I'm developing an game which has a component based on UISliders. The player must slide them from left to right one at a time, and on occasion two at a time. The problem lies in the double slides. When sliding two UISliders at a time, the sliders lag behind the player's touches, and often create noticeable lag in the game (this was tested on iPhone 3GS). I'm assuming this is due to the OS trying to recognize a multitouch gesture, but I'm not certain.
My question is what can I do to alleviate the lag? It must be possible because there are drawing apps out there that use up to 5 fingers without much lag, so 2 should be cake.
Let me guess, are you redrawing the screen in the event handler for the UISlider? In which case you are trying to do it redundantly a lot of the time. Instead of redrawing in the event handler, record the change in your view controller. Then you have a timer set up and in that you check to see if your variable is set and if so redraw then.
Related
I want to make an endless vertical scrolling layer that gives the impression that the main character is moving upwards. I have been brainstorming on how to achieve this.
My issue is that I want objects to appear as if they are coming from above and below the screen at the same time. Secondly, I want to be able to move the main character to create and destroy box2d joints between it and some of the objects appearing on the screen. What is the best way to achieve this with consuming too much memory? I would appreciate any help on this.
Apple did a wonderful tutorial of this in a WWDC 2011 video session. It was "UITableView Changes, Tips & Tricks" and it's about 35m40sec into the video.
Since the use of the UITableView is really just a UIScrollView for the purposes of the background, you could just use a UIScrollView and you can either have it move on timer or events as needed.
Think of your player as moving within a stationary bounding box. The background can scroll using the aforementioned pooling method (as the background tile scrolls off the screen it is placed into a pool, and before a new tile is instantiated the pool is checked for available reusable tiles). Thirdly, your enemy objects will simply approach from either the bottom of the screen or the top.
Imagine your idea without the scrolling background (flying effect) and you should find that the problem is relatively straightforward.
I also needed and endless scrolling background layer. This can do exactly that, and it is super simple to set up and use. Just copy the four files in to the cocos2d folder in your project, then follow the quick tutorial seen on the github. Make sure the image you use is seamless (when you line them up vertically you can't tell where one ends.
I'm making an iPhone game and using UIView objects to draw sprites. Most of the time, I have no performance problems. However, once I have around 15 to 20 objects on the screen (and maybe 5 of them moving around), the game becomes considerably slower, especially on the iPhone 3G. The frame rate can drop to as low as a single frame per second.
Is this simply a limitation of using UIView objects, or should iOS be able to handle this many UIView objects on screen at the same time?
In order to isolate the problem, I've made drawing my views very simple — drawing a red rectangle. drawRect is only getting called once per view. The view hierarchy is very simple and shallow. I'm using CADisplayLink to update the UIView locations every frame.
There's very little else going on, so I'd like to hear if anyone else has had success using this number of UIView objects.
The key to my problems ended up being that I had labels on top of my game content. The labels are not opaque, which likely was a large part of the problem, as phix23 suggested.
The first thing that made a big difference was removing a frames per second label that was on top of the content. Having a label that changed content on every frame caused a lot of slowdown.
I also had a large label that displayed on top of much of the game and changed shape when you level up. It turned out that drawing this label on top of everything caused a lot of slowdown as well.
In answer to my original question, I've found that on an iPhone 3G I can support about 30-40 opaque UIViews onscreen at the same time, with 2 or 3 non-opaque views as well. Non-opaque UIViews that change size, shape, or location are by far the worst, and even one of these that covers a significant amount of the screen can quickly cause problems.
If you're setting the opaque property of each view to NO, keep in mind that this seriously affects the speed of drawing the views. If your views aren't transparent, you should leave this set to YES, which is default.
for such type of application you should use CoreGraphics / Quartz / OpenGL but anyway I don't think there is a limitation on such low count. For example if I have a table view with 9 rows and each row has 5 subviews its still displayed acceptable fast. Have you tried using UIView animation to change the position in view?
good luck in learning OpenGL ;)
For my iPhone app I'm creating some rotating gears with the help of some subclassed UIViews.
I have created subclasses that rotate themselves triggered by a timer.
In one place I have one of these subclasses within another one (so rotation within rotation, think moon rotation around earth and it's own axle). It all rotates fine and dandy, but sometime, like once or twice a minute, I see a very quick white blink in the area of the UIViews. Sometimes in the upper half, sometimes in the lower one and sometimes the whole area (which is only about 128 x 128 pixels).
I rotate by using CGAffineTransformMakeRotation.
I guessed it was due to performance problem, but after simplifying images (no more photoshop made drop shadows in PNG for example) and reducing the number per second the timer is called (2 times per second instead of 5) I still have the problem. CPU load is now down to between 9-25% (from around 47%) when measured in Instruments on a iPhone 3G. Still blinking!
Any clues on where to begin troubleshooting or any better way to rotate images within a view?
All ideas appreciated!
Basically I had an animation in an animation. Not technically skilled enough to say WHY that caused a problem, but removing the second animation solved the problem. My animations were of the type [UIView animateWithDuration... in which I did several CGAffineTransformMakeRotation's
I have a graphic that is 3 times the width of an iphone landscape view.
I am trying to auto scroll it so that it appears that it is moving sideways, without using the touchscreen scrolling method.
My aim is to maybe have a button you can press and it moves it left or right across the screen like an animation.
I can deal with everything else but am having trouble finding a solution.
Any example code would be appreciated or even any info on whether it is possible or not.
Thanks. Dave
You can wrap a UIView in an animation block. The animation sweeps the origin value in its frame property from one point to another, over a set period of time.
I have custom slider that I use the following touch event to respond to:
[bSlider addTarget:self action:#selector(sliderAction:) forControlEvents:UIControlEventValueChanged];
I find it very difficult to use, it does not respond to touches about 50% of the time. Compared to the volume slider with the music player that works great every time you touch it. Are there any secrets to creating a slider in code that will make it more responsive?
I had the same problem with my custom UISlider and solved it by using a larger "thumb" image with transparency around the outside.
I also had problems with my callback function running slowly and causing the slider to be very laggy and clumsy to use, which I fixed by adding a simple check at the top of the function:
int val = ceil(sliderView.value);
if (val == _lastSliderVal) return;
_lastSliderVal = val;
// .. code to update various display elements based on slider value
After changing both of these, the slider works beautifully.
The problem is the event you are tracking. UIControlEventTouchUpInside means that your -start method will only get called if you lift your finger up while it is still in the bounds of the control, something that's not easy to do on a slider.
What you probably want is UIControlEventTouchUpOutside and/or UIControlEventTouchDragExit, which will call -start either when you lift your finger outside of the control's bounds, or when your finger is dragged from within a control to outside its bounds, respectively.
See the UIControl reference for more info.
Well I tried several things including the suggestions above but never got my slider to work as well as the iPhone volume slider in the music app. The only thing that helped was to add a clear background around the button image to make the touch space larger. That created problems getting the button to slide all the way to the bottom and top of slider that I never completely resolved. Now with OS 3.0 is seems to be working much better.