Question

我试图在我的应用中实现以下功能：

带有图像视图和视图作为子视图的滚动视图。
当我从滚动视图的顶部向下拖动时，图像视图的高度增加，在宽高比填充模式下，给人以缩放的印象。
当我放手时，图像会恢复到原来的高度。

所以基本上，我试图复制Facebook应用程序的即时文章页面。

问题是我无法动画图像视图恢复原始大小。它似乎总是挺身而出。由于某种原因，UIView.animateWithDuration（）在这里不起作用：/

这是我的代码：（imageHeight是UIImageView高度约束的IBOutlet）

    func scrollViewDidScroll(scrollView: UIScrollView) {

    let y = self.scrollView.contentOffset.y

    if y < 0 && self.imageHeight.constant < 500
    {
        self.imageHeight.constant += (-1*y)*0.5;
    }

}

func scrollViewDidEndDecelerating(scrollView: UIScrollView) {

    self.stoppedScrolling()

}


func scrollViewDidEndDragging(scrollView: UIScrollView, willDecelerate decelerate: Bool) {


    if !decelerate
    {
        self.stoppedScrolling()
    }

}

func stoppedScrolling()
{

    UIView.animateWithDuration(1) { 

        self.imageHeight.constant = 180

    }

}

Here's a gif of the result 此外，它并没有显示在gif中，但是在结束触摸和调整大小之间有半秒的延迟

Answer 1

看起来它是由UIImageView的高度约束导致的，我尝试通过代码创建UI并使用frame属性来控制它，它可以工作。

很抱歉我不知道如何编写swift代码，但我认为我可以知道你的意思，你必须也可以阅读我的代码，如下：

#import "MainViewController.h"

@interface MainViewController ()

@property UIScrollView *scrollView;
@property UIImageView *imageView;
@property bool needReceiveDraggingFlag;

@end

@implementation MainViewController

- (void)viewDidLoad {
[super viewDidLoad];
// Do any additional setup after loading the view.

_scrollView = [[UIScrollView alloc] initWithFrame:[UIScreen mainScreen].bounds];
_scrollView.backgroundColor = [UIColor grayColor];
_scrollView.delegate = self;
_scrollView.scrollEnabled = YES;
_scrollView.contentSize = CGSizeMake(_scrollView.frame.size.width,_scrollView.frame.size.height*1.2f);
[self.view addSubview:_scrollView];

UILabel *lbInfo = [[UILabel alloc] initWithFrame:CGRectMake(50, 300, 200, 30)];
lbInfo.backgroundColor = [UIColor greenColor];
lbInfo.text = @"Test label";
[_scrollView addSubview:lbInfo];

_imageView = [[UIImageView alloc] initWithFrame:CGRectMake(0, 0, 100, 100)];
_imageView.backgroundColor = [UIColor redColor];
[self.view addSubview:_imageView];

_needReceiveDraggingFlag = YES;
}

- (void)didReceiveMemoryWarning {
[super didReceiveMemoryWarning];
// Dispose of any resources that can be recreated.
}

-(void)scrollViewDidScroll:(UIScrollView *)scrollView{
NSLog(@"scrollViewDidScroll");
if(_needReceiveDraggingFlag){
    float y = _scrollView.contentOffset.y;
    if (y<0 && _imageView.frame.size.width<300) {
        float nowImageLength = _imageView.frame.size.width;
        float targetImageLength = nowImageLength + -y*0.5f;
        _imageView.frame = CGRectMake(0, 0, targetImageLength, targetImageLength);
    }
}
}

-(void)scrollViewDidEndDragging:(UIScrollView *)scrollView willDecelerate:(BOOL)decelerate{
NSLog(@"scrollViewDidEndDragging");
[self stoppedScrolling];
}

-(void)stoppedScrolling{
_needReceiveDraggingFlag = NO;
[UIView animateWithDuration:1 animations:^{
    self.imageView.frame = CGRectMake(0, 0, 100, 100);
} completion:^(BOOL isFinished){
    _needReceiveDraggingFlag = YES;
}];
}

@end

希望它可以帮到你。

试图实现Facebook即时文章页面，但我无法使图像视图高度动画

1 个答案: