前言
相信大家在项目中很多都遇到过这样的需求，要求实现图片的循环滚动播放，我这里使用scrollview实现，先来说大体思路：首先创建一个scrollview，将其等分为三等份，然后根据定时器触发滚动，当滚动到最后或者第一个区域时，将当前的contentoffset手动设置到中间2号区域，相当于每次的滚动完之后当前位置都在2号区域；接下来，就看代码了
image
代码实现
首先，设置好scrollview，并且拿到需要显示的images，我这快使用代理模式，拿到需要显示的图片总数和当前三个区域需要显示的图片，然后设置当前contenoffset为二号区域，最后开启定时器，进行滚动播放，这里的imageviews实现了复用，只需要创建三个imageview：
- (void)reloadData
{
_currentPage = 0;
_totalPageCount = 0;
if (self.delegate && [self.delegate respondsToSelector:@selector(numberOfTotalScrollCount)]) {
_totalPageCount = [self.delegate numberOfTotalScrollCount];
if (_totalPageCount <= 1) {
[_timer pause];
}
}else{
}
[self resetScrollView];
}
- (void)resetScrollView
{
[_scrollView.subviews makeObjectsPerformSelector:@selector(removeFromSuperview)];
NSInteger preIndex = [self getPreIndex:_currentPage];
NSInteger curIndex = _currentPage;
NSInteger nextIndex = [self getNextIndex:_currentPage];
if (self.delegate && [self.delegate respondsToSelector:@selector(imageForScrollInIndex:)]) {
UIImage *preImage = [self.delegate imageForScrollInIndex:preIndex];
UIImage *curImage = [self.delegate imageForScrollInIndex:curIndex];
UIImage *nextImage = [self.delegate imageForScrollInIndex:nextIndex];
NSArray *images = @[preImage, curImage, nextImage];
for (int i = 0; i < images.count; i++) {
UIImageView *imageView = _imageViews[i];
switch (_direction) {
case ScrollPictureDirectionRight:
case ScrollPictureDirectionLeft:
[imageView setFrame:CGRectMake(i * OwnWidth_LCY, 0, OwnWidth_LCY, OwnHeight_LCY)];
break;
case ScrollPictureDirectionTop:
case ScrollPictureDirectionBottom:
[imageView setFrame:CGRectMake(0, i * OwnHeight_LCY, OwnWidth_LCY, OwnHeight_LCY)];
break;
default:
break;
}
[imageView setImage:images[i]];
[_scrollView addSubview:imageView];
}
[_scrollView setContentOffset:(_direction == ScrollPictureDirectionRight || _direction == ScrollPictureDirectionLeft) ? CGPointMake(OwnWidth_LCY, 0) : CGPointMake(0, OwnHeight_LCY)];
}
}
在定时器中，我们需要实现scrollview的滚动，即，根据方向设置其contentoffset代码如下：
- (void)start:(NSTimer *)timer
{
CGFloat contentOffsetX = _scrollView.contentOffset.x;
CGFloat contentOffSetY = _scrollView.contentOffset.y;
switch (_direction) {
case ScrollPictureDirectionLeft:
contentOffsetX += OwnWidth_LCY;
break;
case ScrollPictureDirectionRight:
contentOffsetX -= OwnWidth_LCY;
break;
case ScrollPictureDirectionTop:
contentOffSetY += OwnHeight_LCY;
break;
case ScrollPictureDirectionBottom:
contentOffSetY -= OwnHeight_LCY;
break;
default:
break;
}
CGPoint contentOffset = CGPointMake(contentOffsetX, contentOffSetY);
[_scrollView setContentOffset:contentOffset animated:YES];
}
边界处理，当当前显示的图片是数组中最后一个或者第一个图片时，需要进行处理，刷新当前需要显示的image；
那么我们在什么时候得知试图当前的滚动位置呢，无疑我们应该在其代理函数里面获取，并且进行处理，这里我实现了上下左右四个方向的滚动，可以根据参数选取不同的方向，原理是一样的：
- (void)scrollViewDidScroll:(UIScrollView *)scrollView
{
CGPoint contentSize = _scrollView.contentOffset;
switch (_direction) {
case ScrollPictureDirectionRight:
{
if (contentSize.x <= 0){
_currentPage = [self getPreIndex:_currentPage];
[self resetScrollView];
if (self.delegate && [self.delegate respondsToSelector:@selector(scrollAtTheIndex:)]) {
[self.delegate scrollAtTheIndex:_currentPage];
}
}
}
break;
case ScrollPictureDirectionBottom:
{
if (contentSize.y <= 0){
_currentPage = [self getPreIndex:_currentPage];
[self resetScrollView];
if (self.delegate && [self.delegate respondsToSelector:@selector(scrollAtTheIndex:)]) {
[self.delegate scrollAtTheIndex:_currentPage];
}
}
}
break;
case ScrollPictureDirectionLeft:
{
if (contentSize.x >= OwnWidth_LCY * 2) {
_currentPage = [self getNextIndex:_currentPage];
[self resetScrollView];
if (self.delegate && [self.delegate respondsToSelector:@selector(scrollAtTheIndex:)]) {
[self.delegate scrollAtTheIndex:_currentPage];
}
}
}
break;
case ScrollPictureDirectionTop:
{
if (contentSize.y >= OwnHeight_LCY * 2) {
_currentPage = [self getNextIndex:_currentPage];
[self resetScrollView];
if (self.delegate && [self.delegate respondsToSelector:@selector(scrollAtTheIndex:)]) {
[self.delegate scrollAtTheIndex:_currentPage];
}
}
}
break;
default:
break;
}
}
- (NSInteger)getPreIndex:(NSInteger)currentIndex
{
if (currentIndex == 0) {
return _totalPageCount - 1;
}
return currentIndex - 1;
}
- (NSInteger)getNextIndex:(NSInteger)currentIndex
{
if (currentIndex == _totalPageCount - 1) {
return 0;
}
return currentIndex + 1;
}
至此，所有的的关键代码就结束了，这里的关键点是要理解当scrollview滚动到1号或者3号区域时，需要重新设置当前的contentoffset为2号区域，以此来实现无限滚动；
ps：这里是代码链接和使用～～
