在自定义 UIView 中动画 UIBezierPath 不起作用

Question

当用户触摸我的视图 (touchesEnded) 时，我正在尝试在我的自定义 UIView 中为 UIBezierPath（从一条路径到另一条路径）设置动画。

我的绘图代码：

- (void)drawRect:(CGRect)rect {
    // Drawing code
    [self createStartPath];
    [self createEndPath];

    CGContextRef currentContext = UIGraphicsGetCurrentContext();
    CGContextAddPath(currentContext, _startPath.CGPath);
    CGContextDrawPath(currentContext, kCGPathStroke);

}

- (void) createStartPath
{
    _startPath = UIBezierPath.bezierPath;
    [_startPath moveToPoint: CGPointMake(18, 22.5)];
    [_startPath addCurveToPoint: CGPointMake(18.38, 22.32) controlPoint1: CGPointMake(18.14, 22.5) controlPoint2: CGPointMake(18.29, 22.44)];
    [_startPath addCurveToPoint: CGPointMake(18.32, 21.62) controlPoint1: CGPointMake(18.56, 22.11) controlPoint2: CGPointMake(18.53, 21.79)];
    [_startPath addLineToPoint: CGPointMake(6.78, 12)];
    [_startPath addLineToPoint: CGPointMake(18.32, 2.38)];
    [_startPath addCurveToPoint: CGPointMake(18.38, 1.68) controlPoint1: CGPointMake(18.53, 2.21) controlPoint2: CGPointMake(18.56, 1.89)];
    [_startPath addCurveToPoint: CGPointMake(17.68, 1.62) controlPoint1: CGPointMake(18.21, 1.47) controlPoint2: CGPointMake(17.89, 1.44)];
     [_startPath addLineToPoint: CGPointMake(5.68, 11.62)];
    [_startPath addCurveToPoint: CGPointMake(5.5, 12) controlPoint1: CGPointMake(5.56, 11.71) controlPoint2: CGPointMake(5.5, 11.85)];
    [_startPath addCurveToPoint: CGPointMake(5.68, 12.38) controlPoint1: CGPointMake(5.5, 12.15) controlPoint2: CGPointMake(5.56, 12.29)];
    [_startPath addLineToPoint: CGPointMake(17.68, 22.38)];
    [_startPath addCurveToPoint: CGPointMake(18, 22.5) controlPoint1: CGPointMake(17.77, 22.46) controlPoint2: CGPointMake(17.89, 22.5)];
    [_startPath closePath];

    [self.fillColor setFill];

    [_startPath fill];
}

- (void) createEndPath
{

     _endPath = UIBezierPath.bezierPath;
    [_endPath moveToPoint: CGPointMake(6, 22.5)];
    [_endPath addCurveToPoint: CGPointMake(5.62, 22.32) controlPoint1: CGPointMake(5.86, 22.5) controlPoint2: CGPointMake(5.71, 22.44)];
    [_endPath addCurveToPoint: CGPointMake(5.68, 21.62) controlPoint1: CGPointMake(5.44, 22.11) controlPoint2: CGPointMake(5.47, 21.79)];
    [_endPath addLineToPoint: CGPointMake(17.22, 12)];
    [_endPath addLineToPoint: CGPointMake(5.68, 2.38)];
    [_endPath addCurveToPoint: CGPointMake(5.62, 1.68) controlPoint1: CGPointMake(5.47, 2.21) controlPoint2: CGPointMake(5.44, 1.89)];
    [_endPath addCurveToPoint: CGPointMake(6.32, 1.62) controlPoint1: CGPointMake(5.79, 1.47) controlPoint2: CGPointMake(6.11, 1.44)];
    [_endPath addLineToPoint: CGPointMake(18.32, 11.62)];
    [_endPath addCurveToPoint: CGPointMake(18.5, 12) controlPoint1: CGPointMake(18.44, 11.71) controlPoint2: CGPointMake(18.5, 11.85)];
    [_endPath addCurveToPoint: CGPointMake(18.32, 12.38) controlPoint1: CGPointMake(18.5, 12.15) controlPoint2: CGPointMake(18.44, 12.29)];
    [_endPath addLineToPoint: CGPointMake(6.32, 22.38)];
    [_endPath addCurveToPoint: CGPointMake(6, 22.5) controlPoint1: CGPointMake(6.23, 22.46) controlPoint2: CGPointMake(6.11, 22.5)];
    [_endPath closePath];

    [self.fillColor setFill];

    //[_endPath fill];
}

我从这里开始我的动画（希望将一条路径“变形”到另一条路径）：

- (void)touchesEnded:(NSSet *)touches withEvent:(UIEvent *)event
 {
    [super touchesEnded:touches withEvent:event];

    CAShapeLayer * myLineShapeLayer = [[CAShapeLayer alloc] init];
    
    CABasicAnimation * pathAnimation = [CABasicAnimation animationWithKeyPath:@"path"];
    pathAnimation.fromValue = (__bridge id)[_startPath CGPath];
    pathAnimation.toValue = (__bridge id)[_endPath CGPath];
    pathAnimation.duration = 3.0f;
    [myLineShapeLayer addAnimation:pathAnimation forKey:@"animationKey"];
}

我看到startPath 和我的touchesEnded 被调用，但没有任何动画显示endPath。

Answer 1

为了让您的动画正常工作，请将您的myLineShapeLayer 添加为您视图的layer 的子层：

例如在viewDidLoad:

[self.view.layer addSublayer:myLineShapeLayer];

为了在动画结束后仍能在屏幕上看到endPath，我们可以先将endPath 分配给path 的path 属性：

myLineShapeLayer.path = [endPath CGPath];

因此我们在没有toValue 的情况下制作动画：

CABasicAnimation * pathAnimation = [CABasicAnimation animationWithKeyPath:@"path"];
pathAnimation.fromValue = (__bridge id)[_startPath CGPath];
pathAnimation.duration = 3.0f;
[myLineShapeLayer addAnimation:pathAnimation forKey:@"animationKey"];

动画的结束效果会在动画结束后保留​​在屏幕上。