UIScrollView的无限左滑轮播一点也不难

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UIScrollView的轮播在如今的app中用得十分广泛，最初实现的时候方式比较拙劣，滚动到最后一个视图时再返回到第一个看起来非常的不连贯。

今天查询UIScrollView轮播资料，总结两种比较喜欢也易于理解的方法：

1、UIScrollView显示的子视图左右各放一个多出来的子视图，如本来有A/B/C三张图片，在A前面放一个ImageView显示C，在C后天放一个ImageView显示A，即C/A/B/C/A。

初始化ScrollView的时候，contentoffset 从A开始，然后 setContentOffset:offSetanimated:YES 依次轮播，当播放到C之后，跳转到A后，在

- (void)scrollViewDidScroll:(UIScrollView *)scrollView 中替换其contentoffset为第一个A的contentoffset。

代码如下：

- (void)viewDidLoad
{[super viewDidLoad];_scrollView = [[UIScrollView alloc] initWithFrame:CGRectMake(10, 0, 300, 300)];_scrollView.frame = CGRectMake(10, 0, 300, 300);_scrollView.contentSize = CGSizeMake(300*5, 300);_scrollView.contentOffset = CGPointMake(300, 0);_scrollView.delegate = self;[self.view addSubview:_scrollView];UIImageView *imageView1 = [[UIImageView alloc] initWithFrame:CGRectMake(0, 0, 300, 300)];imageView1.image = [UIImage imageNamed:@"3.jpg"];[_scrollView addSubview:imageView1];UIImageView *imageView2 = [[UIImageView alloc] initWithFrame:CGRectMake(300, 0, 300, 300)];imageView2.image = [UIImage imageNamed:@"1.jpg"];[_scrollView addSubview:imageView2];UIImageView *imageView3 = [[UIImageView alloc] initWithFrame:CGRectMake(300*2, 0, 300, 300)];imageView3.image = [UIImage imageNamed:@"2.jpg"];[_scrollView addSubview:imageView3];UIImageView *imageView4 = [[UIImageView alloc] initWithFrame:CGRectMake(300*3, 0, 300, 300)];imageView4.image = [UIImage imageNamed:@"3.jpg"];[_scrollView addSubview:imageView4];UIImageView *imageView5 = [[UIImageView alloc] initWithFrame:CGRectMake(300*4, 0, 300, 300)];imageView5.image = [UIImage imageNamed:@"1.jpg"];[_scrollView addSubview:imageView5];//  设置时钟动画 定时器NSTimer *timer = [NSTimer scheduledTimerWithTimeInterval:1.0f target:self selector:@selector(update:) userInfo:nil repeats:YES];//  将定时器添加到主线程[[NSRunLoop mainRunLoop] addTimer:timer forMode:NSRunLoopCommonModes];
}

- (void)update:(NSTimer *)timer{CGPoint offSet = self.scrollView.contentOffset;offSet.x += 300;[self.scrollView setContentOffset:offSet animated:YES];
}- (void)scrollViewDidScroll:(UIScrollView *)scrollView
{CGFloat X = self.scrollView.contentOffset.x;if (X == 0) {self.scrollView.contentOffset = CGPointMake(300*3, 0);}if (X == 300*4) {self.scrollView.contentOffset = CGPointMake(300, 0);}
}

这是方法1。里面的图片是随意在网上找的。

2、方法二是用固定的三个UIImageView控件，然后替换其图片来实现。

具体思路：先初始化三个图片控件，然后第一个控件放最后一张图，第二个图片放第一张图，第三个控件放第2张图。如轮播A/B/三个图片时，显示顺序是C/A/B。

后面的思路与上面类似，只不过要进行image替换。直接上代码：

- (void)viewDidLoad {[super viewDidLoad];// Do any additional setup after loading the view, typically from a nib.UIScrollView *scrollView =[[UIScrollView alloc] init];scrollView.frame = CGRectMake(0, 0, width, height);[self.view addSubview:scrollView];self.scrollView = scrollView;[self.scrollView setContentSize:CGSizeMake(width * 3, height)];//  设置隐藏横向条self.scrollView.showsHorizontalScrollIndicator = NO;//  设置自动分页self.scrollView.pagingEnabled = YES;//  设置代理self.scrollView.delegate = self;//  设置当前点self.scrollView.contentOffset = CGPointMake(width, 0);//  设置是否有边界self.scrollView.bounces = NO;//  初始化当前视图UIImageView *currentImageView =[[UIImageView alloc] init];currentImageView.image = [UIImage imageNamed:@"1.jpg"];[self.scrollView addSubview:currentImageView];self.currentImageView = currentImageView;self.currentImageView.frame = CGRectMake(width, 0, width, height);self.currentImageView.contentMode = UIViewContentModeScaleAspectFill;//  初始化下一个视图UIImageView *nextImageView = [[UIImageView alloc] init];nextImageView.image = [UIImage imageNamed:@"2.jpg"];[self.scrollView addSubview:nextImageView];self.nextImageView = nextImageView;self.nextImageView.frame = CGRectMake(width * 2, 0, width, height);self.nextImageView.contentMode = UIViewContentModeScaleAspectFill;//  初始化上一个视图UIImageView *preImageView =[[UIImageView alloc] init];preImageView.image = [UIImage imageNamed:@"3.jpg"];preImageView.frame = CGRectMake(0, 0, width, height);[self.scrollView addSubview:preImageView];self.preImageView = preImageView;self.preImageView.contentMode =UIViewContentModeScaleAspectFill;//  设置时钟动画 定时器self.timer = [NSTimer scheduledTimerWithTimeInterval:1.0f target:self selector:@selector(update:) userInfo:nil repeats:YES];//  将定时器添加到主线程[[NSRunLoop mainRunLoop] addTimer:self.timer forMode:NSRunLoopCommonModes];}

- (void)update:(NSTimer *)timer{//定时移动if (_isDragging == YES) {return ;}CGPoint offSet = self.scrollView.contentOffset;offSet.x +=offSet.x;[self.scrollView setContentOffset:offSet animated:YES];}

// 开始拖动
- (void) scrollViewDidScroll:(UIScrollView *)scrollView{static int i =1; //   当前展示的是第几张图片float offset = self.scrollView.contentOffset.x;if (self.nextImageView.image == nil || self.preImageView.image == nil) {//  加载下一个视图NSString *imageName1 = [NSString stringWithFormat:@"%d.jpg",i == KOUNT ? 1:i +1];_nextImageView.image = [UIImage imageNamed:imageName1];// 加载上一个视图NSString *imageName2 = [NSString stringWithFormat:@"%d.jpg",i==1 ? KOUNT :i-1];_preImageView.image = [UIImage imageNamed:imageName2];}if(offset ==0){_currentImageView.image = _preImageView.image;scrollView.contentOffset = CGPointMake(width, 0);_preImageView.image = nil;if (i == 1) {i =KOUNT;} else{i-=1;}}if (offset == width * 2) {_currentImageView.image = _nextImageView.image;scrollView.contentOffset = CGPointMake(width, 0);_nextImageView.image = nil;if (i == KOUNT) {i  =1 ;}else{i +=1 ;}}}

主要思路都是在滑动的动画执行完毕后，在用非动画方法移动的相同区域。

这篇关于UIScrollView的无限左滑轮播一点也不难的文章就介绍到这儿，希望我们推荐的文章对编程师们有所帮助！

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