Network connection / Internet access

• isConnectedOrConnecting()(在大多数答案中使用)判断任何network连接
• 要知道这些网络是否有internet个访问权限，请使用以下选项之一

a)Ping服务器(简单)

// 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

-在一些旧设备(Galays S3等)上不工作，如果没有可用的互联网，它会阻塞一段时间.

B) 连接到Internet上的插座(高级)

// 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; }
}

+速度非常快(无论采用哪种方式)，可在所有设备上运行，very可靠

-无法在UI线程上运行

这在每一台设备上都能非常可靠地工作，而且速度非常快.不过，它需要在单独的任务中运行(例如，ScheduledExecutorService或AsyncTask).

可能的问题

• 它真的够快吗？

  Yes, very fast ;-)

• 除了在网上测试之外，有没有可靠的方式来判断互联网？

  Not as far as I know, but let me know, and I will edit my answer.

• 如果DNS关闭了怎么办？

  Google DNS (e.g. 101) is the largest public DNS in the world. As of 2018 it handled over a trillion queries a day [100]. 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" />
  

  Just internet access - surprise ^^ (Btw have you ever thought about, how some of the methods suggested here could even have a remote glue about internet access, without this permission?)个

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 */}

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

public static Single<Boolean> hasInternetConnection() {
    return Single.fromCallable(() -> {
        try {
            // Connect to Google DNS to check for connection
            int timeoutMs = 1500;
            Socket socket = new Socket();
            InetSocketAddress socketAddress = new InetSocketAddress("8.8.8.8", 53);

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

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

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

    hasInternetConnection().subscribe((hasInternet) -> {
        if(hasInternet) {

        }else {

        }
    });

Extra: One-shot AsyncTask Example

Caution:这显示了另一个如何处理请求的示例.然而，由于AsyncTask已经被弃用，它应该被你的应用程序的线程调度取代，Kotlin Coroutines，Rx，.

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 */ });