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
