问形状层的动画路径

EN

CABasicAnimation *morph = [CABasicAnimation animationWithKeyPath:@"path"];
morph.duration  = 1;
morph.fromValue = (__bridge id)oldPath.path;
morph.toValue   = (__bridge id)newPath.CGPath;
[line addAnimation:morph forKey:@"change line path"];
line.path=linePath.CGPath;

    #import "ViewController.h"

    @interface ViewController ()

    //the view to animate, nothing but a simple empty UIView here.
    @property (nonatomic, strong) IBOutlet UIView *targetView;
    @property (nonatomic, strong) CAShapeLayer *shapeLayer;
    @property NSTimeInterval animationDuration;
    @end

    @implementation ViewController

    - (void)viewDidLoad {
        [super viewDidLoad];

        //the shape layer appearance
        self.shapeLayer = [[CAShapeLayer alloc]init];
        self.shapeLayer.strokeColor = [UIColor blackColor].CGColor;
        self.shapeLayer.fillColor = [UIColor clearColor].CGColor;
        self.shapeLayer.opacity = 1.0;
        self.shapeLayer.lineWidth = 2.0;
        [self.view.layer insertSublayer:self.shapeLayer below:self.targetView.layer];

        //animation config
        self.animationDuration = 2;
    }

    - (UIBezierPath *)pathFrom:(CGPoint)pointA to:(CGPoint)pointB {
        CGFloat halfY = pointA.y + 0.5*(pointB.y - pointA.y);
        UIBezierPath *linePath=[UIBezierPath bezierPath];
        [linePath moveToPoint: pointA];
        [linePath addLineToPoint:CGPointMake(pointA.x, halfY)];
        [linePath addLineToPoint:CGPointMake(pointB.x, halfY)];
        [linePath addLineToPoint:pointB];
        return linePath;
    }

    - (void) moveViewTo: (CGPoint) point {
        UIBezierPath *linePath= [self pathFrom:self.targetView.center to:point];

        self.shapeLayer.path = linePath.CGPath;

        //Use CAKeyframeAnimation to animate the view along the path
        //animate the position of targetView.layer instead of the center of targetView
        CAKeyframeAnimation *viewMovingAnimation = [CAKeyframeAnimation animationWithKeyPath:@"position"];
        viewMovingAnimation.duration = self.animationDuration;
        viewMovingAnimation.path = linePath.CGPath;
        //set the calculationMode to kCAAnimationPaced to make the movement in a constant speed
        viewMovingAnimation.calculationMode =kCAAnimationPaced;
        [self.targetView.layer addAnimation:viewMovingAnimation forKey:viewMovingAnimation.keyPath];

        //draw the path, animate the keyPath "strokeEnd"
        CABasicAnimation *lineDrawingAnimation = [CABasicAnimation animationWithKeyPath:@"strokeEnd"];
        lineDrawingAnimation.duration = self.animationDuration;
        lineDrawingAnimation.fromValue = [NSNumber numberWithDouble: 0];
        lineDrawingAnimation.toValue = [NSNumber numberWithDouble: 1];
        [self.shapeLayer addAnimation:lineDrawingAnimation forKey:lineDrawingAnimation.keyPath];


        //This part is crucial, update the values, otherwise it will back to its original state
        self.shapeLayer.strokeEnd = 1.0;
        self.targetView.center = point;
    }

    //the IBAction for a UITapGestureRecognizer
    - (IBAction) viewDidTapped:(id)sender {
        //move the view to the tapped location
        [self moveViewTo:[sender locationInView: self.view]];
    }

    @end