What does the onclick listener (this) mean?

Question

btn_Login.setOnClickListener(this);

In android studio.

I've seen this in countless places. What does this mean? I know how this operates but what is the listener called then?

This example is from: Link

Answer 1

Suppose that you have 16 Buttons and every button has setOnclicklistener this means that you are creating many repetitions of similar code to this in your class. And that makes your code ugly, also this is not the efficient way to write your code. So to make your code efficient you have to implement OnClickListener() on your activity and then for each button use buttonX.setOnClickListener(this). Now use the override onClick method. In this method, you can use either the switch case block or if-else to identify which button is pressed. So in the onClick method you just have to give ids of the button.

Implement OnClickListener in Activity

public class MyActivity extends Activity implements View.OnClickListener {
}

For each button use this:

buttonX.setOnClickListener(this);

After this implement override the onClick method

@Override
public void onClick(View view) {
    switch(view.getId){
        case R.id.buttonX: 
            // Do something
            break;
}