Add a Click Listener

This section explain, also referring to here, how to add a listener to a button. The same logic can be applicable to apply the listener to other graphic objects. The section explains also the differences between OnClickListener, setOnclickListener and View.OnClickListener.

First of all, there is no difference between View.OnClickListener and OnClickListener. If you just use View.OnClickListener directly, then you don't need to write "import android.view.View.OnClickListener"
You set an OnClickListener instance (e.g. myListener named object) as the listener to a view via setOnclickListener(). When a click event is fired, that myListener gets notified and it's onClick(View view) method is called
View is the superclass for all widgets and the OnClickListener interface belongs to this class. All widgets inherit this. You would have to override the onClick(View view) method from this listener to achieve the action that you want for your button
To tell Android to listen to click events for a widget, you need to do:

widget.setOnClickListener(new View.OnClickListener() {

    @Override

    public void onClick(View view) {

        // Do something here

});

The View parameter passed in the onClick() method simply lets Android know that a view has been clicked. It can be a Button or a TextView or something else
It is up to you to set an OnClickListener for every widget or to simply make the class containing all these widgets implement the interface
In this case you will have a common onClick() method for all the widgets and all you have to do is to check the id of the view that is passed into the method and then match that against the id for each element that you want and take action for that element

Here the three solutions assuming to add three buttons

public class MainActivity extends AppCompatActivity{

    @Override

    protected void onCreate(Bundle savedInstanceState) {

        super.onCreate(savedInstanceState);

        setContentView(R.layout.activity_main);

        // Capture our button from layout

        Button button = (Button)findViewById(R.id.corky);

        Button button2 = (Button)findViewById(R.id.corky2);

        Button button3 = (Button)findViewById(R.id.corky3);

        // Register the onClick listener with the implementation above

        button.setOnClickListener(mCorkyListener);

        button2.setOnClickListener(mCorkyListener);

        button3.setOnClickListener(mCorkyListener);

    // Create an anonymous implementation of OnClickListener

    private View.OnClickListener mCorkyListener = new View.OnClickListener() {

        public void onClick(View v) {

            // do something when the button is clicked

            // Yes we will handle click here but which button clicked??? We don't know

};

Option1: only one OnClickListener and one onClick where all three click events are managed

public class MainActivity extends AppCompatActivity{

    @Override

    protected void onCreate(Bundle savedInstanceState) {

        super.onCreate(savedInstanceState);

        setContentView(R.layout.activity_main);

        // Capture our button from layout

        Button button = (Button)findViewById(R.id.corky);

        Button button2 = (Button)findViewById(R.id.corky2);

        Button button3 = (Button)findViewById(R.id.corky3);

        // Register the onClick listener with the implementation above

        button.setOnClickListener(mCorkyListener);

        button2.setOnClickListener(mCorkyListener);

        button3.setOnClickListener(mCorkyListener);

    // Create an anonymous implementation of OnClickListener

    private View.OnClickListener mCorkyListener = new View.OnClickListener() {

        public void onClick(View v) {

            // do something when the button is clicked

            // Yes we will handle click here but which button clicked??? We don't know

            // So we will make

            switch (v.getId() /*to get clicked view id**/) {

                case R.id.corky:

                    // do something when the corky is clicked

                    break;

                case R.id.corky2:

                    // do something when the corky2 is clicked

                    break;

                case R.id.corky3:

                    // do something when the corky3 is clicked

                    break;

                default:

                    break;

};

Option2: each button has its own setOnClickListener and inside its own onClick

public class MainActivity extends AppCompatActivity{

    @Override

    protected void onCreate(Bundle savedInstanceState) {

        super.onCreate(savedInstanceState);

        setContentView(R.layout.activity_main);

        // Capture our button from layout

        Button button = (Button)findViewById(R.id.corky);

        Button button2 = (Button)findViewById(R.id.corky2);

        Button button3 = (Button)findViewById(R.id.corky3);

        // Register the onClick listener with the implementation above

        button.setOnClickListener(new View.OnClickListener() {

            @Override

            public void onClick(View v) {

                // do something when the corky is clicked

});

        button2.setOnClickListener(new View.OnClickListener() {

            @Override

            public void onClick(View v) {

                // do something when the corky2 is clicked

});

        button3.setOnClickListener(new View.OnClickListener() {

            @Override

            public void onClick(View v) {

                // do something when the corky3 is clicked

});

Option3: only one onClick that manage the three events but the main class implements View.OnClickListener

public class MainActivity extends AppCompatActivity implements View.OnClickListener {

    @Override

    protected void onCreate(Bundle savedInstanceState) {

        super.onCreate(savedInstanceState);

        setContentView(R.layout.activity_main);

        // Capture our button from layout

        Button button = (Button)findViewById(R.id.corky);

        Button button2 = (Button)findViewById(R.id.corky2);

        Button button3 = (Button)findViewById(R.id.corky3);

        // Register the onClick listener with the implementation above

        button.setOnClickListener(this);

        button2.setOnClickListener(this);

        button3.setOnClickListener(this);

    @Override

    public void onClick(View v) {

        // do something when the button is clicked

        // Yes we will handle click here but which button clicked??? We don't know

        // So we will make

        switch (v.getId() /*to get clicked view id**/) {

            case R.id.corky:

                // do something when the corky is clicked

                break;

            case R.id.corky2:

                // do something when the corky2 is clicked

                break;

            case R.id.corky3:

                // do something when the corky3 is clicked

                break;

            default:

                break;

Finally there is no real differences here; just "Way better than the other" .

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