1-创建新的Java文件(右键单击包。新建>类>，命名为文件ConnectionDetector.java

2-在文件中添加以下代码

package <add you package name> example com.example.example;

import android.content.Context;
import android.net.ConnectivityManager;

public class ConnectionDetector {

    private Context mContext;

    public ConnectionDetector(Context context){
        this.mContext = context;
    }

    public boolean isConnectingToInternet(){

        ConnectivityManager cm = (ConnectivityManager)mContext.getSystemService(Context.CONNECTIVITY_SERVICE);
        if(cm.getActiveNetworkInfo() != null && cm.getActiveNetworkInfo().isConnected() == true)
        {
            return true; 
        }

        return false;

    }
}

3-打开MainActivity.java -要检查连接的活动，并执行以下操作

创建并定义函数。

ConnectionDetector mConnectionDetector;</pre>

在“OnCreate”中添加以下内容

mConnectionDetector = new ConnectionDetector(getApplicationContext());

C -检查连接使用以下步骤

if (mConnectionDetector.isConnectingToInternet() == false) {
//no connection- do something
} else {
//there is connection
}

下面是一个函数，我使用作为我的Utils类的一部分:

public static boolean isNetworkConnected(Context context) {
    ConnectivityManager cm = (ConnectivityManager) context.getSystemService(Context.CONNECTIVITY_SERVICE);
    return (cm.getActiveNetworkInfo() != null) && cm.getActiveNetworkInfo().isConnectedOrConnecting();
}

像这样使用它:Utils.isNetworkConnected(MainActivity.this);

当您连接到Wi-Fi源或通过手机数据包时，上述方法都有效。但在Wi-Fi连接的情况下，有时你会被进一步要求登录，就像在咖啡馆一样。所以在这种情况下，你的应用程序将失败，因为你连接的是Wi-Fi源，而不是互联网。

这个方法很有效。

    public static boolean isConnected(Context context) {
        ConnectivityManager cm = (ConnectivityManager)context
                .getSystemService(Context.CONNECTIVITY_SERVICE);

    NetworkInfo activeNetwork = cm.getActiveNetworkInfo();
    if (activeNetwork != null && activeNetwork.isConnected()) {
        try {
            URL url = new URL("http://www.google.com/");
            HttpURLConnection urlc = (HttpURLConnection)url.openConnection();
            urlc.setRequestProperty("User-Agent", "test");
            urlc.setRequestProperty("Connection", "close");
            urlc.setConnectTimeout(1000); // mTimeout is in seconds
            urlc.connect();
            if (urlc.getResponseCode() == 200) {
                return true;
            } else {
                return false;
            }
        } catch (IOException e) {
            Log.i("warning", "Error checking internet connection", e);
            return false;
        }
    }

    return false;

}

请在与主线程分开的线程中使用此线程，因为它会进行网络调用，如果不遵循将抛出networkkonmainthreadexception。

也不要把这个方法放在onCreate或任何其他方法中。把它放到一个类中并访问它。

检查以确保它“连接”到网络:

public boolean isNetworkAvailable(Context context) {
    ConnectivityManager connectivityManager = ((ConnectivityManager) context.getSystemService(Context.CONNECTIVITY_SERVICE));
    return connectivityManager.getActiveNetworkInfo() != null && connectivityManager.getActiveNetworkInfo().isConnected();
}

检查以确保它“连接”到互联网:

public boolean isInternetAvailable() {
    try {
        InetAddress address = InetAddress.getByName("www.google.com");
        return !address.equals("");
    } catch (UnknownHostException e) {
        // Log error
    }
    return false;
}

需要许可:

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

https://stackoverflow.com/a/17583324/950427

接受的答案的EDIT显示了如何检查internet上的某些内容是否可以到达。我不得不等了很长时间才得到答案，但事实并非如此(使用的是没有互联网连接的wifi)。不幸的是InetAddress。getByName没有超时参数，所以下面的代码围绕它工作:

private boolean internetConnectionAvailable(int timeOut) {
    InetAddress inetAddress = null;
    try {
        Future<InetAddress> future = Executors.newSingleThreadExecutor().submit(new Callable<InetAddress>() {
            @Override
            public InetAddress call() {
                try {
                    return InetAddress.getByName("google.com");
                } catch (UnknownHostException e) {
                    return null;
                }
            }
        });
        inetAddress = future.get(timeOut, TimeUnit.MILLISECONDS);
        future.cancel(true);
    } catch (InterruptedException e) {
    } catch (ExecutionException e) {
    } catch (TimeoutException e) {
    } 
    return inetAddress!=null && !inetAddress.equals("");
}

试试下面的代码:

public static boolean isNetworkAvailable(Context context) {
        boolean outcome = false;

        if (context != null) {
            ConnectivityManager cm = (ConnectivityManager) context
                    .getSystemService(Context.CONNECTIVITY_SERVICE);

            NetworkInfo[] networkInfos = cm.getAllNetworkInfo();

            for (NetworkInfo tempNetworkInfo : networkInfos) {


                /**
                 * Can also check if the user is in roaming
                 */
                if (tempNetworkInfo.isConnected()) {
                    outcome = true;
                    break;
                }
            }
        }

        return outcome;
    }