I have a uitableview, where custom tableview cell inserts another uiview subclass to its contentView to display each cell content, I use the views drawRect method to write more than 20 numbers on each cell.
Now I need to animate the color of each numbers depending on whether its value has increased or decreased from its previous value.
I am using CATextLayer for this purpose, so that I can animate the foregroundColor property using CAAnimation. But in this process iOS is trying to trigger almost 400 CAAnimation simultaneously as I have 20 or more rows too. And this is seriously affecting the performance.
I found CAShapeLayer far more heavier for this job.
And moreover when I am using CATextLayer my font looks really jagged, and edgy.
My question is what would be the best method to do such thing.
Does a collection of animations in a CAAnimationGroup run under one thread, actually my point is will it improve the performance if I try to group 20 CAAnimations for a particular row into a CAAnimationGroup, than firing them individually.
For one of my requirement i was also requiring animation group and here is the reference:
How to animate one image over the unusual curve path in my iPad application?
Hope this will help you out.
Enjoy Coding :)
Related
Is there a way to check when a SKSpriteNode / SKNode is onscreen (i.e. visible) I have a large scrolling background where I am spawning mobs, but I want to limit their animations and sounds if they are not visible. Is there a way to do this, I could write something in the update loop but I wanted to see if there was anything I could test before I start querying mob positions every frame?
I think you are doing this wrong. You should stick to the MVC pattern. As such, you only have data/points that are moving in a large area and in update method, if any data is within screen area, only would you draw them. If it is out, remove them.
I am creating an app for practice that is a simple drawing app. The user drags his/her finger along the screen and it colors in a 100px x 100px square.
I currently achieve this by creating a new colored UIView where the user taps, and that is working. But, after a little time coloring in, there is substantial lag, which I believe is down to there being too many UIViews as a subview of the main view.
How can I, and others who similarly create UIViews on dragging a finger reduce the lag to none at all, no matter how many UIViews there are. I also think that perhaps this is an impossible task, so how else can someone like me color a cube of the size stated above in the main view on a finger dragged along the screen?
I know that this may seem like a specific question, but I believe that it could help others understand how to reduce lag if there are a very large amount of UIViews where a less performance reducing option is available.
One approach is to draw each square into an image and display that image, rather than keeping around an UIView for each square.
If your drawing is simple enough, though, you can use OpenGL to do this, which is much faster. You should look at Apple's GL Paint Sample Code which shows how to do this in OpenGL.
If your drawing is too complex for OpenGL, you could create, for example, a CGBitmapContext, and draw each square into that context when the user drags their finger. Whenever you draw a new square into that bitmap, you can turn the bitmap into an image (via CGBitmapConxtextCreateImage) and display that image an a UIImageView.
There are two things that come to my mind:
1- Use Instruments tool to check if you are leaking any memory
2- If you are just coloring the views than instead of creating images for each of them, either set the background color property of UIView or override the drawRect method to do custom drawing
I think what you are looking for is the drawRect: method of UIView. You could create your custom UIView (you propably have that already) and override the drawRect method and do your drawing there! You will have to save your drawings in an array or another container and call the setNeedsDisplay method whenever the array content is changed.
I have a problem. I want for each record in my core data database to draw an UIImage view on screen. But the problem is that I want to make a sort of grid. On the link below you see what I want to achieve.
picture
So my question is, how do I draw an image on screen in code. And place those images in a sort of a grid. using a collection view is no option, because the app should be running on all IOS devices.
While you could implement a custom UIView and implement the drawRect: method and draw UIImages there, I suggest just using multiple UIImageViews as subviews on your "main" view. Your view might be embedded in a UIScrollView, or you could use a UITableView with custom UITableViewCells. Whichever is easier is probably related to how you can interact with the view.
Building that one huge image view is something that I'd definitely try to avoid - it costs many many (probably unnecessary) memory, and it might be slow as well. Definitely not very flexible to handle, and a pain to update dynamically.
A quick cheat for something like this is to use a Table View and then in each cell to place another TableView but rotated at 90 degrees.
You can then use this second TableView to display the pictures etc...
This will give you a table that scrolls up and down and then each cell can scroll left to right.
I'd suggest subclassing UITableViewCell and setting it up as a UITableViewDelegate and UITableViewDatasource.
You will also have to remember to rotate the content of these "sub"tables by 90 degrees also so that they are the right way up.
This sounds like a lot of work but if you push the management of the sub Tables into the cells then it actually becomes quite easy.
I'm trying to add a way for my app to display data in an easily comprehensible form. I tried doing this with graphs, but found it to be a bit awkward, so I'm off to find a better solution.
Here's a problem:
I want to show up to 30 days of data, with user reported events plotted against a timeline.
The events should align vertically, to visually provide a reference of when certain events cluster together.
To solve the problem, I thought of using a UITableView with a background which has a scale, and superimpose upon that background a set of "pins", indicating user events. As the table is scrolled, the events would align one under another, providing a good indication historic event development:
I know that this is possible to be done with a UIScrollView, where I can just position a series of rulers and add events as pins. In order to do this efficiently, I'll have to use Tiling, a technique that I don't have much experience with.
I'm interested in knowing if this is possible with a UITableView, where caching and tiling is already done for me.
I tried adding UIImageViews to a tableViewCell.backgroundview , but this does not produce the desired results. I'd like to be able to dynamically add any number of subviews to the table cell. I can do this by adding a certain pre-determined number of images to an .xib and then trying to reposition them, but this does not seem like an ideal solution.
Is what I'm trying to do possible with UITableView, or should I abandon these efforts and look at UIScrollView with tiling?
Thank you!
yes this should be possible. Add the ruler image to the background of the UITableViewCell.
Then create a subclass of UITableViewCell that takes an array of pins objects that it will place within its view. The pin objects would contain the pin image and a horizontal location on the scale. Then in the tableView dataSource method cellForRowAtIndexPath method you set the tableViewCell's pin array to the correct array (or NSSet) of pins.
To make it even more lightweight, you could draw the pins yourself in the UITableViewCell subclasses drawRect method. Then you could just pass the locations of the pins.
Good luck
I'm trying to draw a graph that is indefinitely large horizontally, and the same height as the screen. I've added a UIScrollView, and a subclass of a UIView within it, which implements the -drawRect: method. In the simulator, everything works fine, but on the device, it can't seem to draw the graph after it reaches a certain size.
I'm already caching pretty much everything I can, and basically only calling CGContextAddLineToPoint in the -drawRect: section. I'm only drawing what's visible on the screen. I have a delegate to the UIScrollView which listens for -scrollViewDidScroll: which then tells the graph to redraw itself ([graphView setNeedsDisplay]).
I found one method that tells me to override the +layerClass method and return [CATiledLayer class]. This does allow the graph to actually draw on the device, but it functions very poorly. It's incredibly slow to actually draw, and the fade in that occurs is undesirable.
Any suggestions?
Well, here's my answer: I basically did something similar to how the UITableView works with cells: I have an NSMutableSet of GraphView objects which store unused graphs. When a section of the scroll view becomes visible, I take a graph view from that set (or make a new one if the set is empty). It already had a scrollX property to determine which part of it was supposed to draw. I set the scrollX property to the correct value and, instead of using the screen width, I gave it an arbitrary width to draw. When it goes out of the scroll view, it is removed from the UIScrollView and added to the set.
I wonder though if I really even need to remove them when they go outof the view? It may be prudent to try leaving them in and remove the ones not on screen only if I get a low memory warning? This might get rid of the pause whenever it needs to redraw a section of graph that hasn't changed.
My saving grace here was that my GraphView already was set up to draw only a portion of the graph. All I needed to do then was just make more than one of them.
I think this is a limitation of the iPhone graphics hardware. Through experimentation, I have seen that the iPhone will refuse to draw a frame that is bigger than 2000 pixels in either height or width. It probably has something to do with limited size for frame buffers in hardware.
Watch the 2011 WWDC session video entitled "Session 104 - Advanced Scroll View Techniques".
Thanks, that's helpful. One question -- what did you use for the contentSize of the UIScrollView? Does UIScrollView tolerate large content sizes (over 2000 px) as long as you're not creating buffers to fill the entire space in your content view? Or are you keeping the UIScrollView a constant size (say, 2 screen widths) and resting the UIScrollView contentOffset property each time you draw (using scrollX instead of the contentOffset to store your position)?
I think I answered my own question (the latter seems like a better alternative), heh, but I'll go ahead and post this in case other people need clarification.