I'm trying to learn how to use and implement CALayer in a Mac Objective-C application, but I can't seem to probably do the most basic thing - add a new layer and set its background colour/frame size. Can anyone see what is wrong with my code?
CALayer *layer = [CALayer layer];
[layer setFrame:CGRectMake(0, 0, 100, 100)];
[layer setBackgroundColor:CGColorCreateGenericRGB(1.0, 0.0, 0.0, 1.0)];
[self.layer addSublayer:layer];
[layer display];
I put this in the - (void)drawRect:(NSRect)rect method of my custom NSView subclass, but when I run the application, it just shows a blank view, with no background colour or evidence of the layer I created.
First of all, you don't want to add a layer in the drawRect: method of a view, this gets called automatically by the system and you'd probably end up with a lot more layers than you actually want. initWithFrame: or initWithCoder: (for views that are in a nib file) are better places to initialize your layer hierarchy.
Furthermore, NSViews don't have a root layer by default (this is quite different from UIView on iOS). There are basically two kinds of NSViews that use a layer: layer-backed views and layer-hosting views. If you want to interact with the layer directly (add sublayers etc.), you need to create a layer-hosting view.
To do that, create a CALayer and call the view's setLayer: method. Afterwards, call setWantsLayer:. The order is important, if you'd call setWantsLayer: first, you'd actually create a layer-backed view.
You need to make a call to the "setWantsLayer" method.
Check out the following documentation for the description for setWantsLayer:
https://developer.apple.com/library/mac/#documentation/Cocoa/Reference/ApplicationKit/Classes/NSView_Class/Reference/NSView.html
In a nutshell, your view needs to be layer-hosting view. Because it is a layer-hosting view, you should interact with the layer, and NOT interact with the view itself and don't add subviews to it.
[self setLayer:[CALayer new]];
[self setWantsLayer:YES]; // the order of setLayer and setWantsLayer is crucial!
[self.layer setBackgroundColor:[backgroundColor CGColor]];
Put this out of the drawRect. I normally put my layer setup in either the init method or the viewDidLoad.
Otherwise anytime the view is drawn a new layer is added and allocated. Also I've never used the [layer display] line before. The docs actually tell you not to call this method directly.
Updated info (Swift): first call view.makeBackingLayer() then set wantsLayer to true.
https://developer.apple.com/documentation/appkit/nsview/1483695-wantslayer
Related
I have made a video player,and images are draw in a NSView.Have any method to convert NSView to CALayer?I try to use layer-hosting view,but developer document said can not add any subviews to layer-hosting view.Anyone can give me some suggestions?This code can run in OSX 10.6.8,but OSX 10.7 and 10.8.
mDisplayView = [[NSView alloc] initWithFrame:NSMakeRect(0, 0, width, height)];
mDisplayLayer = [[CALayer layer] retain];
[mDisplayView setLayer:mDisplayAudioLayer];
[mDisplayView setWantsLayer:YES];
[mDisplayView addSubview:mContentView];
[mRootLayer addSublayer:mDisplayAudioLayer];
The image of video had been drawn on mContentView.I just need find a way to make the mContentView into CALayer,is that possible？
You do not convert a view to a layer - you either draw into a view traditionally by overriding drawRect: or you switch it to layer-backed view and use CoreAnimation.
Best to start here to understand the basic concepts involved:
Core Animation Programming Guide
I am designing a user interface containing several labels and text fields. I would like to style the UI like this:
setting a background pattern for the content view of my NSWindow
adding a custom icon to the background in the upper left corner
I solved the first problem by making the content view a layer-backed view as described in Apple's documentation of NSView:
A layer-backed view is a view that is backed by a Core Animation layer. Any drawing done by the view is the cached in the backing layer. You configured a layer-backed view by simply invoking setWantsLayer: with a value of YES. The view class will automatically create the a backing layer for you, and you use the view class’s drawing mechanisms. When using layer-backed views you should never interact directly with the layer.
A layer-hosting view is a view that contains a Core Animation layer that you intend to manipulate directly. You create a layer-hosting view by instantiating an instance of a Core Animation layer class and setting that layer using the view’s setLayer: method. After doing so, you then invoke setWantsLayer: with a value of YES. When using a layer-hosting view you should not rely on the view for drawing, nor should you add subviews to the layer-hosting view.
and then generating a CGColorRef out of a CGPattern which draws my CGImage:
NSView *mainView = [[self window]contentView];
[mainView setWantsLayer:YES];
To set the background image as a pattern I used the answer from How to tile the contents of a CALayer here on SO to get the first task done.
However for the second task, adding the icon I used the code below:
CGImageRef iconImage = NULL;
NSString *path = [[NSBundle mainBundle] pathForResource:#"icon_128" ofType:#"png"];
if(path != nil) {
NSURL *imageURL = [NSURL fileURLWithPath:path];
provider = CGDataProviderCreateWithURL((CFURLRef)imageURL);
iconImage = CGImageCreateWithPNGDataProvider(provider,NULL,FALSE,kCGRenderingIntentDefault);
CFRelease(provider);
}
CALayer *iconLayer = [[CALayer alloc] init];
// layer is the mainView's layer
CGRect layerFrame = layer.frame;
CGFloat iconWidth = 128.f;
iconLayer.frame = CGRectMake(0.f, CGRectGetHeight(layerFrame)-iconWidth, 128.f, 128.f);
iconLayer.contents = (id)iconImage;
CGImageRelease(iconImage);
[layer insertSublayer:iconLayer atIndex:0];
[iconLayer release];
The Questions
I am not sure if I am violating Apple's restrictions concerning layer-backed views that you should never interact directly with the layer. When setting the layer's background color I am interacting directly with the layer or am I mistaken here?
I have a bad feeling about interacting with the layer hierarchy of a layer-backed view directly and inserting a new layer like I did for my second task. Is this possible or also violating Apple's guidelines? I want to point out that this content view of course has several subviews such as labels, a text view and buttons.
It seems to me that just using one single layer-hosting NSView seems to be the cleanest solution. All the text labels could then be added as CATextLayers etc. However if I understand Apple's documentation correctly I cannot add any controls to the view anymore. Would I have to code all the controls myself in custom CALayers to get it working? Sounds like reinventing the wheel de luxe. I also have no idea how one would code a NSTextField solely in CoreAnimation.
Any advice on how split designing user interfaces with CoreAnimation and standard controls is appreciated.
Please note that I am talking about the Mac here.
no layer backing needed IMHO:
for 1. I do a pattern image
NSImage *patternImage = [NSImage imageNamed:#"pattern"];
[window setBackgroungdColor:[NSColor colorWithPatternImage:patternImage]];
for 2. add an NSImageView as a subview of the contentview
NSImageView *v = ...
[[window contentView] addSubview:v];
on mac some views dont respond nicely IF layer backed
:: e.g. pdfview
Make a superview container A. Add a subview B to A for all your NSView needs (buttons, etc.). Add a subview C to A for all your Core Animation needs.
Edit:
Even better: use superview A for all your NSView needs and one subview C for your Core Animation needs, ignoring view B altogether.
I am trying to use this bit of code:
[[myUIView layer] addSublayer: layer];
[myScrollView addSubview:myUIView];
[layer addAnimation:[self imagesAnimation] forKey:#"images"];
What I am doing to do is taking a layer that will later get a CAKeyFrameAnimate and placing that layer inside a UIView so I can use the standard view function:
-(UIView *)viewForZoomingInScrollView:(UIScrollView *)scrollView {
return myUIView;
}
But I digress... Then placing the UIView & layer inside of a UIScrollView so I get all of that good UIScrollView functionality.
At least this is how I believe it to work atm.
Hoping for some help currently it just shows a white screen but when I replace the first to lines with:
[[myScrollView layer] addSublayer: layer];
I get an animation that plays but now zooming goodness.
Any help would be appreciated.
EDIT: In summary what I am trying to do is is have a CAKeyFrameAination inside of a layer inside of a UIView inside of a UIScrollView. The reason for this packing is because I need an Animation that can stop start and zoom in. the First three lines of code produce a blank white screen but when I replace them with the last bit where I'm putting the layer on myScrollView it plays but as expected I get no zooming as
-(UIView *)viewForZoomingInScrollView:(UIScrollView *)scrollView {
is expecting an UIView and doesn't work if I tell it to expect a layer.
Hope this is clearer.
I thought I was adding the UIView in via code but apparently I needed to add it in via the IB and link it up to the code.
I have two circles which move around the screen. The circles are both UIViews which contain other UIViews. The area outside each circle is transparent.
I have written a function to create a CGPath which connects the two circles with a quadrilateral shape. I fill this path in a transparent CALayer which spans the entire screen. Since the layer is behind the two circular UIViews, it appears to connect them.
Finally, the two UIViews are animated using Core Animation. The position and size of both circles change during this animation.
So far the only method that I have had any success with is to interrupt the animation at regular intervals using an NSTimer, then recompute and draw the beam based on the location of the circle's presentationLayer. However, the quadrilateral lags behind the circles when the animation speeds up.
Is there a better way to accomplish this using Core Animation? Or should I avoid Core Animation and implement my own animation using an NSTimer?
I faced a similar problem. I used layers instead of views for the animation. You could try something like this.
Draw each element as a CALayer and include them as sublayers for your container UIVIew's layer. UIViews are easier to animate, but you will have less control. Notice that for any view you can get it's layer with [view layer];
Create a custom sublayer for your quadrilateral. This layer should have a property or several of properties you want to animate for this layer. Let's call this property "customprop". Because it is a custom layer, you want to redraw on each frame of the animation. For the properties you plan to animate, your custom layer class should return YES needsDisplayForKey:. That way you ensure -(void)drawInContext:(CGContextRef)theContext gets called on every frame.
Put all animations (both circles and the quad) in the same transaction;
For the circles you can probably use CALayers and set the content, if it is an image, the standard way:
layer.contents = [UIImage imageNamed:#"circle_image.png"].CGImage;
Now, for the quad layer, subclass CALayer and implement this way:
- (void)drawInContext:(CGContextRef)theContext{
//Custom draw code here
}
+ (BOOL)needsDisplayForKey:(NSString *)key{
if ([key isEqualToString:#"customprop"])
return YES;
return [super needsDisplayForKey:key];
}
The transaction would look like:
[CATransaction begin];
CABasicAnimation *theAnimation=[CABasicAnimation animationWithKeyPath:#"customprop"];
theAnimation.toValue = [NSValue valueWithCGPoint:CGPointMake(1000, 1000)];
theAnimation.duration=1.0;
theAnimation.repeatCount=4;
theAnimation.autoreverses=YES;
theAnimation.timingFunction = [CAMediaTimingFunction functionWithName:kCAMediaTimingFunctionEaseIn];
theAnimation.delegate = self;
[lay addAnimation:theAnimation forKey:#"selecting"];
[CATransaction setValue:[NSNumber numberWithFloat:10.0f]
forKey:kCATransactionAnimationDuration];
circ1.position=CGPointMake(1000, 1000);
circ2.position=CGPointMake(1000, 1000);
[CATransaction commit];
Now all the draw routines will happen at the same time. Make sure your drawInContext: implementation is fast. Otherwise the animation will lag.
After adding each sublayer to the UIViews's layer, rememeber to call [layer setNeedsDisplay]. It does not get called automatically.
I know this is a bit complicated. However, the resulting animations are better than using a NSTimer and redrawing on each call.
If you need to find the current visible state of the layers, you can call -presentationLayer on the CALayer in question, and this will give you a layer that approximates the one used for rendering. Note I said approximates - it's not guaranteed to be fully accurate. However it may be good enough for your purposes.
I am using a CALayer to display a path via drawLayer:inContext delegate method, which resides in the view controller of the view that the layer belongs to. Each time the user moves their finger on the screen the path is updated and the layer is redrawn. However, the drawing doesn't keep up with the touches: there is always a slight lag in displaying the last two points of the path. It also flickers, but only while displaying the last two-three points again. If I just do the drawing in the view's drawRect, it works fine and the drawing is definitely fast enough.
Does anyone know why it behaves like this? I suspect it is something to do with the layer buffering, but I couldn't find any documentation about it.
[UIView new] is simply shorthand for [[UIView alloc] init].
Give the following before setNeedsDisplay method::
[CATransaction begin];
[CATransaction setValue:[NSNumber numberWithFloat:someDelay] forKey:kCATransactionAnimationDuration];
[aLayer setNeedsDisplay];
[CATransaction commit];
You might have better luck using a layer hosting view.
Instead of using the drawLayer:inContext: method, setup the view you want and add a CALayer to it:
UIView *layerHosting = [[UIView alloc] initWithFrame:frame];
[layerHosting setLayer:[[CALayer new] autorelease]];
Hope that helps!