我希望沿着一个弧线,从位置1到位置2的图像所示的动画.
实际发生的是视图动画描述了一个完整的圆形而不是圆弧.我的问题是：
>我应该使用CGPathAddArc还是CGPathAddArcToPoint？
>我需要使用CGPathMovetoPoint来描述视图的初始位置吗？
当我通过代码时,CGPoints值正如我预期的那样,角度也是如此.
我使用以下函数获取一个圆圈上的CGPoint
CGPoint pointOnCircle(CGPoint centre,float radius,float angle)
{
float x = centre.x + radius * cosf(angle);
float y = centre.y + radius * sinf(angle);
return CGPointMake(x,y);
}
我使用以下代码和变体,但是我还没有设法破解它.
CAKeyframeAnimation *pathAnimation = [CAKeyframeAnimation animationWithKeyPath:@"position"]; pathAnimation.calculationMode = kCAAnimationPaced; pathAnimation.fillMode = kCAFillModeForwards; pathAnimation.removedOnCompletion = NO; pathAnimation.duration = duration; pathAnimation.repeatCount = 1; CGPoint viewCenter = dynamicView.objectCenter; CGMutablePathRef arcPath = CGPathCreateMutable(); // CGPathMovetoPoint(arcPath,NULL,viewCenter.x,viewCenter.y); //work out the half way point float halfwayAngle = dynamicView.angle + (0.5f * self.angleIncrement); float fullwayAngle = dynamicView.angle + self.angleIncrement; CGPoint halfwayPoint = pointOnCircle(self.center,self.radius,halfwayAngle); CGPoint fullwayPoint = pointOnCircle(self.center,fullwayAngle); CGPathAddArc(arcPath,halfwayPoint.x,halfwayPoint.y,dynamicView.angle,fullwayAngle,clockwise); // CGPathAddArcToPoint(arcPath,viewCenter.y,fullwayPoint.x,fullwayPoint.y,self.radius); pathAnimation.path = arcPath; CGPathRelease(arcPath); [dynamicView.layer addAnimation:pathAnimation forKey:@"arc"];
解决方法
我编写了一个快速的例子,希望把它放在一起.我从“单一视图”应用程序模板开始,并将该操作添加到视图控制器以及一个按钮来触发操作.
- (IBAction)animateArc:(id)sender
{
// Create the arc
CGPoint arcStart = CGPointMake(0.2 * self.view.bounds.size.width,0.5 * self.view.bounds.size.height);
CGPoint arcCenter = CGPointMake(0.5 * self.view.bounds.size.width,0.5 * self.view.bounds.size.height);
CGFloat arcRadius = 0.3 * MIN(self.view.bounds.size.width,self.view.bounds.size.height);
CGMutablePathRef arcPath = CGPathCreateMutable();
CGPathMovetoPoint(arcPath,arcStart.x,arcStart.y);
CGPathAddArc(arcPath,arcCenter.x,arcCenter.y,arcRadius,M_PI,NO);
// The layer we're going to animate (a 50x50pt red Box)
UIView* dynamicView = [[UIView alloc] initWithFrame: CGRectMake(0,50,50)];
dynamicView.layer.backgroundColor = [[UIColor redColor] CGColor];
[self.view addSubview: dynamicView];
dynamicView.center = arcStart;
// An additional view that shows the arc.
BOOL showArc = NO;
UIView* drawArcView = nil;
if (showArc)
{
drawArcView = [[UIView alloc] initWithFrame: self.view.bounds];
CAShapeLayer* showArcLayer = [[CAShapeLayer alloc] init];
showArcLayer.frame = drawArcView.layer.bounds;
showArcLayer.path = arcPath;
showArcLayer.strokeColor = [[UIColor blackColor] CGColor];
showArcLayer.fillColor = nil;
showArcLayer.linewidth = 3.0;
[drawArcView.layer addSublayer: showArcLayer];
[self.view insertSubview: drawArcView belowSubview: dynamicView];
}
// The animation
CAKeyframeAnimation *pathAnimation = [CAKeyframeAnimation animationWithKeyPath:@"position"];
pathAnimation.calculationMode = kCAAnimationPaced;
pathAnimation.duration = 5.0;
pathAnimation.path = arcPath;
CGPathRelease(arcPath);
// Add the animation and reset the state so we can run again.
[CATransaction begin];
[CATransaction setCompletionBlock:^{
[drawArcView removeFromSuperview];
[dynamicView removeFromSuperview];
}];
[dynamicView.layer addAnimation:pathAnimation forKey:@"arc"];
[CATransaction commit];
}