I form and send a request to the server:

@Override protected void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.activity_main); TextView tx = (TextView) findViewById(R.id.txt); String url = "https://mail.ru/"; try { HttpURLConnection conn = (HttpURLConnection) new URL(url).openConnection(); conn.setDoInput(true); InputStream is = conn.getInputStream(); BufferedReader br = new BufferedReader( new InputStreamReader(is, "UTF-8")); StringBuilder sb = new StringBuilder(); String bfr_st = null; while ((bfr_st = br.readLine()) != null) { sb.append(bfr_st); } tx.setText(bfr_st); } catch (IOException e) { e.printStackTrace(); } }

In response, I receive:

  main java.lang.RuntimeException: Unable to start activity ComponentInfo{com.example.maksim.myapplication/com.example.maksim.myapplication.MainActivity}: android.os.NetworkOnMainThreadException at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2180) at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2230) at android.app.ActivityThread.access$600(ActivityThread.java:141) at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1234) at android.os.Handler.dispatchMessage(Handler.java:99) at android.os.Looper.loop(Looper.java:137) at android.app.ActivityThread.main(ActivityThread.java:5041) at java.lang.reflect.Method.invokeNative(Native Method) at java.lang.reflect.Method.invoke(Method.java:511) at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:793) at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:560) at dalvik.system.NativeStart.main(Native Method) Caused by: android.os.NetworkOnMainThreadException at android.os.StrictMode$AndroidBlockGuardPolicy.onNetwork(StrictMode.java:1117) at java.net.InetAddress.lookupHostByName(InetAddress.java:385) at java.net.InetAddress.getAllByNameImpl(InetAddress.java:236) at java.net.InetAddress.getAllByName(InetAddress.java:214) at libcore.net.http.HttpConnection.<init>(HttpConnection.java:70) at libcore.net.http.HttpConnection.<init>(HttpConnection.java:50) at libcore.net.http.HttpConnection$Address.connect(HttpConnection.java:340) at libcore.net.http.HttpConnectionPool.get(HttpConnectionPool.java:87) at libcore.net.http.HttpConnection.connect(HttpConnection.java:128) at libcore.net.http.HttpEngine.openSocketConnection(HttpEngine.java:316) at libcore.net.http.HttpsURLConnectionImpl$HttpsEngine.makeSslConnection(HttpsURLConnectionImpl.java:461) at libcore.net.http.HttpsURLConnectionImpl$HttpsEngine.connect(HttpsURLConnectionImpl.java:433) at libcore.net.http.HttpEngine.sendSocketRequest(HttpEngine.java:290) at libcore.net.http.HttpEngine.sendRequest(HttpEngine.java:240) at libcore.net.http.HttpURLConnectionImpl.getResponse(HttpURLConnectionImpl.java:282) at libcore.net.http.HttpURLConnectionImpl.getInputStream(HttpURLConnectionImpl.java:177) at libcore.net.http.HttpsURLConnectionImpl.getInputStream(HttpsURLConnectionImpl.java:271) at com.example.maksim.myapplication.MainActivity.onCreate(MainActivity.java:32) at android.app.Activity.performCreate(Activity.java:5104) at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1080) at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2144) at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2230) at android.app.ActivityThread.access$600(ActivityThread.java:141) at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1234) at android.os.Handler.dispatchMessage(Handler.java:99) at android.os.Looper.loop(Looper.java:137) at android.app.ActivityThread.main(ActivityThread.java:5041) at java.lang.reflect.Method.invokeNative(Native Method) at java.lang.reflect.Method.invoke(Method.java:511) at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:793) at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:560) at dalvik.system.NativeStart.main(Native Method)

    1 answer 1

    Nothing comes back to you, and the NetworkOnMainThreadException exception that you receive says that you are working with the network in the main thread, which you cannot do.

    You can perform your network request, for example, using AsyncTask .

    • one
      Better with the help of ready-made libraries, like okHTTP Retrofit and so on. - pavlofff