iOS开发之实现图片自动切换（类似android画廊效果）

#import ViewController.h

#define ImageViewCount 5

 

@interface ViewController ()<uiscrollviewdelegate>

 

@property (weak, nonatomic) IBOutlet UIScrollView *imageScrollView;

@property (weak, nonatomic) IBOutlet UIPageControl *imageViewPageControl;

@property (strong, nonatomic) NSTimer *timer;

@end

 

@implementation ViewController

 

- (void)viewDidLoad {

    [super viewDidLoad];

   

    [self addImageView2ScrollView];

    self.imageScrollView.contentSize = CGSizeMake(self.imageScrollView.frame.size.width * ImageViewCount, 0);

 

    self.imageScrollView.delegate = self;

    self.imageScrollView.pagingEnabled = YES;//UIScrollView支持拖动分页

    self.imageViewPageControl.numberOfPages  = ImageViewCount;

     

    [self addScrollTimer];

}

 

- (void)rotatePic{

    int currentPageIndex = self.imageViewPageControl.currentPage;

    if(++currentPageIndex == 5){

        currentPageIndex = 0;

    }

    CGFloat offsetX = currentPageIndex * self.imageScrollView.frame.size.width;

    [UIView animateWithDuration:1 animations:^{

        self.imageScrollView.contentOffset = CGPointMake(offsetX, 0);

    }];

}

 

/**添加图片到imageScrollView*/

- (void)addImageView2ScrollView{

    CGFloat imageWidth = self.imageScrollView.frame.size.width;

    CGFloat imageHeight = self.imageScrollView.frame.size.height;

    for(int i = 0;i <= ImageViewCount;i++){

        UIImageView *imageInScroll = [[UIImageView alloc] init];

        imageInScroll.frame = CGRectMake(i * imageWidth, 0, imageWidth, imageHeight);

        imageInScroll.image = [UIImage imageNamed:[NSString stringWithFormat:@img_%02d,i + 1]];

        [self.imageScrollView addSubview:imageInScroll];

    }

}

 

// 正滚动时执行

- (void)scrollViewDidScroll:(UIScrollView *)scrollView{

    CGFloat offX = self.imageScrollView.contentOffset.x;//（0，0）距离content内部左上顶点的x轴长度

    NSLog(@~~~~~~~%f ^^^^^^%f, offX, self.imageScrollView.frame.size.width);

    int currentPageIndex = (offX + .5f * self.imageScrollView.frame.size.width) / self.imageScrollView.frame.size.width;

    self.imageViewPageControl.currentPage = currentPageIndex;

}

 

- (void)addScrollTimer{

    self.timer = [NSTimer timerWithTimeInterval:2 target:self selector:@selector(rotatePic) userInfo:nil repeats:YES];

    [[NSRunLoop mainRunLoop] addTimer:self.timer forMode:NSRunLoopCommonModes];

}

 

- (void)removeScrollTimer{

    [self.timer invalidate];//释放定时器

    self.timer = nil;

}

 

// 开始准备滚动时执行 移除定时滚动操作

- (void)scrollViewWillBeginDragging:(UIScrollView *)scrollView{

    NSLog(@~~~scrollViewWillBeginDragging);

    [self removeScrollTimer];

}www.2cto.com

 

// 结束滚动后执行 添加定时滚动操作

- (void)scrollViewDidEndDragging:(UIScrollView *)scrollView willDecelerate:(BOOL)decelerate{

    NSLog(@~~~scrollViewDidEndDragging);

    [self addScrollTimer];

}

@end

</uiscrollviewdelegate>

对UIScrollView的运用，以上代码中有详细注释，需注意2点：

1.注意设置contentSize属性。其中contentSize表示scroll内容尺寸大小

2.注意设置代理UIScrollViewDelegate，才可调用其中的方法

对于定时器NSTimer的运用需注意

1.在线程的loop中添加定时器

2.注意使用完成回收NSTimer

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