view.View.performClick(View.java:5198) 
at android.view.View$PerformClick.run(View.java:21147) 
at android.os.Handler.handleCallback(Handler.java:739) 
at android.os.Handler.dispatchMessage(Handler.java:95) 
at android.os.Looper.loop(Looper.java:148) 
at android.app.ActivityThread.main(ActivityThread.java:5417) 
at java.lang.reflect.Method.invoke(Native Method) 
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:726) 
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:616) 

can anybody please help? thanks in return.