Android ViewFlipper with listener

README.md

Usage (Java)

mViewFlipper.setOnChildChangeListener(new ViewFlipper.OnChildChangeListener() {  
  @Override  
  public void onChange(int whichChild) {  
      Toast.makeText(mActivity, String.valueOf(whichChild), Toast.LENGTH_SHORT).show();  
  }  
});

Cheatsheet

Old	New
setDisplayedChild(args)	setActiveChild(args)
showPrevious()	previous()
showNext()	next()

ViewFlipper.java

import android.content.Context;
import android.util.AttributeSet;

public class ViewFlipper extends android.widget.ViewFlipper {
	private OnChildChangeListener mListener;

	public ViewFlipper(Context context) {
		super(context);
	}

	public ViewFlipper(Context context, AttributeSet attrs) {
		super(context, attrs);
	}

	public void setOnChildChangeListener(OnChildChangeListener listener) {
		this.mListener = listener;
	}

	public void setActiveChild(int whichChild) {
		this.setDisplayedChild(whichChild);

		if (this.mListener != null) {
			this.mListener.onChange(whichChild);
		}
	}

	public void previous() {
		this.showPrevious();

		if (this.mListener != null) {
			this.mListener.onChange(this.getDisplayedChild());
		}
	}

	public void next() {
		this.showNext();

		if (this.mListener != null) {
			this.mListener.onChange(this.getDisplayedChild());
		}
	}

	public interface OnChildChangeListener {
		void onChange(int whichChild);
	}
}

ViewFlipper.kt

class ViewFlipper(context: Context, attrs: AttributeSet? = null) : ViewFlipper(context, attrs) {
    var listener: OnChildChangeListener? = null

    private fun currentView(): View = getChildAt(displayedChild)

    private fun previousView(): View {
        if (displayedChild - 1 > 0) {
            return getChildAt(displayedChild - 1)
        }

        return getChildAt(0)
    }

    private fun nextView(): View {
        if (displayedChild + 1 < childCount) {
            return getChildAt(displayedChild + 1)
        }

        return getChildAt(0)
    }

    override fun showPrevious() {
        super.showPrevious()
        listener?.onChildChanged(displayedChild, currentView(), previousView(), nextView())
    }

    override fun showNext() {
        super.showNext()
        listener?.onChildChanged(displayedChild, currentView(), previousView(), nextView())
    }

    interface OnChildChangeListener {
        fun onChildChanged(index: Int, currentView: View, previousView: View, nextView: View)
    }
}