I'm trying to set a delay within a for loop in an iphone app. Basically I'll have a for loop with a few actions and I want a 1 sec delay between each action:
for loop { action 1, delay 1sec, action 2, delay 1sec, action 3, delay 1sec}
How would I code this?
for (loop) {
[self action1];
[self performSelector:#selector(action2) withObject:nil afterDelay:1.0];
[self performSelector:#selector(action3) withObject:nil afterDelay:1.0];
}
Hope this is what you are looking for!!
Edit
Try this.. It will finish up running the current method and move to the next.
for (loop) {
[self performSelectorOnMainThread:#selector(action1) withObject:nil waitUntilDone:YES];
[self performSelectorOnMainThread:#selector(action2) withObject:nil waitUntilDone:YES];
[self performSelectorOnMainThread:#selector(action3) withObject:nil waitUntilDone:YES];
}
This doesn't involve a for loop but will take a list of actions and perform them with increasing delays.
NSArray *selectorStrings = #[ #"action1", #"action2", #"action3" ];
[selectorStrings enumerateObjectsUsingBlock:^(id obj, NSUInteger idx, BOOL *stop) {
SEL selector = NSSelectorFromString((NSString *)obj);
NSTimeInterval delay = (NSTimeInterval)idx;
[self performSelector:selector withObjet:nil afterDelay:delay];
}];
Hope this helps! Let me know if you have questions.
Related
I am using...
[self addChild:self.blue_action];
[self schedule:#selector(updateTimer1:) interval:1.0f];
Via this line, I want to show an image in the any position and after some time that image will remove, through '[self removeChild: self.blue_action cleanUp:Yes];'
-(void)updateTimer1:(id)sender {
if(time_1 == 0) {
NSLog(#"time value ");
[self removeChild:self.blue_action cleanup:YES];
[self schedule: #selector(updateTimer1:) interval:0.10];
}
else {
--time_1;
}
}
In this case the updateTimer1:(id)sender method was already scheduled.
To schedule this again you obvious must unscheduled this method by [self unschedule:_cmd];
And it's a good practice do not remove sprite every time when you want it to disappear, try to just make it invisible self.blue_action.visible = NO
You want to fire method once after specific time? Action is helpful.
-(void)addBlueAction {
[self addChild:self.blue_action];
[self runAction:[CCSequence actions:
[CCDelayTime actionWithDuration:1],
[CCCallFunc actionWithTarget:self
selector:#selector(removeBlueAction)],
nil]];
}
-(void)removeBlueAction {
[self removeChild:self.blue_action cleanup:YES];
}
If your app's target is for after iOS 4.0, you can use Blocks.
-(void)addBlueAction {
[self addChild:self.blue_action];
[self runAction:[CCSequence actions:
[CCDelayTime actionWithDuration:1],
[CCCallBlock actionWithBlock:^{
[self removeChild:self.blue_action cleanup:YES];
}],
nil]];
}
When my main viewController is first clicked, it starts showing a demo (on repeat) as follows:
showingDemo = YES;
[self startDemo];
- (void)startDemo {
if (showingDemo) {
[self performSelector:#selector(stepone) withObject:nil afterDelay:1.5f];
[self performSelector:#selector(steptwo) withObject:nil afterDelay:2.0f];
[self performSelector:#selector(stepthree) withObject:nil afterDelay:3.8f];
[self performSelector:#selector(stepfour) withObject:nil afterDelay:4.3f];
[self performSelector:#selector(startDemo) withObject:nil afterDelay:5.6f];
}
}
When it is clicked a second time, I bring a new ViewController to the screen
showingDemo = NO;
[self.view addSubview:newView];
I thought this would stop the endless loop.
When the user returns back to my main viewController:
[newView.view removeFromSuperview];
And clicks on the screen again:
showingDemo = YES;
[self startDemo];
In testing my app, if I click back quickly (before the loop has had time to end, the program seems to be running through the loop twice - the one that was previously going and the new one - and therefore it looks all weird, with the 'stepthree' function happening before 'stepone' and so forth.
Anybody know a better way to STOP the loop I've programmed for good so that when I go to start it again later, it doesn't run multiple loops thinking that the previous one hasn't been finished?
Thanks so much!
When you set showingDemo to NO, call NSObject's cancelPreviousPerformRequestsWithTarget: to cancel any pending perform requests:
showingDemo = NO;
[NSObject cancelPreviousPerformRequestsWithTarget:self];
[self.view addSubview:newView];
I'm trying to do something basic to understand threads with a counter that just increments when a button is pressed, and every time the button is pressed, a new thread incrementing the same counter starts. Then I have a stop button to stop a thread that is running. How can I tell how many threads, or which thread is running? Here is my basic template I am working on. Thanks.
-(int)count {
return count;
}
-(void)setCount:(int) value {
count = value;
}
-(void)updateDisplay {
countLabel = [NSString stringWithFormat:#"%i", count];
count++;
}
-(void)myThread {
NSAutoreleasePool *pool = [[NSAutoreleasePool alloc] init];
[self performSelectorOnMainThread:#selector(updateDisplay)
withObject:nil
waitUntilDone:NO];
[pool release];
}
-(void)startThread {
[self performSelectorInBackground:#selector(myThread) withObject:nil];
}
-(void)myThreadStop {
NSAutoreleasePool *pool = [[NSAutoreleasePool alloc] init];
[self performSelectorOnMainThread:#selector(updateDisplay)
withObject:nil
waitUntilDone:NO];
[pool release];
}
-(void)stopThread {
[self performSelectorInBackground#selector(myThreadStop) withObject:nil];
}
Basically, you want to keep track of the number of threads you have running, and also assign each thread a unique ID. Assuming that startThread is an event handler for your button, you might have something like:
static int threadIndex = 0;
static int threadsRunning = 0;
-(void)startThread {
NSNumber* threadId = [NSNumber numberWithInt:threadIndex++];
threadsRunning++;
[self performSelectorInBackground:#selector(myThread) withObject:threadId];
}
Then when you stop a thread, you just decrement threadsRunning.
Looking at your code, though, I'm confused by your stopTread method, since it seems to be doing the exact same thing as the myThread method, i.e., not stopping the thread at all.
You're performing stuff in the background, which is distinct from explicitly creating threads (e.g. it might reuse threads in a thread pool).
If you want really inefficient threading code, you could use something like this:
NSThread * thread = [[[NSThread alloc] initWithTarget:self selector:#selector(myThread) object:nil] autorelease];
[thread start];
while ([thread isExecuting])
{
NSLog(#"Still running");
[NSThread sleepForTimeInterval:0.1];
}
EDIT: If you're actually going to do iPhone development, I recommend looking at NSOperation/NSInvocationOperation/NSBlockOperation instead. Thread management is a real pain to get right.
I have a background task that updates a view. That task calls -setNeedsDisplay to have the view drawn.
This works:
- (void) drawChangesTask;
{
NSAutoreleasePool *pool = [[NSAutoreleasePool alloc] init];
if (pixels) {
drawChanges((UInt32 *) origPixels, (UInt32 *) pixels, CGBitmapContextGetBytesPerRow(ctx)/4, CGBitmapContextGetHeight(ctx), count--);
if (count < 0) {
count = 150;
}
else
[self performSelectorInBackground:#selector(drawChangesTask) withObject:nil ];
[self performSelectorOnMainThread:#selector(setNeedsDisplay) withObject:nil waitUntilDone:NO ];
}
[pool release];
}
This does not work:
- (void) drawChangesTask;
{
NSAutoreleasePool *pool = [[NSAutoreleasePool alloc] init];
if (pixels) {
drawChanges((UInt32 *) origPixels, (UInt32 *) pixels, CGBitmapContextGetBytesPerRow(ctx)/4, CGBitmapContextGetHeight(ctx), count--);
if (count < 0) {
count = 150;
}
else
[self performSelectorInBackground:#selector(drawChangesTask) withObject:nil ];
[self setNeedsDisplay];
}
[pool release];
}
Anyone know why? When I say it doesn't work, I mean that it runs tens of iterations, sometimes I see portions of my image shifted up or down, or entirely blank, and then the deugger give me an “EXC_BAD_ACCESS” somewhere in CoreGraphics.
Also, if I don't handle the autorelease pool myself, then I get leaking error messages. Don't understand why that is either. My drawChanges() doesn't create any new objects. Here's the error:
2009-08-17 11:41:42.358 BlurApp[23974:1b30f] *** _NSAutoreleaseNoPool(): Object 0xd78270 of class NSThread autoreleased with no pool in place - just leaking
UIKit simply isn't thread-safe — you need to call methods that update UIKit controls on the main thread.
I think that this line:
[self performSelectorInBackground:#selector(drawChangesTask) withObject:nil];
Is causing trouble. Have you tried simply calling it again on the current thread? If you need the runloop to execute between the calls, use:
[self performSelector:#selector(drawChangesTask) withObject:nil afterDelay:0.0];
This will call the method on the current thread after the method you're in has finished and the runloop has gone round once.
Problem here is that UIKit is not thread safe, if you tell your UI to do something from a background thread nothign is guaranteed, what you want to do is use the performSelectorOnMainThread method to do updates t o your UI elements
all! I want to create multiple threads in my application. I' using following code for creating a thread.
This' buttonPress method where I'm creating a thread:
- (void) threadButtonPressed:(UIButton *)sender {
threadStartButton.hidden = YES;
threadValueLabel.text = #"0";
threadProgressView.progress = 0.0;
[NSThread detachNewThreadSelector:#selector(startMethod) toTarget:self withObject:nil];
}
This' where I'm calling the method for the thread:
- (void)startMethod {
NSAutoreleasePool *pool = [[NSAutoreleasePool alloc] init];
[self performSelectorOnMainThread:#selector(threadMethod) withObject:nil waitUntilDone:NO];
[pool release];
}
- (void)threadMethod {
float actual = [threadProgressView progress];
threadValueLabel.text = [NSString stringWithFormat:#"%.2f", actual];
if (actual < 1) {
threadProgressView.progress = actual + 0.01;
[NSTimer scheduledTimerWithTimeInterval:0.5 target:self selector:#selector(makeMyProgressBarMoving) userInfo:nil repeats:NO];
}
else
threadStartButton.hidden = NO;
}
This thread works properly.
But when I try to create another thread in the same class using the same method, it gets created properly, but at the method "performSelectorOnMainThread", it doesn't execute that method. Can anybody please help me?
It seems that you are trying to queue up methods to be executed on the main thread. You might want to look into an NSOperationQueue and NSOperation objects. If you want to proceed on this path, you might consider changing the repeats parameter to YES. The problem seems to be that the main thread is busy when it's being passed this message. This will cause the main thread to block. You may also consider not using a second threadMethod and calling back to the main thread, but instead wrapping the contents of threadMethod in an #synchronized(self) block. This way, you get the benefits of multi-threading (multiple pieces of code executing at the same time and thus a reactive user interface) without doing some weird stuff with the main thread.
I'm missing the context here. I see a call that creates a new thread, and then I see a call that performs a selector (calls a method) on the main thread..
As I understand, you are calling a function in a new thread (entryMethod), in which you call a method to perform on the main thread (myMethod). I do not understand the point of this, without some background info and possibly some code.
Is it possible that the main thread is busy performing the 'myMethod' function, and thus does not respond to other calls?
Why cant you do it with the same call, by replacing
-(void)startMethod {
NSAutoreleasePool *pool = [[NSAutoreleasePool alloc] init];
[self performSelectorOnMainThread:#selector(threadMethod) withObject:nil waitUntilDone:NO];
[pool release];
}
with
-(void)startMethod {
NSAutoreleasePool *pool = [[NSAutoreleasePool alloc] init];
float actual = [threadProgressView progress];
threadValueLabel.text = [NSString stringWithFormat:#"%.2f", actual];
if (actual < 1) {
threadProgressView.progress = actual + 0.01;
[NSTimer scheduledTimerWithTimeInterval:0.5 target:self selector:#selector(makeMyProgressBarMoving) userInfo:nil repeats:NO];
}
else
threadStartButton.hidden = NO;
}
[pool release];
}