UIScrollView实现循环滚动

来源：互联网发布：seo研究中心seo8 编辑：程序博客网时间：2024/05/16 08:32

项目中会需要一些循环滚动的视图,而这些资源我们并不知道有多少或者有很多图片需要循环显示,这样如果设置很多imageview势必会浪费很多内存.所以,博主写了一个小Demo希望可以给大家一点启发.

实现的思想大致是:设置3个view放在scrollview上,通过改变view的fream和scrollview的contentoffset来实现循环滚动,好了,不多说,贴代码..~~

#define SC_Width 200#define SC_Hight 300@interface JLRootViewController ()<UIScrollViewDelegate>@end@implementation JLRootViewController{    UIView *view1;    UIView *view2;    UIView *view3;    UIScrollView *_scroll;}- (void)viewDidLoad {    [super viewDidLoad];    // Do any additional setup after loading the view.    [self createUI];}- (void)createUI{    [self.view setBackgroundColor:[UIColor whiteColor]];        _scroll = [[UIScrollView alloc] init];    [_scroll setBounds:CGRectMake(0, 0, SC_Width, SC_Hight)];    [_scroll setCenter:self.view.center];    [_scroll setDelegate:self];    _scroll.contentSize = CGSizeMake(SC_Width*3,SC_Hight);        // 这个属性设置成yes,viewcontroller的automaticallyAdjustsScrollViewInsets属性会自动调整scrollview的内容,此处不让其自动调整    self.automaticallyAdjustsScrollViewInsets = NO;        _scroll.pagingEnabled = YES;    [self.view addSubview:_scroll];        // 三个view    view1 = [[UIView alloc] initWithFrame:CGRectMake(0, 0, SC_Width, SC_Hight)];    [view1 setBackgroundColor:[UIColor greenColor]];        view2 = [[UIView alloc] initWithFrame:CGRectMake(SC_Width, 0, SC_Width, SC_Hight)];    [view2 setBackgroundColor:[UIColor blueColor]];        view3 = [[UIView alloc] initWithFrame:CGRectMake(SC_Width*2, 0, SC_Width, SC_Hight)];    [view3 setBackgroundColor:[UIColor purpleColor]];    // 添加到self.view    [_scroll addSubview:view1];    [_scroll addSubview:view2];    [_scroll addSubview:view3];}- (void)scrollViewDidScroll:(UIScrollView *)scrollView{    // 左滑    if (scrollView.contentOffset.x >= SC_Width*2) {        // 将三个view的fream的x-SC_Width,如果fream超出范围则加到最后边        view1.frame = CGRectMake(view1.frame.origin.x >= SC_Width ? view1.frame.origin.x-SC_Width : SC_Width*2, 0, SC_Width, SC_Hight);        view2.frame = CGRectMake(view2.frame.origin.x >= SC_Width ? view2.frame.origin.x-SC_Width :SC_Width*2, 0, SC_Width, SC_Hight);        view3.frame = CGRectMake(view3.frame.origin.x >= SC_Width ? view3.frame.origin.x-SC_Width :SC_Width*2, 0, SC_Width, SC_Hight);                // 将中间的view显示在scroll上        scrollView.contentOffset = CGPointMake(SC_Width, 0);    }    // 右滑    if (scrollView.contentOffset.x <=0) {        // 将三个view的fream的x+SC_Width,如果fream超出范围则加到最前边        view1.frame = CGRectMake(view1.frame.origin.x >= SC_Width*2 ? 0: view1.frame.origin.x+SC_Width, 0, SC_Width, SC_Hight);        view2.frame = CGRectMake(view2.frame.origin.x >= SC_Width*2 ? 0 : view2.frame.origin.x+SC_Width, 0, SC_Width, SC_Hight);        view3.frame = CGRectMake(view3.frame.origin.x >= SC_Width*2 ? 0 : view3.frame.origin.x+SC_Width, 0, SC_Width, SC_Hight);                // 将中间的view显示在scroll上        scrollView.contentOffset = CGPointMake(SC_Width, 0);    }}

以上的代码就可以实现循环滚动的问题,而且不需要创建多个view.

2 0