CustomViewPager.java

package com.github.jjobes.slidedaytimepicker;

import android.content.Context;
import android.support.v4.view.ViewPager;
import android.util.AttributeSet;
import android.view.MotionEvent;
import android.view.View;
import android.view.ViewConfiguration;
import android.widget.NumberPicker;
import android.widget.TimePicker;

/**
 * A custom {@link android.support.v4.view.ViewPager} implementation that corrects
 * the height of the ViewPager and also dispatches touch events to either the ViewPager
 * or the day or time picker depending on the direction of the swipe.
 *
 * @author jjobes
 *
 */
public class CustomViewPager extends ViewPager
{
    private NumberPicker mDayPicker;
    private TimePicker mTimePicker;
    private float x1, y1, x2, y2;
    private float mTouchSlop;

    public CustomViewPager(Context context)
    {
        super(context);

        init(context);
    }

    public CustomViewPager(Context context, AttributeSet attrs)
    {
        super(context, attrs);

        init(context);
    }

    private void init(Context context)
    {
        mTouchSlop = ViewConfiguration.get(context).getScaledPagingTouchSlop();
    }

    /**
     * Setting wrap_content on a ViewPager's layout_height in XML
     * doesn't seem to be recognized and the ViewPager will fill the
     * height of the screen regardless. We'll force the ViewPager to
     * have the same height as its immediate child.
     */
    @Override
    public void onMeasure(int widthMeasureSpec, int heightMeasureSpec)
    {
        super.onMeasure(widthMeasureSpec, heightMeasureSpec);

        if (getChildCount() > 0)
        {
            View childView = getChildAt(0);

            if (childView != null)
            {
                childView.measure(widthMeasureSpec, heightMeasureSpec);
                int h = childView.getMeasuredHeight();
                setMeasuredDimension(getMeasuredWidth(), h);
                getLayoutParams().height = h;
            }
        }

        mDayPicker = (NumberPicker) findViewById(R.id.dayPicker);
        mTimePicker = (TimePicker) findViewById(R.id.timePicker);
    }

    /**
     * When the user swipes their finger horizontally, dispatch
     * those touch events to the ViewPager. When they swipe
     * vertically, dispatch those touch events to the day or
     * time picker (depending on which page we're currently on).
     *
     * @param event
     */
    @Override
    public boolean dispatchTouchEvent(MotionEvent event)
    {
        switch (event.getAction())
        {
            case MotionEvent.ACTION_DOWN:
                x1 = event.getX();
                y1 = event.getY();

                break;

           case MotionEvent.ACTION_MOVE:
               x2 = event.getX();
               y2 = event.getY();

               if (isScrollingHorizontal(x1, y1, x2, y2))
               {
                   // When the user is scrolling the ViewPager horizontally,
                   // block the pickers from scrolling vertically.
                   return super.dispatchTouchEvent(event);
               }

               break;
         }

        // As long as the ViewPager isn't scrolling horizontally,
        // dispatch the event to the NumberPicker or TimePicker,
        // depending on which page the ViewPager is currently on.

         switch (getCurrentItem())
         {
         case 0:

             if (mDayPicker != null)
                 mDayPicker.dispatchTouchEvent(event);

             break;

         case 1:

             if (mTimePicker != null)
                 mTimePicker.dispatchTouchEvent(event);

             break;
         }

         // need this for the ViewPager to scroll horizontally at all
         return super.onTouchEvent(event);

    }

    /**
     * Determine whether the distance between the user's ACTION_DOWN
     * event (x1, y1) and the current ACTION_MOVE event (x2, y2) should
     * be interpreted as a horizontal swipe.
     *
     * @param x1
     * @param y1
     * @param x2
     * @param y2
     * @return
     */
    private boolean isScrollingHorizontal(float x1, float y1, float x2, float y2)
    {
        float deltaX = x2 - x1;
        float deltaY = y2 - y1;

        if (Math.abs(deltaX) > mTouchSlop &&
            Math.abs(deltaX) > Math.abs(deltaY))
        {

            return true;
        }

        return false;
    }
}