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
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 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.
I'm working on an app that lets the user stack graphics on top of each other.
The graphics are instantiated as a UIImageView, and is transparent outside of the actual graphic. I'm also using pan gestures to let the user drag them around the screen.
So when you have a bunch of graphics of different sizes and shapes on top of one another, you may have the illusion that you are touching a sub-indexed view, but you're actually touching the top one because some transparent part of it its hovering over your touch point.
I was wondering if anyone had ideas on how we could accomplish ONLY listening to the pan gesture on the solid part of the imageview. Or something that would tighten up the user experience so that whatever they touched was what they select. Thanks
Create your own subclass of UIImageView. In your subclass, override the pointInside:withEvent: method to return NO if the point is in a transparent part of the image.
Of course, you need to determine if a point is in a transparent part. :)
If you happen to have a CGPath or UIBezierPath that outlines the opaque parts of your image, you can do it easily using CGPathContainsPoint or -[UIBezierPath containsPoint:].
If you don't have a handy path, you will have to examine the image's pixel data. There are many answers on stackoverflow.com already that explain how to do that. Search for get pixel CGImage or get pixel UIImage.
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.