android-auto-scroll-view-pager

【核心代码】

package cn.trinea.android.view.autoscrollviewpager;

import java.lang.reflect.Field;

import android.content.Context;
import android.os.Handler;
import android.os.Message;
import android.support.v4.view.PagerAdapter;
import android.support.v4.view.ViewPager;
import android.util.AttributeSet;
import android.view.MotionEvent;
import android.view.animation.Interpolator;

/**
 * Auto Scroll View Pager
 * <ul>
 * <strong>Basic Setting and Usage</strong>
 * <li>{@link #startAutoScroll()} start auto scroll, or {@link #startAutoScroll(int)} start auto scroll delayed</li>
 * <li>{@link #stopAutoScroll()} stop auto scroll</li>
 * <li>{@link #setInterval(long)} set auto scroll time in milliseconds, default is {@link #DEFAULT_INTERVAL}</li>
 * </ul>
 * <ul>
 * <strong>Advanced Settings and Usage</strong>
 * <li>{@link #setDirection(int)} set auto scroll direction</li>
 * <li>{@link #setCycle(boolean)} set whether automatic cycle when auto scroll reaching the last or first item, default
 * is true</li>
 * <li>{@link #setSlideBorderMode(int)} set how to process when sliding at the last or first item</li>
 * <li>{@link #setStopScrollWhenTouch(boolean)} set whether stop auto scroll when touching, default is true</li>
 * </ul>
 * 
 * @author <a href="http://www.trinea.cn" target="_blank">Trinea</a> 2013-12-30
 */
public class AutoScrollViewPager extends ViewPager {

    public static final int        DEFAULT_INTERVAL            = 1500;

    public static final int        LEFT                        = 0;
    public static final int        RIGHT                       = 1;

    /** do nothing when sliding at the last or first item **/
    public static final int        SLIDE_BORDER_MODE_NONE      = 0;
    /** cycle when sliding at the last or first item **/
    public static final int        SLIDE_BORDER_MODE_CYCLE     = 1;
    /** deliver event to parent when sliding at the last or first item **/
    public static final int        SLIDE_BORDER_MODE_TO_PARENT = 2;

    /** auto scroll time in milliseconds, default is {@link #DEFAULT_INTERVAL} **/
    private long                   interval                    = DEFAULT_INTERVAL;
    /** auto scroll direction, default is {@link #RIGHT} **/
    private int                    direction                   = RIGHT;
    /** whether automatic cycle when auto scroll reaching the last or first item, default is true **/
    private boolean                isCycle                     = true;
    /** whether stop auto scroll when touching, default is true **/
    private boolean                stopScrollWhenTouch         = true;
    /** how to process when sliding at the last or first item, default is {@link #SLIDE_BORDER_MODE_NONE} **/
    private int                    slideBorderMode             = SLIDE_BORDER_MODE_NONE;
    /** whether animating when auto scroll at the last or first item **/
    private boolean                isBorderAnimation           = true;

    private Handler                handler;
    private boolean                isAutoScroll                = false;
    private boolean                isStopByTouch               = false;
    private float                  touchX                      = 0f, downX = 0f;
    private CustomDurationScroller scroller                    = null;

    public static final int        SCROLL_WHAT                 = 0;

    public AutoScrollViewPager(Context paramContext) {
        super(paramContext);
        init();
    }

    public AutoScrollViewPager(Context paramContext, AttributeSet paramAttributeSet) {
        super(paramContext, paramAttributeSet);
        init();
    }

    private void init() {
        handler = new MyHandler();
        setViewPagerScroller();
    }

    /**
     * start auto scroll, first scroll delay time is {@link #getInterval()}
     */
    public void startAutoScroll() {
        isAutoScroll = true;
        sendScrollMessage(interval);
    }

    /**
     * start auto scroll
     * 
     * @param delayTimeInMills first scroll delay time
     */
    public void startAutoScroll(int delayTimeInMills) {
        isAutoScroll = true;
        sendScrollMessage(delayTimeInMills);
    }

    /**
     * stop auto scroll
     */
    public void stopAutoScroll() {
        isAutoScroll = false;
        handler.removeMessages(SCROLL_WHAT);
    }

    /**
     * set the factor by which the duration of sliding animation will change
     */
    public void setScrollDurationFactor(double scrollFactor) {
        scroller.setScrollDurationFactor(scrollFactor);
    }

    private void sendScrollMessage(long delayTimeInMills) {
        /** remove messages before, keeps one message is running at most **/
        handler.removeMessages(SCROLL_WHAT);
        handler.sendEmptyMessageDelayed(SCROLL_WHAT, delayTimeInMills);
    }

    /**
     * set ViewPager scroller to change animation duration when sliding
     */
    private void setViewPagerScroller() {
        try {
            Field scrollerField = ViewPager.class.getDeclaredField("mScroller");
            scrollerField.setAccessible(true);
            Field interpolatorField = ViewPager.class.getDeclaredField("sInterpolator");
            interpolatorField.setAccessible(true);

            scroller = new CustomDurationScroller(getContext(), (Interpolator)interpolatorField.get(null));
            scrollerField.set(this, scroller);
        } catch (Exception e) {
            e.printStackTrace();
        }
    }

    /**
     * scroll only once
     */
    public void scrollOnce() {
        PagerAdapter adapter = getAdapter();
        int currentItem = getCurrentItem();
        int totalCount;
        if (adapter == null || (totalCount = adapter.getCount()) <= 1) {
            return;
        }

        int nextItem = (direction == LEFT) ? --currentItem :   currentItem;
        if (nextItem < 0) {
            if (isCycle) {
                setCurrentItem(totalCount - 1, isBorderAnimation);
            }
        } else if (nextItem == totalCount) {
            if (isCycle) {
                setCurrentItem(0, isBorderAnimation);
            }
        } else {
            setCurrentItem(nextItem, true);
        }
    }

    /**
     * <ul>
     * if stopScrollWhenTouch is true
     * <li>if event is down, stop auto scroll.</li>
     * <li>if event is up, start auto scroll again.</li>
     * </ul>
     */
    @Override
    public boolean onTouchEvent(MotionEvent ev) {
        if (stopScrollWhenTouch) {
            if (ev.getAction() == MotionEvent.ACTION_DOWN && isAutoScroll) {
                isStopByTouch = true;
                stopAutoScroll();
            } else if (ev.getAction() == MotionEvent.ACTION_UP && isStopByTouch) {
                startAutoScroll();
            }
        }

        if (slideBorderMode == SLIDE_BORDER_MODE_TO_PARENT || slideBorderMode == SLIDE_BORDER_MODE_CYCLE) {
            touchX = ev.getX();
            if (ev.getAction() == MotionEvent.ACTION_DOWN) {
                downX = touchX;
            }
            int currentItem = getCurrentItem();
            PagerAdapter adapter = getAdapter();
            int pageCount = adapter == null ? 0 : adapter.getCount();
            /**
             * current index is first one and slide to right or current index is last one and slide to left.<br/>
             * if slide border mode is to parent, then requestDisallowInterceptTouchEvent false.<br/>
             * else scroll to last one when current item is first one, scroll to first one when current item is last
             * one.
             */
            if ((currentItem == 0 && downX <= touchX) || (currentItem == pageCount - 1 && downX >= touchX)) {
                if (slideBorderMode == SLIDE_BORDER_MODE_TO_PARENT) {
                    getParent().requestDisallowInterceptTouchEvent(false);
                } else {
                    if (pageCount > 1) {
                        setCurrentItem(pageCount - currentItem - 1, isBorderAnimation);
                    }
                    getParent().requestDisallowInterceptTouchEvent(true);
                }
                return super.onTouchEvent(ev);
            }
        }
        getParent().requestDisallowInterceptTouchEvent(true);
        return super.onTouchEvent(ev);
    }

    private class MyHandler extends Handler {

        @Override
        public void handleMessage(Message msg) {
            super.handleMessage(msg);

            switch (msg.what) {
                case SCROLL_WHAT:
                    scrollOnce();
                    sendScrollMessage(interval);
                default:
                    break;
            }
        }
    }

    /**
     * get auto scroll time in milliseconds, default is {@link #DEFAULT_INTERVAL}
     * 
     * @return the interval
     */
    public long getInterval() {
        return interval;
    }

    /**
     * set auto scroll time in milliseconds, default is {@link #DEFAULT_INTERVAL}
     * 
     * @param interval the interval to set
     */
    public void setInterval(long interval) {
        this.interval = interval;
    }

    /**
     * get auto scroll direction
     * 
     * @return {@link #LEFT} or {@link #RIGHT}, default is {@link #RIGHT}
     */
    public int getDirection() {
        return (direction == LEFT) ? LEFT : RIGHT;
    }

    /**
     * set auto scroll direction
     * 
     * @param direction {@link #LEFT} or {@link #RIGHT}, default is {@link #RIGHT}
     */
    public void setDirection(int direction) {
        this.direction = direction;
    }

    /**
     * whether automatic cycle when auto scroll reaching the last or first item, default is true
     * 
     * @return the isCycle
     */
    public boolean isCycle() {
        return isCycle;
    }

    /**
     * set whether automatic cycle when auto scroll reaching the last or first item, default is true
     * 
     * @param isCycle the isCycle to set
     */
    public void setCycle(boolean isCycle) {
        this.isCycle = isCycle;
    }

    /**
     * whether stop auto scroll when touching, default is true
     * 
     * @return the stopScrollWhenTouch
     */
    public boolean isStopScrollWhenTouch() {
        return stopScrollWhenTouch;
    }

    /**
     * set whether stop auto scroll when touching, default is true
     * 
     * @param stopScrollWhenTouch
     */
    public void setStopScrollWhenTouch(boolean stopScrollWhenTouch) {
        this.stopScrollWhenTouch = stopScrollWhenTouch;
    }

    /**
     * get how to process when sliding at the last or first item
     * 
     * @return the slideBorderMode {@link #SLIDE_BORDER_MODE_NONE}, {@link #SLIDE_BORDER_MODE_TO_PARENT},
     *         {@link #SLIDE_BORDER_MODE_CYCLE}, default is {@link #SLIDE_BORDER_MODE_NONE}
     */
    public int getSlideBorderMode() {
        return slideBorderMode;
    }

    /**
     * set how to process when sliding at the last or first item
     * 
     * @param slideBorderMode {@link #SLIDE_BORDER_MODE_NONE}, {@link #SLIDE_BORDER_MODE_TO_PARENT},
     *        {@link #SLIDE_BORDER_MODE_CYCLE}, default is {@link #SLIDE_BORDER_MODE_NONE}
     */
    public void setSlideBorderMode(int slideBorderMode) {
        this.slideBorderMode = slideBorderMode;
    }

    /**
     * whether animating when auto scroll at the last or first item, default is true
     * 
     * @return
     */
    public boolean isBorderAnimation() {
        return isBorderAnimation;
    }

    /**
     * set whether animating when auto scroll at the last or first item, default is true
     * 
     * @param isBorderAnimation
     */
    public void setBorderAnimation(boolean isBorderAnimation) {
        this.isBorderAnimation = isBorderAnimation;
    }
}