I have a UIAnimation that pulls out a message log, but I need to populate the message log using a for loop as well. I have the animation taking place before the for loop begins, however, the animation doesn't actually begin until after the for loop finishes executing (even though the loop is located after the UIAnimation).
I've tried putting the contents of the for loop within an autoreleasepool (did not work)
I've tried running the for loop on a background thread, however, most of the code within the loop needs to be executed on the main thread, and I haven't had success with that approach.
The for loop is very large, and most of the code is irrelevant to the question, so you can set this up using any UIAnimation, and any relatively time consuming for loop...
for example:
let someView = UIView(frame:CGRect(x:self.view.frame.size.width,y:0,width:self.view.frame.size.width,height:self.view.frame.size.height))
someView.backgroundColor = .red
UIView.animate(withDuration:0.3,animations:{
self.someView.frame.origin.x = 0
})
//You can wrap this with something like:
//DispatchQueue.global(qos: .background).async(execute: {
//But this^ doesn't work on the majority of the code within the loop
for i in 0...1000{
print("hopefully this loop takes a few seconds to finish executing")
print("mainthread tasks being executed")
print("populating UITable in my particular case, and rendering Images/Video/text")
}
The closest that I can get to making it better is to add a "completion" to my UIAnimation, (which will allow the UIView to pull out completely/immediately) but then there is still a second of wait time before the first messages appear...
Also, I am populating a UITableView within the for loop. Not sure if that has any extra relevance to the primary issue I'm having or not...
I'm pretty familiar with DispatchQueue and the differences between async/sync. If you have any potential solutions, or ideas, please let me know.
The animation does not happen immediately, when you call UIView.animate. In stead all the animations are collected and run at some appropriate time. This is why the animation only starts after your for loop is done.
So the way to fix it is to get the animation to run before your for loop runs. Now, accepting what you say, that the for must run on the main thread, you have a number of options. You could put the for loop inside a DispatchQueue.main.async{} or somehow throttle it down so that the animation gets going first. Your idea of using the completion is a good one but you mention some practical issues you picked up with it. So either solve those practical issues, try to run the for inside a DispatchQueue.main.async{} or even, based on practical considerations, start the for loop on the main thread but somewhere else, say in something like didLayoutSubviews (fixed) or as now together with the animation but after a few millis delay to allow the animation to get going.
It's an interesting question. This made me think!
Yes, you mentioned that you understand differences between async/sync but didn't mention if you tried animating in the main thread.
Did you try putting the
UIView.animate(...) in DispatchQueue.main.async{}?
Related
I am curious what to use for my game. A timer:
let goodFPS = SKAction.wait(forDuration: 0.01666)
let mainGameRunner = SKAction.run {
//my code is here
}
let toRepeat = SKAction.repeatForever(SKAction.sequence([goodFPS,mainGameRunner]))
inGameHighScore.run(toRepeat,withKey:"mainGame")
or the update function:
override func update(_ currentTime: TimeInterval){
//my code is here
}
Which provides faster more consistent updates?
note: my frame rate is in the range of 45 to 58
First I think you are taking the FPS problem the wrong way around. You cannot "force" a faster frame rate than the device can give you. If you are basing the movements in your game on the assumption that every frame will be consistent, you are doing it wrong. It's actually how they did in the early days because CPUs were so slow and the difference from one generation to the new one wasn't too bad at first. But running an old DOS game on younger hardware will be tricky because the framerate is so high that the whole game mechanic becomes unstable or simply too fast to be playable.
The concept here is to think "over time" and to scale down any action in relation with the time elapsed between two frames.
The update() method gives you that opportunity by providing the current system clock state every frame. By keeping track of the time on the last frame, you can calculate the time difference with the current frame and use that difference to scale down what you are doing.
Using a timer to get the update on a consistent frame rate is not recommended nor practical. You may be calling the update closure at a given time interval, but the code inside that closure is taking time to execute on its own, and depending on your game logic, it might even have different execution times. So maybe the pause timing is consistent, but the code running before and after that pause might not be consistent. Then what happens if you run your game on a slower CPU? The code speed will change even more, making your timing inaccurate.
Another point against using an SKAction for your game loop is simply what they are. An action is an object in memory, meany to be reused by multiple objects. If you are making a "jump" action, for example, it is recommended to store that action somewhere and to reuse the same object every time you need something that "jumps", no matter what node it is. Your game loop is meant to be executed every frame, but not by different objects. Actions are also disposable. Meaning that you can kill an action even while it's running. If you put your game loop in an action, it will probably be run by the SKScene. If you use another action on your scene it becomes a puzzle right away because there are only two ways of removing an action besides letting it come to term: removing all actions or creating the action with an identifier key and use that key to remove any action with that key. If you don't see it already, it then forces you to put identifiers on every action that will be run by the scene and remove them one by one. And them again it leave a door open for a mistake that will get rid of your game loop because, keep it in mind, actions are DISPOSABLE! Then there is also no guarantee that your action will get executed first every single frame.
Why use the update() method? Simply because it is built IN your scene. No matter what, every frame, update() gets called first. THEN, the actions get executed. You cannot flush the update() method accidentally like you can with an action. You don't have to be careful about strong/weak relationships causing memory leaks because you are referring to objects from inside a closure like you do with an action.
Suggested reads:
SKAction API reference
SKScene API reference : read about the frame processing in SpriteKit. It will help you understand how they put everything together at every frame.
I hope it makes things clearer.
I'm pretty sure that SKAction's timing facilities are based on the same game loop that is calling update.
The advantage of SKAction is that it's fire and forget for you, while using update would get awkward with setting and checking a bunch of timer variables.
I don't have a ton of experience with SpriteKit but I do have some experience making games and animations in iOS.
There is a class called CADisplayLink that fires a call to a delegate every time the screen is refreshed, this is a great way to update the screen, either in a game or in an animation, because you can know it will be called every frame and no more.
I'm not sure if SpriteKit uses that class to fire the update method, but I'm sure it uses something similar. This is usually called the run loop.
SKActions run on top of this run loop.
By creating your own run loop using a wait action, not only you're not gaining any benefits, you could be introducing inconsistencies in the way your logic is run.
Imagine that you have your wait action set to 0.01 seconds (I rounded it down for simplicity). If the screen is refreshing faster than you expect, and the action is updated every 0.009 seconds, the first time it's checked, it won't fire because there's a remaining 0.001 second on the wait command, so another 0.009 seconds will pass, and your code will be executed after 0.018 seconds, instead of your desired 0.01. Not only that, but two frames will have passed between the execution.
If you use the update function, you can know that your logic will be executed once every screen refresh, and no more.
I am using processing within Scala (although I don't think this is really relevant to my question).
I am constructing a searchtree within a loop that runs until a valid path has been found. That can take a few seconds and I would like to draw the graphical representation of the tree while it is being build so the user can see something is happening.
I tried to solve this by calling redraw() within the loop but that doesn't work. I guess because redraw() doesn't force a redraw but only sets a flag that a redraw should be done.
So is there a way I can force a redraw or how would you normally solve such a problem?
#George Profenza's comment is correct. Processing tasks all happen on the Animation Thread. Any tasks you execute within draw() will lock that thread until they complete. If you want to update the screen while a task is executing, either run the task on a separate thread (beyond the scope of the Processing API, you have to use Java for this), or break the task up into segments and let the draw() method return at the end of each segment so PApplet can render to the screen.
Earlier this month I asked this question 'What is a runloop?' After reading the answers and did some tries I got it to work, but still I do not understand it completely. If a runloop is just an loop that is associated with an thread and it don't spawn another thread behind the scenes how can any of the other code in my thread(mainthread to keep it simple) execute without getting "blocked"/not run because it somewhere make an infinite loop?
That was question number one. Then over to my second.
If I got something right about this after having worked with this, but not completely understood it a runloop is a loop where you attach 'flags' that notify the runloop that when it comes to the point where the flag is, it "stops" and execute whatever handler that is attached at that point? Then afterwards it keep running to the next in que.
So in this case no events is placed in que in connections, but when it comes to events it take whatever action associated with tap 1 and execute it before it runs to connections again and so on. Or am I as far as I can be from understanding the concept?
"Sort of."
Have you read this particular documentation?
It goes into considerable depth -- quite thorough depth -- into the architecture and operation of run loops.
A run loop will get blocked if it dispatches a method that takes too long or that loops forever.
That's the reason why an iPhone app will want to do everything which won't fit into 1 "tick" of the UI run loop (say at some animation frame rate or UI response rate), and with room to spare for any other event handlers that need to be done in that same "tick", either broken up asynchronously, on dispatched to another thread for execution.
Otherwise stuff will get blocked until control is returned to the run loop.
What is the best way to handle this situation on an iPhone device: My program ramps the pitch of a sound between two values. A button pressed calls a method that has a while loop that does the ramping in small increments. It will take some time to finish. In the meantime the user has pressed another button calling the same method. Now I want the loop in the first call to stop and the second to start from the current state. Here is the something like what the method should look like:
-(void)changePitchSample: (float) newPitch{
float oldPitch=channel.pitch;
if (oldPitch>newPitch) {
while (channel.pitch>newPitch) {
channel.pitch = channel.pitch-0.001;
}
}
else if (oldPitch<newPitch) {
while (channel.pitch<newPitch) {
channel.pitch = channel.pitch+0.001;
}
}
}
Now how to best handle the situation where the method is called again? Do I need some kind of mulitthreading? I do not need two processes going at the same time, so it seems there must be some easier solution that I cannot find (being new to this language).
Any help greatly appreciated!
You cannot do this like that. While your loop is running no events will be processed. So if the user pushes the button again nothing will happen before your loop is finished. Also like this you can’t control the speed of your ramp. I’d suggest using a NSTimer. In your changePitchSample: method you store the new pitch somewhere (don’t overwrite the old one) and start a timer that fires once. When the timer fires you increment your pitch and if it is less than the new pitch you restart the timer.
Have a look at NSOperation and the Concurrency Programming Guide. You can first start you operation the increase the pitch and also store the operation object. On the second call you can call [operation cancel] to stop the last operation. Start a second operation to i.e. decrease the pitch and also store the new object.
Btw: What you are doing right now is very bad since you "block the main thread". Calculations that take some time should not be directly executed. You should probably also have a look at NSTimer to make your code independent of the processor speed.
Don't use a while loop; it blocks everything else. Use a timer and a state machine. The timer can call the state machine at the rate at which you want things to change. The state machine can look at the last ramp value and the time of the last button hit (or even an array of UI event times) and decide whether and how much to ramp the volume during the next time step (logic is often just a pile of if and select/case statements if the control algorithm isn't amenable to a nice table). Then the state machine can call the object or routine that handles the actual sound level.
I'm developing a game in which I'm reducing the frame size of an imageView. When I'm introducing a condition using while loop, I'm not able to see the image reducing its size gradually, since it immediately jumps to the final result. So, I want to introduce a delay after every instruction so that I can see the effect of its size reduction little by little.
I can't use timer since it needs me to specify a function to be executed after that time interval.
while(ravanImage1.frame.origin.y>=end.y)
{
ravanImage1.frame=CGRectMake(150,((ravanImage1.frame.origin.y)-5),q,z);
if(ravanImage1.center.y>=300&&ravanImage1.center.y<=370)
{
q=60;
z=60;
ravanImage1.frame=CGRectMake(150,((ravanImage1.frame.origin.y)-5),q,z);
}
if(ravanImage1.center.y>=230&&ravanImage1.center.y<=299)
{
q=40;
z=40;
ravanImage1.frame=CGRectMake(150,((ravanImage1.frame.origin.y)-5),q,z);
}
if(ravanImage1.center.y>=150&&ravanImage1.center.y<=229)
{
q=20;
z=20;
ravanImage1.frame=CGRectMake(150,((ravanImage1.frame.origin.y)-5),q,z);
}
}
I want to introduce delay after every frame change.
Can anybody please help me?
How about using
[NSThread sleepForTimeInterval:]
inbetween every instruction?
If you just need to pause the change during development, use the debugger's breakpoints.
For release, you should use an animation block to make the changes. Create a separate block for each possible change and then set the animation duration to what you'd like.
As a general rule, you never change the frame of a view directly anymore unless you wish it to be instantaneous. Animations exist precisely for this purpose i.e. to create an effect that communicates a change in view state to the user. They're not just eye candy.
If for some reason, you don't want to use animations, you could move each size change into it's own method and then call each method with a timer. You could call the first method, which would set a timer to call the second, which would set a timer to call the third and so on.
So use the timer and give it a function which will take up the right amount of time to execute but have no impact on your display ? Maybe run a long loop of meaningless calculations at the right place in your program ?