I have an iOS Xcode project that previously would load fast, but from time to time, now will hang for five seconds or more during loading. When the app is run on an iPhone, the launch screen displays instantly, but sometimes, not always, and unpredictably, the app just hangs for around 5 seconds or more until the actual interface is displayed. It occurs both on the simulator and device across different iOS versions 7, 8, 9.
Recently, a UIView's class that contains a drawRect function was changed slightly, it has an outlet connection to one of the ViewControllers, but no significant changes made overall. One ViewController has code in the ViewDidLoad, ViewWillAppear, ViewDidAppear functions. All these things I'm investigating if they are impacting the load time.
When I terminate the app, the next time I try running it, it loads super fast without issue. I have no idea what to make of this load behaviour.
Questions
1 - What methods can I use in Xcode to debug an app that loads slowly at irregular and unpredictable times?
2 - What obvious items should I be on the look out in the project that typically cause slow or prolonged load times?
3 - Does Xcode include tools to monitor the processes operating live while loading occurs?
4 - Is it possible to print output for load processes I can review?
Any experienced advice really appreciated. Thanks.
Not sure if you have looked instrumentation. It is the best way to determine this kind of issues with your app.
https://developer.apple.com/library/watchos/documentation/DeveloperTools/Conceptual/InstrumentsUserGuide/index.html
When I terminate the app, the next time I try running it, it loads super fast without issue. I have no idea what to make of this load behavior.
Do you mean exiting the app? Or actually killing it? Cause if it is the former, then the reason is the app was just launched from a suspended state.
I would suggest take a closer look at didFinishLaunchingWithOptions:, and check if you are doing something that takes more time than needed. Run your app with the time profiler instrument, it will tell you where is your bottleneck.
I have created a spriteKit game and have a problem with performance issues.
Problem:
FPS gets stuck at 40.0
How and when does it happen
1. I have a pause function in my game by just using view!.scene?.paused = true Sometimes when I hit the home button, launch another app, then go back to the game the FPS gets 'stuck' at 40 and doesnt climb back up to 60.0. (Sometimes it does)
2. I have a 'sharing' Facebook and Twitter icon where when you tap on it you can post/share/tweet something on your account. This icon can be seen in the pause menu. After posting or returning back to the game FPS gets stuck at 40 FPS (And again, sometimes it does climb back up to 60. Sometimes it does not)
3. To clarify, this doesnt happen mid-game. This only happens if I minimize the app, launch the Facebook/Twitter icons, during reminder pop-ups.
Temporary fix
There is a temporary fix to this, which is to minimize the app and then launching it again. However, I wouldnt want my users to experience this at all. If possible Id like to eliminate this problem altogether.
What I have tried so far to fix this
1.Ive tried running this on instruments (time Profiler) but nothing really caught my eye. Thought I have to say I am quite new with instruments.
2. There is a similar question here but for him disabling UIKit items fixed it for him, and I dont have any of that.
3. I initially thought it was a SKShapeNode issue so I changed my sprites to SKSpriteNode. No help here either.
4. I have tried without the USB cable attached to the phone and tried running it using the Run button on XCode. No difference.
5. Ive tried rebooting device and laptop. Didnt help.
6. Tried this on multiple devices. Same issue.
Stats?
Game typically starts out at 20 nodes and 5 draws and can go up to 60 nodes 6 draws but it will actually still run smooth as long as I dont initiate any of the triggering methods mentioned above.
I have spent alot of time trying to find a solution for this. Changing codes and streamlining it. Googling it. I really need help on this one. I would really appreciate some help.
Update for comment #1
For you first inquiry
1) I have a SKSpriteNode as the pause button during gameplay for the user to pause the game if he wants to.
2) I have func applicationWillResignActive(application: UIApplication) {} in my AppDelegate.swift file that triggers a GameScene.swift function that changes a flag from true to false so that I know when the user goes out and come back in again. And I have my update block searching for that flag. If it is true, display the pause menu. However, this 40FPS issue happened before I added this whole pause/unpause thing. (The 40 FPS issue is what made me create the pause menu for this) (I know too in the latest ver. of swift that it will auto-pause when the app is minimized and unpause when I bring it back up.)
I wrote this (what should be) crazy-simple app. (iOS 8.4.1, xcode 6.4, iPhone 6.) But it's not behaving the way I expected.
All it's supposed to do is display the current time, have the screen darken when face down on a surface, and never sleep.
I can supply actual code, and all sorts of investigative output, but here's the gist of it.
It has two NSLabels that display the time.
I created an NSTimer (1.0 secs) that calls a func that: updates the content of the two NSLabels, and calls setNeedsDisplay for both of them.
I set proximityMonitoringEnabled to true
I set idleTimerDisabled to true
At first glance the app seems to function properly. The screen darkens when put face down, and lights up when lifted. The time updates just fine.
The problem is that the screen will occasionally fail to light back up when picked up. It seems like, in this case, the device has gone to sleep while it was face down. (I've checked the console logs, and it's not crashing.)
I can post the full source, and a lot of other debug data if it's useful, but my first question is, have I missed anything obvious here in trying to prevent the device from ever sleeping? Or, is there some known issue that requires special handling?
UPDATE, as a result another post on this site, about a seemingly related problem, I now don't simply set idleTimerDisabled to true, I first set it to false, then true. Also, I added another NSTimer which toggles idleTimerDisabled to false then true every 20 seconds. Neither of these seem to have solved the problem.
???
I'm making a game for iOS where you mostly drag big objects across the screen. When I run the game on an actual iPad/iPhone for a while (continuously dragging the object in circles across the screen) every 5 minutes or so the dragged object goes all stuttery for about 10-30 seconds. Then, it goes back to moving silky-smooth.
Visually, it looks like the game's frame rate dropped to 15 fps for a while, but in actual fact it's running at rock-solid 60 fps all the time. However, I noticed that the only thing that doesn't move smoothly is the dragged object, while the rest of the game is all running perfectly smooth.
This led me to believe that the stuttering is related to the touch input in iOS. So I started looking at touchesMoved, and saw that it's normally called every 16 milliseconds (so touch input runs at 60 fps). So far so good.
Then I noticed that when the object starts stuttering, touchesMoved starts being called at weird time intervals, fluctuating wildly between 8 milliseconds and 50 milliseconds.
So while the touchscreen is in this weird state, sometimes touchesMoved will get called just 8 milliseconds after the previous call, and sometimes it won't get called until 50 ms after the previous call. Of course, this makes the dragged object look all choppy because its position is updated at irregular intervals.
Do you have any idea what could be causing touchesMoved to stop being called at regular intervals, as it normally does?
Bonus:
-Whenever I tilt the screen to force the screen orientation to change, roughly 70% of the time the touchscreen goes into the aforementioned state where touchesMoved starts being called irregularly. Then after 10-20 seconds it goes back to normal and everything looks smooth again.
-I've tried this on two iPads and two iPhones, with iOS 6 and 7, and the issue appears in all of these devices.
-An OpenGLES view is used to display the graphics. It syncs to the display refresh rate using CADisplayLink.
-The Xcode project I'm using to test this has been generated by the unity3d game development tool, but I've found several non-unity games where the same issue appears. this appears to be a system-wide problem. note I'm measuring the timings in objective-c using CFAbsoluteTimeGetCurrent, completely outside unity.
This is not a bug in Unity.
Something inside the OS is getting into a bad state and the touch-drag messages stop flowing smoothly. Sometimes you'll get multiple updates in a frame and sometimes you'll get none.
The issue does not happen on iPhone4 or below, or if the game is running at 30Hz frame rate.
I experienced this bug while using an in-house engine I'd written while working at a previous company. It first manifest itself after upgrading the UI system of a scrabble genre game, where you drag the tiles about on the screen. This was utterly bizarre, and I was never able to pin down the exact reproduction steps, but they seem to be timing related, somehow.
It can also be seen on Angry Birds (unless they've fixed it by now), and a variety of other games on the market, basically anything with touch-drag scrolling or movement. For Angry Birds, just go into a level and start scrolling sideways. Most of the time it'll be silky smooth, but maybe 1 in 10 times, it'll be clunky. Re-start the app and try again.
A workaround is to drop the input update frequency to 30Hz for a few frames. This jolts the internals of the OS somehow and gives it time to straighten itself out, so when you crank it back up to 60Hz, it runs smoothly again.
Do that whenever you detect that the bad state has been entered.
I've also run into this. I can verify that it's a bug in Unity 4.3.x.
My 4.2.x builds process touches on device at 60Hz with TouchPhase.Moved on every frame.
My 4.3.x builds get 20-40Hz with TouchPhase.Stationary being emitted on dropped frames.
TestFlight history saved my sanity here.
Don't forget to file a bug with UT.
It's a real disaster. Sometimes it's lag and sometimes it's really smooth. It lags even when GPU and CPU utilization are below 10%. it's not Unity bug. I'm using cocos2d v3.
If someone found a cure, please post it!
I've been running into this as well. My current hypothesis which I still have to verify is that if you ask for a given frame rate (eg. 60fps), but your actually achieved frame rate is less than that (eg. 45fps) that this causes a timing/race condition issue between Unity requesting inputs from iOS at a higher frame rate than it actually is running at. However, if you set it to 30fps (at least in my UNity 5.2 tests with iOS 9.1) then you get a solid 30Hz of input. When I disabled a chunk of my game and it was running at a very solid 60fps, then I would consistently get 60Hz of input from the touch screen. This is what I have for now, but I have to prove this in a simple project which I haven't had time to do yet. Hope this helps someone else.
I found a potential solution to this problem here: https://forums.developer.apple.com/thread/62315 (posting here because it took me a lot of research to stumble across that link whereas this StackOverflow question was the first Google result).
To follow up on this, I got a resonse on my bug report to Apple. This
is the response:
"As long as you don't cause any display updates the screen stays in
low power and therefore 30hz mode, which in turn also keeps the event
input stream down at 30 hz. A workaround is to actually cause a
display update on each received move, even if it is just a one pixel
move of a view if input is needed while no explicit screen update will
be triggered."
In my application, using a GLKView, I set its
preferredFramesPerSecond to 60. Occasionally, my input rate would
randomly drop to 30hz. The response from Apple doesn't fully explain
why this would happen, but apparently the expected method of handling
this is to call display() directly from touchesMoved() while dragging.
I've subclassed GLKView and I set preferredFramesPerSecond to 60. On
touchesBegan(), I set isPaused=true, and start calling display()
within touchesMoved(). On touchesEnd(), I set isPaused=false. Doing
this, I'm no longer having any issues - the app is more performant
than it's ever been.
Apple's example TouchCanvas.xcodeproj does all drawing from within
touchesMoved() as well, so I guess this is the intended way to handle
this.
As far as I can tell, your best bet to achieve a smooth look may be to interpolate between touch events, rather than immediately mapping your objects to your touch position.
tl;dr: It seems just having a CADisplayLink causing any OpenGL context or Metal device to draw at 60fps can cause this.
I was repro'ing this on my iPhone 7 Plus w/ iOS 10.2.1.
I made a small sample simple app with a CADisplayLink with preferredFramesPerSecond = 60, and tried the following rendering approaches:
GLKView w/ display()
CAEAGLLayer, used as prescribed by Apple at WWDC (opaque, sole layer, fullscreen, nothing drawn above it)
MTLDevice
In each case, the render method would only clear the screen, not try drawing anything else.
In each case, I saw the input rate problem.
The following "tricks" also seemed to do nothing, when called inside touchesMoved:
Calling glkView.setNeedsDisplay() (with enableSetNeedsDisplay set to true)
Moving some other view
Calling glkView.display() (actually, seems like it can raise your input rate to 40 events per second. But it doesn't look any better, as far as I can tell, and seems wrong to do, so I wouldn't recommend it.)
I gave up, after running all these tests. Instead, I interpolate my object between the touch positions instead. So it's what I'd recommend, too.
But I figured I'd include my research here in case somebody else takes a stab at it and finds a better solution.
I have an iPad drawing app which uses core data and Quartz 2D. Users and I have been experiencing freeze problems that happen one or two times every hour if I am unlucky. I have tried everything I can to debug the problem, making sure there is no dead locks, no UI code being called from background threads and no core data methods called in different threads. (I used method swizzling to check them.)
But the problem is still here, and there is no crash log because the whole iPad just freeze and the user has to do a hard restart. It usually happens when I am drawing but I have no clue why it happens. It seems to be related to the fact that it updates some CAShapeLayers every time an UITouch is moved. (It is not feasible to use bitmaps instead because of memory usage) I even used Instruments to manually check every function that is called when I am drawing.
What else can I try to fix the problem? It has been bothering me for a few months now... and I begin to wonder if it is a bug from iOS.