I have an app where I want to save the current state of a project before every change so that undo and redo will be able to step back and forth within those states. When I make a change the code to save the position is:
if(!undoManager){
undoManager = [[NSUndoManager alloc] init];
}
[[undoManager prepareWithInvocationTarget:self] replaceSelf:currentState];
And my undo/redo functions:
-(void)undo{
if(undoManager){
[undoManager disableUndoRegistration];
[undoManager undo];
[undoManager enableUndoRegistration];
}
}
-(void)redo{
if(undoManager){
[undoManager disableUndoRegistration];
[undoManager redo];
[undoManager enableUndoRegistration];
}
}
The replace self function just takes the project state property and distributes the information so that the state is restored.
Undo works perfect, i can perform 5 steps and then hit undo 5 times to rewind to the start, but redo does nothing at all! Shouldn't invoking redo cause it to hit my selector with the last object that was undone? What am I misunderstanding here?
I got this working, in the replaceSelf function that was being called by the undo/redo, I added this code:
[undoManager registerUndoWithTarget:self selector:#selector(replaceSelf:) object:ps];
Where ps is the current project state before the undo/redo is done.
This got it working for me!
Related
in my iOS app I do the following.
viewDidAppear(){
// Load a spinner in a view on the top
[DSBezelActivityView newActivityViewForView:self.view];
// Execute code that require 3 seconds
...
// Stop the spinner
[DSBezelActivityView removeViewAnimated:YES];
}
The problem is that the spinner doesn't appear, because the the cpu is working hard (something similar). It's like that the code betweek the start and stop has precedence on the rendering of the view.
I would love to find a way to show effectively the start of the spinner, without using a timer to delay the code execution.
Thanks
If you have a method like
-(void) showSpinner:(UIView*)view {
dispatch_async(dispatch_get_main_queue(), ^{
[DSBezelActivityView newActivityViewForView:view];
});
}
there are several ways to call it from a different thread. Choose one from the following:
[NSThread detachNewThreadSelector:#selector(showSpinner:) toTarget:self withObject:self.view];
// or
[self performSelectorInBackground:#selector(showSpinner:) withObject:self.view];
// or
NSInvocationOperation *invOperation = [[NSInvocationOperation alloc] initWithTarget:self selector:#selector(showSpinner:) object:self.view];
NSOperationQueue *opQueue = [[NSOperationQueue alloc] init];
[opQueue addOperation:invOperation];
// or
dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0), ^{
[self showSpinner:self.view];
});
Alt + click for details.
Move code between start and stop activity indicator into separate thread because it's blocking main thread. That's why activity indicator is not showing.
Edit: Example
I agree with the 1st answer with a couple of modifications. I just went through this exact same problem. The problem is that anything graphical is going to automatically move to the background updating when you have code that takes time to get through. Throwing the spinner to the background is what it essantially doing anyway. What you want is (sadly) for you main code to run in the background and the spinner to run in the foreground. I know this sounds bad, but in some cases allowing your code to run a bit slower to give indication that the app is doing something useful is beneficial to the user.
In order to get the spinner to work:
1) Take all the code that takes the 3 seconds to run, and put that into a function that is a void function
2) Instantiate your spinner but store it to a variable that is accessible outside your viewDidAppear routine.
3) Startup a new NSTimer with that runs continuously with an increment of about every quarter second or so. I will define what goes into the routine that gets called every cycle later.
4) Call the routine you created in step 1 using the performSelectorInBackground capability. This essentially is now going to run your startup (3 seconds worth) in the background which is really the only way to allow the animated spinner to show up and truly animate.
5) In the routine you created in step 1, add a line of code right at the top that updates a (global to the object) boolean to true, stating that we are in the middle of our main 3 second routine.
6) At the end of the routine defined in step 1 add a line of code setting the same global defined in step 5 to false indicating that our 3 second routine is completed.
7) In the timer routine, we now want to do something that looks like the following:
// If busy that start the spinner
if(YES == busy){
[spinner startAnimating];
}else{
[spinner stopAnimating];
// Here we can also stop and deallocate the timer
}
If you need more aid on this subject, I can indeed provide exact code. Take a look at the example app that I have developed for the Pepperdine News Group. When you press a button, the spinner comes up on the top right of the screen.
http://itunes.apple.com/us/app/pepperdine-graphic-for-iphone/id516343215?mt=8
I have the following code:
[self.view bringSubviewToFront:loggingIn];
[self loginWithUsername:user Password:pw];
This is inside an IBAction method for a button press. The button stays highlighted until the user is logged in (this could take several seconds) and THEN the view appears. How come the view isn't appearing before the login method is called?
John's answer would work, but it has to do with the Run Loop than blocking threads. Basically, whenever your app receives an event such as a button getting clicked, your handler gets run in the main thread. Any changes you make to the UI happen after your handler finishes. This lets Cocoa optimize the graphics updates by analyzing/performing them together.
Run Loop:
Event -> Your Handler Code -> System Updates UI
So you need to let your handler code finish in order to let the system start updating the UI - before invoking your loginWithUsername:Password: [sic] method. Scheduling a timer will bump it to the next iteration of the run loop (the timer going off becomes the "event" that triggers the next loop). So,
Run Loop (2 iterations):
Mouse Click -> Your Handler Code (reorder views) -> System reorders views
Timer Fires -> Your Handler Code (trigger login) -> Any addl UI updates
So do something like this:
- (void) buttonHandler: (id)sender {
[self.view bringSubviewToFront:loggingIn];
[self performSelector: #selector(performLogin)
withObject: [NSArray arrayWithObjects:user, pw, nil]
afterDelay: 0];
}
- (void) performLogin: (NSArray *)args {
[self loginWithUsername:[args objectAtIndex:0] Password:[args objectAtIndex:1]];
}
It doesn't have to be an array. You could also pack your username and password in a dictionary and use that as your argument instead.
The first call runs in a different thread which is blocked by the second line. Try delaying the second call by .1 seconds or so by using the:
- (void)performSelector:(SEL)aSelector withObject:(id)anArgument afterDelay:(NSTimeInterval)delay
method of NSObject. Since you are using two arguments you will need to either pass both as a single object or use instance variables.
I am working on a web-services data processing app and I am trying to make the app run as quickly as possible. When a certain 3 finger pan gesture is performed, I call a method that sends updated information off to the server to get a new batch of images to update the existing ones with.
So lets say there are 15 images in an array, I filter through them with a 2 finger gesture, and then if I want to change something about them, I can do the 3 finger gesture, and I get that same set back, just tweaked a bit (contrast/brightness, etc.).
Is what I want though is to be able to update the imageView that is displaying the images after the first image has been retrieved, so as to give the user a feel for what the rest in the series are going to look like. But no matter what I try, and no matter how many different threads I try and implement, I can't get the imageView to update before the entire download is complete. Once the batch download is done (which is handled on a separate thread) the imageView updates with the new images and everything is great.
The first step in the process is this:
if(UIGestureRecognizerStateEnded == [recognize state]){
[self preDownload:windowCounter Level:levelCounter ForPane:tagNumber];// Where this method is what gets the first image, and tries to set it to the imageView
[self downloadAllImagesWithWL:windowCounter Level:levelCounter ForPane:tagNumber]; //And this method goes and gets all the rest of the images
}
This is my preDownload method:
-(void)preDownload:(int)window Level:(int)level ForPane:(int) pane{
int guidIndex = [[globalGuids objectAtIndex:pane] intValue];
UIImage *img = [DATA_CONNECTION getImageWithSeriesGUID:[guids objectAtIndex:guidIndex] ImageID:counter Window:window Level:level];
if(pane==0){
NSLog(#"0");
[imageView3 setImage:img];
}else if(pane==1){
NSLog(#"1");
[imageView31 setImage:img];
}else if(pane==2){
NSLog(#"2");
[imageView32 setImage:img];
}else if(pane==3){
NSLog(#"3");
[imageView33 setImage:img];
}
}
So by separating this out into two different methods (there are no threads being implemented at this point, these methods are being called before all that) I was thinking that after the preDownload method completed, that the imageView would update, and then control would continue on down into the downloadAllImagesWithWL method, but that doesn't appear to be the case.
Am I missing something simple here? What can I do to update my GUI elements before that second method is through running?
You are right. However the viewn won't refresh until your code reaches runloop. You can do 2 things:
Make your downloadAllImagesWithWL method async, so it will return after you called it, your main thread reaches runloop, gui updates, and the download method will tell your logic through a callback when its done.
OR
A simplier hackier (and bad) solution would be to run runloop for some time before you call your download method. Something like this: [[NSRunloop currentRunLoop] runUnitlDate: [Date dateWithTimeIntervalSinceNow: 0.1]]; It will run runloop for 0.1 second.
When the image is set, the image view will mark itself as needing display. The actual display won't occur until the beginning of the next run loop. In OS X, you can use -display to draw the view immediately, but I don't think Apple created a public method to do this on iOS. However, if the next method simply creates the background thread, then it will return quickly and the display update will probably occur before the thread finishes.
I want to add a undo manager to a coredata backed iphone application. When the user tries to add a new object (by tapping on + button) I load a new modal viewcontroller and start a new undo group in viewDidLoad.
When the user presses Cancel button, I want to rollback the changes in cancelAction callback.
Queries:
Is it possible to start a nested Undo group and persist it through event loop and collate all the changes done in one single undo group? Right now, when I call beginUndoGrouping in cancelAction, I get a missing beginUndoGrouping exception.
What is the significance of groupsByEvent API for NSUndoManager? Do I require to set it to NO to persist an undo group through event loop?
What needs to be done in saveAction callback to make changes permanent (apart from calling save on mangedObjectContext)? How do I tell Undo Manager to stop tracking the changes?
Error Message:
* Terminating app due to uncaught exception 'NSInternalInconsistencyException', reason: '_endUndoGroupRemovingIfEmpty:: NSUndoManager 0x75415f0 is in invalid state, endUndoGrouping called with no matching begin
Sample Code:
// RootViewController.m
- (void) addAction {
// Load Modal View Controller to add new object
}
// AddViewController.m
- (void) viewDidLoad {
// Start nested undo group
[self.managedObjectContext processPendingChanges];
[self.managedObjectContext.undoManager beginUndoGrouping];
[self createModel];
}
- (void) cancelAction {
// Revert all changes
[self.managedObjectContext processPendingChanges];
[self.managedObjectContext.undoManager endUndoGrouping];
[self.managedObjectContext.undoManager undoNestedGroup];
...
}
- (void) saveAction {
// Save changes
}
Beginning with your specific questions - Yes, you can manually define the bounds of an undo operation using beginUndoGrouping and endUndoGrouping.
In this case, the undo operation should work whether or not groupsByEvent is set. This is because all the undo groups that are generated by the event loop are nested under your main open undo grouping started with beginUndoGrouping, and as long as you call undoNestedGroup directly after you call endUndoGrouping, it should work. If you are not using the event loop undo groupings, don't worry about it and set it to NO.
To make your changes permanent, close the undo group with endUndoGrouping and call save on your context. The processPendingChanges calls are not needed, and may cause issues in nested groups. If you want clear the undo operations, call removeAllActions on your undomanager after endUndoGrouping - this guarantees the changes will never be un-did.
Use breakpoints/nslog to make sure your begin/end calls are one for one.
If you want your cancel action to be like an 'undo button', you'll have to do the following:
Move beginUndoGrouping to viewWillAppear
Call endUndoGrouping in viewWillDisappear
re-open undo grouping at the end of your cancel action
re-open undo grouping at the end of your save action
Otherwise, if you leave it as is, make sure you close the dialog in your save and cancel actions, to avoid possibility of endUndoGrouping being called multiple times.
If you have any questions, please comment and I'll update.
Good luck!
I just cannot imagine what the hell the problem could be.
I made a pretty app, and decided to use only CALayers to "render".
When I saw that the changes in the position property gets animated, decided to implement a custom getter-setter "abstract" property called tanCenter to set the position without animating.
-(void) setTanCenter: (CGPoint) sentCenter
{
//Remove any transactions.
[CATransaction begin];
[CATransaction setValue:(id)kCFBooleanTrue forKey:kCATransactionDisableActions];
//Set position.
self.position = sentCenter;
[CATransaction commit];
//Set value.
tanCenter = sentCenter;
}
-(CGPoint) tanCenter { return tanCenter; }
Since I merged this into the project, it crashes without any "understandable" (for me) error message. I can see only those "out of scope"-s. I cant even get this tanCenter property NSLog-ged without crash.
Help me, Obi-Wan Kenobi; you're my only hope.
If you run in the debugger (Command-Y) and make sure you have global breakpoints enabled, the debugger should stop at the place where the crash occurred giving you an idea of what is nil or over-released.
hey I had the same problem till now. Finally I have found my bug after investigating 2 weeks of bug tracking (it really sucks)
maybe my problem helps you:
I started with a TableView that opens on click another view. So I created in:
-(void)tableView:didSelectRowAtIndexPath:
first the controller for the other view and set the value for a global variable:
SomeView *dtview = [[SomeView alloc] initWithNibName:#"SomeView" bundle:nil];
dtview.lblTitle = cl.textLabel.text; // cl is the cell
[self presentModalViewController:dtview animated:NO];
[dtview release];
So opened the other view and done much functions with much memory usage :)
When I after that close the other view and go back to the table and scroll some times the App terminates with the message "out of scope"
I searched really, really long to find out what was the effect. It seems that when the other view is released also the text of the first table is released.
After putting a copy to the call it worked for me:
dtview.lblTitle = [cl.textLabel.text copy];
For int and bool the first solutions works fine, because these aren't objects but for NSObject's you should copy the values to another view.