我希望沿着弧线设置一个视图动画,如图像从位置1到位置2所示。
实际发生的是视图动画描述了一个完整的圆而不是弧。我的问题是:
当我单步执行代码时,CGPoints值与我预期的一样,角度也是如此。
我使用以下函数在圆圈上获取CGPoints
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);
}
我正在使用以下代码及其变体,但到目前为止我还没有成功破解它。
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, self.radius, fullwayAngle);
CGPathAddArc(arcPath, NULL, halfwayPoint.x, halfwayPoint.y, self.radius, dynamicView.angle, fullwayAngle, clockwise);
// CGPathAddArcToPoint(arcPath, NULL, viewCenter.x, viewCenter.y, fullwayPoint.x, fullwayPoint.y, self.radius);
pathAnimation.path = arcPath;
CGPathRelease(arcPath);
[dynamicView.layer addAnimation:pathAnimation forKey:@"arc"];
答案 0 :(得分:9)
我编写了一个快速的例子,希望将它们放在一起。我从"单一视图开始#34;应用程序模板并将此操作添加到视图控制器以及触发操作的按钮。
- (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, NULL, arcStart.x, arcStart.y);
CGPathAddArc(arcPath, NULL, arcCenter.x, arcCenter.y, arcRadius, M_PI, 0, NO);
// The layer we're going to animate (a 50x50pt red box)
UIView* dynamicView = [[UIView alloc] initWithFrame: CGRectMake(0, 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];
}
答案 1 :(得分:1)
最终我使用 CGPathAddRelativeArc 来获得我想要的转换。
CGPoint viewCenter = dynamicView.objectCenter;
CGMutablePathRef arcPath = CGPathCreateMutable();
CGPathMoveToPoint(arcPath, NULL, viewCenter.x, viewCenter.y);
float angleOfRotation = self.angleIncrement;
if (clockwise == NO)
{
angleOfRotation *= -1.0f;
}
float fullwayAngle = dynamicView.angle + angleOfRotation;
CGPoint fullwayPoint = pointOnCircle(self.center, self.radius, fullwayAngle);
CGPathAddRelativeArc(arcPath, NULL, self.center.x, self.center.y, self.radius, dynamicView.angle, angleOfRotation);
pathAnimation.path = arcPath;
CGPathRelease(arcPath);
[dynamicView.layer addAnimation:pathAnimation forKey:@"arc"];
dynamicView.angle = fullwayAngle;
dynamicView.objectCenter = fullwayPoint;