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What is an OnClickListener?

Educative Answers Team

Listener

A listener (or observer) is an abstract class or interface that is used to provide functionality for an interactable UI component (e.g., a button). It is a part of the observer design pattern that detects any events related to the UI; for example, clicking or tapping a part of the screen executes a certain action. Every listener has a function (callback method) that is overridden when implementing a concrete listener.

A UI component is known as a view in Android.

onClick(View v)

In Android, the OnClickListener() interface has an onClick(View v) method that is called when the view (component) is clicked. The code for a component’s functionality is written inside this method, and the listener is set using the setOnClickListener() method.

svg viewer

Code

Since the functionality of a component is usually different from other components, a listener (in Java) is commonly implemented using an anonymous class. Declaring a separate listener for each component also works, but it ​is not a good practice.

// Get button using its ID:
Button btn = findViewById(R.id.my_btn);

// Set OnCLickListener() using anonymous class:
btn.setOnClickListener(new View.OnClickListener(){
    @Override
    public void onClick(View v){
        // Functionality for the button...
    }
});

RELATED TAGS

interface
ui/ux
button
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