如果你需要检查网络连接，使用ping到服务器的方法:

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

您可以使用端口进行检查

public boolean checkIntCON() {
    try {
        Socket sock = new Socket();
        SocketAddress sockaddr = new InetSocketAddress("8.8.8.8", 80); 
        // port will change according to protocols

        sock.connect(sockaddr, 1250);
        sock.close();

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

有不止一种方法

第一，最短但效率低的方法

只需要网络状态权限

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

然后这个方法，

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

        NetworkInfo activeNetwork = cm.getActiveNetworkInfo();
        boolean isConnected = activeNetwork != null &&
                activeNetwork.isConnected();

        return isConnected;

    }

正如在回答中所看到的ConnectivityManager是一个解决方案，我只是在一个方法中添加了它，这是一个简化的方法 ConnectivityManager返回true，如果有网络访问而不是互联网访问，这意味着如果你的WiFi连接到路由器，但路由器没有互联网，它返回true，它检查连接可用性

二、高效的方式

需要网络状态和Internet权限

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

然后这门课，

 public class CheckInternetAsyncTask extends AsyncTask<Void, Integer, Boolean> {

        private Context context;

        public CheckInternetAsyncTask(Context context) {
            this.context = context;
        }

        @Override
        protected Boolean doInBackground(Void... params) {

            ConnectivityManager cm =
                    (ConnectivityManager)context.getSystemService(Context.CONNECTIVITY_SERVICE);

            assert cm != null;
            NetworkInfo activeNetwork = cm.getActiveNetworkInfo();
            boolean isConnected = activeNetwork != null &&
                    activeNetwork.isConnected();


            if (isConnected) {
                try {
                    HttpURLConnection urlc = (HttpURLConnection)
                            (new URL("http://clients3.google.com/generate_204")
                                    .openConnection());
                    urlc.setRequestProperty("User-Agent", "Android");
                    urlc.setRequestProperty("Connection", "close");
                    urlc.setConnectTimeout(1500);
                    urlc.connect();
                    if (urlc.getResponseCode() == 204 &&
                            urlc.getContentLength() == 0)
                        return true;

                } catch (IOException e) {
                    Log.e("TAG", "Error checking internet connection", e);
                    return false;
                }
            } else {
                Log.d("TAG", "No network available!");
                return false;
            }


            return null;
        }

        @Override
        protected void onPostExecute(Boolean result) {
            super.onPostExecute(result);
            Log.d("TAG", "result" + result);

            if(result){
                // do ur code
            }

        }


    }

叫CheckInternetAsyncTask

new CheckInternetAsyncTask(getApplicationContext()).execute();

部分解释:-

you have to check Internet on AsyncTask, otherwise it can throw android.os.NetworkOnMainThreadException in some cases ConnectivityManager used to check the network access if true sends request (Ping) Request send to http://clients3.google.com/generate_204, This well-known URL is known to return an empty page with an HTTP status 204 this is faster and more efficient than http://www.google.com , read this. if you have website it's preferred to put you website instead of google, only if you use it within the app Timeout can be changed range (20ms -> 2000ms), 1500ms is commonly used

正如Android文档建议的那样，之后

getActiveNetworkInfo()在Android 10中已弃用。使用 而不是针对Android 10 (API级别)的应用程序的NetworkCallbacks 29)更高。

下面是我们目前检查网络连接的方法:

val cm = context.getSystemService(Context.CONNECTIVITY_SERVICE) as ConnectivityManager
val activeNetwork: NetworkInfo? = cm.activeNetworkInfo
val isConnected: Boolean = activeNetwork?.isConnectedOrConnecting == true

使用NetworkCallbacks检查网络连接的新方法

步骤1:

    private lateinit var connectivityManager:ConnectivityManager

    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        ...
        connectivityManager = getSystemService(Context.CONNECTIVITY_SERVICE) as ConnectivityManager
    }

步骤2:创建回调:

private val callback = object : ConnectivityManager.NetworkCallback() {
    override fun onAvailable(network: Network) {
        super.onAvailable(network)
        Timber.e("Network:onAvailable")
    }

    override fun onLost(network: Network) {
        super.onLost(network)
        Timber.e("Network:onLost")
    }

}

步骤3:注册和取消注册回调:

private fun registerNetworkCallback() {
    if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.N) {
        connectivityManager.registerDefaultNetworkCallback(callback)
    } else {
        // Old way to check network connection
    }
}

override fun onStop() {
    unRegisterNetworkCallback()
    super.onStop()
}

private fun unRegisterNetworkCallback() {
    connectivityManager.unregisterNetworkCallback(callback)
}

结帐更新详情如下链接:

https://developer.android.com/training/monitoring-device-state/connectivity-status-type

if(isConnected()){
                Toast.makeText(getApplication(),"Thank you",Toast.LENGTH_SHORT).show();
        }
        else{

            AlertDialog.Builder builder =
                    new AlertDialog.Builder(this, R.style.AppCompatAlertDialogStyle);
            builder.setTitle("Amar Bhat");
            builder.setMessage("Oops...You are not connected to Internet!!!");
            builder.setPositiveButton("OK", null);
            builder.setNegativeButton("Cancel", null);
            builder.show();
            //Toast.makeText(getApplication(),"You are not connected",Toast.LENGTH_SHORT).show();
        }




//And outside the class define isConnected()

 public boolean isConnected(){
        ConnectivityManager connMgr = (ConnectivityManager) getSystemService(Activity.CONNECTIVITY_SERVICE);
        NetworkInfo networkInfo = connMgr.getActiveNetworkInfo();
        if (networkInfo != null && networkInfo.isConnected())
            return true;
        else
            return false;
    }

// In minifest add these permission
<uses-permission android:name="android.permission.INTERNET" />

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

Android提供了ConnectivityManager类来了解互联网连接状态。下面的方法将是非常有用的，以了解互联网连接状态。

首先在AndroidManifest.xml中添加INTERNET和ACCESS_NETWORK_STATE权限

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

然后使用下面的方法检查设备是否连接到互联网。如果设备已连接到互联网，此方法将返回true。

public boolean isInternetAvailable(Context context) {
    ConnectivityManager connectivityManager = (ConnectivityManager) 
    context.getSystemService(Context.CONNECTIVITY_SERVICE);
    NetworkInfo activeNetwork = connectivityManager.getActiveNetworkInfo();
    return activeNetwork != null
            && activeNetwork.isConnectedOrConnecting();
}

参考链接:—http://www.androidtutorialshub.com/android-check-internet-connection-status/

检查这段代码…这对我很有用:)

public static void isNetworkAvailable(final Handler handler, final int timeout) {
    // ask fo message '0' (not connected) or '1' (connected) on 'handler'
    // the answer must be send before before within the 'timeout' (in milliseconds)

    new Thread() {
        private boolean responded = false;   
        @Override
        public void run() { 
            // set 'responded' to TRUE if is able to connect with google mobile (responds fast) 
            new Thread() {      
                @Override
                public void run() {
                    HttpGet requestForTest = new HttpGet("http://m.google.com");
                    try {
                        new DefaultHttpClient().execute(requestForTest); // can last...
                        responded = true;
                    } 
                    catch (Exception e) {
                    }
                } 
            }.start();

            try {
                int waited = 0;
                while(!responded && (waited < timeout)) {
                    sleep(100);
                    if(!responded ) { 
                        waited += 100;
                    }
                }
            } 
            catch(InterruptedException e) {} // do nothing 
            finally { 
                if (!responded) { handler.sendEmptyMessage(0); } 
                else { handler.sendEmptyMessage(1); }
            }
        }
    }.start();
}

然后，我定义处理程序:

Handler h = new Handler() {
    @Override
    public void handleMessage(Message msg) {

        if (msg.what != 1) { // code if not connected

        } else { // code if connected

        }   
    }
};

.．.并启动测试:

isNetworkAvailable(h,2000); // get the answser within 2000 ms