I want to use a speech synthesised sentence in an application demo. After pressing a button, a timer runs and after for example 12 seconds the first sentence is being spoken, then after 1.30min and so on.
The approach I was thinking of, is an NS Timer. But as far as I can see it only plays after a defined time. So do I need for any timespan a new timer? or can I track the time left and invoke a method call when a specific time is reached?
Thanks
I would do this using a dictionary with NSNumbers as the keys (representing seconds), and the sentence you want spoken as the value. Use a simple timer firing once every second, that updates an int, which (when converted to an NSNumber) would be checked against the dictionaries keys. I'm just logging in this example, but this should get you started,
- (void)viewDidLoad {
[super viewDidLoad];
self.dict = #{#3:#"First", #5:#"second", #11:#"Third", #35:#"Fourth"};
[NSTimer scheduledTimerWithTimeInterval:1 target:self selector:#selector(doStuff:) userInfo:nil repeats:YES];
}
-(void)doStuff:(NSTimer *) aTimer {
static int i = 0;
i++;
if ([self.dict.allKeys containsObject:#(i)]) {
NSLog(#"%#", self.dict[#(i)]);
}
}
Related
I want to use NSTimer to increase the number which show on a label.
Here is my code:
- (void)viewDidLoad {
[super viewDidLoad];
// Do any additional setup after loading the view, typically from a nib.
self.numberLabel = [[UILabel alloc]initWithFrame:CGRectMake(90, 90, 90, 30)];
[self.view addSubview:self.numberLabel];
self.timer = [NSTimer scheduledTimerWithTimeInterval:0.01 target:self selector:#selector(refreshText) userInfo:nil repeats:YES];
[[NSRunLoop currentRunLoop]addTimer:self.timer forMode:NSRunLoopCommonModes];
}
- (void)refreshText{
NSDate *beginDate = [NSDate date];
static NSInteger a = 0;
a ++;
self.numberLabel.text = [NSString stringWithFormat:#"%ld",a];
if (a == 1000) {
NSDate *endDate = [NSDate date];
NSTimeInterval durationTime = [endDate timeIntervalSinceDate:beginDate];
NSTimeInterval intervalTime = self.timer.timeInterval;
NSLog(#"durationTime = %f",durationTime);
NSLog(#"intervalTime = %f",intervalTime);
[self.timer invalidate];
self.timer = nil;
}
}
and the console showed:
then I changed the timer's timeInterval from 0.01 to 0.001,the console showed:
What confused me is that why the durationTime is not 0.0000056 when the timeInterval is 0.001.What's more,is there a min value for NSTimer's timeInterval we can set?
The time period of an NSTimer is a value of type NSTimeInterval, while this provides sub-millisecond precision that does not help you. From the start of the NSTimer documentation:
Timers work in conjunction with run loops. Run loops maintain strong references to their timers, so you don’t have to maintain your own strong reference to a timer after you have added it to a run loop.
To use a timer effectively, you should be aware of how run loops operate. See Threading Programming Guide for more information.
A timer is not a real-time mechanism. If a timer’s firing time occurs during a long run loop callout or while the run loop is in a mode that isn't monitoring the timer, the timer doesn't fire until the next time the run loop checks the timer. Therefore, the actual time at which a timer fires can be significantly later. See also Timer Tolerance.
So the minimum time interval for an NSTimer is tied to the the length of a run loop iteration. While internal optimisations, if they exist, could fire a timer as soon as it is set if the interval is really small in general the shortest period you'll get is dependent on the remaining execution time of the run loop iteration in which the timer is set, which is pretty much indeterminate for general purpose programming.
If you really need a high-resolution timer (see #bbum's comment on your question) then you'll need to research that topic - just search something like "high resolution timing macOS" as a starting point.
HTH
There is a better approach to your problem. Use CADisplayLink instead of NSTimer. CADisplayLink allows you to update a UI every time the screen refreshes - as quickly as possible. There is no point to updating the UI more often than the screen can refresh it, so NSTimer is not the best tool fast UI updates.
func beginUpdates() {
self.displayLink = CADisplayLink(target: self, selector: #selector(tick))
displaylink.add(to: .current, forMode: .defaultRunLoopMode)
}
func tick() {
// update label
}
func endUpdates(){
self.displayLink.invalidate()
self.displayLink = nil
}
I have surfed on a bunch of resources from the internet but still couldn't get any idea of what I'm trying to implement.
I would like to record user preferences by detecting how much time they have stayed in each information pages.
In order to make this question simpler, that says I have a entrance page with 5 different theme pages which represent different information.
I would like to know which page is the page that user most interesting.
What I wish to do is to put a counter in each theme pages and calculate how much time they stay in that page (the counter should be able to pause for reentrance), and then when I press a button on the entrance page, an alert will tell me which page is the page that user spent most of time on it.
I hope this make sense!
Does anyone have any experience on this? I would be most appreciative if anyone can provide some codes and examples for me.
ViewController A:
- (void)viewDidLoad {
[super viewDidLoad];
//create iVar of NSInteger *seconds
seconds = 0;
NSTimer *timer = [NSTimer timerWithTimeInterval:1.0 target:self selector:#selector(increaseTimeCount) userInfo:nil repeats:YES];
[timer fire];
}
- (void)increaseTimeCount {
seconds++;
}
- (void)dealloc {
NSUserDefaults *defaults = [NSUserDefaults standardUserDefaults];
// you can add to array too , if you want and get average of all values later
[defaults setInteger:seconds forKey: NSStringFromClass(self)];
}
now in Entrance View ..
get the time as
NSUserDefaults *defaults = [NSUserDefaults standardUserDefaults];
NSInteger *secondsInView = [defaults integerForKey:NSStringFromClass(View1ClassName)];
Firstly I'd like to draw your attention to the Cocoa/CF documentation (which is always a great first port of call). The Apple docs have a section at the top of each reference article called "Companion Guides", which lists guides for the topic being documented (if any exist). For example, with NSTimer, the documentation lists two companion guides:
Timer Programming Topics for Cocoa
Threading Programming Guide
For your situation, the Timer Programming Topics article is likely to be the most useful, whilst threading topics are related but not the most directly related to the class being documented. If you take a look at the Timer Programming Topics article, it's divided into two parts:
Timers
Using Timers
For articles that take this format, there is often an overview of the class and what it's used for, and then some sample code on how to use it, in this case in the "Using Timers" section. There are sections on "Creating and Scheduling a Timer", "Stopping a Timer" and "Memory Management".There are a couple of ways of using a timer. From the article, creating a scheduled, non-repeating timer can be done something like this:
1) scheduled timer & using selector
NSTimer *t = [NSTimer scheduledTimerWithTimeInterval: 2.0
target: self
selector:#selector(onTick:)
userInfo: nil repeats:NO];
if you set repeats to NO, the timer will wait 2 seconds before
running the selector and after that it will stop;
if repeat: YES, the timer will start immediatelly and will repeat
calling the selector every 2 seconds;
to stop the timer you call the timer's -invalidate method: [t
invalidate]; As a side note, instead of using a timer that doesn't
repeat and calls the selector after a specified interval, you could
use a simple statement like this:
[self performSelector:#selector(onTick:) withObject:nil afterDelay:2.0];
this will have the same effect as the sample code above; but if you want to call the selector every nth time, you use the timer with repeats:YES;
2) self-scheduled timer
NSDate *d = [NSDate dateWithTimeIntervalSinceNow: 60.0];
NSTimer *t = [[NSTimer alloc] initWithFireDate: d
interval: 1
target: self
selector:#selector(onTick:)
userInfo:nil repeats:YES];
NSRunLoop *runner = [NSRunLoop currentRunLoop];
[runner addTimer:t forMode: NSDefaultRunLoopMode];
[t release];
this will create a timer that will start itself on a custom date
specified by you (in this case, after a minute), and repeats itself
every one second
3) unscheduled timer & using invocation
NSMethodSignature *sgn = [self methodSignatureForSelector:#selector(onTick:)];
NSInvocation *inv = [NSInvocation invocationWithMethodSignature: sgn];
[inv setTarget: self];
[inv setSelector:#selector(onTick:)];
NSTimer *t = [NSTimer timerWithTimeInterval: 1.0
invocation:inv
repeats:YES];
and after that, you start the timer manually whenever you need like this:
NSRunLoop *runner = [NSRunLoop currentRunLoop];
[runner addTimer: t forMode: NSDefaultRunLoopMode];
And as a note, onTick: method looks like this:
-(void)onTick:(NSTimer *)timer {
//do smth
}
Try this simple method:
- (void)viewDidLoad
{
[super viewDidLoad];
count = 0; // Declare int * count as global variable;
[NSTimer scheduledTimerWithTimeInterval:2 target:self selector:#selector(timerAction) userInfo:nil repeats:YES];
}
- (void)timerAction
{
[self custom_method:count++]
}
Might I suggest a different route. If you take the time since reference date, when the user enters the page:
NSTimeINterval time = [NSDate timeIntervalSinceReferenceDate]
then do the same when they leave the page and compare them.
timeOnPage = time - time2;
This is much more efficient than firing a timer on another thread unnecessary.
You do not need to use NSTimers for this at all.
Store the date/time when the user starts viewing, and calculate the time difference when they stop viewing using simple time arithmetic.
Exactly As Dave Wood says You should use date and time for starting and ending viewing that screen and calculate the difference and then save it to any integer variable.Using NSTimer will make the performance effect in your app and make the compiler busy while incrementing the count.
I am making an application that randomly selects a picture from a preset group of pictures and displays it to a image view. This should happen every second or so until it has gone through 20 cycles.
Hear is my header and implementation code:
#interface spinController : UIViewController
{
IBOutlet UIImageView *imageHolder;
NSTimer *MovementTimer;
}
-(IBAction)Button:(id)sender;
-(void)displayPic;
#end
#implementation spinController
-(IBAction)Button:(id)sender
{
int count = 0;
while (count <20)
{
[NSTimer scheduledTimerWithTimeInterval:1 target:self selector:#selector(displayPic) userInfo:nil repeats:NO];
count++;
}
}
-(void)displayPic
{
int r = arc4random() % 2;
if(r==0)
{
imageHolder.image = [UIImage imageNamed:#"puppy1.jpg"];
}
else
{
imageHolder.image = [UIImage imageNamed:#"puppy2.jpg"];
}
}
-(void)viewDidLoad
{
[super viewDidLoad];
// Do any additional setup after loading the view.
}
#end
I have made this application in a much more advanced form in WPF and ran into similar issues where the pictures do no cycle through properly. If I hit spin it randomizes but does not go through the 20 cycles... just one. This is my first application in objective-c and realize the efficiency of the method I choose will determine how good my application will run in a more complex form. Any help would be greatly appreciated.
The problem is that you're calling the timer repeatedly within the while loop; and since that particular while loop will complete within a millisecond or so, you're creating 20 timers one after another in immediate succession. Because of this, only the final image will show up in the imageHolder view. Edit: Even if the loop were to take more than a millisecond per iteration, I believe the NSTimer wouldn't actually fire until the method exits anyway.
In order to show the images one after another as you're trying to do, (1) use the NSTimer without the while loop, (2) keep track of the iterations using a count class instance variable so as not to lose the value of the variable upon the completion of the various methods, and (3) pass along the NSTimer to the displayPic method so you can invalidate the timer from there upon the 20th iteration. For example:
// Declare the "count" instance variable.
int count;
-(void)viewDidLoad {
[super viewDidLoad];
// Do any additional setup after loading the view.
}
-(IBAction)Button:(id)sender {
// The count starts at 0, so initialize "count" to 0.
count = 0;
// Use an NSTimer to call displayPic: repeatedly every 1 second ("repeats" is set to "YES")
[NSTimer scheduledTimerWithTimeInterval:1 target:self selector:#selector(displayPic:) userInfo:nil repeats:YES];
}
// Pass along the NSTimer to the displayPic method so that it can be invalidated within this method upon the 20th iteration
-(void)displayPic:(NSTimer *)timer {
// Get the random number
int r = arc4random() % 2;
// If the number is 0, display puppy1.jpg, else display puppy2.jpg.
if(r == 0) {
imageHolder.image = [UIImage imageNamed:#"puppy1.jpg"];
}
else {
imageHolder.image = [UIImage imageNamed:#"puppy2.jpg"];
}
// Increment "count" to reflect the number of times the NSTimer has called this method since the button press
count ++;
// If the count == 20, stop the timer.
if (count == 20)
[timer invalidate];
}
#end
Change repeats to YES. This causes the timer to run again and again. Then instead of a while loop check the count in the method itself.
Is there any method for slide show of an array of strings in UILabel in iphone app?(ie, strings will appear one by one). Anyone please help me.
Look at NSTimer.
This can get you a repeated callback every X seconds. You can use this to swap the strings in an array.
[NSTimer scheduledTimerWithTimeInterval:1.0 target:self selector:#selector(swapStrings:) userInfo:nil repeats:YES];
_myStrings = #[ #"a" , #"b", ..... ];
...
- (void) swapStirings:(id)sender
{
myInt ++;
if (myInt >= [_myStrings count]) myInt = 0;
myLabel.text = [_myStrings objectAtIndex:myInt];
}
No, there is not. But, the good news it should be trivial to implement. I suggest creating a subclass of uilabel that has an array of strings as an ivar. The subclass has an init method that sets the array and a time interval. Then it uses an nstimer to change its label and redisplay itself. Good luck!
I'm having trouble with incrementing an int from one function by calling it in another function.
At the moment the bit I'm working on looks like this:
in the .h file I declare the int and timer as this:
int count;
NSTimer *sequenceOn;
in the .m file the segment of my function looks like this:
-(void) sequence {
count = 1;
while (count < (target)) {
sequenceOn = [NSTimer scheduledTimerWithTimeInterval:0.5 target:self selector:#selector(imagePlayer) userInfo:nil repeats:NO];
}
}
-(void)imagePlayer {
--CODE HERE FOR PLAYING ANIMATION--
count = count + 1;
}
All my other code is working fine and it should play through a series of images using the count value to decide which one to play. At the moment though it only plays the first animation and wont increment to the next one.
Any help would be much appreciated.
Thanks.
The timers will be fired from the run loop, which your code is blocking while running the loop. You probably want to have a timer regularly call your method:
-(void)stopTimer {
[sequenceOn invalidate];
sequenceOn = nil;
}
-(void)sequence {
[self stopTimer];
count = 1;
// start a repeating timer:
sequenceOn = [NSTimer scheduledTimerWithTimeInterval:0.5 target:self
selector:#selector(imagePlayer) userInfo:nil repeats:YES];
}
-(void)imagePlayer {
//--CODE HERE FOR PLAYING ANIMATION--
count = count + 1;
if (count >= target) {
[self stopTimer];
}
}
I don't see anything in your while loop that increments count or decrements target, so either it's an infinite loop or it never executes, depending on the value of target.
You have the last argument of scheduledTimerWithTimeInterval:target:selector:userInfo:repeats: set to NO, is that what you want, it will only fire once. If not you will have to give us more code to show how imagePlayer is being called repeatedly.