UninterceptableViewPager

UninterceptableViewPager.java

import android.content.Context;
import android.support.v4.view.ViewPager;
import android.util.AttributeSet;
import android.view.GestureDetector;
import android.view.GestureDetector.SimpleOnGestureListener;
import android.view.MotionEvent;

/**
 * Custom {@link ViewPager} implementation that will handle horizontal scroll events by himself. Default ViewPager
 * becomes hardly usable when it's nested into ScrollView based containers (such as ScrollView, ListView, etc.). It is
 * due to the fact that ScrollView based views will intercept any motion event with minimal (even 1px) vertical shift.
 * So to scroll ViewPager user will need to move his finger horizontally with zero vertical shift, which is obvious
 * quite irritating.
 */
public class UninterceptableViewPager extends ViewPager {

	// -----------------------------------------------------------------------
	//
	// Constructor
	//
	// -----------------------------------------------------------------------
	public UninterceptableViewPager(Context context, AttributeSet attrs) {
		super(context, attrs);
		mGestureDetector = new GestureDetector(context, new YScrollDetector());
	}

	// -----------------------------------------------------------------------
	//
	// Fields
	//
	// -----------------------------------------------------------------------
	private GestureDetector mGestureDetector;

	// -----------------------------------------------------------------------
	//
	// Methods
	//
	// -----------------------------------------------------------------------
	@Override
	public boolean onTouchEvent(MotionEvent event) {
		boolean isScrollY = mGestureDetector.onTouchEvent(event);
		getParent().requestDisallowInterceptTouchEvent(!isScrollY);
		return super.onTouchEvent(event);
	}

	// -----------------------------------------------------------------------
	//
	// Inner Classes
	//
	// -----------------------------------------------------------------------
	private class YScrollDetector extends SimpleOnGestureListener {
		/**
		 * @return true - if we're scrolling in Y direction, false - in X direction.
		 */
		@Override
		public boolean onScroll(MotionEvent e1, MotionEvent e2, float distanceX, float distanceY) {
			return Math.abs(distanceY) > Math.abs(distanceX);
		}
	}
}