UIScrollView-contentSize-contentOffset-contentInset-滚动条

1.设置滚动范围 contentSize

self.scrollView.contentSize = CGSizeMake(400, 250);

// 如果想禁止某个方向的滚动，那么就可以直接设置width或者height==0
self.scrollView.contentSize = CGSizeMake(400, 0);

2.contentOffset / UIView动画 block delegate

#import "ViewController.h"

@interface ViewController ()
@property (weak, nonatomic) IBOutlet UIScrollView *scrollView;
@end

@implementation ViewController

- (void)viewDidLoad {
    [super viewDidLoad];
    
    UIImageView *imageView = [[UIImageView alloc] initWithImage:[UIImage imageNamed:@"minion"]];
    [self.scrollView addSubview:imageView];
    // 设置内容大小
    self.scrollView.contentSize = imageView.image.size;
}

- (IBAction)left:(id)sender {
    // self.scrollView.contentOffset ： 偏移量
    // 记录UIScrollView滚动的位置，滚到哪
    // 总结：内容的左上角 和 scrollView自身左上角 的 X\Y差值
    
    // [UIView animateWithDuration:2.0 animations:^{
    //     self.scrollView.contentOffset = CGPointMake(0, self.scrollView.contentOffset.y);
    // }];
    
    [UIView animateWithDuration:2.0 animations:^{
        self.scrollView.contentOffset = CGPointMake(0, self.scrollView.contentOffset.y);
    } completion:^(BOOL finished) {
        NSLog(@"执行完毕");
    }];
}

- (IBAction)top:(id)sender {
    // self.scrollView.contentOffset = CGPointMake(self.scrollView.contentOffset.x, 0);
    
    CGPoint offset = CGPointMake(self.scrollView.contentOffset.x, 0);
    [self.scrollView setContentOffset:offset animated:YES];
}

- (IBAction)bottom:(id)sender {
    [UIView animateWithDuration:2.0 animations:^{
        CGFloat offsetY = self.scrollView.contentSize.height - self.scrollView.frame.size.height;
        CGPoint offset = self.scrollView.contentOffset;
        offset.y = offsetY;
        self.scrollView.contentOffset = offset;
    }];
}

- (IBAction)right:(id)sender {
    [UIView beginAnimations:nil context: nil];
    [UIView setAnimationDuration:2.0];
    [UIView setAnimationDelegate:self]; // 代理
    [UIView setAnimationDidStopSelector:@selector(stop)];
    [UIView setAnimationWillStartSelector:@selector(start)];
    
    CGFloat offsetX = self.scrollView.contentSize.width - self.scrollView.frame.size.width;
    self.scrollView.contentOffset = CGPointMake(offsetX, self.scrollView.contentOffset.y);
    
    [UIView commitAnimations];
}

- (void)start
{
    NSLog(@"start");
}

- (void)stop
{
    NSLog(@"stop");
}
@end

OC语法细节：不允许直接修改OC对象的结构体属性的成员

[V] self.scrollView.contentOffset = CGPointMake(self.scrollView.contentOffset.x, offsetY);
[X] self.scrollView.contentOffset.y = offsetY;

3.contentInset

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

UIImageView *imageView = [[UIImageView alloc] initWithImage:[UIImage imageNamed:@"minion"]];
// [self.scrollView addSubview:imageView];
[self.scrollView insertSubview:imageView atIndex:0];

// 设置内容大小
self.scrollView.contentSize = imageView.image.size;

// 设置contentInset
self.scrollView.contentOffset = CGPointMake(0, -64);

// UIEdgeInsetsMake(<#CGFloat top#>, <#CGFloat left#>, <#CGFloat bottom#>, <#CGFloat right#>)
// 顶部额外增加 64 高度的可滚动范围
self.scrollView.contentInset = UIEdgeInsetsMake(64, 0, 0, 0);

1-顶部额外增加64高度的可滚动范围.png

顶部额外增加64高度的可滚动范围，scrollView滚动后能停在右图位置,图片距离scrollView顶部有64高度空间

没有设置

self.scrollView.contentInset = UIEdgeInsetsMake(64, 0, 0, 0);

2-图片顶部位于scrollView顶部.png

scrollView滚动后，图片顶部位于scrollView顶部，没有64高度的空间

4.UIScrollView滚动条

#import "ViewController.h"

@interface ViewController ()
{
    CGRect _lastRect;
}
@property (weak, nonatomic) IBOutlet UIScrollView *scrollView;
@property(nonatomic,strong) UIView *gird;
@end

@implementation ViewController

- (void)viewDidLoad {
    [super viewDidLoad];
    
    //self.scrollView.showsHorizontalScrollIndicator = NO;
    //self.scrollView.showsVerticalScrollIndicator = NO;
    
    NSMutableArray *girdArr = [NSMutableArray array];
    for (int i = 0; i<50; i++) {
        int row = i / 3; // 行号
        int col = i % 3; // 列号
        CGFloat x = col * (50 + 30); // 列号决定了X
        CGFloat y = row * (50 + 30); // 行号决定了Y
        self.gird =  [self addGridWithX:x y:y];
        if (i == 49) {
            _lastRect = self.gird.frame;
        }
        [girdArr addObject:self.gird];
    }
    
    // self.scrollView.subviews[49];
    UIView *lastView = [girdArr lastObject];
    
    // UIView *lastView = [self.scrollView.subviews lastObject];
    // CGFloat contentH = lastView.frame.origin.y + lastView.frame.size.height;
    CGFloat contentH = CGRectGetMaxY(lastView.frame);
    
    NSLog(@"%@", [self.scrollView.subviews lastObject]);
    // 水平方向不显示滚动条
    self.scrollView.contentSize = CGSizeMake(0, contentH);
    NSLog(@"%@", [self.scrollView.subviews lastObject]);
}

- (UIView *)addGridWithX:(CGFloat)x y:(CGFloat)y{
    UIView *grid = [[UIView alloc] init];
    grid.frame = CGRectMake(x, y, 50, 50);
    grid.backgroundColor = [UIColor blueColor];
    [self.scrollView addSubview:grid];
    return grid;
}

@end

2-显示垂直滚动条隐藏水平滚动条.png