I have an UIView in which I draw many shapes. I just want to keep redrawing this view in order to make kind of an animation. I searched for animation options, but all animations looks like they only work with properties, like transform, alpha... I just want a timed animation option, and that do not block the screen, I mean, that allows the application to realize the screen was tapped. Is it possible?
It is totally possible and you have a few different ways that you can go about doing it. If you want a simple png sequence style animation you can just fill a UIImageView like this:
imageView.animationImages = myImages;
imageView.animationDuration = 3;
[imageView startAnimating];
or you can override the drawrect function in a custom UIView, set up an NSTimer to tick however frequently you want to change the animation and call setNeedsDisplay on the view to draw the next frame.
Assuming you have a bezier path that represents each shape, try looking at CAShapeLayer - this can be used to draw a path on the screen, and you can animate the position, fill colour and many other properties of it.
Have one CAShapeLayer per shape, and add them as sub layers to your main view's layer.
You need to add the QuartzCore framework to use it, but it is very straightforward and there are plenty of tutorials out there.
Related
I need to create an animated chevron effect using the bitmap tile below. I am hoping that a UIView with a pattern fill will be sufficient, but I need to be able to animate the origin of the pattern over time, and I can't see that this is possible.
I think this is possible with Quartz, or CoreGraphics at the low level. What would be the best way to do this, and can you provide some example code in Swift that demonstrates the solution?
I would add the image as contents of multiple sublayers (CALayer instances) aligned one below the other and animate those sublayers y position.
The main layer would clip its sublayers on the border and sublayers that go offscreen would move to the bottom to be reused, similarly to how UITableView reuses its cells.
You might also want to look at CADisplayLink to have better control of the rendering.
I'm trying to draw a graphic equaliser for an iOS project.
The equaliser will have 7 bars, representing different frequency bands, than move up and down based on real-time audio data.
Can anyone suggest the best way to approach this in iOS?
New frequency data comes in at about 11Hz, and so the bars would have to animate to a new size 11 times per second.
Do I create a UIView for each bar and dynamically resize it's frame height?
Do I draw the bars as thick CGStrokes and redraw them within the parent view as needed?
Another option?
Thanks in advance
You want to use Core Animation. The basic principle is to create a bunch of "layer" objects, which can either be bitmap images, vector shapes, or text. Each layer is stored on the GPU and most operations can be animated at 60 frames per second.
Think of layers like a DOM node in a HTML page, they can be nested inside each other and you can apply attributes to each one similar to CSS. The list of attributes available matches everything the GPU can do efficiently.
It sounds like you want vector shapes. Basically you create all your shapes at startup, for example in the awakeFromNib method of a UIView subclass. For simple rectangles use CALayer and set a background colour. For more complicated shapes create a CAShapeLayer and a UIBezierPath, then apply it with shapeLayer.path = bezierPath.CGPath;.
Then, whenever you want to change something, you apply those changes to the layer object. For example, here I'm rotating a layer with a 1 second linear animation:
[CATransaction begin];
[CATransaction setAnimationDuration:1];
[CATransaction setAnimationTimingFunction:[CAMediaTimingFunction functionWithName:kCAMediaTimingFunctionLinear]];
[self.needleLayer setValue:[NSNumber numberWithFloat:DegreesToRadians(degrees) forKeyPath:#"transform.rotation.z"];
[CATransaction commit];
// you'll want to declare this somewhere
CGFloat DegreesToRadians(CGFloat degrees)
{
return degrees * M_PI / 180;
}
More complicated animations, eg a series of changes scheduled to execute back to back, can be done using a CAKeyframeAnimation: https://developer.apple.com/library/ios/documentation/Cocoa/Conceptual/CoreAnimation_guide/CreatingBasicAnimations/CreatingBasicAnimations.html
Note Core Animation only does 2D graphics. Apple has Scene Kit which is basically the same thing for 3D, but so far it's only available on OS X. Hopefully iOS 8 will include it, but until then if you want 3D graphics on iOS you need to use Open GL.
CALayers which you resize on demand would probably be the most efficient way to do this, if the bars are solid colours. This allows you to optionally animate between sizes as well.
View resizing triggers off layout cycles, which you don't want. Drawing using CG calls is pretty slow.
Obviously the only real way to find out is to profile (on a device) using instruments and the core animation tool. But from experience, layer sizing is faster than drawing.
Definitely not a UIView for each - instead, a single UIView for the entire equalizer. Fill in the drawRect method with the appropriate CG calls to draw whatever is required. You can queue the view to refresh as needed with the appropriate data. Tapping into CADisplayLink will help you get the frame-rate you're looking for.
https://developer.apple.com/library/ios/documentation/QuartzCore/Reference/CADisplayLink_ClassRef/Reference/Reference.html
NOTE: You can also subclass CALayer and draw in it if you prefer something lighter-weight than UIView but I think you'll be fine with the former.
On my table view, I want to display small circles of certain colors that will provide context for the information. The circles should be in the location that the image would usually be in (the left hand side). Is there an easy way to do this? I was thinking that I could create a new image view and simply draw on it using some drawing routines. The problem is I don't know any of these drawing routines, or at least I don't know how to use them outside of a drawRect function.
Well, the easiest way would be to include the different images in your bundle and conditionally set them to the cell's imageView's image property in cellForRowAtIndexPath:.
However, if you're looking for alternative's you could subclass UITableViewCell, and use CAShapeLayers to draw them programmatically and add them to the cells layer in what ever position you want.
Here's an example of how to use CAShapeLayer to draw a circle:
iPhone Core Animation - Drawing a Circle
i have a subclass of UIView that displays own content. I'd like to animate the content.
The content is self-drawn in an own drawRect:, i wonder what possibilities are there to animate it. The content itself consists of graphical shapes that change their form.
I don't see a way to construct the content with subviews that can then be animated themselves.
Is there a way to use an UIView animation block?
Are there other possibilities? I would not want to animate this using OpenGL ES, this would be my last choice.
Thanks for any hints
Torsten
are you sure you can't use CALayer? They are made for this! You can create complex frames/textures (you wrote you have geometric shapes) and apply animated transforms to them.
Consider that if your shapes don't fit in the (really wide array of possibility) of shapes, you can basically draw any line using a CALayer: you create a layer of the proper length and width then simply translate and rotate it as needed (and of course translation an rotation are "animatable").
On iOS, if there are two circles, both of which are UIView objects, then their center or frame can animate using UIView animation.
But the difficulty is, the container UITreeView containing these two circles, draw a line connecting the centers of the circles, using drawRect. In drawRect, I could use CG or UIKit to draw the line, and I chose to use UIBezierPath's moveToPoint and addLineToPoint to draw the line, which should actually just be CG calls underneath, but easier to use.
But when one circle animates to the other position, the line won't animate with it, so the animation can look kind of weird. Is there a way to make it animate?
I tried animating in the TreeView class instead of inside the UINodeView class (the circle), but that won't help. In fact, if I draw the circle using a random color in its drawRect method, when the circle moves slowly in the animation, the color won't change rapidly, suggesting that its drawRect isn't called. It probably is just CALayer that hold a cached image being animated.
So is there a way to make the line animate as well?
The other methods I can think of is:
1) Use a hack to use a UIView to hold the line also, so its frame can animate, but what if the circle moves so that the line needs to be drawn inside the UIView from (0, 0) to (200, 200), but now the line needs to slant the other way, drawing from (200, 0) to (0, 200), so in this case, it probably won't work. (But if I use some kind of transform to flip the image at the same time, it probably will work, but it seems complicated to consider when the transform should be used)
2) use CADisplayLink to do the animation, and just let it call [treeView setNeedsDisplay]; and in this case, the drawRect will be called for sure. (it can be an overkill, and since the whole background of the TreeView will be first erased, there might be a little flashing on the screen going on)
Or is there a simpler or better way?
You could assign your path to a CAShapeLayer (such as wrapping it in a UIView subclass that returns CAShapeLayer as its +layerClass). The path is assigned to the CGPath -path property (and note that UIBezierPath provides a CGPath property).
Then you have a line in a view that you can animate (such as a group animation using UIView +beginAnimations
.