How to Execute a Method by Clicking a Notification

calling a method in service after click on notification

You can specify a Broadcast in your Service and launch that via a PendingIntent in your notification.

Intent stopIntent = new Intent("my.awersome.string.name");
PendingIntent stopPi = PendingIntent.getBroadcast(this, 4, stopIntent, PendingIntent.FLAG_CANCEL_CURRENT);

Then, in your notification builder:

NotificationCompat.Builder builder;
builder = new NotificationCompat.Builder(context)
    ...     
    .setContentIntent(stopPi);

In your Service you can setup a BroadcastReceiver as:

private final BroadcastReceiver myReceiver = new BroadcastReceiver() {
    @Override
    public void onReceive(Context context, Intent intent) {
        // Code to run
    }
};

You register this receiver in your Service (possibly in onStartCommand()) only using:

registerReceiver(myReceiver, new IntentFilter("my.awersome.string.name"));

Your Service MUST be running for this to work.

How to call a non-activity method on Notification Click

You could do something like this:

When creating your PendingIntent to put in the Notification:

Intent notificationIntent = new Intent(MainActivity.this, MyClass.class);
notificationIntent.putExtra("fromNotification", true);
PendingIntent pendingIntent = PendingIntent.getActivity(MainActivity.this, 0, notificationIntent,
         PendingIntent.FLAG_UPDATE_CURRENT);

Now, in MyClass.onCreate():

if (getIntent().hasExtra("fromNotification")) {
    callMethod();
}

Execute an action on notification click

You'll have to use a BroadcastReceiver for that. Take a look at the following code. Put it in your Service

private MyBroadcastReceiver mBroadcastReceiver;
@Override
onCreate() {
    super.onCreate();
    mBroadcastReceiver = new MyBroadcastReceiver();
    IntentFilter intentFilter = new IntentFilter();
    intentFilter.addCategory(Intent.CATEGORY_DEFAULT);
    // set the custom action
    intentFilter.addAction("do_something");

    registerReceiver(mBroadcastReceiver, intentFilter);
}

// While making notification
Intent i = new Intent("do_something");
PendingIntent pendingIntent = PendingIntent.getBroadcast(this, 0, i, 0);
notification.contentIntent = pendingIntent;

public class MyBroadcastReceiver extends BroadcastReceiver {
        @Override
        public void onReceive(Context context, Intent intent) {
            String action = intent.getAction();
            switch(action) {
                case "do_something":
                    doSomething();
                    break;
            }
        }
    }

public void doSomething() {
    //Whatever you wanna do on notification click
}

This way the doSomething() method will be called when your Notification is clicked.

How to invoke a method on a foreground service by clicking on a notification action?

Define a constant:

private const val EXTRA_STOP = "stop";

Then create an intent for your service and put an extra flag:

val intent = Intent(context, YourService::class.java);
intent.putExtra(EXTRA_STOP, true);

Now you can create a pending intent as your handler:

val pendingIntent: PendingIntent = PendingIntent.getService(context, YOUR_REQUEST_CODE, intent, PendingIntent.FLAG_IMMUTABLE)

This pending intent will trigger the onStartCommand method on your service, where you can check whether the stop flag was set.

override fun onStartCommand(intent: Intent?, flags: Int, startId: Int): Int {
    if (intent != null && intent.getBooleanExtra(EXTRA_STOP, false)) {
        stopAction()
    }
    ...
}

Android call method on notification click

Add android:launchMode="singleTop" in your activity in your manifest file, have the method protected void onNewIntent(Intent intent) { ... } and use this code:

private static final int MY_NOTIFICATION_ID = 1;
private NotificationManager notificationManager;
private Notification myNotification;

void notification() {   
    notificationManager = (NotificationManager) getSystemService(Context.NOTIFICATION_SERVICE);
    myNotification = new Notification(R.drawable.next, "Notification!", System.currentTimeMillis());
    Context context = getApplicationContext();
    String notificationTitle = "Exercise of Notification!";
    String notificationText = "http://android-er.blogspot.com/";
    Intent myIntent = new Intent(this, YourActivity.class);
    PendingIntent pendingIntent = PendingIntent.getActivity(YourActivity.this, 0, myIntent, Intent.FILL_IN_ACTION);
    myNotification.flags |= Notification.FLAG_AUTO_CANCEL;
    myNotification.setLatestEventInfo(context, notificationTitle, notificationText, pendingIntent);
    notificationManager.notify(MY_NOTIFICATION_ID, myNotification);
}