iPhone Quartz2D render expanding circle

余生颓废 提交于 2019-12-04 18:11:35

Here's one way to do it. Add the following code to your UIViewController subclass and you'll get a circle that grows and then fades away wherever you touch:

- (void)touchesBegan:(NSSet *)touches withEvent:(UIEvent *)event {
    [self addGrowingCircleAtPoint:[[touches anyObject] locationInView:self.view]];
}

- (void)animationDidStop:(CAAnimation *)anim finished:(BOOL)flag {
    if (flag && [[anim valueForKey:@"name"] isEqual:@"grow"]) {
        // when the grow animation is complete, we fade the layer
        CALayer* lyr = [anim valueForKey:@"layer"];
        CABasicAnimation *animation = [CABasicAnimation animationWithKeyPath:@"opacity"];
        animation.fromValue = [lyr valueForKey:@"opacity"];
        animation.toValue = [NSNumber numberWithFloat:0.f];
        animation.duration = .5f;
        animation.delegate = self;
        lyr.opacity = 0.f;  
        [animation setValue:@"fade" forKey:@"name"];
        [animation setValue:lyr forKey:@"layer"];
        [lyr addAnimation:animation forKey:@"opacity"];
    } else if (flag && [[anim valueForKey:@"name"] isEqual:@"fade"]) {
        // when the fade animation is complete, we remove the layer
        CALayer* lyr = [anim valueForKey:@"layer"];
        [lyr removeFromSuperlayer];
        [lyr release];
    }

}

- (void)addGrowingCircleAtPoint:(CGPoint)point {
    // create a circle path
    CGMutablePathRef circlePath = CGPathCreateMutable();
    CGPathAddArc(circlePath, NULL, 0.f, 0.f, 20.f, 0.f, (float)2.f*M_PI, true);

    // create a shape layer
    CAShapeLayer* lyr = [[CAShapeLayer alloc] init];
    lyr.path = circlePath;

    // don't leak, please
    CGPathRelease(circlePath);
    lyr.delegate = self;

    // set up the attributes of the shape layer and add it to our view's layer
    lyr.fillColor = [[UIColor redColor] CGColor];
    lyr.position = point;
    lyr.anchorPoint = CGPointMake(.5f, .5f);
    [self.view.layer addSublayer:lyr];

    // set up the growing animation
    CABasicAnimation *animation = [CABasicAnimation animationWithKeyPath:@"transform"];
    animation.fromValue = [lyr valueForKey:@"transform"];
    // this will actually grow the circle into an oval
    CATransform3D t = CATransform3DMakeScale(6.f, 4.f, 1.f);
    animation.toValue = [NSValue valueWithCATransform3D:t];
    animation.duration = 2.f;
    animation.delegate = self;
    lyr.transform = t;  
    [animation setValue:@"grow" forKey:@"name"];
    [animation setValue:lyr forKey:@"layer"];
    [lyr addAnimation:animation forKey:@"transform"];
}
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