利用bounds简单实现scrollView的滑动

对bounds的理解

先贴代码:(只是简单的实现上下滑动)

#import "ViewController.h"

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

@implementation ViewController

- (void)viewDidLoad {
    [super viewDidLoad];
    
    UIView *scrollView = [[UIView alloc] initWithFrame:self.view.bounds];
    [self.view addSubview:scrollView];
    //添加滑动手势
    UIPanGestureRecognizer *pan = [[UIPanGestureRecognizer alloc] initWithTarget:self action:@selector(pan:)];
    self.scrollView = scrollView;
    [scrollView addGestureRecognizer:pan];
    //添加子控件,便于观察
    UIView *redView = [[UIView alloc] initWithFrame:CGRectMake(50, 50, 100, 100)];
    redView.backgroundColor = [UIColor redColor];
    [scrollView addSubview:redView];
}
- (void)pan:(UIPanGestureRecognizer *)pan
{
    //获取偏移的点
    CGPoint transP = [pan translationInView:pan.view];
    //偏移量等于下一个点减去上一个点
    CGFloat y = self.scrollView.bounds.origin.y - transP.y;
    //子视图位置的变化相当于其bounds坐标系的变化
    self.scrollView.bounds = CGRectMake(0, y, self.scrollView.bounds.size.width, self.scrollView.bounds.size.height);
    //复位,表示相对于上一次
    [pan setTranslation:CGPointZero inView:pan.view];
   
}

• frame: 以父控件的内容的左上角为坐标原点,看一下自己的矩形框 在哪
  bounds: 以自己的内容的左上角为坐标原点,和frame一样都是代表一块区域