I have a UIProgressView called progTimer that I placed on my View Controller via Interface Builder. On the iOS simulator, the UIProgressView shows up just fine, but when I test it on my iPhone it doesn't appear.
Here is the code that modifies it.
- (IBAction)scanbtn
{
[progTimer invalidate];//cancels timer if currently running
progTimer=nil;
progNum = 0;
progTimer = [NSTimer scheduledTimerWithTimeInterval:0.1 //timer to update the progress view
target:self
selector:#selector(progIncrease)
userInfo:nil
repeats:YES];
[self scan];
}
-(void) progIncrease
{
progNum = progNum + 0.01;
scanProg.progress = progNum;
if (progNum >=1)
{
[progTimer invalidate];
progTimer=nil;
//[alert show];
}
}
Any ideas? Thanks in advance. .
ALL: For some reason, I changed the style of the Progress View to "Bar" and it shows up fine. No idea what caused the initial problem, but now it works albeit having a different style bar.
My guess would be that on the device, the scanning process is moving so fast that you just can't see it. To make sure it's working ad and NSLog in the ProgressIncrease method to see how fast it scans. I had the same problem with my preloading notifiers, that were showing on the simulator but not on the device.
You call [self scan]; which seems to be the culprit. How long does that scan operation run?
Its very important to note that while any long running operation runs in main thread which is UI thread, no other code in the main thread loop will be executed(until that long running operation finishes) which means your timer function or even pressing button after pressed once pressed won't work. You need to use either NSOperation and dispatch queue or create a thread and run the scan operation in the background and send notifications to main thread using NSMachPort or NSObject performSelectr:OnThread:... etc for it to update the progress bar.
By the way, the scanning process and the progress bar has no relation at all; The progress bar should ideally update how much of scanning is done which means the scanning process must inform progress bar to update that also in main thread if scanning is running in secondary thread.
Related
is it possible not to pause the application while in background mode (when you press the home button and the app minimizes)? I have some timers and variables that i don't want to get paused.
EDIT:
I have followed this example http://evilrockhopper.com/2010/01/iphone-development-keeping-the-ui-responsive-and-a-background-thread-pattern/
I have called a timer inside however it's not getting called when i enter background mode:
- (void)applicationDidEnterBackground:(UIApplication *)application {
if(self.viewController.timerquest != NULL)
{
if(self.viewController.timerquest.timerRunning){
// Save varibales
[self performSelectorInBackground:#selector(performLongTaskInBackground) withObject:nil];
}
}
}
- (void) performLongTaskInBackground
{
// Set up a pool for the background task.
NSAutoreleasePool* pool = [[NSAutoreleasePool alloc] init];
// perform some long task here, say fetching some data over the web.
//...
timer = [NSTimer scheduledTimerWithTimeInterval:1 target:self selector:#selector(updateTimer) userInfo:nil repeats:YES];
// Always update the components back on the main UI thread.
[self performSelectorOnMainThread:#selector(completeLongRunningTask) withObject:nil waitUntilDone:YES];
[pool release];
}
-(void) updateTimer{
// Update my timer. This method is not being called in background mode
}
What should I do?
Thanks.
use Long Running Background tasks according to manual: http://developer.apple.com/library/ios/#documentation/iphone/conceptual/iphoneosprogrammingguide/BackgroundExecution/BackgroundExecution.html
Have a read here at the Apple non-technical documentation or at the technical reference.
Could you replace the timer with delayed background notifications?
Depending on what happens when your timers fire, you want to set up a local notification that fires at the same time the timer would have; this is useful when the timer would present something for the user to act on. As far as saving variables, you'll want to use -applicationDidEnterBackground: to save whatever state you need to, so that the correct variables can be loaded/generated when the app relaunches (which may not happen until the app has been exited and completely restarted again).
The types of tasks that are allowed to perform long running background tasks are pretty limited, specifically for things like GPS and playing audio. Everything else needs to decide on a task-by-task basis whether to simulate continued running (such as turning a timer to a local notification), pausing and saving necessary state to continue the next time the app is run, simply cancelling the task and gracefully restarting/notifying the user upon resuming the app, or asking for a finite length of time to finish a task (for things like finishing a download).
I had the UIActivityIndicatorView working fine in simulator and other 3.0 devices in my app. But I found out that it was not spinning (or showing) in the new iphone 4. Basically I need to show the activity indicator when a button is clicked and hide it when the button click event is complete. I was using the approach below.
[NSThread detachNewThreadSelector: #selector(spinBegin) toTarget:self withObject:nil];
from this link. As mentioned, it correctly spins the activity indicator on all except 4.*.. not sure why. To get around this, I also followed another approach something like (from developer.apple.com)
`
(IBAction)syncOnThreadAction:(id)sender
{
[self willStartJob];
[self performSelectorInBackground:
#selector(inThreadStartDoJob:)
withObject:theJobToDo
];
}
(void)inThreadStartDoJob:(id)theJobToDo
{
NSAutoreleasePool * pool;
NSString * status;
pool = [[NSAutoreleasePool alloc] init];
assert(pool != nil);
status = [... do long running job specified by theJobToDo ...]
[self performSelectorOnMainThread:
#selector(didStopJobWithStatus:)
withObject:status
waitUntilDone:NO
];
[pool drain];
}
`
The problem with this was that, it is showing the acitivityVIewIndicator spinning correctly (at least on the simulator) but after it stops, the built in activity indicator in the top bar (where it shows the battery% etc) is still spinning.
I'm new to objective C. I have finished my app completely but for this silly thing. I realize there is no way to display UIActivityView without starting another thread. and finally, just to rant, I don't understand why they have to make it so complicated. I mean they knew it was going to have this problem, why not provide a sample code everyone can use rather than deriving their own solutions.
Finally, can anyone please provide me with a direction or some sample code. I would really appreciate it. I have been searching for a few hours now and have not found anything really that works!
Why are you starting/stopping the indicator on a separate thread? Any methods you send to your UIActivityIndicatorView must be sent on the main (UI) thread.
Any events sent by a button pressed will automatically be run on the main thread. If you're using background threads to complete the process, you could do something like:
- (IBAction)buttonPressed:(id)sender {
// This runs on the main thread
[activityIndicator startAnimating];
[self performSelectorInBackground:#selector(inThreadStartDoJob:) withObject:theJobToDo];
}
- (void)inThreadStartDoJob:(id)theJobToDo {
// Set up autorelease pool
...
// Run your long-running action
...
// Stop the spinner. Since we're in a background thread,
// we need to push this to the UI Thread
[activityIndicator performSelectorOnMainThread:#selector(stopAnimating) withObject:nil waitUntilDone:YES];
}
Edit: As for the activity indicator in the top bar (where the battery is), doesn't this automatically start/stop based on network activity?
How would i show that the progress bar is working there is no Refresh() in objective-c like there is in .net what would i use
for example
contactprogress.progress = 0.5;
StatusLabel.text = #"Status: Address Found";
How would i refresh the view to show that the progress has changed & show user the StatusLabel status?
Thanks
Mason
Based on your comments to the other two responses, you're doing some computationally intensive task that takes a few seconds, and the view is not updating during the task. You could try using two threads (not as scary as it sounds) so that the UI can continue updating while the task is doing its thing.
Here is an example.
iOS Reference Library Threading Programming Guide
It sounds like you want to update a progress bar and some text repeatedly with some time interval between. You could use a simple timer. Read about timers here. Perhaps something like this:
[NSTimer scheduledTimerWithTimeInterval:0.1f target:self selector:#selector(refreshProgress) userInfo:nil repeats:YES];
and:
- (void) refreshProgress:(id)sender {
// figure out new progress bar and text values
contactprogress.progress = 0.5;
StatusLabel.text = #"Status: Address Found";
// check if we should stop the timer and hide the progress bar/status text
}
That would update your progress bar with new values every 0.1 seconds.
To redraw an UIView, you can use
[UIView setNeedsDisplay];
However, you will need this only in very rare cases. When you change, let's say the contents of a label, your UI should update instantly. You might want to provide more code/context for your problem.
I am creating an iPhone application where I need to show a login screen for few minutes, hence I created the custom view and added to the custom view controller which is added to the window for display. Now at the same time I need to check for some background database so, I am creating that in separate delegate and while after database operation is in finished it gives an callback to the main thread to display the new screen. But the first view is never getting displayed and my application directly lands up in the new view.
Please find below my code snippet:
(void)CheckForExistingData : (DatabaseSource *)theDatabaseConnection
{
BOOL isRecordExist = theDatabaseConnection.isrecordExist;
// Release the connection....
[theDatabaseConnection release];
theDatabaseConnection = nil;
if (isRecordExist == FALSE)
{
textLabel.text = #"Preparing the application for first time use, please wait....";
[activityIndicator startAnimating];
[self setNeedsDisplay];
}
else
{
// Now all categories are successfully downloaded, launch the category screen...
sleep(2); // sleep for 1 second to allow to show the splash screen....
[self.viewController LaunchCategoryViewController:self];
}
}
Here CheckForExistingData is an callback mechanism which will be called from the other thread.
You need to exit your method to see anything displayed. Not sleep or wait on a synchronous network call.
That probably means you need to break your sequential code into multiple methods, the subsequent parts being called by a splash wait timer, the view button handler, or the async network activity completion callback.
sleep() blocks your main thread, thus the UI has no chance to update.
But you can always send messages delayed. In your case, it would look like this:
[self.viewController performSelector:#selector(LaunchCategoryViewController:) withObject:self afterDelay:2.0];
I have a question that we might answer together i have a tickertape in my iphone app (Like those stick tickers) and i use a NSThread to keep the memory away from the main thread so it will not slow down the app. Now the thing is it does its job well but when i scroll on a UITableView that i have on the same view i notice that my ticker tape animation stops to work.
ViewController.m (Main view of this object has the ticker tape on it)
-(void)startTicker {
[NSThread detachNewThreadSelector:#selector(start) toTarget:ticker withObject:nil];
}
TickerView.c (This handles the tickertape animation)
// Called from the viewcontroller
-(void) start {
NSAutoreleasePool *pool = [[NSAutoreleasePool alloc] init];
[self performSelectorOnMainThread:#selector(loop) withObject:nil waitUntilDone:YES];
[pool release];
}
-(void)loop {
timerHandle = [NSTimer scheduledTimerWithTimeInterval:.01f target:self selector:#selector(render) userInfo:nil repeats:YES];
}
-(void) render {
// Does a *** load of calculations here and moves the items in the tickertape..
}
My Question: How can i prevent the UITableview or any other view / touch event to block this thread from updating the tickertape animation ?.
Your NSTimer is not running on a background thread, but on the main thread. It will block anytime something else runs on the main thread. -performSelectorOnMainThread: means that anything done within the method called will run on the main thread.
To make your loop truly independent of the main thread, you could set up a while loop within your start method that sleeps for a given interval on every pass, then calls your render method. You'd need to make sure that all user interface updates within your render method get performed on the main thread, but make waitUntilDone NO for those method calls. I've also done this using NSOperations, where as one operation finishes I add another to the queue.
Also, running this render operation 100 times per second is excessive. I'd back that down a bit, or even better, look at using Core Animation for your ticker to make your drawing more efficient.