如何将 CALayer 从变量起点动画到给定终点

Question

CALayer 动画

我的应用程序的目的是在 TableView 中显示 ToDos/Tasks。所有任务都有一个开始值和一个结束值。

对于第一个任务，我想显示一个进度指示器，以便更好地了解剩余时间。对于背景，我的 ViewController 中有一个带有 autoLayout 约束的 UIView。我用于动画的 CALayer 是 backgroundView 的子层。 x 轴上图层的起点是变量，因此即使重新加载应用程序，计时器也设置正确。终点是一个绝对值（背景视图的全宽）。这些参数都可以正常工作，只是动画不起作用。我正在设置动画应该从哪里开始的值，以及剩下的持续时间，但 CALayer 不会移动。我尝试使用 UIView.animate 和 CABasicAnimation 操作图层，但在每种情况下，将图层设置为其起始位置后，动画都不会开始。

(https://ise-technology.com/cdn/stack-overflow/calayertimer/timer)

// func for setting setting the CALayer and the BackgroundView for the given values

func setTimerView(isActive: Bool, color: UIColor, animationDuration: Double){
    
    if isActive == true {
        
        configureBackgroundView(bool: true) // just sets the height for the background view
        
        backgroundTimerView.backgroundColor = color.withAlphaComponent(0.3)
        
        timerView.backgroundColor = color.cgColor
        
        setAnimationForDuration(duration: animationDuration)
        
    } else {
        configureBackgroundView(bool: false)
        timerView.backgroundColor = UIColor.clear.cgColor
    }
}


// func where the animation should be embedded 

func setAnimationForDuration(duration: Double) {

    let startPoint = setStartPoint(duration: duration)

    timerView.frame.origin.x = CGFloat(-startPoint)
    

    // after updating the origin X of the Layer to the current   position, its not possible to start an animation. My attempts to here place in this func


    let animation = CABasicAnimation()
    
    animation.duration = duration
    animation.toValue = timerView.frame.origin.x = 0 

    timerView.add(animation, forKey: nil)
     
}

Answer 1

您应该能够使用 CABasicAnimation 来完成您想要完成的任务。我已经在 Objective-C 中发布了我的答案，但我确信它也相对容易适应 Swift。

我认为您还缺少几件事：

设置图层的锚点和位置：

    self.progressLayer.position = CGPointZero;
    self.progressLayer.anchorPoint = CGPointZero;

为 bounds.size.width 键路径设置 CABasicAnimation

CABasicAnimation *progressAnimation = [CABasicAnimation animationWithKeyPath:@"bounds.size.width"];

将填充模式设置为转发，完成后删除为 NO

    progressAnimation.fillMode = kCAFillModeForwards;
    [progressAnimation setRemovedOnCompletion:NO];

这是一个仅使用一个视图控制器的示例，将进度条从中间点动画化到完整点：

@interface ViewController ()
@property (strong, nullable) IBOutlet UIView *backgroundView;
@property (strong, nullable) CALayer *progressLayer;
@end

@implementation ViewController

- (void)viewDidLoad {
    [super viewDidLoad];
    self.progressLayer = [[CALayer alloc] init];
    [self.progressLayer setFrame:CGRectMake(self.backgroundView.bounds.origin.x, self.backgroundView.bounds.origin.y, self.backgroundView.bounds.size.width / 2.0f, self.backgroundView.bounds.size.height)];
    self.progressLayer.position = CGPointZero;
    self.progressLayer.anchorPoint = CGPointZero;
    self.progressLayer.backgroundColor = [UIColor greenColor].CGColor;
    [self.backgroundView.layer addSublayer:self.progressLayer];
}

- (IBAction)animateProgress:(id)sender {
    [self.progressLayer removeAnimationForKey:@"progressAnimation"];
    CABasicAnimation *progressAnimation = [CABasicAnimation animationWithKeyPath:@"bounds.size.width"];
    progressAnimation.duration = 2.0f;
    progressAnimation.toValue = @(self.backgroundView.bounds.size.width);
    progressAnimation.fillMode = kCAFillModeForwards;
    [progressAnimation setRemovedOnCompletion:NO];
    [self.progressLayer addAnimation:progressAnimation forKey:@"progressAnimation"];
}

@end

您应该能够在自定义表格视图单元格的 awakeFromNib + 一些触发动画的方法中执行类似的操作。

上面的例子是这样的：

Answer 2

import UIKit

class ViewController: UIViewController {

    @IBOutlet weak var backgroundView: UIView!
    
    var progressLayer : CALayer!
    
    
    override func viewDidLoad() {
        super.viewDidLoad()
        
        self.setUpLayer()
        
    }
    
    
    func setUpLayer(){
        
    
        let x = self.backgroundView.bounds.origin.x
        let y = self.backgroundView.bounds.origin.y
        let height = self.backgroundView.bounds.size.height
        let width  = self.backgroundView.bounds.size.width
        
        self.progressLayer = CALayer.init()
        self.progressLayer.frame = CGRect(x: x, y: y, width: 0, height: height)
        self.progressLayer.position = CGPoint.zero
        self.progressLayer.anchorPoint = CGPoint.zero;
        self.progressLayer.backgroundColor = UIColor.red.cgColor;
        self.backgroundView.layer.addSublayer(self.progressLayer)
     
    
    }
    
    @IBAction func buttonAction(_ sender: Any) {
        
     //   self.progressLayer.removeAnimation(forKey: "progressAnimation")
        
        var progressAnimation = CABasicAnimation(keyPath: "bounds.size.width")
         progressAnimation.duration = 2.0
        progressAnimation.toValue =  self.backgroundView.bounds.width
        progressAnimation.fillMode = .forwards
        
        progressAnimation.isRemovedOnCompletion = false
        
        self.progressLayer.add(progressAnimation, forKey: "progressAnimation")

        
    }
    

}