Android - setOnClickListener vs OnClickListener vs View.OnClickListener

Question

My understanding is that when I'm creating a button object that listens for a click, I have to:

1. Create the button object
2. Use OnClickListner to make it listen to the user's click
3. Use onClick to execute actions after the user clicks the button

Now,

• Where does setOnClickListener fit into the above logic?
• Which one actually listens to the button click?
• setOnClickListener?
• OnClickListener?
• View.OnClickListener?
• What are the differences between those three?

Here is what I found in Android Dev:

//The example below shows how to register an on-click listener for a Button.

// Create an anonymous implementation of OnClickListener
private OnClickListener mCorkyListener = new OnClickListener() {
    public void onClick(View v) {
      // do something when the button is clicked
    }
};

protected void onCreate(Bundle savedValues) {
    ...
    // Capture our button from layout
    Button button = (Button)findViewById(R.id.corky);
    // Register the onClick listener with the implementation above
    button.setOnClickListener(mCorkyListener);
    ...
}

You may also find it more convenient to implement OnClickListener as a part of your Activity. This will avoid the extra class load and object allocations. For example:

public class ExampleActivity extends Activity implements OnClickListener {
    protected void onCreate(Bundle savedValues) {
        ...
         Button button = (Button)findViewById(R.id.corky);
         button.setOnClickListener(this);
    }

    // Implement the OnClickListener callback
    public void onClick(View v) {
      // do something when the button is clicked
    }
}

Answer 1

Imagine that we have 3 buttons for example

public class MainActivity extends ActionBarActivity {

    @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 what we will do?

public class MainActivity extends ActionBarActivity {

    @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;
            }
        }
    };

}

Or we can do this:

public class MainActivity extends ActionBarActivity {

    @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
            }
        });

    }

}

Or we can implement View.OnClickListener and i think it's the best way:

public class MainActivity extends ActionBarActivity 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"