In your App you might be having UI elements like buttons on click of which some action happens in the background.
Let’s take a button for example.
<Button android:layout_width="wrap_content" android:layout_height="wrap_content" android:layout_gravity="center" android:id="@+id/testButtonId" />
There are two ways to handle events on Button click. One is to define an android:onClick attribute in the layout xml file and specify the method in the Java class.
The problem with this approach is – if you have buttons defined in a Fragment then you need to define corresponding methods in the Activity class. This will lead to tight coupling between Activity and Fragment.
To avoid this use a onClickListener.
For this you need to implement an onClickListener and bind the Button to this.
Follow the video and refer to the source code here to understand this better.