UIView锚点->拖动->旋转变换导致闪烁
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【中文标题】UIView锚点->拖动->旋转变换导致闪烁【英文标题】:UIView anchorPoint->drag->rotate transform causes flickering 【发布时间】:2013-06-19 10:18:26 【问题描述】:目标
我正在尝试复制 UI Dynamics 拉动动画/行为。我在UIView
上设置了一个UIPanGestureRecognizer
用于拖动它。发生拖动时,我将触摸点设置为UIView.layer.anchorPoint
以允许围绕触摸点旋转。在拖动过程中,我检查触摸速度方向并顺时针或逆时针应用CGAffineTransformRotate
。这就是我所说的。
问题
动画不流畅,UIView 在拖动和应用旋转时闪烁(在短实例中出现多条视图痕迹)。视频录制为 30fps,因此看不到闪烁。我希望我的解释清楚。
我的视图控制器中的源代码如下。我正在 ios5.0+ 上尝试这个
- (void)viewDidLoad
[super viewDidLoad];
// Do any additional setup after loading the view, typically from a nib.
UIView *animationView = [[UIView alloc] initWithFrame:CGRectMake(50, 50, 100, 100)];
animationView.layer.backgroundColor = [UIColor redColor].CGColor;
animationView.layer.shouldRasterize = YES; // Does not help :(
animationView.autoresizingMask = UIViewAutoresizingNone; // Does not help :(
[self.view addSubview:animationView];
UIPanGestureRecognizer *pan = [[UIPanGestureRecognizer alloc] initWithTarget:self action:@selector(pan:)];
[animationView addGestureRecognizer:pan];
[animationView release];
[pan release];
- (void) pan:(UIPanGestureRecognizer*) gesture
if(gesture.state==UIGestureRecognizerStateBegan)
CGPoint anchor = [gesture locationInView:gesture.view];
gesture.view.layer.anchorPoint = CGPointMake(anchor.x/gesture.view.bounds.size.width,
anchor.y/gesture.view.bounds.size.height);
gesture.view.center = CGPointMake(anchor.x/gesture.view.bounds.size.width,
anchor.y/gesture.view.bounds.size.height);
else if(gesture.state==UIGestureRecognizerStateChanged)
CGPoint point1 = [gesture locationInView:self.view];
gesture.view.center=point1;
CGPoint velocity = [gesture velocityInView:gesture.view];
if(velocity.x > 0)
// Dragged right
if(velocity.y > 0)
// Dragged down
// counter clock
CGFloat angle = -0.2;
gesture.view.transform = CGAffineTransformRotate(gesture.view.transform, angle);
else
// Dragged up
// clock
CGFloat angle = 0.2;
gesture.view.transform = CGAffineTransformRotate(gesture.view.transform, angle);
else
// Dragged left
if(velocity.y > 0)
// Dragged down
// clock
CGFloat angle = 0.2;
gesture.view.transform = CGAffineTransformRotate(gesture.view.transform, angle);
else
// Dragged up
// counter clock
CGFloat angle = -0.2;
gesture.view.transform = CGAffineTransformRotate(gesture.view.transform, angle);
我尝试将CATransform3DMakeRotation (angle, 0.0f, 0.0f, 1.0f)
应用于图层而不是视图CGAffineTransformRotate
。但是闪烁仍然发生。有什么想法为什么会出现这个问题?我欢迎任何其他方法的建议,以达到相同的结果。
【问题讨论】:
我能够解决这个问题。请参阅下面的答案。 为什么要投反对票?有人不高兴? 【参考方案1】:在解决这个问题经过认真思考后,我意识到这是一个微不足道的错误。闪烁是因为我正在旋转以使拖动方向发生最轻微的变化。为了解决这个问题,我在进行旋转之前假设了像素变化的任意余量。
解决问题的修改代码如下
- (void) pan:(UIPanGestureRecognizer*) gesture
if(gesture.state==UIGestureRecognizerStateBegan)
CGPoint anchor = [gesture locationInView:gesture.view];
gesture.view.layer.anchorPoint = CGPointMake(anchor.x/gesture.view.bounds.size.width,
anchor.y/gesture.view.bounds.size.height);
else if(gesture.state==UIGestureRecognizerStateChanged)
CGPoint point1 = [gesture locationInView:self.view];
gesture.view.layer.position=point1;
CGPoint velocity = [gesture velocityInView:gesture.view];
CGFloat angle = 0.0;
if(velocity.x > self.view.bounds.size.width*0.15)
// Dragged right
if(velocity.y > self.view.bounds.size.height*0.02)
// Dragged down
// counter clock
angle = -0.05;
else if (velocity.y < -self.view.bounds.size.height*0.02)
// Dragged up
// clock
angle = 0.05;
else if (velocity.x < -self.view.bounds.size.width*0.15)
// Dragged left
if(velocity.y > self.view.bounds.size.height*0.02)
// Dragged down
// clock
angle = 0.05;
else if (velocity.y < -self.view.bounds.size.height*0.02)
// Dragged up
// counter clock
angle = -0.05;
[self applyRotationToView:gesture.view byAngle:angle];
- (void) applyRotationToView:(UIView*)rotationView byAngle:(CGFloat)angle
rotationView.transform = CGAffineTransformRotate(rotationView.transform, angle);
动画仍然没有人们想象的那么流畅,但是我已经设法减少了烦人的闪烁。
【讨论】:
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