iOS - UIScrollView 相关属性代理详解

一、UIScrollView的属性和代理方法详解

属性：

- (void)viewDidLoad {
    [super viewDidLoad];
    _scrollView.backgroundColor = [UIColor redColor];
    //设置contentSize（必须设置）
    _scrollView.contentSize = CGSizeMake(, );
    //偏移量
    _scrollView.contentOffset = CGPointMake(, );
    //contentInset(在原有的基础上调整内容滚动区域的大小)
    //_scrollView.contentInset = UIEdgeInsetsMake(-100, 0, 0, 0);

    //锁定方向(当系统识别滚动方向的时候，会把另外一个方向锁定，如果识别不了，就不锁定方向)
    _scrollView.directionalLockEnabled = YES;
    //反弹效果(默认为yes)
    _scrollView.bounces = YES;
    //默认是no，假如是yes并且bounces是yes,甚至如果内容大小小于bounds的时候，允许垂直拖动
    _scrollView.alwaysBounceVertical = YES;
    //分页（默认no）
    _scrollView.pagingEnabled = YES;
    //滚动(默认yes允许滚动)
    _scrollView.scrollEnabled = YES;

    //滚动条
    //showsHorizontalScrollIndicator默认yes 显示
    _scrollView.showsHorizontalScrollIndicator = NO;
    //滚动条滚动的范围(垂直滚动条滚动范围上下各缩小50)
    _scrollView.scrollIndicatorInsets = UIEdgeInsetsMake(, , , );
    //样式
    _scrollView.indicatorStyle = UIScrollViewIndicatorStyleWhite;
    // Do any additional setup after loading the view, typically from a nib.
}

代理

- (void)viewDidLoad {
    [super viewDidLoad];
    //创建并添加scrollView
    UIScrollView *scrollView = [[UIScrollView alloc] initWithFrame:CGRectMake(, , , )];
    [self.view addSubview:scrollView];

    scrollView.backgroundColor = [UIColor redColor];
    //设置内容视图的大小
    scrollView.contentSize = CGSizeMake(, );
    //设置内容视图
    UIImageView *imageView = [[UIImageView alloc] initWithFrame:CGRectMake(, , , )];
    imageView.image = [UIImage imageNamed:@"new_feature_1"];
    [scrollView addSubview:imageView];

    _imageView = imageView;
    //设置代理
    scrollView.delegate = self;

    //[self performSelector:@selector(changeScrollViewContentOffSet:) withObject:scrollView afterDelay:3];

    //设置缩放内容视图的缩放比例范围
    scrollView.minimumZoomScale = 0.5;
    scrollView.maximumZoomScale = 1.5;
    //当缩放比例超出范围之后，是否有反弹效果（no:不会超出范围，yes:超出范围之后反弹）
    scrollView.bouncesZoom = YES;

    //属性设置滚动至顶部
    //scrollView.scrollsToTop = YES;
    // Do any additional setup after loading the view, typically from a nib.
}

-(void)changeScrollViewContentOffSet:(UIScrollView *)scrollView{
    [scrollView setContentOffset:CGPointMake(, ) animated:YES];
}

#if 0
#pragma mark -UIScrollViewDelegate 滚动
//当scrollView滚动的时候，不停调用（可以监听scrollView的contentOffset）
- (void)scrollViewDidScroll:(UIScrollView *)scrollView{
    //NSLog(@"%@",NSStringFromCGPoint(scrollView.contentOffset));
    //NSLog(@"decelerating：%d",scrollView.decelerating);
    //NSLog(@"dragging：%d",scrollView.dragging);
    //NSLog(@"tracking:%d",scrollView.tracking);
    NSLog(@"%s",__func__);
}

//开始拖动的时候调用
- (void)scrollViewWillBeginDragging:(UIScrollView *)scrollView{
    //NSLog(@"tracking:%d",scrollView.tracking);
    NSLog(@"%s",__func__);
}

// called on finger up if the user dragged. velocity is in points/millisecond. targetContentOffset may be changed to adjust where the scroll view comes to rest
//将要结束拖动
- (void)scrollViewWillEndDragging:(UIScrollView *)scrollView withVelocity:(CGPoint)velocity targetContentOffset:(inout CGPoint *)targetContentOffset {
//    NSLog(@"velocity:%@",NSStringFromCGPoint(velocity));
//    NSLog(@"targetContentOffset:%@",NSStringFromCGPoint(*targetContentOffset));
    //强制设置scrollView的偏移量
    //*targetContentOffset = CGPointMake(0, 200);
    NSLog(@"%s",__func__);
}

// 已经结束拖动
- (void)scrollViewDidEndDragging:(UIScrollView *)scrollView willDecelerate:(BOOL)decelerate{
    //NSLog(@"dragging：%d",scrollView.dragging);
    NSLog(@"%s",__func__);
}

//将要开始减速
- (void)scrollViewWillBeginDecelerating:(UIScrollView *)scrollView{
    //NSLog(@"decelerating：%d",scrollView.decelerating);
    NSLog(@"%s",__func__);
}

//减速完成（停止）
- (void)scrollViewDidEndDecelerating:(UIScrollView *)scrollView{
    //NSLog(@"contentOffset:%@",NSStringFromCGPoint(scrollView.contentOffset));
    NSLog(@"%s",__func__);
}

// called when setContentOffset/scrollRectVisible:animated: finishes. not called if not animating
- (void)scrollViewDidEndScrollingAnimation:(UIScrollView *)scrollView{
    NSLog(@"%s",__func__);
}
#endif
#pragma mark -UIScrollViewDelegate(缩放)
//指定缩放视图
- (nullable UIView *)viewForZoomingInScrollView:(UIScrollView *)scrollView{
    NSLog(@"%s,zooming:%d",__func__,scrollView.zooming);
    return _imageView;
}
//缩放之前调用
- (void)scrollViewWillBeginZooming:(UIScrollView *)scrollView withView:(nullable UIView *)view {
    NSLog(@"%s,zooming:%d",__func__,scrollView.zooming);
}
//完成缩放
- (void)scrollViewDidEndZooming:(UIScrollView *)scrollView withView:(nullable UIView *)view atScale:(CGFloat)scale{
    NSLog(@"%s,zooming:%d",__func__,scrollView.zooming);
}
//缩放时调用
- (void)scrollViewDidZoom:(UIScrollView *)scrollView{
    NSLog(@"%s,zooming:%d",__func__,scrollView.zooming);
}

#pragma mark -UIScrollViewDelegate(滚动至顶部)
//允许滚动至顶部
- (BOOL)scrollViewShouldScrollToTop:(UIScrollView *)scrollView{
    return YES;
}

//已经滚动至顶部
- (void)scrollViewDidScrollToTop:(UIScrollView *)scrollView{
    NSLog(@"加载新数据，刷新界面");
}

一、UIScrollView的重要的三大属性contentSize、contentInset、contentOffset

重要说明

（1）UIScrollView的frame与contentsize属性的区分：UIScrollView的frame指的是这个scrollview的可视范围（可看见的区域），contentsize是其滚动范围。

（2）contentinset（不带*号的一般不是结构体就是枚举），为UIScrollView增加额外的滚动区域。（上，左，下，右）逆时针。contentinset可以使用代码或者是视图控制器进行设置，但两者有区别（注意区分）。

（3）contentsize属性只能使用代码设置。

（4）contentoffset是个CGpoint类型的结构体，用来记录ScrollView的滚动位置，即记录着“框”跑到了哪里。知道了这个属性，就知道了其位置，可以通过设置这个属性来控制这个“框”的移动。