I have a multithreaded application that has many concurrent operations going on at once. When each thread is finished it calls one of two methods on the main thread
performSelectorOnMainThread:#selector(operationDidFinish:)
// and
performSelectorOnMainThread:#selector(operationDidFail:withMessage:)
When an operation fails, I launch a sheet that displays the error message and present the user with 2 buttons, "cancel" and "try again". Here is the code I use to launch the sheet:
// failureSheet is a NSWindowController subclass
[NSApp beginSheet:[failureSheet window]
modalForWindow:window
modalDelegate:self
didEndSelector:#selector(failureSheetDidEnd:returnCode:contextInfo:)
contextInfo:nil];
The problem is that if 2 concurrent operations fail at the same time, then the current sheet that is displayed gets overwritten with the last failure message, and then the user's "try again" action will only retry the last failed operation. Ideally, I would like to "queue" these failure sheets. If 2 operations fail at the same time then you should see 2 sheets one right after the other, allowing the user to cancel or retry them individually.
I've tried using:
[NSApp runModalSessionForWindow:[failureSheet window]]
which seems to do what I want, but doesn't work in my situation. Maybe it isn't thread safe?
For example the following code works...
- (void)displaySheet
{
[NSApp beginSheet:[failureSheet window]
modalForWindow:window
modalDelegate:self
didEndSelector:#selector(failureSheetDidEnd:returnCode:contextInfo:)
contextInfo:nil];
[NSApp runModalForWindow:[failureSheet window]];
[NSApp endSheet:[failureSheet window]];
[[failureSheet window] orderOut:nil];
}
// Calling this method from a button press works...
- (IBAction)testDisplayTwoSheets
{
[self displaySheet];
[self displaySheet];
}
However if I have 2 different threaded operations invoke displaySheet (on the main thread) when they are done, I only see one sheet and when I close it the modal session is still running and my app is essentially stuck.
Any suggestions as to what I'm doing wrong?
If you want to queue them, then just queue them. Create an NSMutableArray of result objects (you could use the operation, or the failure sheet itself, or a data object that gives you the information for the sheet; whatever is convenient). In operationDidFinish: (which always runs on the main thread, so no locking issues here), you'd do something like this:
[self.failures addObject:failure];
if ([[self window] attachedSheet] == nil)
{
// Only start showing sheets if one isn't currently being shown.
[self displayNextFailure];
}
Then you'd have:
- (void)displayNextFailure
{
if ([self.failures count] > 0)
{
MYFailure runFailure = [self.failures objectAtIndex:0];
[self.failures removeObjectAtIndex:0];
[displaySheetForFailure:failure];
}
}
And at the end of failureSheetDidEnd:returnCode:contextInfo:, just make sure to call [self displayNextFailure].
That said, this is probably a horrible UI if it can happen often (few things are worse than displaying sheet after sheet). I'd probably look for ways to modify the existing sheet to display multiple errors.
I don't think you're using the "runModalForWindow:" command properly. You wouldn't use both [NSApp beginSheet...] and "runModalForWindow:" at the same time. One is for document modal (where the application keeps running but the window with the sheet is locked) and one is for application modal (which stops everything in the entire app until the sheet is dismissed). You only want the application modal dialog so do this...
For application modal start the window with the following only:
[[failureSheet window] center];
[NSApp runModalForWindow:[failureSheet window]];
Hook the "OK" button and others to regular IBAction methods. They'll get called when a button is pressed. In the IBAction methods you need to do something like this to dismiss the window and process the action:
-(IBAction)okBtnPressed:(id)sender {
[NSApp stopModal];
NSLog(#"ok button");
[[sender window] close];
}
Related
In my document-based application, I have overridden the method openDocument: in my subclass of NSDocumentcontroller so that I can display my own openPanel. I pass the chosen URLs to the method openDocumentWithContentsOfURL:display:completionHandler:. I use this code for the call:
[self openDocumentWithContentsOfURL:[chosenFiles objectAtIndex:i] display:YES completionHandler:^(NSDocument *document, BOOL documentWasAlreadyOpen, NSError *error) {
if (document == nil)
{
NSAlert* alert = [NSAlert alertWithError:error];
[alert runModal];
}
}];
So I want to display the passed error if nil gets returned as a reference to the document. The problem is, that the program just "freezes" after I press the "Open" button in the open panel. Then I need to manually stop the program with the "stop" button in Xcode. No spinning beach ball appears, though. If I comment the line "[alert runModal]", the program does not freeze any more, but no alert is displayed, of course.
Now the strange thing: The code works sometimes. If I switch from Xcode to my browser and back and I run the program again, it sometimes works flawlessly and the error is displayed. After some time it stops working again. It is unpredictable, but most of the time it doesn't work.
All this sounds like a race-condition to me. It certainly has something to do with the block? But what do I do wrong?
Converting my comment to an answer:
runModel on the main thread.
[alert performSelectorOnMainThread:#selector(runModal) withObject:nil waitUntilDone:NO];
I think runModel needs to be called on the main thread because it's part of the AppKit framework, and it's estentially triggering UI graphics. I believe all calls to the AppKit framework or to any method that manipulates graphics needs to be on the main thread.
I'm currently learning (by doing) objective-c by implementing a feature I felt is missing in the Titanium Appcelerator Desktop SDK: A way to do modal dialog with custom button texts and optionally to display them as a "sheet".
All is dandy and working, however, when displaying the NSAlert as a "sheet" my method that's creating the alert returns immediately and that's what I want to prevent.
The method's creating the alert returns an int (the return code from the NSAlert).
The code inside basically boils down to:
int returnCode = -1;
if (displayAsSheet) {
[alert beginSheetModalForWindow:nativeWindow modalDelegate:delegate didEndSelector:#selector(alertDidEnd:returnCode:contextInfo:) contextInfo:nil];
} else {
returnCode = [alert runModal];
}
return returnCode;
The modalDelegate is an object that's implementing the needed:
- (void)alertDidEnd:(NSAlert *)alert returnCode:(NSInteger)returnCode contextInfo:(void *)contextInfo;
and for now it just does a NSLog of the returnCode.
So my question is:
How can I block my method from returning until the "sheet" has been dismissed?
Or am I going about this the wrong way?
You must start a modal session for you sheet after showing it and stop the session after closing sheet.
Check this: https://github.com/incbee/NSAlert-SynchronousSheet, I think it will be helpfull.
You could use this after beginSheetModalForWindow:...:
[[NSRunLoop mainRunLoop] runMode:NSModalPanelRunLoopMode beforeDate:[NSDate distantFuture]]
However, it will make any other windows in your app unusable until the sheet is dismissed. It would be better not to block those windows.
my method that's creating the alert returns immediately
I believe that's because, as #Josh says, the sheet is running modal only relative to the window to which it is attached; it is not freezing the entire app. Therefore, as soon as beginSheetModal... executes, the rest of your method continues to run, concluding with return returnCode (here returning -1), without waiting for the user to respond to the alert.
The return code is a stand-in for which button on the alert panel the user ends up pushing (NSAlertFirstButtonReturn, NSAlertSecondButtonReturn, etc. -- they're listed at the end of the NSAlert class ref). You use it in your alertDidEnd method to act upon whichever button the user pushed to dismiss the alert. That's why the alertDidEnd selector includes the returnCode.
On the other hand, when you use the runModal method in your else block, you need to explicitly call alertDidEnd and feed it the number returned when the runModal method ends -- which is when the user dismisses the alert.
Here's a revised version of your code:
int returnCode = -1;
if (displayAsSheet) {
[alert beginSheetModalForWindow:nativeWindow modalDelegate:delegate didEndSelector:#selector(alertDidEnd:returnCode:contextInfo:) contextInfo:nil];
// The selector alertDidEnd has the returnCode int. The alert will then set that code to whatever the user chooses, and will send the altered int on to alertDidEnd.
}
else {
// Here, everything stops once runModal is called, until the user dismisses the alert, at which time the runModal method returns the int representing the button the user pushed, and you assign the return to your variable "returnCode."
returnCode = [alert runModal];
[self alertDidEnd:alert returnCode:returnCode contextInfo:nil];
}
// Omit the line returning the returnCode.
Then the alertDidEnd method does something like this:
- (void)alertDidEnd:(NSAlert *)alert returnCode:(NSInteger)returnCode contextInfo:(void *)contextInfo {
switch (returnCode) {
case NSAlertFirstButtonReturn:
// Do whatever should happen when first button is pushed.
break;
case NSAlertSecondButtonReturn:
// Do whatever should happen when second button is pushed.
break;
default:
break;
}
// Unfreeze things.
[[NSApplication sharedApplication] stopModal];
}
By the way, there is a way of running a sheet and freezing the entire app, not just the window to which the sheet is attached, if that's what you want: modal tips
You're thinking about this slightly the wrong way. If your method were able to wait for the sheet to end, the app's event loop would be blocked and there would be no way for the user to interact with the UI. When you use runModal for the alert, a new run loop is created to handle the alert -- this is why nothing else can be done to the app. The point of the sheet option is to allow the user to do other things while the alert is displayed -- i.e., it expressly does not take over the event handling.
You could look into faking the sheet by attaching a child window.
You could try to set a boolean that freezes anything you want to freeze on your app (set freeze = YES) until the sheet is removed (set freeze = NO).
In the general case, you don't need to block a method : you just want some things not to happen until the user has made a choice.
For example, I have an app that uses gyroscope. It has some behaviour with, and some other behaviour without.
So I have a boolean that is used in any method that uses the gyro data to route the behaviour to the good one. My useGyro Boolean is NO when : the user is choosing what kind of hardware feature it want to enable or not, and when gyro is not available on the device.
The same thing with a mapView I have : when the user is aked by the system if it wants to be located, there is a moment where I freeze any behaviour using the user location. When he has made his choice, I change that bool value.
I have a Mac OS X app written in objetive-c Cocoa. You can see most of the code in this previous question. Essentially you click a button on the main window (the app delegate) and it opens another window where the user can enter information.
In the following code (that gets called when the user press the button in the app's main window)
- (IBAction)OnLaunch:(id)sender {
MyClass *controllerWindow = [[MyClass alloc] initWithWindowNibName:#"pop"];
[controllerWindow showWindow:self];
NSLog(#"this is a log line");
}
The NSLog line gets printer immediately after I called showWindow. Is there any way to wait until controllerWindow is closed to continue with the NSlog?
The reason for this is that the user set's a value on the new window I opened and I need to collect that value on the same OnLaunch so I need to wait.
I know that modal windows are bad form in Mac, but I have no control over this feature.
I've tried with
[NSApp runModalForWindow:[controllerWindow window]];
and then setting the popup window to
[[NSApplication sharedApplication] runModalForWindow:popupwin];
and it works but then the focus never gets passed to the main window anymore
Thanks!
If you want the window to be modal for your application, use a sheet: https://developer.apple.com/library/archive/documentation/Cocoa/Conceptual/Sheets/Tasks/UsingCustomSheets.html
However, there is no way to suspend execution of a method while the sheet is displayed, this would be tantamount to blocking the current run loop. You would have to break you code into the begin and end methods as described in the linked documentation.
Here are the steps you need to follow:
In TestAppAppDelegate create an NSWindow outlet to hold your sheet and an action to dismiss the sheet
Create a nib with an NSWindow as the root object. I think you already have this in "pop". Set the Visible at Launch option to NO (this is very important)
Set the file's owner of this nib to TestAppAppDelegate and connect the window to your new outlet, and the close button to your new action
In your method to launch the sheet (OnLaunch), use the following code:
(ignore this it's to make the code format properly!)
if(!self.sheet)
[NSBundle loadNibNamed:#"Sheet" owner:self];
[NSApp beginSheet:self.sheet
modalForWindow:self.window
modalDelegate:self
didEndSelector:#selector(didEndSheet:returnCode:contextInfo:)
contextInfo:nil];
Your close button action should be [NSApp endSheet:self.sheet];
Your didEndSheet: method should be [self.sheet orderOut:self];
You can use UIVIew method animateWithDuration:delay:options:animations:completion: to accomplish this.
You said you want the next line to execute once the window is closed, rather than after it is opened. In any case, you may end the OnLaunch method this way:
- (IBAction)OnLaunch:(id)sender {
MyClass *controllerWindow = [[MyClass alloc] initWithWindowNibName:#"pop"];
[controllerWindow animateWithDuration:someDelay:options: someUIAnimationOption
animations:^{
[controllerWindow showWindow:self]; // now you can animate it in the showWindow method
}
completion:^{
[self windowDidFinishShowing]; // or [self windowDidFinishDisappearing]
}
}
- (void) windowDidFinishShowing {
NSLog(#"this is a log line");
}
I'm in the midst of debugging an extremely unusual problem, and I was wondering if anybody might have any insight into what might be going wrong:
In a controller class from a NIB, I take an NSPanel from that same NIB, and then show it app modally on a NSWindow (that was created by hand in code):
[[NSApplication sharedApplication] beginSheet: myPanel
modalForWindow: window
modalDelegate: self
didEndSelector: #selector(sheetDidEnd:returnCode:contextInfo:)
contextInfo: nil];
[[NSApplication sharedApplication] runModalForWindow: myPanel];
Now, when the "finish" button on that sheet is clicked, I run some code to disable some buttons and fire off a thread to make sure the user input is valid (I have to validate with a remote service). This thread is fired from a separate validator object I create:
// controller calls:
[validator validateCreds: creds
notify: #selector(validationComplete:)
onObject: self];
// validator object
validateInfo: (NSDictionary *)parms
notify: (SEL)notifySelector
onObject: (id)notifyObject
{
// build up data with parms and notify info
[[NSThread detachNewThreadSelector: #selector(remotevalidate:)
toTarget: self withObject: data];
}
Next, when the validation is finished, the validator notifies my controller object:
[notifyObject performSelectorOnMainThread: notifySelector
withObject: results waitUntilDone: NO];
And then my controller object, in the method that the validator object calls, kills the dialog:
- (void)validationComplete: (id)data
{
[[NSApplication sharedApplication] stopModal];
[createTwitterPanel orderOut: nil];
[[NSApplication sharedApplication] endSheet: createTwitterPanel
returnCode: NSOKButton];
}
- (void)sheetDidEnd:(NSWindow *)sheet
returnCode:(int)returnCode
contextInfo:(void *)contextInfo
{
m_returnCode = returnCode;
}
My problem: Although the panel is closed / disappears, the top NSApp runModalForWindow: does not exit until some system event is sent to the window that was showing the dialog. Trying to move, resize, or do anything to the window, or otherwise switching away from the application suddenly causes the method to exit and execution to continue. No amount of waiting seems to help, otherwise, however.
I have verified that all methods being invoked on the controller class are all being invoked on the main app thread.
An even more interesting clue is that the dialog has two controls, a WebView, and an NSTextField: Even if I force the exit of runModalForWindow: by clicking on the window, TABbing between the two controls remains screwed up — it simply never works again. It's like my event loop is horked.
I've tried changing validationComplete: to instead post a notification to the main thread, and I've also played with the waitUntilDone on the performSelectorOnMainThread method, all to no effect.
Any ideas? Things I should try looking at?
From the NSApplication documentation:
abortModal must be used instead of
stopModal or stopModalWithCode: when
you need to stop a modal event loop
from anywhere other than a callout
from that event loop. In other words,
if you want to stop the loop in
response to a user’s actions within
the modal window, use stopModal;
otherwise, use abortModal. For
example, use abortModal when running
in a different thread from the
Application Kit’s main thread or when
responding to an NSTimer that you have
added to the NSModalPanelRunLoopMode
mode of the default NSRunLoop.
So, I learned something today.
I'm trying to show a NSPanel as a sheet. I'm naively doing something along those lines:
SheetController *sheetController = [[[SheetController alloc]
initWithWindowNibName:#"Sheet"] autorelease];
[[NSApplication sharedApplication] beginSheet:sheetController.window
modalForWindow:self.window
modalDelegate:self
didEndSelector:#selector(sheetDidEnd:returnCode:contextInfo:)
contextInfo:nil];
For some reason that eludes me, this isn't working. When this part of the code is called, the sheet momentarily flashes (because of the autorelease message). The sheet is never hooked to window.
If anyone can point me to where I can find more information, that would be very appreciated.
This sounds like a classic case of having checked the "Visible at Launch" box for the panel in IB. Turn that off.
Yes, you need to own this controller for as long as you want it to continue functioning. You can't just create it, autorelease it, and let it die—you need to hold onto it for as long as you need it.
Don't forget that if you're trying to run this as a "modal" sheet (i.e. it takes over the app until the user dismisses it), you'll need to push a new run loop.
What you've done is shown the sheet, and then not pushed a new loop, so the OS just shows the sheet, sees there's no reason to keep it running, and thus shuts it down and resumes execution on the next line:
I typically do sheets the following way:
- (id)showPanelModalAgainstWindow: (NSWindow *)window
{
[[NSApplication sharedApplication] beginSheet: panelToShow
modalForWindow: window
modalDelegate: self
didEndSelector: #selector(sheetDidEnd:returnCode:contextInfo:)
contextInfo: nil];
[[NSApplication sharedApplication] runModalForWindow: panelToShow];
if (m_returnCode == NSCancelButton) return nil;
}
- (void)sheetDidEnd:(NSWindow *)sheet
returnCode:(int)returnCode
contextInfo:(void *)contextInfo
{
UNUSED(sheet);
UNUSED(contextInfo);
m_returnCode = returnCode;
}
Then, in your accept and/or cancel button routines:
- (IBAction)continueButtonClicked:(id)sender
{
UNUSED(sender);
[[NSApplication sharedApplication] stopModal];
[createAccountWizardPanel orderOut: nil];
[[NSApplication sharedApplication] endSheet: createAccountWizardPanel
returnCode: NSOKButton];
}
I'm sure there is a slightly less code-y way of doing this, but I've not looked to deeply into it, because this way works perfectly fine thus far ....
Previous comments about the lifetime of the controller and panel objects are also relevant -- be sure to understand exactly what objects you need for what lifetimes when showing a modal panel.