如何从 android 设备获取主机名

Question

我正在实施一种获取 android 设备主机名的方法。为此，我正在使用 InetAddress class。但是，我遇到了致命的异常。这是方法。我添加了一个 try/catch 块，但仍然无法正常工作。任何帮助表示赞赏。编辑并添加异常错误

/**
     * getHostname returns the hostname of android device as string
     *
     * @param context
     * @return hostname
     */

    public String getHostname(Context context) {
        String hostName;
        try {
            InetAddress netHost = InetAddress.getLocalHost();
            hostName = netHost.getHostName();
        } catch (UnknownHostException ex) {
            hostName = null;
        }

        return hostName;
    }

致命异常

E/AndroidRuntime: FATAL EXCEPTION: main
                  Process: com.example.george.droidnet, PID: 23439
                  java.lang.RuntimeException: Unable to start activity ComponentInfo{com.example.george.droidnet/com.example.george.droidnet.TcpConfigActivity}: android.os.NetworkOnMainThreadException
                      at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2416)
                      at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2476)
                      at android.app.ActivityThread.-wrap11(ActivityThread.java)
                      at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1344)
                      at android.os.Handler.dispatchMessage(Handler.java:102)
                      at android.os.Looper.loop(Looper.java:148)
                      at android.app.ActivityThread.main(ActivityThread.java:5417)
                      at java.lang.reflect.Method.invoke(Native Method)
                      at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:726)
                      at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:616)
                   Caused by: android.os.NetworkOnMainThreadException
                      at android.os.StrictMode$AndroidBlockGuardPolicy.onNetwork(StrictMode.java:1273)
                      at java.net.InetAddress.lookupHostByName(InetAddress.java:431)
                      at java.net.InetAddress.getLocalHost(InetAddress.java:409)
                      at com.example.george.droidnet.TcpConfigActivity.getHostname(TcpConfigActivity.java:100)
                      at com.example.george.droidnet.TcpConfigActivity.onCreate(TcpConfigActivity.java:40)
                      at android.app.Activity.performCreate(Activity.java:6237)
                      at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1107)
                      at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2369)
                      at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2476) 
                      at android.app.ActivityThread.-wrap11(ActivityThread.java) 
                      at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1344) 
                      at android.os.Handler.dispatchMessage(Handler.java:102) 
                      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)

Answer 1

Caused by: android.os.NetworkOnMainThreadException

使用另一个线程进行联网。 AsyncTask可能对你有帮助。

Answer 2

伙计，在 Java 中你不能在主线程上 "do network things"。为此，您必须将其放入 AsyncTask，如下所示：

public String getHostName() {
    AsyncTack<Void, Void, String> task = new AsyncTask<Void, Void, String>() {
        @Override
        protected Void doInBackground(Void... voids) {
            String hostName;
            try {
                InetAddress netHost = InetAddress.getLocalHost();
                hostName = netHost.getHostName();
            } catch (UnknownHostException ex) {
                hostName = null;
            }

            return hostName;
        }
    };

    task.execute();
    try {
        return task.get();
    } catch (Exception e) {
        return null;
    }
}

此代码应该有效。

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