Ios – Animate scrolling of UIScrollView with CoreAnimation

core-animationiosiphoneuiscrollview

Sorry for a big question, real question are bold in bottom, now some explanation.

I'm use CoreAnimation in my project for animate some objects moving like this.

CABasicAnimation *moveAnimation;        
moveAnimation=[CABasicAnimation animationWithKeyPath:@"position"];      
moveAnimation.duration = 2.0;       
moveAnimation.repeatCount=1;        
moveAnimation.autoreverses=NO;  
moveAnimation.delegate = self;
moveAnimation.fromValue = [NSValue valueWithCGPoint:[crawler.layer position]];
moveAnimation.fillMode = kCAFillModeForwards;
moveAnimation.removedOnCompletion = NO;
CGPoint p;
moveAnimation.toValue = [NSValue valueWithCGPoint:CGPointMake(100, 100)];
[crawler.layer addAnimation:moveAnimation forKey:@"moveAnimation"];

And now I need to animate scrolling of some UIScrollView. I can't use setContentOffset:(CGPoint)contentOffset animated:(BOOL)animated method, because it can't customise animation duration.

I can make it like this

CGContextRef context = UIGraphicsGetCurrentContext();
[UIView beginAnimations:nil context:context];
[UIView setAnimationCurve:UIViewAnimationCurveLinear];
[UIView setAnimationDuration:2];
[UIView setAnimationDelegate:self];
scrollView.contentOffset = CGPointMake(scrollView.contentOffset.x + 200, scrollView.contentOffset.y);
[UIView commitAnimations];

but it's not CoreAnimation, and using 2 different kinds of animation techniques in one app is not a good practice, I think.

Is there a way to use a CoreAnimation to animate scrolling of UIScrollView content to custom point with custom animation duration?
P.S. Sorry for the bad English.

Best Answer

You could use:

[UIView animateWithDuration:duration animations:^ {
    [scrollView setContentOffset:destination animated:NO];
}];

You can set the duration of the animation this way.

Related Solutions

Ios – Finding the direction of scrolling in a UIScrollView

Determining the direction is fairly straightforward, but keep in mind that the direction can change several times over the course of a gesture. For example, if you have a scroll view with paging turned on and the user swipes to go to the next page, the initial direction could be rightward, but if you have bounce turned on, it will briefly be going in no direction at all and then briefly be going leftward.

To determine the direction, you'll need to use the UIScrollView scrollViewDidScroll delegate. In this sample, I created a variable named lastContentOffset which I use to compare the current content offset with the previous one. If it's greater, then the scrollView is scrolling right. If it's less then the scrollView is scrolling left:

// somewhere in the private class extension
@property (nonatomic, assign) CGFloat lastContentOffset;

// somewhere in the class implementation
- (void)scrollViewDidScroll:(UIScrollView *)scrollView {

    ScrollDirection scrollDirection;

    if (self.lastContentOffset > scrollView.contentOffset.x) {
        scrollDirection = ScrollDirectionRight;
    } else if (self.lastContentOffset < scrollView.contentOffset.x) {
        scrollDirection = ScrollDirectionLeft;
    }

    self.lastContentOffset = scrollView.contentOffset.x;

    // do whatever you need to with scrollDirection here.    
}

I'm using the following enum to define direction. Setting the first value to ScrollDirectionNone has the added benefit of making that direction the default when initializing variables:

typedef NS_ENUM(NSInteger, ScrollDirection) {
    ScrollDirectionNone,
    ScrollDirectionRight,
    ScrollDirectionLeft,
    ScrollDirectionUp,
    ScrollDirectionDown,
    ScrollDirectionCrazy,
};

Ios – UIScrollView not scrolling

It's always good to show a complete working code snippet:

// in viewDidLoad (if using Autolayout check note below):

UIScrollView *myScrollView;
UIView *contentView;
// scrollview won't scroll unless content size explicitly set

[myScrollView addSubview:contentView];//if the contentView is not already inside your scrollview in your xib/StoryBoard doc

myScrollView.contentSize = contentView.frame.size; //sets ScrollView content size

Swift 4.0

let myScrollView
let contentView

// scrollview won't scroll unless content size explicitly set

myScrollView.addSubview(contentView)//if the contentView is not already inside your scrollview in your xib/StoryBoard doc

myScrollView.contentSize = contentView.frame.size //sets ScrollView content size

I have not found a way to set contentSize in IB (as of Xcode 5.0).

Note: If you are using Autolayout the best place to put this code is inside the -(void)viewDidLayoutSubviews method .

Best Answer

Related Solutions

Ios – Finding the direction of scrolling in a UIScrollView

Ios – UIScrollView not scrolling

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