[Kotlin] 에러 해결: android.os.NetworkOnMainThreadException at android.os.StrictMode$AndroidBlockGuardPolicy.onNetwork(StrictMode.java:1668) at java.net.Inet6AddressImpl.lookupHostByName(Inet6AddressImpl.java:115)

문제/에러

2022-05-08 18:49:17.767 5797-5797/com.example.myapplication_kotlin2_https D/AndroidRuntime: Shutting down VM 2022-05-08 18:49:17.769 5797-5797/com.example.myapplication_kotlin2_https E/AndroidRuntime: FATAL EXCEPTION: main     Process: com.example.myapplication_kotlin2_https, PID: 5797     android.os.NetworkOnMainThreadException         at android.os.StrictMode$AndroidBlockGuardPolicy.onNetwork(StrictMode.java:1668)         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$1.lookup(Dns.java:41)         at com.android.okhttp.internal.http.RouteSelector.resetNextInetSocketAddress(RouteSelector.java:178)         at com.android.okhttp.internal.http.RouteSelector.nextProxy(RouteSelector.java:144)         at com.android.okhttp.internal.http.RouteSelector.next(RouteSelector.java:86)         at com.android.okhttp.internal.http.StreamAllocation.findConnection(StreamAllocation.java:176)         at com.android.okhttp.internal.http.StreamAllocation.findHealthyConnection(StreamAllocation.java:128)         at com.android.okhttp.internal.http.StreamAllocation.newStream(StreamAllocation.java:97)         at com.android.okhttp.internal.http.HttpEngine.connect(HttpEngine.java:289)         at com.android.okhttp.internal.http.HttpEngine.sendRequest(HttpEngine.java:232)         at com.android.okhttp.internal.huc.HttpURLConnectionImpl.execute(HttpURLConnectionImpl.java:465)         at com.android.okhttp.internal.huc.HttpURLConnectionImpl.getResponse(HttpURLConnectionImpl.java:411)         at com.android.okhttp.internal.huc.HttpURLConnectionImpl.getInputStream(HttpURLConnectionImpl.java:248)         at com.example.myapplication_kotlin2_https.MainActivity.onCreate$lambda-3(MainActivity.kt:41)         at com.example.myapplication_kotlin2_https.MainActivity.$r8$lambda$gTDMxezOd-x6BAT1hD8fuyv1HOo(Unknown Source:0)         at com.example.myapplication_kotlin2_https.MainActivity$$ExternalSyntheticLambda1.onClick(Unknown Source:2)         at android.view.View.performClick(View.java:7792)         at android.widget.TextView.performClick(TextView.java:16112)         at com.google.android.material.button.MaterialButton.performClick(MaterialButton.java:1194)         at android.view.View.performClickInternal(View.java:7769)         at android.view.View.access$3800(View.java:910)         at android.view.View$PerformClick.run(View.java:30218)         at android.os.Handler.handleCallback(Handler.java:938)         at android.os.Handler.dispatchMessage(Handler.java:99)         at android.os.Looper.loopOnce(Looper.java:226)         at android.os.Looper.loop(Looper.java:313)         at android.app.ActivityThread.main(ActivityThread.java:8663)         at java.lang.reflect.Method.invoke(Native Method)         at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:567)         at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:1135) 2022-05-08 18:49:17.806 5797-5797/com.example.myapplication_kotlin2_https I/Process: Sending signal. PID: 5797 SIG: 9

 

원인

안드로이드에서 Policy에 의해, block되어 에러 발생.

 

 

해결방법

아래의 소스코드를 onCreate쪽 메서드에 추가한다.

        if (Build.VERSION.SDK_INT > 9) {
            val policy = StrictMode.ThreadPolicy.Builder().permitAll().build()
            StrictMode.setThreadPolicy(policy)
        }

 

예를 들어, 아래와 같다.

...
    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        setContentView(binding.root)
        if (Build.VERSION.SDK_INT > 9) {
            val policy = StrictMode.ThreadPolicy.Builder().permitAll().build()
            StrictMode.setThreadPolicy(policy)
        }
...