Get a list of all the implementations of an Interface in Android

Question

I am working on a project in Android and want to know the Inte.net Connection State in every Activity and my App has more than 15 activities so, I don't want to implement and initialize my.networkstatechanged class and interface in every activity. So, I have created it's instance in a class that extends Application in which I create a object of my interface.

My NetworkStateChanged Class:

NetworkConnected.java

package time.real.identify.location.tracker.gps.saksham.com.emptrackerhost;

import java.io.IOException;
import java.net.InetSocketAddress;
import java.net.Socket;
import java.net.SocketAddress;
import java.util.ArrayList;
import java.util.List;

interface NetworkListener {
    void isConnected();
    void isDisconnected();
}


public class NetworkConnected {

    private List<NetworkListener> listeners = new ArrayList<NetworkListener>();
    private boolean isConnected = false;
    private boolean wasConnected = false;

    NetworkConnected() {
        new Thread(new Runnable() {
            @Override
            public void run() {
                isConnected = isOnline();
                wasConnected = isConnected;
                notifySomethingHappened();
                while(true){
                    isConnected = isOnline();
                    if(wasConnected != isConnected){
                        wasConnected = isConnected;
                        notifySomethingHappened();
                    }
                    try {
                        Thread.sleep(100);
                    } catch (InterruptedException e) {
                        e.printStackTrace();
                    }
                }
            }
        }).start();
    }
    private boolean isOnline() {
        try {
            int timeoutMs = 3000;
            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;
        }
    }
    void addListener(NetworkListener listener) { listeners.add(listener); }
    private void notifySomethingHappened() {
        for (NetworkListener listener : listeners) {
            if(isConnected){
                listener.isConnected();
            }
            else{
                listener.isDisconnected();
            }
        }

    }

}

ApplicationClass.java

package time.real.identify.location.tracker.gps.saksham.com.emptrackerhost;

import android.app.Application;

public class ApplicationClass extends Application {

    public static boolean isNetworkConnected = false;
    @Override
    public void onCreate() {
        super.onCreate();
        new NetworkConnected().addListener(new time.real.identify.location.tracker.gps.saksham.com.emptrackerhost.NetworkListener() {
            @Override
            public void isConnected() {
                isNetworkConnected = true;
            }

            @Override
            public void isDisconnected() {
                isNetworkConnected = false;
            }
        });
    }

}

After this I would just like to implement a interface in every class which would not need to be added as listener or initialized since one object is already running.

I want something like this:-

public class LoginPageClass extends Activity implements NetworkListener
{
public void isConnected(){
//Make a Snackbar
}
public void isDisconnected(){
//Make a Snackbar
}
}

Note:- I don't want to call object of myNetworkListener Class from ApplicationClass to add listener(this);

I just want to get a list of classes that implement my NetworkConnected Class in order to provide a state change callback to them. Is it possible? If so, how?

Answer 1

Of course on Java you can't extends two classes, so you can create a new class BaseAcivity that extends class Activity and make the job done on the NetworkConnected on this class (BaseActivity), and extend it on your activities instead of class Activity.

Answer 2

You can use BaseActivity As abstract and check the the inte.net as per the.network changes.

• Require permissions

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

• NetworkChangeListener.java

/* Interface required to call in each activity with whom you extends BaseActivity.java */
public interface NetworkChangeListener {
    void networkAvailable();

    void networkUnavailable();
}

• BaseActivity.java

@SuppressLint("Registered")
public abstract class BaseActivity extends AppCompatActivity implements NetworkChangeListener {

    private BroadcastReceiver networkStateReceiver = new BroadcastReceiver() {
        @Override
        public void onReceive(Context context, Intent intent) {
            ConnectivityManager manager = (ConnectivityManager) context.getSystemService(Context.CONNECTIVITY_SERVICE);
            /* previous way of doing it*/
            NetworkInfo ni = null;
            if (manager != null) {
                ni = manager.getActiveNetworkInfo();
            }
            if (ni != null && ni.isConnected()) {
                networkAvailable();
            } else {
                networkUnavailable();
            }
        }
    };

    /*
     * If you like to check it manually you also cam use the bellow function for it
     * */

    public void checkInternet() {
        ConnectivityManager manager = (ConnectivityManager) context.getSystemService(Context.CONNECTIVITY_SERVICE);
        /* previous way of doing it*/
        NetworkInfo ni = null;
        if (manager != null) {
            ni = manager.getActiveNetworkInfo();
        }
        if (ni != null && ni.isConnected())
            networkAvailable();
        else
            networkUnavailable();
    }

    @Override
    protected void onResume() {
        super.onResume();
        Log.e("NETWORK_STATE", "networkStateReceiver registerReceiver");
        registerReceiver(networkStateReceiver, new IntentFilter(android.net.ConnectivityManager.CONNECTIVITY_ACTION));
    }

    @Override
    protected void onPause() {
        super.onPause();
        Log.e("NETWORK_STATE", "networkStateReceiver unregisterReceiver");
        unregisterReceiver(networkStateReceiver);
    }
}

if you like to check the Inte.net manually you can use

    /*
     * If you like to check it manually you also cam use the bellow function for it
     * */
    public void checkInternet() {
        ConnectivityManager manager = (ConnectivityManager) context.getSystemService(Context.CONNECTIVITY_SERVICE);
        /* previous way of doing it*/
        NetworkInfo ni = null;
        if (manager != null) {
            ni = manager.getActiveNetworkInfo();
        }
        if (ni != null && ni.isConnected())
            networkAvailable();
        else
            networkUnavailable();
    }

• MainActivity.java

public class MainActivity extends BaseActivity {

    /*
     * Check the log for the proper results
     * */
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
    }

    @Override
    public void networkAvailable() {
        Log.e("NETWORK_STATE", "Connected");
    }

    @Override
    public void networkUnavailable() {
        Log.e("NETWORK_STATE", "Not Connected");
    }
}

Also if anything missed please refer Github repo