ios - ImageView 的平滑滚动

Question

我已将图像动态添加到 ScrollView 。以下是代码:

-(void)displayimages {
    for (int i=0; i<[featuredarray count]; i++) {
        NSString *image=[[featuredarray objectAtIndex:i]objectForKey:@"img"];

        if (i==0) {
            webview=[[UIImageView alloc]initWithFrame:CGRectMake(i*290+15, 0, 270, 380)];
        }
        else {
            webview=[[UIImageView alloc]initWithFrame:CGRectMake(i*290+15, 0, 270, 380)];
        }
        webview.backgroundColor=[UIColor clearColor];
        webview.layer.borderWidth=4;
        webview.layer.cornerRadius=4;
        webview.layer.borderColor=[[UIColor whiteColor]CGColor];
        [webview setTag:i];
        webview.userInteractionEnabled=YES;
        NSURL *url = [NSURL URLWithString:image];
        [webview setImageWithURL:url placeholderImage:[UIImage 
           imageNamed:@"placeholder.png"]];
        [scroll addSubview:webview];

        UITapGestureRecognizer *tap1 =
        [[UITapGestureRecognizer alloc] initWithTarget:self action:@selector(handlefirstTap:)];
        tap1.delegate=self;
        tap1.numberOfTapsRequired=1;
        [webview addGestureRecognizer:tap1];
        [tap1 release];
        [webview release];
   }

   pages.defersCurrentPageDisplay=YES;
   scroll.delegate =self;

   scroll.contentSize = CGSizeMake(290*[featuredarray count],300);
   scroll.pagingEnabled = YES;
   pages.numberOfPages = [featuredarray count]-1;
   pages.currentPage =0;
}

-(void)scrollViewWillBeginDecelerating:(UIScrollView *)scrollView{
    int gallerypage = scrollView.contentOffset.x /scrollView.frame.size.width;
    CGRect frame = scroll.frame;
    frame.origin.x = frame.size.width-15*gallerypage;
    NSLog(@"frame.origin.x..%f",frame.origin.x);
    frame.origin.y =0;
    [scroll scrollRectToVisible:frame animated:YES];
}

-(void)scrollViewDidEndDecelerating:(UIScrollView *)scrollView {
    int gallerypage = scrollView.contentOffset.x /scrollView.frame.size.width;
    CGRect frame = scroll.frame;
    frame.origin.x=gallerypage*290;
    frame.origin.y =0;
    [scroll scrollRectToVisible:frame animated:YES];
}

当我使用 pagecontroller action 时它显示图像很好

-(IBAction)pagecontrolaction:(id)sender {
    int page = pages.currentPage;
    CGRect frame = scroll.frame;
    frame.origin.x=page*290;
    frame.origin.y =0;
    [scroll scrollRectToVisible:frame animated:YES];
}

但是当我对 imageview 使用触摸事件时，它无法流畅地显示图像。它在滚动过程中卡住。

这些是显示当前图像和第二张图像开始的预览。

Answer 1

这两种方法:scrollViewWillBeginDecelerating 和 scrollViewDidEndDecelerating 包含两个具有不同 x 位置的动画:

frame.origin.x = frame.size.width-15*gallerypage;

和

frame.origin.x=gallerypage*290;

最好关闭其中一个函数:scrollViewWillBeginDecelerating 或 scrollViewDidEndDecelerating。否则，您可能应该调整动画的 x 位置(必须对两个函数同步)。