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I recently started coding with Kotlin on Android Studio and was referred to Jsoup's library. I began using their Jsoup.connect function but when I executed this line I was met with these errors

val doc: Document = Jsoup.connect("https://www.google.com").get()

2021-01-19 02:04:25.391 669-669/com.example.myapplication E/AndroidRuntime: FATAL EXCEPTION: main
    Process: com.example.myapplication, PID: 669
    java.lang.RuntimeException: Unable to start activity ComponentInfo{com.example.myapplication/com.example.myapplication.MySignOff}: android.os.NetworkOnMainThreadException
        at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:3449)
        at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:3601)
        at android.app.servertransaction.LaunchActivityItem.execute(LaunchActivityItem.java:85)
        at android.app.servertransaction.TransactionExecutor.executeCallbacks(TransactionExecutor.java:135)
        at android.app.servertransaction.TransactionExecutor.execute(TransactionExecutor.java:95)
        at android.app.ActivityThread$H.handleMessage(ActivityThread.java:2066)
        at android.os.Handler.dispatchMessage(Handler.java:106)
        at android.os.Looper.loop(Looper.java:223)
        at android.app.ActivityThread.main(ActivityThread.java:7656)
        at java.lang.reflect.Method.invoke(Native Method)
        at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:592)
        at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:947)
     Caused by: android.os.NetworkOnMainThreadException
        at android.os.StrictMode$AndroidBlockGuardPolicy.onNetwork(StrictMode.java:1605)
        at java.net.Inet6AddressImpl.lookupHostByName(Inet6AddressImpl.java:115)
        at java.net.Inet6AddressImpl.lookupAllHostAddr(Inet6AddressImpl.java:103)
        at java.net.InetAddress.getAllByName(InetAddress.java:1152)
        at com.android.okhttp.Dns$1.lookup(Dns.java:41)
        at com.android.okhttp.internal.http.RouteSelector.resetNextInetSocketAddress(RouteSelector.java:178)
        at com.android.okhttp.internal.http.RouteSelector.nextProxy(RouteSelector.java:144)
        at com.android.okhttp.internal.http.RouteSelector.next(RouteSelector.java:86)
        at com.android.okhttp.internal.http.StreamAllocation.findConnection(StreamAllocation.java:176)
        at com.android.okhttp.internal.http.StreamAllocation.findHealthyConnection(StreamAllocation.java:128)
        at com.android.okhttp.internal.http.StreamAllocation.newStream(StreamAllocation.java:97)
        at com.android.okhttp.internal.http.HttpEngine.connect(HttpEngine.java:289)
        at com.android.okhttp.internal.http.HttpEngine.sendRequest(HttpEngine.java:232)
        at com.android.okhttp.internal.huc.HttpURLConnectionImpl.execute(HttpURLConnectionImpl.java:465)
        at com.android.okhttp.internal.huc.HttpURLConnectionImpl.connect(HttpURLConnectionImpl.java:131)
        at com.android.okhttp.internal.huc.DelegatingHttpsURLConnection.connect(DelegatingHttpsURLConnection.java:90)
        at com.android.okhttp.internal.huc.HttpsURLConnectionImpl.connect(HttpsURLConnectionImpl.java:30)
        at org.jsoup.helper.HttpConnection$Response.execute(HttpConnection.java:732)
        at org.jsoup.helper.HttpConnection$Response.execute(HttpConnection.java:707)
        at org.jsoup.helper.HttpConnection.execute(HttpConnection.java:297)
        at org.jsoup.helper.HttpConnection.get(HttpConnection.java:286)
        at com.example.myapplication.MySignOff.onCreate(MySignOff.kt:23)
        at android.app.Activity.performCreate(Activity.java:8000)
        at android.app.Activity.performCreate(Activity.java:7984)
        at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1309)
        at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:3422)
        at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:3601) 
        at android.app.servertransaction.LaunchActivityItem.execute(LaunchActivityItem.java:85) 
        at android.app.servertransaction.TransactionExecutor.executeCallbacks(TransactionExecutor.java:135) 
        at android.app.servertransaction.TransactionExecutor.execute(TransactionExecutor.java:95) 
        at android.app.ActivityThread$H.handleMessage(ActivityThread.java:2066) 
        at android.os.Handler.dispatchMessage(Handler.java:106) 
        at android.os.Looper.loop(Looper.java:223) 
        at android.app.ActivityThread.main(ActivityThread.java:7656) 
        at java.lang.reflect.Method.invoke(Native Method) 
        at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:592) 
        at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:947) 

I've looked up what was wrong and cleaned and rebuilt my whole project, but it didn't work. Is there something I am missing? Thanks.

Cheng Poh
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  • 3
  • You are attempting to do network I/O on the main application thread. That is a bad idea. Please use a background thread for network I/O. – CommonsWare Jan 18 '21 at 18:10
  • Hi. I do not really understand what you are saying. What does it mean to use a background thread? Thanks. – Cheng Poh Jan 18 '21 at 18:13
  • The concept of threads should be covered in the book you are reading or the course that you are taking on Android app development. The general concept of using background threads in Android is also covered in [the documentation](https://developer.android.com/guide/background/threading). Threads have been a standard feature of operating systems for decades. – CommonsWare Jan 18 '21 at 18:16
  • Unfortunately not, as I am doing some self-learning. Thanks for pointing me the right way! – Cheng Poh Jan 18 '21 at 18:20

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