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").
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 have a custom scroll view with a rectangle inside.
I would like to animate a curve along the top line of this rectangle so that it responds to scroll velocity. When done, it would look something like this:
video: http://capptivate.co/2015/02/01/skype-qik/
How would I accomplish this? Both high-level approaches and specific implementations are welcome, I'm not sure how to get started. (core animation? drawrect?)
This is nicely explained here http://holko.pl/2014/06/26/recreating-skypes-action-sheet-animation/
You can use a bezier path (either in a custom UIView w/ drawRect:, or easier with a CAShapeLayer), whose curvature can be controlled via its control points. So change the control points based on the scrollview's offset and you should have this effect.
I have multiple views with many UILabels on the views. (all constructed in Interface Builder).
I am then trying to create a "smaller" replica of my view when you pinch the screen.
To do this I apply:
view.transform = CGAffineTransformMakeScale(.5, .5);
and then I also adjust the frame of view.
The problem is that after the transformation, the text in all of my UILabels becomes "blurry". It doesn't stay pixel perfect as it is in full-scale view.
Is there a way to increase the pixelation of the labels after the transformation?
Applying a transform to a UIView or CALayer merely scales the rasterized bitmap of that layer or view. This can lead to blurriness of the resulting UI element, because they aren't re-rendered at that new scale.
If you really want your text or images to be crisp at the new scale factor, you're going to need to manually resize them and cause them to redraw instead of applying a transform. I described one way that I did this with a UIView hosted in a UIScrollView in this answer.
You might be able to create a single method that traverses your view hierarchy for your one main view, recursively reads each subview's frame, scales that down, and then forces a redraw of its contents. Transforms are still great to use for interactive manipulation or animation, but you can then trigger a full manual scaling and redraw at the end of the manipulation or animation.
I have a custom view with some drawing on it.
I want to resize it to a new proportion and I want the pattern I drew in it's drawRect to also be resized by the same proportion.
Is there anyway I can accomplish this without refreshing and redrawing everything.
This should be happening for you automatically with the default contentMode, which is UIViewContentModeScaleToFill. contentMode determines how to adjust the cached bitmap without forcing a new call to drawRect:. Also see contentStretch which allows you to control which part of the view is scaled.
you will have to redraw it for the new proportion.
For that you have to store the points that made the CGPath and scale the points according to the new proportion and render it again.
Redrawing CGPath needs attention.
If you have used simple moveTopoint / AddlinePoint you can do it just by storing points in an array. You can scale and redraw it later.
If you can used functions like addcurveTopoint etc., storing points in array won't work.A general purpose way is needed.For that you have to use the CGpathApply function. You can see an example it here. http://www.mlsite.net/blog/?p=1312
If you need to zoom and no interation neeeded you can take a scrrenshot and and zoom the image.
I have this app using which one can draw basic shapes like rectangle, eclipse, circle, text etc.
I also allow free form drawing, which is stored as set-of-points, on the canvas.
Also a user can resize and move around these objects by operating on the selection handles that appear when an object is selected.
In addition the user should be able to zoom and pan the canvas.
I need some inputs on how to efficiently implement this drawing functionality.
I have following things in mind -
Use UIView's InvalidateRect and drawRect
Have a UIView for the main canvas and for each inserted object - invalidate the correspoding rect and redraw all the objects which intersects that rect in the drawRect function of the UIView.
Have a UIView and use CALayer ?
every one keep mentioning about the CALayer , I dont have much idea on this, before I venture into this I wanted a quick input on whether this route is worth taking.
like, https://developer.apple.com/library/ios/#qa/qa1708/_index.html
Have a UIImageView as canvas and when drawing each object, we do this
i) Draw the object into offscreen CGContext, basically, create a new CGContext by using UIGraphicsBeginImageContext, draw the shape, extract the image out of this CG context and use that as source of UIImageView's image property, but here how do I invalidate only a part of the UIImageView so that only that area gets refreshed.
Could you please suggest what is the best approach?
Is there any other efficient way to get this done?
Thanks.
Using a UIImage is more efficient for rendering multiple objects. But Using a CALayer is more efficient when moving and modifying a single object because you don't have to modify the other objects. So I think the best approach is to use a UIImage for general drawing and a CALayer for the shape that is being modified. In other words:
use a CALayer to draw the shape being added or modified, but don't draw it on the UIImage
use a UIImage to draw the other shapes
But OpenGL is still the most efficient solution, but don't bother with that if you don't have too many objects to draw.
If you want to draw polygons, you'll have to use Quartz framework, and have your drawing methods based on CALayer. It doesn't really matter which view you'll put your CALayers in, UIImageView or UIView. I'll say UIView since you won't be needing UIImageView's properties or methods for drawing.