如何在Android上检查互联网访问? InetAddress永不超时 [英] How to check internet access on Android? InetAddress never times out

问题描述

我得到了一个AsyncTask，它应该检查对主机名的网络访问.但是doInBackground()永远不会超时.有人有线索吗?

I got a AsyncTask that is supposed to check the network access to a host name. But the doInBackground() is never timed out. Anyone have a clue?

public class HostAvailabilityTask extends AsyncTask<String, Void, Boolean> {

    private Main main;

    public HostAvailabilityTask(Main main) {
        this.main = main;
    }

    protected Boolean doInBackground(String... params) {
        Main.Log("doInBackground() isHostAvailable():"+params[0]);

        try {
            return InetAddress.getByName(params[0]).isReachable(30); 
        } catch (UnknownHostException e) {
            e.printStackTrace();
        } catch (IOException e) {
            e.printStackTrace();
        }
        return false;       
    }

    protected void onPostExecute(Boolean... result) {
        Main.Log("onPostExecute()");

        if(result[0] == false) {
            main.setContentView(R.layout.splash);
            return;
        }

        main.continueAfterHostCheck();
    }   
}

推荐答案

网络连接/互联网访问

• isConnectedOrConnecting()(用于大多数答案)检查是否有任何网络连接
• 要了解这些网络中的任何一个是否具有 internet 访问权限，请使用以下其中一项

Network connection / Internet access

• isConnectedOrConnecting() (used in most answers) checks for any network connection
• To know whether any of those networks have internet access, use one of the following

// ICMP 
public boolean isOnline() {
    Runtime runtime = Runtime.getRuntime();
    try {
        Process ipProcess = runtime.exec("/system/bin/ping -c 1 8.8.8.8");
        int     exitValue = ipProcess.waitFor();
        return (exitValue == 0);
    }
    catch (IOException e)          { e.printStackTrace(); }
    catch (InterruptedException e) { e.printStackTrace(); }

    return false;
}

+可以在主线程上运行

-在某些旧设备(Galays S3等)上不起作用，如果没有可用的互联网，则会阻止一段时间.

- does not work on some old devices (Galays S3, etc.), it blocks a while if no internet is available.

// TCP/HTTP/DNS (depending on the port, 53=DNS, 80=HTTP, etc.)
public boolean isOnline() {
    try {
        int timeoutMs = 1500;
        Socket sock = new Socket();
        SocketAddress sockaddr = new InetSocketAddress("8.8.8.8", 53);

        sock.connect(sockaddr, timeoutMs);
        sock.close();

        return true;
    } catch (IOException e) { return false; }
}

+非常快(无论哪种方式)，都可以在所有设备上运行，非常可靠

+ very fast (either way), works on all devices, very reliable

-无法在UI线程上运行

- can't run on the UI thread

这在每个设备上都非常可靠地工作，并且速度非常快.不过，它需要在单独的任务中运行(例如ScheduledExecutorService或AsyncTask).

This works very reliably, on every device, and is very fast. It needs to run in a separate task though (e.g. ScheduledExecutorService or AsyncTask).

• 真的够快吗?

• Is it really fast enough?

是的，非常快；-)

除了在Internet上进行测试以外，没有可靠的方法来检查Internet吗?

Is there no reliable way to check internet, other than testing something on the internet?

据我所知，不过请告诉我，我将编辑我的答案.

如果DNS关闭，该怎么办?

What if the DNS is down?

Google DNS(例如8.8.8.8)是世界上最大的公共DNS.截至2013年，它每天处理1300亿个请求.只是说，您的应用可能不会成为今天的话题.

Google DNS (e.g. 8.8.8.8) is the largest public DNS in the world. As of 2013 it served 130 billion requests a day. Let 's just say, your app would probably not be the talk of the day.

需要哪些权限?

<uses-permission android:name="android.permission.INTERNET" />

仅需Internet访问-惊喜^^(顺便说一句，您是否曾想过，如果没有此许可，此处建议的某些方法甚至可能对Internet访问具有遥远的吸引力?)

 

class InternetCheck extends AsyncTask<Void,Void,Boolean> {

    private Consumer mConsumer;
    public  interface Consumer { void accept(Boolean internet); }

    public  InternetCheck(Consumer consumer) { mConsumer = consumer; execute(); }

    @Override protected Boolean doInBackground(Void... voids) { try {
        Socket sock = new Socket();
        sock.connect(new InetSocketAddress("8.8.8.8", 53), 1500);
        sock.close();
        return true;
    } catch (IOException e) { return false; } }

    @Override protected void onPostExecute(Boolean internet) { mConsumer.accept(internet); }
}

///////////////////////////////////////////////////////////////////////////////////
// Usage

    new InternetCheck(internet -> { /* do something with boolean response */ });

额外:单拍RxJava/RxAndroid示例(科特琳)

Extra: One-shot RxJava/RxAndroid Example (Kotlin)

fun hasInternetConnection(): Single<Boolean> {
  return Single.fromCallable {
    try {
      // Connect to Google DNS to check for connection
      val timeoutMs = 1500
      val socket = Socket()
      val socketAddress = InetSocketAddress("8.8.8.8", 53)

      socket.connect(socketAddress, timeoutMs)
      socket.close()

      true
    } catch (e: IOException) {
      false
    }
  }
  .subscribeOn(Schedulers.io())
  .observeOn(AndroidSchedulers.mainThread())
}

///////////////////////////////////////////////////////////////////////////////////
    // Usage

    hasInternetConnection().subscribe { hasInternet -> /* do something */}

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