Change the speed of setContentOffset:animated:?

问题:

Is there a way to change the speed of the animation when scrolling a UITableView using setContentOffset:animated:? I want to scroll it to the top, but slowly. When I try the following, it causes the bottom few cells to disappear before the animation starts (specifically, the ones that won't be visible when the scroll is done):

[UIView beginAnimations:nil context:nil];
[UIView setAnimationDuration:3.0];
[self.tableView setContentOffset:CGPointMake(0, 0)];
[UIView commitAnimations];

Any other way around this problem? There is a private method _setContentOffsetAnimationDuration that works, but I don't want to be rejected from the app store.

回答1:

There is no a direct way of doing this, nor doing the way you wrote it. The only way I can accomplish this is by making the movement/animation by my own.

For example move 1px every 1/10 second should simulate a very slow scroll animation. (Since its a linear animation maths are very easy!)

If you want to get more realistic or fancy and simulate easy-in easy-off effect then you need some maths to calculate a bezier path so you can know the exact position at every 1/10 second, for example

At least the first approach shouldn't be that difficult. Just use or -performSelector:withObject:afterDelay or NSTimerswith

-[UIScrollView setContentOffset:(CGPoint*)];`

Hope it helps

回答2:

[UIView animateWithDuration:2.0 animations:^{
    scrollView.contentOffset = CGPointMake(x, y);
}];

It works.

回答3:

I've taken nacho4d's answer and implemented the code, so I thought it would be helpful for other people coming to this question to see working code:

I added member variables to my class:

CGPoint startOffset;
CGPoint destinationOffset;
NSDate *startTime;

NSTimer *timer;

and properties:

@property (nonatomic, retain) NSDate *startTime;
@property (nonatomic, retain) NSTimer *timer;

and a timer callback:

- (void) animateScroll:(NSTimer *)timerParam
{
    const NSTimeInterval duration = 0.2;

    NSTimeInterval timeRunning = -[startTime timeIntervalSinceNow];

    if (timeRunning >= duration)
    {
        [self setContentOffset:destinationOffset animated:NO];
        [timer invalidate];
        timer = nil;
        return;
    }
    CGPoint offset = [self contentOffset];

    offset.x = startOffset.x +
        (destinationOffset.x - startOffset.x) * timeRunning / duration;

    [self setContentOffset:offset animated:NO];
}

then:

- (void) doAnimatedScrollTo:(CGPoint)offset
{
    self.startTime = [NSDate date];
    startOffset = self.contentOffset;
    destinationOffset = offset;

    if (!timer)
    {
        self.timer = [NSTimer scheduledTimerWithTimeInterval:0.01
                                                      target:self
                                                    selector:@selector(animateScroll:)
                                                    userInfo:nil
                                                     repeats:YES];
    }
}

you'd also need timer cleanup in the dealloc method. Since the timer will retain a reference to the target (self) and self has a reference to the timer, some cleanup code to cancel/destroy the timer in viewWillDisappear is likely to be a good idea too.

Any comments on the above or suggestions for improvement would be most welcome, but it is working very well with me, and solves other issues I was having with setContentOffset:animated:.

回答4:

Setting the content offset directly did not work for me. However, wrapping setContentOffset(offset, animated: false) inside an animation block did the trick.

UIView.animate(withDuration: 0.5, animations: {
                self.tableView.setContentOffset(
               CGPoint(x: 0, y: yOffset), animated: false)
            })

回答5:

I'm curious as to whether you found a solution to your problem. My first idea was to use an animateWithDuration:animations: call with a block setting the contentOffset:

[UIView animateWithDuration:2.0 animations:^{
    scrollView.contentOffset = CGPointMake(x, y);
}];

Side effects

Although this works for simple examples, it also has very unwanted side effects. Contrary to the setContentOffset:animated: everything you do in delegate methods also gets animated, like the scrollViewDidScroll: delegate method.

I'm scrolling through a tiled scrollview with reusable tiles. This gets checked in the scrollViewDidScroll:. When they do get reused, they get a new position in the scroll view, but that gets animated, so there are tiles animating all the way through the view. Looks cool, yet utterly useless. Another unwanted side effect is that possible hit testing of the tiles and my scroll view's bounds is instantly rendered useless because the contentOffset is already at a new position as soon as the animation block executes. This makes stuff appear and disappear while they're still visible, as to where they used to be toggled just outside of the scroll view's bounds.

With setContentOffset:animated: this is all not the case. Looks like UIScrollView is not using the same technique internally.

Is there anyone with another suggestion for changing the speed/duration of the UIScrollView setContentOffset:animated: execution?

回答6:

https://github.com/dominikhofmann/PRTween

subclass UITableview

#import "PRTween.h"


@interface JPTableView : UITableView{
  PRTweenOperation *activeTweenOperation;
}



- (void) doAnimatedScrollTo:(CGPoint)destinationOffset
{
    CGPoint offset = [self contentOffset];

    activeTweenOperation = [PRTweenCGPointLerp lerp:self property:@"contentOffset" from:offset to:destinationOffset duration:1.5];


}

回答7:

You can set the duration as follows:

scrollView.setValue(5.0, forKeyPath: "contentOffsetAnimationDuration") scrollView.setContentOffset(CGPoint(x: 100, y: 0), animated: true)

This will also allow you to get all of your regular delegate callbacks.

回答8:

IF all your trying to do is scroll your scrollview I think you should use scroll rect to visible. I just tried out this code

 [UIView animateWithDuration:.7
                      delay:0
                    options:UIViewAnimationOptionCurveEaseOut
                 animations:^{  
                     CGRect scrollToFrame = CGRectMake(0, slide.frame.origin.y, slide.frame.size.width, slide.frame.size.height + kPaddingFromTop*2);
                     CGRect visibleFrame = CGRectMake(0, scrollView.contentOffset.y,
                                                      scrollView.frame.size.width, scrollView.frame.size.height);
                     if(!CGRectContainsRect(visibleFrame, slide.frame))
                         [self.scrollView scrollRectToVisible:scrollToFrame animated:FALSE];}];

and it scrolls the scrollview to the location i need for whatever duration i am setting it for. The key is setting animate to false. When it was set to true, the animation speed was the default value set by the method

回答9:

For people who also have issues with disappearing items while scrolling a UITableView or a UICollectionView you can expand the view itself so that we hold more visible items. This solution is not recommended for situations where you need to scroll a great distance or in situations where the user can cancel the animation. In the app I'm currently working on I only needed to let the view scroll a fixed 100px.

NSInteger scrollTo = 100;

CGRect frame = self.collectionView.frame;
frame.size.height += scrollTo;
[self.collectionView setFrame:frame];

[UIView animateWithDuration:0.8 delay:0.0 options:(UIViewAnimationOptionCurveEaseIn) animations:^{
    [self.collectionView setContentOffset:CGPointMake(0, scrollTo)];
} completion:^(BOOL finished) {
    [UIView animateWithDuration:0.8 delay:0.0 options:(UIViewAnimationOptionCurveEaseIn) animations:^{
        [self.collectionView setContentOffset:CGPointMake(0, 0)];

    } completion:^(BOOL finished) {
        CGRect frame = self.collectionView.frame;
        frame.size.height -= scrollTo;
        [self.collectionView setFrame:frame];
    }];
}];

回答10:

I use transitionWithView:duration:options:animations:completion:

        [UIView transitionWithView:scrollView duration:3 options:(UIViewAnimationOptionCurveLinear) animations:^{
        transitionWithView:scrollView.contentOffset = CGPointMake(contentOffsetWidth, 0);
    } completion:nil];

UIViewAnimationOptionCurveLinear is an option make animation to occur evenly over.

While I found that in an animation duration, the delegate method scrollViewDidScroll did not called until animation finished.

回答11:

You can simply use block based animation to animate the speed of scrollview. First calculate the offset point to which you want to scroll and then simply pass that offset value as here.....

    [UIView animateWithDuration:1.2
                      delay:0.02 
                      options:UIViewAnimationCurveLinear  
                      animations:^{
     [colorPaletteScrollView setContentOffset: offset ];
 }
 completion:^(BOOL finished)
 { NSLog(@"animate");
 } ];

here colorPaletteScrollView is my custom scrollview and offset is the value passed .

this code works perfectly fine for me.

回答12:

Is there a reason you're using setContentOffset and not scrollRectToVisible:animated:?

- (void)scrollRectToVisible:(CGRect)rect animated:(BOOL)animated

I would recommend doing it like this:

[UIView beginAnimations:nil context:nil];
[UIView setAnimationDuration:3.0];
[self.tableView scrollRectToVisible:CGRectMake(0, 0, 320, 0) animated:NO];
[UIView commitAnimations];

Unless that doesnt work. I still think you should try it.

回答13:

Actually TK189's answer is partially correct.

To achieve a custom duration animated contentOffset change, with proper cell reuse by UITableView and UICollectionView components, you just have to add a layoutIfNeeded call inside the animations block:

[UIView animateWithDuration:2.0 animations:^{
    tableView.contentOffset = CGPointMake(x, y);
    [tableView layoutIfNeeded];
}];

回答14:

On Xcode 7.1 - Swift 2.0 :

func textFieldShouldEndEditing(textField: UITextField) -> Bool {

    dispatch_async(dispatch_get_main_queue()) {
        UIView.animateWithDuration(0, animations: { self.scrollView!.setContentOffset(CGPointZero,animated: true) })
    }
    return true
}

OR

func textFieldShouldReturn(textField: UITextField) -> Bool {

    if(textField.returnKeyType == UIReturnKeyType.Next) {
        password.becomeFirstResponder()
    }

    dispatch_async(dispatch_get_main_queue()) {
        UIView.animateWithDuration(0, animations: { self.scrollView!.setContentOffset(CGPointZero,animated: true) })
    }

    textField.resignFirstResponder()
    return true
}

Note: self.scrollView!.setContentOffset(CGPointZero,animated: true) can have different positions depending on the requirement

Example:

let scrollPoint:CGPoint = CGPointMake(0,textField.frame.origin.y/2);
scrollView!.setContentOffset(scrollPoint, animated: true);

回答15:

I wanted to change the contentOffSet of tableview when textfield begins to edit.

Swift 3.0

func textFieldDidBeginEditing(_ textField: UITextField) {

DispatchQueue.main.async { 
    UIView.animate(withDuration: 0, animations: {

     self.sampleTableView.contentOffset = CGPoint(x: 0, y: 0 - (self.sampleTableView.contentInset.top - 200 ))
    }) 
}    
}