Clicking

View.OnClickListener and View.OnLongClickListener define interfaces for callbacks to be invoked when a view is clicked.

Callbacks can be assigned programatically for any view

imgView.setOnClickListener{
    // do something 
}

imgView.setOnLongClickListener {
    // do something 
    true
}

imgView.setOnClickListener(view -> {
      // ... do something
});
        
imgView.setOnLongClickListener(view ->{
    // ... do something
    return true;
});

Click callback can be assigned from xml layout file. To do this activity must have method that handle click, for example:

fun onClickImage(v: View?) {/* ... */}

void onClickImage(View v){ /* ... */}

Then you can use onClick attribute.

<FrameLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:custom="http://schemas.android.com/apk/res-auto"
    android:layout_width="match_parent"
    android:layout_height="match_parent">

    <ImageView
        android:id="@+id/imgMain"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:adjustViewBounds="true"
        android:src="@drawable/flower_n_2"
        android:scaleType="centerCrop"
        android:onClick="onClickImage"
        >

    </ImageView>

</FrameLayout>