Android自动滚动 轮播循环的ViewPager
来源：http://www.trinea.cn/android/auto-scroll-view-pager/
1.实现方式
没有通过ScheduledExecutorService或Timer定期执行某个任务实现，而是简单的通过handler发送消息去完成一次滚动，在完成一次滚动后发送另外一个delay的滚动消息，如此循环实现。
2.自定义ViewPager
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);
}
}
/**
*
* if stopScrollWhenTouch is true
* - if event is down, stop auto scroll.
* - if event is up, start auto scroll again.
*
*/
@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.
* if slide border mode is to parent, then requestDisallowInterceptTouchEvent false.
* 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;
}
}
自定义ViewPager时用的Scroller
public class CustomDurationScroller extends Scroller {
private double scrollFactor = 1;
public CustomDurationScroller(Context context) {
super(context);
}
public CustomDurationScroller(Context context, Interpolator interpolator) {
super(context, interpolator);
}
/**
* Set the factor by which the duration will change
*/
public void setScrollDurationFactor(double scrollFactor) {
this.scrollFactor = scrollFactor;
}
@Override
public void startScroll(int startX, int startY, int dx, int dy, int duration) {
super.startScroll(startX, startY, dx, dy, (int)(duration * scrollFactor));
}
}3.自动滚动核心代码
用户调用startAutoScroll()后发送一条滚动消息，执行完滚动后重新发送一条滚动消息
/**
* start auto scroll, first scroll delay time is {@link #getInterval()}
*/
public void startAutoScroll() {
isAutoScroll = true;
sendScrollMessage(interval);
}
private void sendScrollMessage(long delayTimeInMills) {
/** remove messages before, keeps one message is running at most **/
handler.removeMessages(SCROLL_WHAT);
handler.sendEmptyMessageDelayed(SCROLL_WHAT, delayTimeInMills);
}
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;
}
}
}---
4.自动滚动和滑动冲突解决
/**
*
* if stopScrollWhenTouch is true
* - if event is down, stop auto scroll.
* - if event is up, start auto scroll again.
*
*/
@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();
}
}
......5.滑动到边界时的处理
/**
* current index is first one and slide to right or current index is last one and slide to left.
* if slide border mode is to parent, then requestDisallowInterceptTouchEvent false.
* 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);
}
至于ViewPager嵌套引起子ViewPager无法触摸问题是通过在子ViewPager的onTouchEvent中添加
禁止父控件对touch event做intercept解决的。
ViewPager滑动速度的设置是通过反射的方式重新设置ViewPager的Scroller，改变Scroller的startScroll的间隔时间完成的。调用setScrollDurationFactor(double)即可。