core-animation

问题 Problem: I'm having issues getting videos I'm creating with AVFoundation to show in the VideoLayer, a CALayer , with correct dimensions. Example: Here is what the video should look like (as its displayed to the user in the app) However, here's the resulting video when it's exported: Details As you can see, its meant to be a square video, with green background, with the video fitting to a specified frame. However, the resulting video doesn't fit the CALayer used to contain it (see the black

问题 This question already has answers here : Closed 7 years ago . Possible Duplicate: iPhone CATransition adds a fade to the start and end of any animation? I'm trying to duplicate the "slide up from the bottom" animation that [UIViewController presentModalViewController:animated:] performs but without calling it because I don't want a modal view. The below core animation code comes very close but appears to be changing transparency values of the views during it. At the start of the animation you

问题 I'm attempting to add the AVCaptureVideoPreviewLayer CALayer as the background to my SKScene. I can add the CALayer to the scene, but no matter what attempts at ordering the CALayer is always the top most object. In the didMoveToView I have the function: - (void) didMoveToView:(SKView *)view { [self addVideo]; } Which calls the addVideo function: -(void) addVideo { AVCaptureSession *captureSession = [[AVCaptureSession alloc] init]; captureSession.sessionPreset = AVCaptureSessionPresetHigh;

问题 I'm slightly used as to what the purpose of CALayer's existence is. Why not just put the properties in a UIView? Thanks. 回答1: A CALayer represents a completely different "thing" from a UIView. A CALayer only deals with drawing itself, and encapsulating the information needed to do that. A view, on the other hand, owns one or many layers, which it uses to draw itself. A view has many other functions and properties though, that are unrelated to its representation on the screen. I would

问题 I have noticed that when placing PNG images into a view using IB and/or animating those images to various positions around a view, the image can sometimes get a slight blur. In most cases I can remedy the blur by adding .5 of a pixel to the images position. [lbLiteButton.layer setPosition:CGPointMake(140.5,159.5)]; Sometimes I have to adjust both x and y like above. Sometimes I only have to adjust x or y. I remember reading somewhere that this has to do with the size of the image and how core

问题 I'm trying to reproduce pieces of small paper falling from top effect, using CAEmitterLayer & CAEmitterCell. So far, I got the 2D animation of it, But I'm having difficulty to make each cell to rotate when falling. How to I apply random rotation on each particle? I tried with 3D Transform with no success so far. This is what I got: -(void) configureEmitterLayer { self.emitterLayer = [CAEmitterLayer layer]; self.emitterLayer.emitterPosition = CGPointMake(self.backgroundContainer.bounds.size

问题 I'm trying to reproduce pieces of small paper falling from top effect, using CAEmitterLayer & CAEmitterCell. So far, I got the 2D animation of it, But I'm having difficulty to make each cell to rotate when falling. How to I apply random rotation on each particle? I tried with 3D Transform with no success so far. This is what I got: -(void) configureEmitterLayer { self.emitterLayer = [CAEmitterLayer layer]; self.emitterLayer.emitterPosition = CGPointMake(self.backgroundContainer.bounds.size

问题 I try to draw rain and snow as particle system using Core Graphics . In simulator rendering proceeded fine but when I run my app on real device rendering is slow down. So, advise me please approaches to increase particle system drawing performance on iPhone . May be I should use OpenGL for this or CoreAnimation ? 回答1: OpenGL would be the lowest level to drop to for the rendering, so should offer the best performance (if done right). CoreAnimation would be close enough if there are not too

问题 I'm expecting the completion closure on this UIView animation to be called after the specified duration, however it appears to be firing immediately... UIView.animateWithDuration( Double(0.2), animations: { self.frame = CGRectMake(0, -self.bounds.height, self.bounds.width, self.bounds.height) }, completion: { finished in if(finished) { self.removeFromSuperview() } } ) Has anyone else experienced this? I've read that others had more success using the center rather than the frame to move the

问题 I'm expecting the completion closure on this UIView animation to be called after the specified duration, however it appears to be firing immediately... UIView.animateWithDuration( Double(0.2), animations: { self.frame = CGRectMake(0, -self.bounds.height, self.bounds.width, self.bounds.height) }, completion: { finished in if(finished) { self.removeFromSuperview() } } ) Has anyone else experienced this? I've read that others had more success using the center rather than the frame to move the