移动设备上的一个重要用例是确保存在实际连接。当移动用户使用“专属门户”进入Wifi网络时，这是一个常见的问题，他们需要在其中登录。我在后台使用这个阻塞功能来确保连接存在。

/*
 * Not Thread safe. Blocking thread. Returns true if it
 * can connect to URL, false and exception is logged.
 */
public boolean checkConnectionHttps(String url){
    boolean responded = false;
    HttpGet requestTest = new HttpGet(url);
    HttpParams params = new BasicHttpParams();
    HttpConnectionParams.setConnectionTimeout(params, 3000);
    HttpConnectionParams.setSoTimeout(params, 5000);
    DefaultHttpClient client = new DefaultHttpClient(params);
    try {
        client.execute(requestTest);
        responded = true;
    } catch (ClientProtocolException e) {
        Log.w(MainActivity.TAG,"Unable to connect to " + url + " " + e.toString());
    } catch (IOException e) {
        Log.w(MainActivity.TAG,"Unable to connect to " + url + " " + e.toString());
        e.printStackTrace();
    }
    return responded;
}

这对我来说确实有用:

验证网络可用性。

private Boolean isNetworkAvailable() {
ConnectivityManager connectivityManager 
      = (ConnectivityManager) getSystemService(Context.CONNECTIVITY_SERVICE);
NetworkInfo activeNetworkInfo = connectivityManager.getActiveNetworkInfo();
return activeNetworkInfo != null && activeNetworkInfo.isConnectedOrConnecting();}

验证互联网接入:

public Boolean isOnline() {
    try {
        Process p1 = java.lang.Runtime.getRuntime().exec("ping -c 1 www.google.com");
        int returnVal = p1.waitFor();
        boolean reachable = (returnVal==0);
        return reachable;
    } catch (Exception e) {
        // TODO Auto-generated catch block
        e.printStackTrace();
    }
    return false;
}

更新29/06/2015 如果你正在使用Xamarin。Android和想要检查连接，你可以使用Nuget包，这将给你在多个平台上的功能。好的候选人在这里和这里。 [更新结束]

The Answers above are quite good, but they are all in Java, and almost all of them check for a connectivity. In my case, I needed to have connectivity with a specific type of connection and I am developing on Xamarin.Android. Moreover, I do not pass a reference to my activities Context in the Hardware layer, I use the Application Context. So here is my solution, in case somebody comes here with similar requirements. I have not done full testing though, will update the answer once I am done with my testing

using Android.App;
using Android.Content;
using Android.Net;

namespace Leopard.Mobile.Hal.Android
{
    public class AndroidNetworkHelper
    {
        public static AndroidNetworkStatus GetWifiConnectivityStatus()
        {
            return GetConnectivityStatus(ConnectivityType.Wifi);
        }

        public static AndroidNetworkStatus GetMobileConnectivityStatus()
        {
            return GetConnectivityStatus(ConnectivityType.Mobile);
        }

        #region Implementation

        private static AndroidNetworkStatus GetConnectivityStatus(ConnectivityType connectivityType)
        {
            var connectivityManager = (ConnectivityManager)Application.Context.GetSystemService(Context.ConnectivityService);
            var wifiNetworkInfo = connectivityManager.GetNetworkInfo(connectivityType);
            var result = GetNetworkStatus(wifiNetworkInfo);
            return result;
        }

        private static AndroidNetworkStatus GetNetworkStatus(NetworkInfo wifiNetworkInfo)
        {
            var result = AndroidNetworkStatus.Unknown;
            if (wifiNetworkInfo != null)
            {
                if (wifiNetworkInfo.IsAvailable && wifiNetworkInfo.IsConnected)
                {
                    result = AndroidNetworkStatus.Connected;
                }
                else
                {
                    result = AndroidNetworkStatus.Disconnected;
                }
            }
            return result;
        } 

        #endregion
    }

    public enum AndroidNetworkStatus
    {
        Connected,
        Disconnected,
        Unknown
    }

不需要太复杂。最简单的框架方式是使用ACCESS_NETWORK_STATE权限并创建一个连接的方法

public boolean isOnline() {
    ConnectivityManager cm =
        (ConnectivityManager) getSystemService(Context.CONNECTIVITY_SERVICE);

    return cm.getActiveNetworkInfo() != null && 
       cm.getActiveNetworkInfo().isConnectedOrConnecting();
}

如果您有特定的主机和连接类型(wifi/移动)，也可以使用requestRouteToHost。

你还需要:

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

在你的android清单中。

这是我解决这个问题的解决方案，并检查有效的互联网连接，因为正如他们所说，网络信息类不能给你预期的结果，它可能会在网络连接但没有互联网时返回true。

所以这是我基于@Levite回答的完整解决方案:

首先，你必须有AsynckTask检查网络可用性，这是我的:

public class Connectivity {
 private static final String TAG = "Connectivity";
private static boolean hasConnected = false, hasChecked = false;
private InternetListener internetListener;
private Activity activity;

public Connectivity(InternetListener internetListener, Activity activity) {
    this.internetListener = internetListener;
    this.activity = activity;
}

public void startInternetListener() {


    CheckURL checkURL = new CheckURL(activity);

    checkURL.execute();

    long startTime = System.currentTimeMillis();

    while (true) {
        if (hasChecked && hasConnected) {
            activity.runOnUiThread(new Runnable() {
                @Override
                public void run() {
                    internetListener.onConnected();
                }
            });

            checkURL.cancel(true);
            return;
        }

        // check if time
        if (System.currentTimeMillis() - startTime >= 1000) {
            activity.runOnUiThread(new Runnable() {
                @Override
                public void run() {
                    internetListener.onDisconnected();
                }
            });


            checkURL.cancel(true);
            return;
        }
    }

    //return hasConnected;
}


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

    private Activity activity;

    public CheckURL(Activity activity) {
        this.activity = activity;
    }

    @Override
    protected Boolean doInBackground(Void... params) {
        if (!isNetWorkAvailable(activity)) {
            Log.i(TAG, "Internet not available!");
            return false;
        }

        int timeoutMs = 3000;

        try {
            Socket sock = new Socket();
            SocketAddress sockaddr = new InetSocketAddress("8.8.8.8", 53);
            sock.connect(sockaddr, timeoutMs);
            sock.close();
            Log.i(TAG, "Internet available :)");
            return true;

        } catch (IOException e) {
            e.printStackTrace();
            return false;
        }

    }

    @Override
    protected void onPostExecute(Boolean result) {
        hasChecked = true;
        hasConnected = result;
        super.onPostExecute(result);}}
     

private static final String TAG = "Connectivity";


private static boolean isNetWorkAvailable(Activity activity) {

    ConnectivityManager connectivityManager =
            (ConnectivityManager) 
   activity.getSystemService(Activity.CONNECTIVITY_SERVICE);
    NetworkInfo networkInfo =
            null;
    if (connectivityManager != null) {
        networkInfo = 
   connectivityManager.getNetworkInfo(ConnectivityManager.TYPE_WIFI);
    }
    boolean isConnected;
    boolean isWifiAvailable = false;
    if (networkInfo != null) {
        isWifiAvailable = networkInfo.isAvailable();
    }
    boolean isWifiConnected = false;
    if (networkInfo != null) {
        isWifiConnected = networkInfo.isConnected();
    }
    if (connectivityManager != null) {
        networkInfo =
                connectivityManager.getNetworkInfo(ConnectivityManager.TYPE_MOBILE);
    }
    boolean isMobileAvailable = false;
    if (networkInfo != null) {
        isMobileAvailable = networkInfo.isAvailable();
    }
    boolean isMobileConnected = false;
    if (networkInfo != null) {
        isMobileConnected = networkInfo.isConnected();
    }
    isConnected = (isMobileAvailable && isMobileConnected) ||
            (isWifiAvailable && isWifiConnected);
    return (isConnected);}
    }}



private static boolean isNetWorkAvailable(Context context) {

    ConnectivityManager connectivityManager =
            (ConnectivityManager) context.getSystemService(Context.CONNECTIVITY_SERVICE);
    NetworkInfo networkInfo =
            null;
    if (connectivityManager != null) {
        networkInfo = connectivityManager.getNetworkInfo(ConnectivityManager.TYPE_WIFI);
    }
    boolean isConnected;
    boolean isWifiAvailable = false;
    if (networkInfo != null) {
        isWifiAvailable = networkInfo.isAvailable();
    }
    boolean isWifiConnected = false;
    if (networkInfo != null) {
        isWifiConnected = networkInfo.isConnected();
    }
    if (connectivityManager != null) {
        networkInfo =
                connectivityManager.getNetworkInfo(ConnectivityManager.TYPE_MOBILE);
    }
    boolean isMobileAvailable = false;
    if (networkInfo != null) {
        isMobileAvailable = networkInfo.isAvailable();
    }
    boolean isMobileConnected = false;
    if (networkInfo != null) {
        isMobileConnected = networkInfo.isConnected();
    }
    isConnected = (isMobileAvailable && isMobileConnected) ||
            (isWifiAvailable && isWifiConnected);
    return (isConnected);

}

}

之后，你应该创建另一个线程来启动AscnkTask并使用InternetListener监听结果。

public interface InternetListener {
void onConnected();
void onDisconnected();
}

而等待AsynckTask结果的线程，你可以把它放在Utility类中:

 private static Thread thread;

public static void startNetworkListener(Context context, InternetListener 
    internetListener) {

    if (thread == null){
        thread = new Thread(new Runnable() {
            @Override
            public void run() {
                Looper.prepare();
                new Connectivity(internetListener,context).startInternetListener();
            }
        });
    }

    thread.start();
 }

最后调用startNetworkListener()方法并监听结果。

My Utils.java类中的activity示例:

     Utils.startNetworkListener(this, new InternetListener() {
        @Override
        public void onConnected() {
           // do your work when internet available. 
        }

        @Override
        public void onDisconnected() {
          // do your work when no internet available. 
        }
    });

快乐编码:)。

最好的方法:

public static boolean isOnline() {
    try {
    InetAddress.getByName("google.com").isReachable(3);

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