i have some problem with nstimer and ui update and drawrect,
I have a viewcontroller and put a timer inside, it runs every 0.02 secs,
in this timer tick function, I make an imageview move from top to bottom( change centre of view),
then add another view on, and when touch begin touchmove and touchend on this view,
draw a line and call setneedsdisplay, when my fingure moves on the view, the imageview i mentioned before, moves slower,
by checking the time tick, I found that, without finger on, it ticks 0.02 secs, but when
move on, it slows to abt 0.1 sec, which make the imageview move slower,
any other way to optimise it,
I think the setneedsdisplay did the thick,
ofcourse, I try to change the runloop mode with
[[NSRunLoop currentRunLoop] addTimer:tickTimer forMode:NSDefaultRunLoopMode];
not help.
pls help, and another question is will another thread help this?
I tried nsthread, seems not help.... lol
For this purpose a much better solution is a CADisplayLink, that calls a method each time a frame is going to be refreshed. That way you'll avoid desynchronization between the timer and the actual framerate.
You set up a display link e.g. like this:
_dl = [CADisplayLink displayLinkWithTarget: self selector:#selector(refreshFrame)];
[_dl addToRunLoop:[NSRunLoop mainRunLoop] forMode:NSRunLoopCommonModes];
[_dl setPaused:NO];
and in the refreshFrame callback you can update the screen. You can make use of the duration and frameInterval to calculate the time that passed from the last refresh and adjust the movement speed accordingly:
-(void) refreshFrame
{
CGFloat speed = 10.0; //points per second
CGFloat timePassed = (_dl.duration * _dl.frameInterval)];
//refresh the view (example)
CGPoint imageCenter = self.imageView.center;
imageCenter y += speed * timePassed;
self.imageView.center = imageCenter;
}
This way the speed of the view stays constant even as the framerate changes in time.
It is wrong to assume the timer event is going to be called with exact intervals. Calculate the new parameters based on the speed and velocity vectors and time from the last update.
Related
Since we are talking about programmatically, Instruments are not under my consideration.
Some reference listed in advance:
Calculate fps (frames per second) for iphone app
Display FPS on iOS onscreen (without Instruments)
At what framerate does the iOS UI run animations at?
1. Using CADisplayLink
According to the doc,
The duration property provides the amount of time between frames. You
can use this value in your application to calculate the frame rate of
the display...
So in my demo project, I add a displayLink to mainRunLoop for UITrackingRunLoopMode:
self.displayLink = [CADisplayLink displayLinkWithTarget:self selector:#selector(screenDidUpdated)];
[self.displayLink addToRunLoop:[NSRunLoop mainRunLoop] forMode:UITrackingRunLoopMode];
and use duration to calculate FPS. But out of my expectation, the duration is always 0.016667 (~ FPS 60) not matter the tableView scrolls smoothly or not.
How I make the tableView lag is to add one line in - (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath:
NSData *data = [NSData dataWithContentsOfURL:url];
Then I turned to displayLink.timestamp, and it worked.
2. Observing drawRect:?
My second idea is to observe drawRect:, I thought when the tableView scrolls, its drawRect: would be called frame by frame, then I could calculate the FPS according to the time diff between drawRect: callings.
But it failed, cause the drawRect: was called only once (while cells for many times). This way is similar to Using CADisplayLink, but maybe I chose the wrong position/method(like drawRect:) to observe, any recommended method for me to observe?
Questions:
How the Instruments measure the FPS accurately?
Is the doc said using duration to calculate FPS wrong?
What's the right/best method to observe to calculate the FPS?
Thanks!
As the documentation for CADisplayLink states, duration is basically just 1 / maximumFramesPerSecond. You need to check the discrepancy between targetTimestamp and timestamp to detect dropped frames:
The duration property provides the amount of time between frames at the maximumFramesPerSecond. To calculate the actual frame duration, use targetTimestamp - timestamp.
This works but requires some setup.
Set up a CADisplayLink and leave the frameInterval as the default (shoots once per frame)
This CADisplayLink needs to actually be added to a runLoop and fire at least once to get to #3
Once that calls back, or inside the callback, you can get the frame rate. Here's some Swift code to give you the idea, but where displayLink is your CADisplayLink instance
var framesPerSecond : Int {
var retVal : Int = 60 // default value, just in case link.duration is still 0
if let link = displayLink where link.duration > 0 {
retVal = Int(round(1000 / link.duration)/1000)
}
return retVal;
}
Ok so recently I made a project which had like a bit of a gravity timer,
int speed = 5;
NSTimer *gravitytimer = [NSTimer scheduledTimerWithTimeInterval:0.01 target:self selector:#selector(gravity) userInfo:nil repeats:YES];
-(void)gravity {
image.center = CGPointMake(image.center.x, image.center.y - speed)
}
The problem is that the speed keeps multiplying or keeps adding and the image goes faster and faster. I don't know what the problem is. I am a newbie so sorry if this is a bad question. Thanks to all the people who take the time to answer.
When you create a timer, while it will try to call it every 0.01 seconds, you actually have no assurances that it will be called precisely at that rate (i.e. if it takes too long, it may skip one or two; if the main thread is blocked doing something else (and it's quite busy when the app first starts), you may skip quite a few). You can request to update image.center 100 times per second, but you have no guarantee that this is how often it actually will end up getting called.
If you wanted to use this technique to animate, you do so in a manner that isolates the speed of the animation from the frequency of the timer's selector is actually called. So, you might capture the start time, e.g.
CFAbsoluteTime start = CFAbsoluteTimeGetCurrent();
CGPoint startPoint = image.center;
And then in your timer routine, you'd capture the elapsed time, multiply your speed times the elapsed time, and go from there:
-(void)gravity {
CFAbsoluteTime elapsed = CFAbsoluteTimeGetCurrent() - self.start;
CGFloat speed = 100.0; // e.g. 100 points per second
CGPoint center = startPoint;
center.y += (elapsed * speed);
image.center = center;
}
As an aside, I assume this is just an exercise in timers. If this were a real animation, there are far more effective ways to do such animation (e.g. block-based animateWithDuration, UIKit Dynamics, and if you really wanted to do something timer-based, you'd often use CADisplayLink rather than a NSTimer). Also, BTW, the frame rate of the display is 60fps, so there's no point in trying to call it more frequently than that.
I have a number of images I run continuous animations on. How does one update these running animations smoothly so that there is no visible transition between them, unless part of the animation.
e.g. rotating and scaling an image, and then updating the animation to rotate as it was, but scale up slightly. I currently get a visible change.
I can imagine that that scaling should be done within an animation block and them just run the rotation animation as before, the issue would be then that the rotation would stop while it scales up.
I need it to be seamless. e.g. this code block does not cause a smooth scaling, even though it uses UIViewAnimationOptionBeginFromCurrentState
[UIView animateWithDuration:0.5
delay:0
options:UIViewAnimationOptionBeginFromCurrentState | UIViewAnimationOptionCurveEaseOut //| UIViewAnimationOptionRepeat
animations:(void (^)(void)) ^{
imageViewToScale.transform = CGAffineTransformMakeScale(1.2, 1.2);
}
completion:^(BOOL finished){
//imageViewToScale.transform=CGAffineTransformIdentity;
}];
To be honest if your going to have continuous animations on your views that will alter there states at run time UIView animations isn't he best approach and might cause jitter whilst the completion handler is called over and over e.t.c.
However is you want to do 2 animations in the block you can either set the scale and the rotation in the same block and they will happend simultaneously. Or you could call a function that starts the block and on completion calls it again to see if there are any new animations for that view. When there are none, the completion block just stops, sort of using them recursively, though this isn't the approach i wouldn't recommend if you are doing a lot of animations on a lot of views continuouly.
In OpenGLES you use NSTimer to run continuous animation that would handle the updating of all animations in your app. If you go this route its a lot more hard work and you need to implement the easing/quadratic curve functions for smooth animation yourself. However if you extend the clases you could set states for each image and then when the timer fires you could update its transformation based one the states you have given it. So when it has rotated a certain amount of degrees/radians then you could set it to scale. Now to keep animation smoothly you will need to use NSTimerIntervals to make sure you multiply the distance moved by time elapsed in order to get smooth animation. Personally this is the route i use for things that might be moving on screen constantly but might be over kill if you need to only move things twice and then be done.
EDIT: The code for doing the second step as you asked!
So you need to declare a NSTimer that wil poll your animation steps and an NSTimeInterval so that you update your animation each step only by the amount of time that has passed.
NSTimer *animationTimer;
NSTimeInterval animationInterval;
NSTimeInterval lastUpdateTime;
float currentRotation;
float current scale;
Thirdly you need to set up an NSTimer to fire off updating of your views:
- (void)startAnimation
{
animationTimer = [NSTimer scheduledTimerWithTimeInterval:animationInterval target:self selector:#selector(drawView:) userInfo:nil repeats:YES];
}
- (void)stopAnimation
{
[animationTimer invalidate];
animationTimer = nil;
}
Then you need to kick the thing off when your view starts or when you want to start anmation something like this works
- (void)setAnimationInterval:(NSTimeInterval)interval
{
animationInterval = interval;
if(animationTimer)
{
[self stopAnimation];
[self startAnimation];
}
}
Then In your drawView: Method you need to update your transforms based on time elapsed between each fire of the timer so that the animation is smooth and constant over time. Essentially a linear transform at this point.
- (void)drawView:(id)sender
{
if(lastUpdateTime == -1)
{
lastUpdateTime = [NSDate timeIntervalSinceReferenceDate];
}
NSTimeInterval timeSinceLastUpdate = [NSDate timeIntervalSinceReferenceDate] - lastUpdateTime;
currentRotation = someArbitrarySCALEValue * timeSinceLastUpdate;
currentScale = someArbitraryROTATIONValue * timeSinceLastUpdate;
CGAffineTransform scaleTrans = CGAffineTransformMakeScale(currentScale,currentScale);
CGAffineTransform rotateTrans = CGAffineTransformMakeRotation(currentRotation * M_PI / 180);
imageViewToScale.transform = CGAffineTransformConcat(scaleTrans, rotateTrans);
lastUpdateTime = [NSDate timeIntervalSinceReferenceDate];
}
Note this will not add easing to your animations nor will it at physics to the stopping you will need to play around with that. Also you may need to make sure that when the rotation goes over 360 you reset it to 0 and that you convert between degrees and radians respectively.
Look into using physics for things like bounces, and friction to make things slow nicely.
Look into quadratic graphs for easing to make things move smoothly over time, quadratic interpolation essentially.
I was animating a ball bouncing on the screen moving an UIView by setting its origin property but I found that the movement of the ball was not smooth. I checked the frequency at which drawInRect was being called and it was 30 times/s, which I don't consider enough to make a fast ball movement smooth.
My question is, is it possible to ask the system to refresh/redraw the screen at 60fps? Can you do the same in OpenGL?
You might consider setting up a display link function. This will allow you to fire a method for every draw call that comes through the system (or every certain number of frames). The class you want to deal with is CADisplayLink, and here is a tutorial. If your animation is not fast enough with this still, then your animation is never going to look smooth ;).
You Don't need to change the fps of ios to get your animation right .You simply need to change it in YOu code , you can do it using NSTimer (An Example):-
Initialize a timer on Some Animation :-
float theInterval = 1.0/30.0;//Here you can set the frame rate , now set on 30
[NSTimer scheduledTimerWithTimeInterval:theInterval target:self
selector:#selector(animateView:) userInfo:nil repeats:YES];
- (void)animateView:(NSTimer *)theTimer
{
// your animation block here....
Something like..
view.center = CGPointMake(view.center.x+viewMovement.x,
view.center.y+viewMovement.y);
BOOL collision = view.center.y >= view2.center.y - 16 &&
view.center.y <= view2.center.y + 16 &&
view.center.x > view2.center.x - 32 &&
view.center.x < view2.center.x + 32;
if(collision)
viewMovement.y = -viewMovement.y
}
It'Just an example , implement your logic accordingly.
I have a custom button which is my own subclass of UIButton. It looks like a circled arrow, starting at some angle startAngle end finishing at some endAngle=startAngle+1.5*M_PI.
startAngle is a button's property which is then used in its drawRect: method.
I want to make this arrow to continuously rotate by 2Pi around its center when this button is pressed. So I thought that I can easily use [UIView beginAnimations: context:] but apparently it can't be used as it doesn't allow to animate custom properties. CoreAnimation also doesn't suite as it only animates the CALayer properties.
So what is the easiest way to implement an animation of a custom property of UIView subclass in iOS?
Or maybe I missed something and it is possible with already mentioned techniques?
Thank you.
Thanks to Jenox I have updated animation code using CADisplayLink which seems to be really more correct solution than NSTimer. So I show the correct implementation with CADisplayLink now. It is very close to the previous one, but even a bit simpler.
We add the QuartzCore framework to our project.
Then we put the following lines in the header file of our class:
CADisplayLink* timer;
Float32 animationDuration; // Duration of one animation loop
Float32 initAngle; // Represents the initial angle
Float32 angle; // Angle used for drawing
CFTimeInterval startFrame; // Timestamp of the animation start
-(void)startAnimation; // Method to start the animation
-(void)animate; // Method for updating the property or stopping the animation
Now in implementation file we set the values for duration of the animation and the other initial values:
initAngle=0.75*M_PI;
angle=initAngle;
animationDuration=1.5f; // Arrow makes full 360° in 1.5 seconds
startFrame=0; // The animation hasn't been played yet
To start the animation we need to create the CADisplayLink instance which will call method animate and add it to main RunLoop of our application:
-(void)startAnimation
{
timer = [CADisplayLink displayLinkWithTarget:self selector:#selector(animate)];
[timer addToRunLoop:[NSRunLoop mainRunLoop] forMode:NSDefaultRunLoopMode];
}
This timer will call animate method every runLoop of the application.
So now comes the implementation of our method for updating the property after each loop:
-(void)animate
{
if(startFrame==0) {
startFrame=timer.timestamp; // Setting timestamp of start of animation to current moment
return; // Exiting till the next run loop
}
CFTimeInterval elapsedTime = timer.timestamp-startFrame; // Time that has elapsed from start of animation
Float32 timeProgress = elapsedTime/animationDuration; // Determine the fraction of full animation which should be shown
Float32 animProgress = timingFunction(timeProgress); // The current progress of animation
angle=initAngle+animProgress*2.f*M_PI; // Setting angle to new value with added rotation corresponding to current animation progress
if (timeProgress>=1.f)
{ // Stopping animation
angle=initAngle; // Setting angle to initial value to exclude rounding effects
[timer invalidate]; // Stopping the timer
startFrame=0; // Resetting time of start of animation
}
[self setNeedsDisplay]; // Redrawing with updated angle value
}
So unlike case with NSTimer we now don't need to calculate the time interval at which to update the angle property and redraw the button. We now only need to count how much time has passed from the start of animation and set the property to value which corresponds to this progress.
And I must admit that animation works a bit more smoothly than in case of NSTimer.
By default, CADisplayLink calls the animate method each run loop. When I calculated the frame rate, it was 120 fps. I think that it is not very efficient so I have decreased the frame rate to just 22 fps by changing the frameInterval property of CADisplayLink before adding it to mainRunLoop:
timer.frameInterval=3;
It means that it will call the animate method at first run loop, then do nothing next 3 loops, and call on the 4-th, and so on. That's why frameInterval can be only integer.
Thanks again to k06a for suggestion to use timer. I've made some study about working with NSTimer and now I want to show my implementation, since I think, it can be useful for others.
So in my case I had a UIButton subclass which was drawing a curved arrow which started from some angle Float32 angle; which is the main property from which the drawing of whole arrow starts. That means that just changing the value of angle will rotate whole arrow. So to make animation of this rotation I put the following lines in the header file of my class:
NSTimer* timer;
Float32 animationDuration; // Duration of one animation loop
Float32 animationFrameRate; // Frames per second
Float32 initAngle; // Represents the initial angle
Float32 angle; // Angle used for drawing
UInt8 nFrames; // Number of played frames
-(void)startAnimation; // Method to start the animation
-(void)animate:(NSTimer*) timer; // Method for drawing one animation step and stopping the animation
Now in implementation file I set the values for duration and frame rate of my animation and the initial angles for drawing:
initAngle=0.75*M_PI;
angle=initAngle;
animationDuration=1.5f; // Arrow makes full 360° in 1.5 seconds
animationFrameRate=15.f; // Frame rate will be 15 frames per second
nFrames=0; // The animation hasn't been played yet
To start the animation we need to create the NSTimer instance which will call method animate:(NSTimer*) timer every 1/15 seconds:
-(void)startAnimation
{
timer = [NSTimer scheduledTimerWithTimeInterval:1.f/animationFrameRate target:self selector:#selector(animate:) userInfo:nil repeats:YES];
}
This timer will call animate: method immediately and then repeat it every 1/15 second until it will be manually stopped.
So now comes the implementation of our method for animating a single step:
-(void)animate:(NSTimer *)timer
{
nFrames++; // Incrementing number of played frames
Float32 animProgress = nFrames/(animationDuration*animationFrameRate); // The current progress of animation
angle=initAngle+animProgress*2.f*M_PI; // Setting angle to new value with added rotation corresponding to current animation progress
if (animProgress>=1.f)
{ // Stopping animation when progress is >= 1
angle=initAngle; // Setting angle to initial value to exclude rounding effects
[timer invalidate]; // Stopping the timer
nFrames=0; // Resetting counter of played frames for being able to play animation again
}
[self setNeedsDisplay]; // Redrawing with updated angle value
}
The first thing I want to mention is that for me just comparison line angle==initAngle didn't work due to rounding effects. They don't are exactly the same after full rotation. That's why I check if they are just close enough and then set angle value to initial value to block small drift of angle value after many repeated animation loops.
And to be totally correct, this code must also manage conversion of angles to always be between 0 and 2*M_PI with something like this:
angle=normalizedAngle(initAngle+animProgress*2.f*M_PI);
where
Float32 normalizedAngle(Float32 angle)
{
while(angle>2.f*M_PI) angle-=2.f*M_PI;
while(angle<0.f) angle+=2.f*M_PI;
return angle
}
And another important thing is that, unfortunately, I don't know any easy way to apply easeIn, easeOut or other default animationCurves to this kind of manual animation. I think it doesn't exist. But it is, of course, possible to do it by hands. The line standing for that timing function is
Float32 animProgress = nFrames/(animationDuration*animationFrameRate);
It can be treated as Float32 y = x;, that means linear behavior, a constant speed, which is the same as speed of time. But you can modify it to be like y = cos(x) or y = sqrt(x) or y = pow(x,3.f) which will give some nonlinear behavior. You can think it yourself taking into account that x will go from 0 (start of animation) to 1 (end of animation).
For better looking code it is better to make some independent timing function:
Float32 animationCurve(Float32 x)
{
return sin(x*0.5*M_PI);
}
But now, since the dependence between animation progress and time is not linear, it's safer to use the time as indicator for stopping the animation. (You might want for example to make your arrow to make 1.5 full turns and than rotate back to the initial angle, that means your animProgress will go from 0 to 1.5 and than back to 1 while timeProgress will go from 0 to 1.)
So to be safe we separate time progress and animation progress now:
Float32 timeProgress = nFrames/(animationDuration*animationFrameRate);
Float32 animProgress = animationCurve(timeProgress);
and then check time progress to decide if should the animation stop:
if(timeProgress>=1.f)
{
// Stop the animation
}
By the way, if somebody knows some sources with list of useful timing functions for animation, I would appreciate if you share them.
Built in MacOS X utility Grapher helps a lot in visualizing the functions, so that you can see how your animation progress will depend on time progress.
Hope it helps somebody...
- (void)onImageAction:(id)sender
{
UIButton *iconButton = (UIButton *)sender;
if(isExpand)
{
isExpand = FALSE;
// With Concurrent Block Programming:
[UIView animateWithDuration:0.4 animations:^{
[iconButton setFrame:[[btnFrameList objectAtIndex:iconButton.tag] CGRectValue]];
} completion: ^(BOOL finished) {
[self animationDidStop:#"Expand" finished:YES context:nil];
}];
}
else
{
isExpand = TRUE;
[UIView animateWithDuration:0.4 animations:^{
[iconButton setFrame:CGRectMake(30,02, 225, 205)];
}];
for(UIButton *button in [viewThumb subviews])
{
[button setUserInteractionEnabled:FALSE];
//[button setHidden:TRUE];
}
[viewThumb bringSubviewToFront:iconButton];
[iconButton setUserInteractionEnabled:TRUE];
// [iconButton setHidden:FALSE];
}
}