iphone - scrollViewDidEndDecelerating 未执行

Question

我似乎无法调用 scrollViewDidEndDecelerating。我有一个滚动视图，里面有 2 个视图。现在，当滚动视图完成滚动到第二个视图时，我需要它为第一个视图中的标签设置一个值。

头文件：

@interface ViewController: UIViewController
{
   UIScrollView *scrollView;
   UIView *view1;
   UIView *view2;
}

@property (strong, nonatomic) IBOutlet UIScrollView *scrollView;
@property (strong, nonatomic) IBOutlet UIView *view1;
@property (strong, nonatomic) IBOutlet UIView *view2;
@property (weak, nonatomic) IBOutlet UILabel *lbl;

实施文件：

@synthesize scrollView, view1, view2;

-(void)viewDidLoad
{
   self.view1=[[UIView alloc] initWithFrame:CGRectMake(0, 0, 320, 480)];
   self.view2=[[UIView alloc] initWithFrame:CGRectMake(320, 0, 320, 480)];

   [self.scrollView addSubView:self.view1];
   [self.scrollView addSubView:self.view2];

   self.scrollView.bounces=NO;
   self.scrollView.contentSize=CGSizeMake(640,460);
   [self.scrollView setShowHorizontalScrollIndicator:NO];
   [self.scrollView scrollRectToVisible:CGRectMake(0, 0, 320, 416) animated:NO];
}

-(void)scrollViewDidEndDecelerating:(UIView *)scrollView
{
   lbl.text=@"0";
}

我看不出有什么问题，它应该可以工作。有人可以帮我吗？会很感激。

Answer 1

如果用户滚动缓慢（即滚动视图在触摸向上时不会继续滚动），则不会调用 scrollViewDidEndDecelerating。在这种情况下，委托调用 scrollViewDidEndDragging。所以当用户停止滚动并且滚动视图停止时做一些事情，你可以将它们组合起来：

func scrollViewDidEndDragging(_ scrollView: UIScrollView, willDecelerate decelerate: Bool) {
  if !decelerate {
     endOfScroll()
  }
}

func scrollViewDidEndDecelerating(_ scrollView: UIScrollView) {
  endOfScroll()
}

func endOfScroll() {
  //The user finished scrolling
}

在 Objective-C 中

- (void)scrollViewDidEndDragging:(UIScrollView *)scrollView willDecelerate:(BOOL)decelerate
{
   if(!decelerate) [self endOfScroll];
}

-(void)scrollViewDidEndDecelerating:(UIScrollView *)scrollView{
  [self endOfScroll];
}

-(void)endOfScroll{
  //Do something
}

Answer 2

要么将滚动视图的委托属性连接到 Interface Builder 中的文件所有者对象，要么只是在 ViewController 的 ViewDidLoad 中手动设置委托。

scrollview.delegate = self

Answer 3

这会做：

头文件：

@interface ViewController: UIViewController <UIScrollViewDelegate> //promise that you'll act as scrollView's delegate
{
   UIScrollView *scrollView;
   UIView *view1;
   UIView *view2;
}

@property (strong, nonatomic) IBOutlet UIScrollView *scrollView;
@property (strong, nonatomic) IBOutlet UIView *view1;
@property (strong, nonatomic) IBOutlet UIView *view2;
@property (weak, nonatomic) IBOutlet UILabel *lbl;

实施文件：

@synthesize scrollView, view1, view2;

-(void)viewDidLoad
{
   self.view1=[[UIView alloc] initWithFrame:CGRectMake(0, 0, 320, 480)];
   self.view2=[[UIView alloc] initWithFrame:CGRectMake(320, 0, 320, 480)];

   [self.scrollView addSubView:self.view1];
   [self.scrollView addSubView:self.view2];

   self.scrollView.bounces=NO;
   self.scrollView.contentSize=CGSizeMake(640,460);
   [self.scrollView setShowHorizontalScrollIndicator:NO];
   [self.scrollView scrollRectToVisible:CGRectMake(0, 0, 320, 416) animated:NO];
   [self.scrollView setDelegate:self];//Set delegate
}

-(void)scrollViewDidEndDecelerating:(UIView *)scrollView
{
   lbl.text=@"0";
}