Broadcast receiver for checking internet connection in android app

I am developing an android broadcast receiver for checking internet connection.

The problem is that my broadcast receiver is being called two times. I want it to get called only when the network is available. If it is unavailable, I don't want notified.

This is the broadcast receiver

public class NetworkChangeReceiver extends BroadcastReceiver {

	@Override
	public void onReceive(final Context context, final Intent intent) {
		final ConnectivityManager connMgr = (ConnectivityManager) context
				.getSystemService(Context.CONNECTIVITY_SERVICE);

		final android.net.NetworkInfo wifi = connMgr
				.getNetworkInfo(ConnectivityManager.TYPE_WIFI);

		final android.net.NetworkInfo mobile = connMgr
				.getNetworkInfo(ConnectivityManager.TYPE_MOBILE);

		if (wifi.isAvailable() || mobile.isAvailable()) {
			// Do something

			Log.d("Network Available ", "Flag No 1");
		}
	}
}

This is the manifest.xml

<manifest xmlns:android="http://schemas.android.com/apk/res/android"
    package="com.example.broadcastreceiverforinternetconnection"
    android:versionCode="1"
    android:versionName="1.0" >

    <uses-sdk
        android:minSdkVersion="8"
        android:targetSdkVersion="17" />
    <uses-permission android:name="android.permission.ACCESS_NETWORK_STATE"/>

    <application
        android:allowBackup="true"
        android:icon="@drawable/ic_launcher"
        android:label="@string/app_name"
        android:theme="@style/AppTheme" >
        <receiver android:name=".NetworkChangeReceiver" >
            <intent-filter>
                <action android:name="android.net.conn.CONNECTIVITY_CHANGE" />
                <action android:name="android.net.wifi.WIFI_STATE_CHANGED" />
            </intent-filter>
        </receiver>
    </application>

</manifest>

Answer to your first question: Your broadcast receiver is being called two times because

You have added two <intent-filter>

1. Change in network connection :
   <action android:name="android.net.conn.CONNECTIVITY_CHANGE" />

2. Change in WiFi state:
   <action android:name="android.net.wifi.WIFI_STATE_CHANGED" />

Just use one:
<action android:name="android.net.conn.CONNECTIVITY_CHANGE" />.

It will respond to only one action instead of two. See here for more information.

Answer to your second question (you want receiver to call only one time if internet connection available):

Your code is perfect; you notify only when internet is available.

UPDATE

You can use this method to check your connectivity if you want just to check whether mobile is connected with the internet or not.

public boolean isOnline(Context context) {
  
    ConnectivityManager cm = (ConnectivityManager) context.getSystemService(Context.CONNECTIVITY_SERVICE);
    NetworkInfo netInfo = cm.getActiveNetworkInfo();
    //should check null because in airplane mode it will be null
    return (netInfo != null && netInfo.isConnected());
}

public class NetworkChangeReceiver extends BroadcastReceiver {

    @Override
    public void onReceive(final Context context, final Intent intent) {
        if (checkInternet(context)) {
            Toast.makeText(context, "Network Available Do operations", Toast.LENGTH_LONG).show();
        }
    }

    boolean checkInternet(Context context) {
        ServiceManager serviceManager = new ServiceManager(context);
        return serviceManager.isNetworkAvailable()
    }
}

ServiceManager.java

public class ServiceManager {

    Context context;

    public ServiceManager(Context base) {
        context = base;
    }

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

permissions:

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

Checking internet status every time using Broadcast Receiver:

Full source code available on Google Drive.

AndroidManifest.xml

<uses-permission android:name="android.permission.ACCESS_NETWORK_STATE"/>
<uses-permission android:name="android.permission.INTERNET"/>
<receiver android:name=".receivers.NetworkChangeReceiver">
            <intent-filter>
                <action android:name="android.net.conn.CONNECTIVITY_CHANGE" />
            </intent-filter>
</receiver>

BroadcastReciever

package com.keshav.networkchangereceiverexample.receivers;

import android.content.BroadcastReceiver;
import android.content.Context;
import android.content.Intent;
import android.net.ConnectivityManager;
import android.net.NetworkInfo;
import android.util.Log;

import static com.keshav.networkchangereceiverexample.MainActivity.dialog;

public class NetworkChangeReceiver extends BroadcastReceiver
{
    @Override
    public void onReceive(Context context, Intent intent)
    {
        try
        {
            if (isOnline(context)) {
                dialog(true);
                Log.e("keshav", "Online Connect Intenet ");
            } else {
                dialog(false);
                Log.e("keshav", "Conectivity Failure !!! ");
            }
        } catch (NullPointerException e) {
            e.printStackTrace();
        }
    }

    private boolean isOnline(Context context) {
        try {
            ConnectivityManager cm = (ConnectivityManager) context.getSystemService(Context.CONNECTIVITY_SERVICE);
            NetworkInfo netInfo = cm.getActiveNetworkInfo();
            //should check null because in airplane mode it will be null
            return (netInfo != null && netInfo.isConnected());
        } catch (NullPointerException e) {
            e.printStackTrace();
            return false;
        }
    }
}

MainActivity.java

package com.keshav.networkchangereceiverexample;

import android.content.BroadcastReceiver;
import android.content.Intent;
import android.content.IntentFilter;
import android.graphics.Color;
import android.net.ConnectivityManager;
import android.os.Build;
import android.os.Handler;
import android.os.Looper;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.util.Log;
import android.view.View;
import android.view.animation.Animation;
import android.view.animation.AnimationUtils;
import android.widget.TextView;

import com.keshav.networkchangereceiverexample.receivers.NetworkChangeReceiver;

public class MainActivity extends AppCompatActivity {

    private BroadcastReceiver mNetworkReceiver;
    static TextView tv_check_connection;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        tv_check_connection=(TextView) findViewById(R.id.tv_check_connection);
        mNetworkReceiver = new NetworkChangeReceiver();
        registerNetworkBroadcastForNougat();

    }

    public static void dialog(boolean value){

        if(value){
            tv_check_connection.setText("We are back !!!");
            tv_check_connection.setBackgroundColor(Color.GREEN);
            tv_check_connection.setTextColor(Color.WHITE);

            Handler handler = new Handler();
            Runnable delayrunnable = new Runnable() {
                @Override
                public void run() {
                    tv_check_connection.setVisibility(View.GONE);
                }
            };
            handler.postDelayed(delayrunnable, 3000);
        }else {
            tv_check_connection.setVisibility(View.VISIBLE);
            tv_check_connection.setText("Could not Connect to internet");
            tv_check_connection.setBackgroundColor(Color.RED);
            tv_check_connection.setTextColor(Color.WHITE);
        }
    }


    private void registerNetworkBroadcastForNougat() {
        if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.N) {
            registerReceiver(mNetworkReceiver, new IntentFilter(ConnectivityManager.CONNECTIVITY_ACTION));
        }
        if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.M) {
            registerReceiver(mNetworkReceiver, new IntentFilter(ConnectivityManager.CONNECTIVITY_ACTION));
        }
    }

    protected void unregisterNetworkChanges() {
        try {
            unregisterReceiver(mNetworkReceiver);
        } catch (IllegalArgumentException e) {
            e.printStackTrace();
        }
    }

    @Override
    public void onDestroy() {
        super.onDestroy();
        unregisterNetworkChanges();
    }
}

activity_main.xml

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    tools:context="com.keshav.networkchangereceiverexample.MainActivity">

    <TextView
        android:id="@+id/tv_check_connection"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:text="Connection establised !"
        android:padding="25dp"
        app:layout_constraintBottom_toBottomOf="parent"
        android:gravity="center"
        app:layout_constraintLeft_toLeftOf="parent"
        app:layout_constraintRight_toRightOf="parent"
        app:layout_constraintTop_toTopOf="parent" />

</LinearLayout>

Use this method to check the network state:

private void checkInternetConnection() {

    if (br == null) {

        br = new BroadcastReceiver() {

            @Override
            public void onReceive(Context context, Intent intent) {

                Bundle extras = intent.getExtras();

                NetworkInfo info = (NetworkInfo) extras
                        .getParcelable("networkInfo");

                State state = info.getState();
                Log.d("TEST Internet", info.toString() + " "
                        + state.toString());

                if (state == State.CONNECTED) {
                      Toast.makeText(getApplicationContext(), "Internet connection is on", Toast.LENGTH_LONG).show();

                } else {
                       Toast.makeText(getApplicationContext(), "Internet connection is Off", Toast.LENGTH_LONG).show();
                }

            }
        };

        final IntentFilter intentFilter = new IntentFilter();
        intentFilter.addAction(ConnectivityManager.CONNECTIVITY_ACTION);
        registerReceiver((BroadcastReceiver) br, intentFilter);
    }
}

remember to unregister service in onDestroy.

Cheers!!

Warning: Declaring a broadcastreceiver for android.net.conn.CONNECTIVITY_CHANGE is deprecated for apps targeting N and higher. In general, apps should not rely on this broadcast and instead use JobScheduler or GCMNetworkManager.

As CONNECTIVITY_CHANGE is deprecated then we should use another way of doing the same stuff

Following NetworkConnectionLiveData will handle all the OS Version till now and also if target SDK is less than Build.VERSION_CODES.LOLLIPOP then only we can use broadcastReceiver

Best Part is this class uses LiveData so no need to register any receiver use LiveData and it will handle all the things

class NetworkConnectionLiveData(val context: Context) : LiveData<Boolean>() {

    private var connectivityManager: ConnectivityManager = context.getSystemService(CONNECTIVITY_SERVICE) as ConnectivityManager

    private lateinit var connectivityManagerCallback: ConnectivityManager.NetworkCallback

    override fun onActive() {
        super.onActive()
        updateConnection()
        when {
            Build.VERSION.SDK_INT >= Build.VERSION_CODES.N -> connectivityManager.registerDefaultNetworkCallback(getConnectivityManagerCallback())
            Build.VERSION.SDK_INT >= Build.VERSION_CODES.LOLLIPOP -> lollipopNetworkAvailableRequest()
            else -> {
                if (Build.VERSION.SDK_INT < Build.VERSION_CODES.LOLLIPOP) {
                    context.registerReceiver(networkReceiver, IntentFilter("android.net.conn.CONNECTIVITY_CHANGE"))
                }
            }
        }
    }

    override fun onInactive() {
        super.onInactive()
        if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.LOLLIPOP) {
            connectivityManager.unregisterNetworkCallback(connectivityManagerCallback)
        } else {
            context.unregisterReceiver(networkReceiver)
        }
    }

    @TargetApi(Build.VERSION_CODES.LOLLIPOP)
    private fun lollipopNetworkAvailableRequest() {
        val builder = NetworkRequest.Builder()
                .addTransportType(android.net.NetworkCapabilities.TRANSPORT_CELLULAR)
                .addTransportType(android.net.NetworkCapabilities.TRANSPORT_WIFI)
        connectivityManager.registerNetworkCallback(builder.build(), getConnectivityManagerCallback())
    }

    private fun getConnectivityManagerCallback(): ConnectivityManager.NetworkCallback {
        if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.LOLLIPOP) {

            connectivityManagerCallback = object : ConnectivityManager.NetworkCallback() {
                override fun onAvailable(network: Network?) {
                    postValue(true)
                }

                override fun onLost(network: Network?) {
                    postValue(false)
                }
            }
            return connectivityManagerCallback
        } else {
            throw IllegalAccessError("Should not happened")
        }
    }

    private val networkReceiver = object : BroadcastReceiver() {
        override fun onReceive(context: Context, intent: Intent) {
            updateConnection()
        }
    }

    private fun updateConnection() {
        val activeNetwork: NetworkInfo? = connectivityManager.activeNetworkInfo
        postValue(activeNetwork?.isConnected == true)
    }
} 

Use of the LiveData into any class:

NetworkConnectionLiveData(context ?: return)
    .observe(viewLifecycleOwner, Observer { isConnected ->
        if (!isConnected) {
            // Internet Not Available
            return@Observer
        }
        // Internet Available
})

just for someone else who wanna register a broadcast dynamicly:

BroadcastReceiver mWifiReceiver = new BroadcastReceiver() {
    @Override
    public void onReceive(Context context, Intent intent) {
        if (checkWifiConnect()) {
            Log.d(TAG, "wifi has connected");
            // TODO
        }
    }
};

private void registerWifiReceiver() {
    IntentFilter filter = new IntentFilter();
    filter.addAction(WifiManager.NETWORK_STATE_CHANGED_ACTION);
    filter.addAction(WifiManager.WIFI_STATE_CHANGED_ACTION);
    filter.addAction(ConnectivityManager.CONNECTIVITY_ACTION);
    mContext.registerReceiver(mWifiReceiver, filter);
}

private void unregisterWifiReceiver() {
    mContext.unregisterReceiver(mWifiReceiver);
}

private boolean checkWifiConnect() {
    ConnectivityManager manager = (ConnectivityManager) mContext.getSystemService(Context.CONNECTIVITY_SERVICE);
    NetworkInfo networkInfo = manager.getActiveNetworkInfo();
    if (networkInfo != null
            && networkInfo.getType() == ConnectivityManager.TYPE_WIFI
            && networkInfo.isConnected()) {
        return true;
    }
    return false;
}

public static boolean isNetworkAvailable(Context context) {
		boolean isMobile = false, isWifi = false;

		NetworkInfo[] infoAvailableNetworks = getConnectivityManagerInstance(
				context).getAllNetworkInfo();

		if (infoAvailableNetworks != null) {
			for (NetworkInfo network : infoAvailableNetworks) {

				if (network.getType() == ConnectivityManager.TYPE_WIFI) {
					if (network.isConnected() && network.isAvailable())
						isWifi = true;
				}
				if (network.getType() == ConnectivityManager.TYPE_MOBILE) {
					if (network.isConnected() && network.isAvailable())
						isMobile = true;
				}
			}
		}

		return isMobile || isWifi;
	}

/* You can write such method somewhere in utility class and call it NetworkChangeReceiver like below */
public class NetworkChangedReceiver extends BroadcastReceiver 
{
@Override
	public void onReceive(Context context, Intent intent) {

		if (isNetworkAvailable(context)) 
                {
		     Toast.makeText(context, "Network Available Do operations",Toast.LENGTH_LONG).show(); 

			
	}
    }
}

This above broadcast receiver will be called only when Network state change to connected and not on disconnected.

CONNECTIVITY_ACTION docs:

>Apps targeting Android 7.0 (API level 24) and higher do not receive this broadcast if they declare the broadcast receiver in their manifest. Apps will still receive broadcasts if they register their BroadcastReceiver with Context.registerReceiver() and that context is still valid.

Here's a comfortable way to do it for activity, fragment or context. It will also auto-unregister if you do it for activity/fragment (in onDestroy), if you wish:

abstract class ConnectionBroadcastReceiver : BroadcastReceiver() {
    companion object {
        @JvmStatic
        fun registerWithoutAutoUnregister(context: Context, connectionBroadcastReceiver: ConnectionBroadcastReceiver) {
            context.registerReceiver(connectionBroadcastReceiver, IntentFilter(ConnectivityManager.CONNECTIVITY_ACTION))
        }

        @JvmStatic
        fun registerToFragmentAndAutoUnregister(context: Context, fragment: Fragment, connectionBroadcastReceiver: ConnectionBroadcastReceiver) {
            val applicationContext = context.applicationContext
            registerWithoutAutoUnregister(applicationContext, connectionBroadcastReceiver)
            fragment.lifecycle.addObserver(object : LifecycleObserver {
                @OnLifecycleEvent(Lifecycle.Event.ON_DESTROY)
                fun onDestroy() {
                    applicationContext.unregisterReceiver(connectionBroadcastReceiver)
                }
            })
        }

        @JvmStatic
        fun registerToActivityAndAutoUnregister(activity: AppCompatActivity, connectionBroadcastReceiver: ConnectionBroadcastReceiver) {
            registerWithoutAutoUnregister(activity, connectionBroadcastReceiver)
            activity.lifecycle.addObserver(object : LifecycleObserver {
                @OnLifecycleEvent(Lifecycle.Event.ON_DESTROY)
                fun onDestroy() {
                    activity.unregisterReceiver(connectionBroadcastReceiver)
                }
            })
        }

        @JvmStatic
        fun hasInternetConnection(context: Context): Boolean {
            val info = (context.getSystemService(Context.CONNECTIVITY_SERVICE) as ConnectivityManager).activeNetworkInfo
            return !(info == null || !info.isConnectedOrConnecting)
        }
    }

    override fun onReceive(context: Context, intent: Intent) {
        val hasConnection = !intent.getBooleanExtra(ConnectivityManager.EXTRA_NO_CONNECTIVITY, false)
//        Log.d("AppLog", "conenctivity changed. hasConnection? $hasConnection")
        onConnectionChanged(hasConnection)
    }

    abstract fun onConnectionChanged(hasConnection: Boolean)
}

Usage in fragment:

    ConnectionBroadcastReceiver.registerToFragmentAndAutoUnregister(activity!!, this, object : ConnectionBroadcastReceiver() {
        override fun onConnectionChanged(hasConnection: Boolean) {
            // Log.d("AppLog", "onConnectionChanged:" + hasConnection)
        }
    })

Try with this

public class ConnectionBroadcastReceiver extends BroadcastReceiver {
@Override
public void onReceive(Context context, Intent intent) {

    
    if (<Check internet connection available >) { 
    	Toast.makeText(context, "connect to the internet", Toast.LENGTH_LONG).show();
    	
    	/*upload background upload service*/
    	Intent serviceIntent = new Intent(context,<your service class>);
        context.startService(serviceIntent);
    	
    	
	}else{
		Toast.makeText(context, "Connection failed", Toast.LENGTH_LONG).show();
		
	}
    }
}

As soon as internet connection trigger, this (BroadcastReciever) will be loaded

I know this thread is old and fully answered but I feel that the following might help some people.

The code in the body of the question contains a bug which no one here addressed. @Nikhil is checking whether the wifi/mobile is available and not if it's connected.

The fix is here:

@Override
public void onReceive(final Context context, final Intent intent) {
    final ConnectivityManager connMgr = (ConnectivityManager) context
            .getSystemService(Context.CONNECTIVITY_SERVICE);

    final android.net.NetworkInfo wifi = connMgr
            .getNetworkInfo(ConnectivityManager.TYPE_WIFI);

    final android.net.NetworkInfo mobile = connMgr
            .getNetworkInfo(ConnectivityManager.TYPE_MOBILE);

    if (wifi.isConnected() || mobile.isConnected()) {
      // do stuff
    }
}

manifest:

<receiver android:name=".your.namepackage.here.ConnectivityReceiver">
    <intent-filter>
        <action android:name="android.net.conn.CONNECTIVITY_CHANGE"/>
    </intent-filter>
</receiver>

class for receiver:

public class ConnectivityReceiver extends BroadcastReceiver{

    @Override
    public void onReceive(Context context, Intent intent) {
        final String action = intent.getAction();
        switch (action) {
            case ConnectivityManager.CONNECTIVITY_ACTION:
                DebugUtils.logDebug("BROADCAST", "network change");
                if(NetworkUtils.isConnect()){
                    //do action here
                }
            break;
        }
    }
}

and classs utils like example:

public class NetworkUtils {

    public static boolean isConnect() {
        ConnectivityManager connectivityManager = (ConnectivityManager) Application.getInstance().getSystemService(Context.CONNECTIVITY_SERVICE);
        if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.LOLLIPOP) {
            Network[] netArray = connectivityManager.getAllNetworks();
            NetworkInfo netInfo;
            for (Network net : netArray) {
                netInfo = connectivityManager.getNetworkInfo(net);
                if ((netInfo.getTypeName().equalsIgnoreCase("WIFI") || netInfo.getTypeName().equalsIgnoreCase("MOBILE")) && netInfo.isConnected() && netInfo.isAvailable()) {
                    //if (netInfo.getState().equals(NetworkInfo.State.CONNECTED)) {
                    Log.d("Network", "NETWORKNAME: " + netInfo.getTypeName());
                    return true;
                }
            }
        } else {
            if (connectivityManager != null) {
                @SuppressWarnings("deprecation")
                NetworkInfo[] netInfoArray = connectivityManager.getAllNetworkInfo();
                if (netInfoArray != null) {
                    for (NetworkInfo netInfo : netInfoArray) {
                        if ((netInfo.getTypeName().equalsIgnoreCase("WIFI") || netInfo.getTypeName().equalsIgnoreCase("MOBILE")) && netInfo.isConnected() && netInfo.isAvailable()) {
                            //if (netInfo.getState() == NetworkInfo.State.CONNECTED) {
                            Log.d("Network", "NETWORKNAME: " + netInfo.getTypeName());
                            return true;
                        }
                    }
                }
            }
        }
        return false;
    }
}

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

public static final int TIME_OUT = 10 * 1000;

private OnCallBack listener;

public interface OnCallBack {

	public void onBack(Boolean value);
}

public AsyncCheckInternet(OnCallBack listener) {
	this.listener = listener;
}

@Override
protected void onPreExecute() {
}

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

	ConnectivityManager connectivityManager = (ConnectivityManager) General.context
			.getSystemService(Context.CONNECTIVITY_SERVICE);

	NetworkInfo networkInfo = connectivityManager.getActiveNetworkInfo();

	if ((networkInfo != null && networkInfo.isConnected())
			&& ((networkInfo.getType() == ConnectivityManager.TYPE_WIFI) || (networkInfo
					.getType() == ConnectivityManager.TYPE_MOBILE))) {
		HttpURLConnection urlc;
		try {
			urlc = (HttpURLConnection) (new URL("http://www.google.com")
					.openConnection());
			urlc.setConnectTimeout(TIME_OUT);
			urlc.connect();
			if (urlc.getResponseCode() == HttpURLConnection.HTTP_OK) {
				return true;
			} else {
				return false;
			}
		} catch (MalformedURLException e) {
			e.printStackTrace();
			return false;

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

		}
	} else {
		return false;
	}
}

@Override
protected void onPostExecute(Boolean result) {
	if (listener != null) {
		listener.onBack(result);
	}
}

}

Add a broadcast receiver which can listen to network connectivity change. Then check wether device is connected to internet or not using ConnectivityManager. Refer to this post or video for detailed understanding. Below is the code:

public class NetworkStateChangeReceiver extends BroadcastReceiver {
  public static final String NETWORK_AVAILABLE_ACTION = "com.ajit.singh.NetworkAvailable";
  public static final String IS_NETWORK_AVAILABLE = "isNetworkAvailable";
 
  @Override
  public void onReceive(Context context, Intent intent) {
    Intent networkStateIntent = new Intent(NETWORK_AVAILABLE_ACTION);
    networkStateIntent.putExtra(IS_NETWORK_AVAILABLE,  isConnectedToInternet(context));
    LocalBroadcastManager.getInstance(context).sendBroadcast(networkStateIntent);
  }
 
  private boolean isConnectedToInternet(Context context) {
    try {
      if (context != null) {
        ConnectivityManager connectivityManager = (ConnectivityManager) context.getSystemService(CONNECTIVITY_SERVICE);
        NetworkInfo networkInfo = connectivityManager.getActiveNetworkInfo();
        return networkInfo != null && networkInfo.isConnected();
      }
      return false;
    } catch (Exception e) {
      Log.e(NetworkStateChangeReceiver.class.getName(), e.getMessage());
      return false;
    }
  }
}

I wrote this receiver to show a notification on the Screen, that's why you see a local broadcast with the network status. Here is the code to show the notification.

public class MainActivity extends AppCompatActivity {
 
  @Override
  protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);
 
    IntentFilter intentFilter = new IntentFilter(NetworkStateChangeReceiver.NETWORK_AVAILABLE_ACTION);
    LocalBroadcastManager.getInstance(this).registerReceiver(new BroadcastReceiver() {
      @Override
      public void onReceive(Context context, Intent intent) {
        boolean isNetworkAvailable = intent.getBooleanExtra(IS_NETWORK_AVAILABLE, false);
        String networkStatus = isNetworkAvailable ? "connected" : "disconnected";
 
        Snackbar.make(findViewById(R.id.activity_main), "Network Status: " + networkStatus, Snackbar.LENGTH_LONG).show();
      }
    }, intentFilter);
  }
}

Activity listens to the intent broadcasted by the network receiver and shows the notification on the screen.

Complete answer here

Menifest file

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

<receiver android:name=".NetworkStateReceiver">
    <intent-filter>
      <action android:name="android.net.conn.CONNECTIVITY_CHANGE" />
    </intent-filter>
  </receiver>

BroadecardReceiver class

public class NetworkStateReceiver extends BroadcastReceiver {
    public void onReceive(Context context, Intent intent) {
     Log.d("app","Network connectivity change");
     if(intent.getExtras()!=null) {
        NetworkInfo ni=(NetworkInfo) intent.getExtras().get(ConnectivityManager.EXTRA_NETWORK_INFO);
        if(ni!=null && ni.getState()==NetworkInfo.State.CONNECTED) {
            Log.i("app","Network "+ni.getTypeName()+" connected");
        } else if(intent.getBooleanExtra(ConnectivityManager.EXTRA_NO_CONNECTIVITY,Boolean.FALSE)) {
            Log.d("app","There's no network connectivity");
        }
   }
}

Registering receiver in MainActivity

@Override
protected void onResume() {
    super.onResume();
    IntentFilter intentFilter = new IntentFilter(ConnectivityManager.CONNECTIVITY_ACTION);
    registerReceiver(networkReceiver, intentFilter);
}

@Override
protected void onPause() {
    super.onPause();
    if (networkReceiver != null)
        unregisterReceiver(networkReceiver);
}

Enjoy!

Broadcast receiver code to check internet connectivity change:

public class BroadCastDetecter extends BroadcastReceiver {
    public static boolean internet_status = false;
    public static void checkInternetConenction(Context context) {
        internet_status = false;
        ConnectivityManager check = (ConnectivityManager) context.getSystemService(Context.CONNECTIVITY_SERVICE);
        if (check != null) {
            NetworkInfo[] info = check.getAllNetworkInfo();
            if (info != null)
                for (int i = 0; i < info.length; i++)
                {
                    if (info[i].getState() == NetworkInfo.State.CONNECTED) {
                        internet_status = true;
                    }
                }
            if(internet_status)
            {
               //do what you want to if internet connection is available
            }
        }
    }

    @Override
    public void onReceive(Context context, Intent intent)
    {
        try {
            checkInternetConenction(context);
        }catch(Exception e){

        }
    }
}

add this in manifest file:

 <receiver android:name=".BroadCastDetecter">
            <intent-filter>
                <action android:name="android.net.conn.CONNECTIVITY_CHANGE" />
            </intent-filter>
        </receiver>

This only checks if the network interface is available, doesn't guarantee a particular network service is available, for example, there could be low signal or server downtime

  private boolean isNetworkInterfaceAvailable(Context context) {
        ConnectivityManager cm = (ConnectivityManager) context.getSystemService(Context.CONNECTIVITY_SERVICE);
        NetworkInfo activeNetwork = cm.getActiveNetworkInfo();
        return activeNetwork != null && activeNetwork.isConnectedOrConnecting();
    }

if you want to make a real connection to make sure your connection can gather data from a server or any url:

  private boolean isAbleToConnect(String url, int timeout) {
        try {
            URL myUrl = new URL(url);
            URLConnection connection = myUrl.openConnection();
            connection.setConnectTimeout(timeout);
            connection.connect();
            return true;
        } catch (Exception e) {
            Log.i("exception", "" + e.getMessage());
            return false;
        }
    }

This function needs to be wrapped in a background thread :

final String action = intent.getAction();
        if (intent.getAction().equals(ConnectivityManager.CONNECTIVITY_ACTION)) {
            checkConnectivity(context);
        }
    }


    private void checkConnectivity(final Context context) {
        if (!isNetworkInterfaceAvailable(context)) {
            Toast.makeText(context, "You are OFFLINE!", Toast.LENGTH_SHORT).show();
            return;
        }

        final Handler handler = new Handler();
        new Thread(new Runnable() {
            @Override
            public void run() {
                final boolean isConnected = isAbleToConnect("http://www.google.com", 1000);
                handler.post(new Runnable() {
                    @Override
                    public void run() {
                        if (isConnected)
                            Toast.makeText(context, "You are ONLINE!", Toast.LENGTH_SHORT).show();
                        else
                            Toast.makeText(context, "You are OFFLINE!", Toast.LENGTH_SHORT).show();
                    }
                });

            }
        }).start();

    }

Add required permissions:

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

Add this line under application in manifest file:

android:usesCleartextTraffic="true"

Add receiver to manifest file:

<receiver android:name=".ConnectivityChangeReceiver" >
            <intent-filter>

                <action android:name="android.net.conn.CONNECTIVITY_CHANGE" />
            </intent-filter>
        </receiver>    

Register/Unregister the BR in you Activity:

@Override
    protected void onStart() {
        super.onStart();
        IntentFilter filter = new IntentFilter("android.net.conn.CONNECTIVITY_CHANGE");
        registerReceiver(connectivityChangeReceiver, filter);
    }

    @Override
    protected void onDestroy() {
        super.onDestroy();
        unregisterReceiver(connectivityChangeReceiver);
    }

this is the entire Broadcast class :

import android.content.BroadcastReceiver;
import android.content.Context;
import android.content.Intent;
import android.net.ConnectivityManager;
import android.net.NetworkInfo;
import android.os.Handler;
import android.util.Log;
import android.widget.Toast;

import java.net.URL;
import java.net.URLConnection;

public class ConnectivityChangeReceiver extends BroadcastReceiver {


    @Override
    public void onReceive(final Context context, final Intent intent) {

        final String action = intent.getAction();
        if (intent.getAction().equals(ConnectivityManager.CONNECTIVITY_ACTION)) {
            checkConnectivity(context);
        }
    }


    private void checkConnectivity(final Context context) {
        if (!isNetworkInterfaceAvailable(context)) {
            Toast.makeText(context, "You are OFFLINE!", Toast.LENGTH_SHORT).show();
            return;
        }

        final Handler handler = new Handler();
        new Thread(new Runnable() {
            @Override
            public void run() {
                final boolean isConnected = isAbleToConnect("http://www.google.com", 1000);
                handler.post(new Runnable() {
                    @Override
                    public void run() {
                        if (isConnected)
                            Toast.makeText(context, "You are ONLINE!", Toast.LENGTH_SHORT).show();
                        else
                            Toast.makeText(context, "You are OFFLINE!", Toast.LENGTH_SHORT).show();
                    }
                });

            }
        }).start();

    }

    //This only checks if the network interface is available, doesn't guarantee a particular network service is available, for example, there could be low signal or server downtime
    private boolean isNetworkInterfaceAvailable(Context context) {
        ConnectivityManager cm = (ConnectivityManager) context.getSystemService(Context.CONNECTIVITY_SERVICE);
        NetworkInfo activeNetwork = cm.getActiveNetworkInfo();
        return activeNetwork != null && activeNetwork.isConnectedOrConnecting();
    }

    //This makes a real connection to an url and checks if you can connect to this url, this needs to be wrapped in a background thread
    private boolean isAbleToConnect(String url, int timeout) {
        try {
            URL myUrl = new URL(url);
            URLConnection connection = myUrl.openConnection();
            connection.setConnectTimeout(timeout);
            connection.connect();
            return true;
        } catch (Exception e) {
            Log.i("exception", "" + e.getMessage());
            return false;
        }
    }
} 

1. In manifest : - call receiver like below code

   http://schemas.android.com/apk/res/android" xmlns:tools="http://schemas.android.com/tools" package="com.safal.checkinternet">

    <uses-permission android:name="android.permission.INTERNET" />
    <uses-permission android:name="android.permission.ACCESS_NETWORK_STATE" />
   
    <application
    	android:allowBackup="true"
    	android:icon="@mipmap/ic_launcher"
    	android:label="@string/app_name"
    	android:roundIcon="@mipmap/ic_launcher_round"
    	android:supportsRtl="true"
    	android:theme="@style/AppTheme"
    	tools:ignore="AllowBackup,GoogleAppIndexingWarning">
    	<receiver android:name=".NetworkChangeReceiver" >
    		<intent-filter>
    			<action android:name="android.net.conn.CONNECTIVITY_CHANGE" />
    		</intent-filter>
    	</receiver>
    	<activity android:name=".MainActivity">
    		<intent-filter>
    			<action android:name="android.intent.action.MAIN" />
   
    			<category android:name="android.intent.category.LAUNCHER" />
    		</intent-filter>
    	</activity>
    </application>
   

2. Make one Broad Cast Receiver Class: - In This class add code of Network Check

   package com.safal.checkinternet;

   import android.content.BroadcastReceiver; import android.content.Context; import android.content.Intent; import android.net.ConnectivityManager; import android.net.NetworkInfo; import android.util.Log; import android.widget.Toast;

   public class NetworkChangeReceiver extends BroadcastReceiver {

    @Override
    public void onReceive(final Context context, final Intent intent) {
    	if (isOnline(context)){
    		Toast.makeText(context, "Available", Toast.LENGTH_SHORT).show();
    	}else {
    		Toast.makeText(context, "Not Available", Toast.LENGTH_SHORT).show();
    	}
    }
    public boolean isOnline(Context context) {
   
    	ConnectivityManager cm = (ConnectivityManager) context.getSystemService(Context.CONNECTIVITY_SERVICE);
    	assert cm != null;
    	NetworkInfo netInfo = cm.getActiveNetworkInfo();
    	return (netInfo != null && netInfo.isConnected());
    }    
   

   }

3. In your Activity call to Broad Cast Receiver : -

   package com.safal.checkinternet;

   import androidx.appcompat.app.AppCompatActivity;

   import android.content.Intent; import android.content.IntentFilter; import android.os.Bundle;

   public class MainActivity extends AppCompatActivity {

    @Override
    protected void onCreate(Bundle savedInstanceState) {
    	super.onCreate(savedInstanceState);
    	setContentView(R.layout.activity_main);
   

   //Call Broad cast Receiver IntentFilter filter = new IntentFilter(); filter.addAction("android.net.conn.CONNECTIVITY_CHANGE"); registerReceiver(new NetworkChangeReceiver(), filter); } }

It's easier to use https://github.com/JobGetabu/DroidNet

 @Override
    public void onInternetConnectivityChanged(boolean isConnected) {
      
        if (isConnected) {
            //do Stuff with internet
            netIsOn();
        } else {
            //no internet
            netIsOff();
        }
    }

    private void netIsOn(){...}

    private void netIsOff(){...}

Add permissions:

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

Create Receiver to check for connection

public class NetworkChangeReceiver extends BroadcastReceiver {

    @Override
    public void onReceive(final Context context, final Intent intent) {

        if(checkInternet(context))
        {
            Toast.makeText(context, "Network Available Do operations",Toast.LENGTH_LONG).show(); 
        }

    }

    boolean checkInternet(Context context) {
        ServiceManager serviceManager = new ServiceManager(context);
        if (serviceManager.isNetworkAvailable()) {
            return true;
        } else {
            return false;
        }
    }

}

ServiceManager.java

public class ServiceManager {

    Context context;

    public ServiceManager(Context base) {
        context = base;
    }

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

First of all we will make a class that will check the connectivity of the network state. So lets create a class :

public class AppStatus {
    private static AppStatus instance = new AppStatus();
    static Context context;
    ConnectivityManager connectivityManager;
    NetworkInfo wifiInfo, mobileInfo;
    boolean connected = false;

    public static AppStatus getInstance(Context ctx) {
        context = ctx.getApplicationContext();
        return instance;
    }

    public boolean isOnline() {
        try {
            connectivityManager = (ConnectivityManager) context
                    .getSystemService(Context.CONNECTIVITY_SERVICE);

            NetworkInfo networkInfo = connectivityManager.getActiveNetworkInfo();
            connected = networkInfo != null && networkInfo.isAvailable() &&
                    networkInfo.isConnected();
            return connected;


        } catch (Exception e) {
            System.out.println("CheckConnectivity Exception: " + e.getMessage());
            Log.v("connectivity", e.toString());
        }
        return connected;
    }
}

Now Make a new Broadcast receiver class :

public class ConnectivityReceiver extends BroadcastReceiver {
    @Override
    public void onReceive(Context context, Intent intent) {
        if (AppStatus.getInstance(context).isOnline()) {

            Intent intent1=new Intent(context,DisplayAct.class);
            intent1.setFlags(Intent.FLAG_ACTIVITY_NEW_TASK);
            context.startActivity(intent1);




        } else {

            Toast.makeText(context, "Please !! Make your network ON", Toast.LENGTH_SHORT).show();

        }
    }
}

and Now register your broadcast receiver on manifest:

<receiver android:name=".ConnectivityReceiver">
            <intent-filter>
                <action android:name="android.net.conn.CONNECTIVITY_CHANGE"/>
            </intent-filter>
        </receiver>