Caused by: android.os.NetworkOnMainThreadException

问题：

Caused by: android.os.NetworkOnMainThreadException at android.os.StrictMode$AndroidBlockGuardPolicy.onNetwork(StrictMode.java:1448) at java.net.Inet6AddressImpl.lookupHostByName(Inet6AddressImpl.java:102) at java.net.Inet6AddressImpl.lookupAllHostAddr(Inet6AddressImpl.java:90) at java.net.InetAddress.getAllByName(InetAddress.java:787) at com.android.okhttp.Dns$1.lookup(Dns.java:39) at com.android.okhttp.internal.http.RouteSelector.resetNextInetSocketAddress(RouteSelector.java:175) at com.android.okhttp.internal.http.RouteSelector.nextProxy(RouteSelector.java:141) at com.android.okhttp.internal.http.RouteSelector.next(RouteSelector.java:83) at com.android.okhttp.internal.http.StreamAllocation.findConnection(StreamAllocation.java:174) at com.android.okhttp.internal.http.StreamAllocation.findHealthyConnection(StreamAllocation.java:126) at com.android.okhttp.internal.http.StreamAllocation.newStream(StreamAllocation.java:95) at com.android.okhttp.internal.http.HttpEngine.connect(HttpEngine.java:281) at com.android.okhttp.internal.http.HttpEngine.sendRequest(HttpEngine.java:224) at com.android.okhttp.internal.huc.HttpURLConnectionImpl.execute(HttpURLConnectionImpl.java:461) at com.android.okhttp.internal.huc.HttpURLConnectionImpl.getResponse(HttpURLConnectionImpl.java:407) at com.android.okhttp.internal.huc.HttpURLConnectionImpl.getInputStream(HttpURLConnectionImpl.java:244) at java.net.URL.openStream(URL.java:1058) at kotlin.io.TextStreamsKt.readBytes(ReadWrite.kt:144) at com.easy.kotlin.bean.MovieContent.<init>(MovieContent.kt:18) at com.easy.kotlin.bean.MovieContent.<clinit>(MovieContent.kt:10) at com.easy.kotlin.MovieListActivity.setupRecyclerView(MovieListActivity.kt:37) at com.easy.kotlin.MovieListActivity.onCreate(MovieListActivity.kt:33) at android.app.Activity.performCreate(Activity.java:6975) at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1213) at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2770) at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2892) at android.app.ActivityThread.-wrap11(Unknown Source:0) at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1593) at android.os.Handler.dispatchMessage(Handler.java:105) at android.os.Looper.loop(Looper.java:164) at android.app.ActivityThread.main(ActivityThread.java:6541) at java.lang.reflect.Method.invoke(Native Method) at com.android.internal.os.Zygote$MethodAndArgsCaller.run(Zygote.java:240) at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:767)

主线程不能访问网络，在访问网络的代码前面添加如下代码即可：

StrictMode.ThreadPolicy policy=new StrictMode.ThreadPolicy.Builder().permitAll().build(); StrictMode.setThreadPolicy(policy);

或者新开子线程（建议这种方法）：

new Thread(new Runnable() { @Override public void run() { Document doc = null; try { doc = Jsoup.connect("http://www.baidu.com").get();// Jsoup是我用的一个牛叉的jar包 } catch (IOException e) { e.printStackTrace(); } Log.d("doc", doc.toString()+""); } }).start();

There are two Solution of this Problem.

1. Don't write network call in Main UI Thread, Use Async Task for that.
2. Write below code into your MainActivity file after setContentView(R.layout.activity_main);

if (android.os.Build.VERSION.SDK_INT > 9) { StrictMode.ThreadPolicy policy = new StrictMode.ThreadPolicy.Builder().permitAll().build(); StrictMode.setThreadPolicy(policy); } And below import statement into your java file.