I have a form on a tabbed view; I mark the form dirty of any of the fields have been changed and I want to pop up an ActionSheet with "save"/"cancel" if the form is dirty (in lieu of a "save" button). Is there any way to stop the view from disappearing (or being removed from the view stack) until the user responds to the ActionSheet being handled?
A couple of thoughts:
It's worth noting that Apple's Human Interface Guidelines (the HIG) explicitly discourages this practice. They suggest that apps should "ask people to save only when necessary" because people "should have confidence that their work is always preserved unless they explicitly cancel or delete it." Perhaps in your case, it's important to have this feature, but it's generally discouraged.
An alternative, if you want to give users the chance to revert to old settings is to provide an "undo" button, that way, you honor the HIG and effectively auto-save, but you also give the user to explicitly revert to prior values if they really need to.
As others have noted, the notion of prompting to save or discard on viewWillDisappear doesn't quite work. It's logically too late in the process. viewWillDisappear could be called for too many reasons, many of which are not under your control, and it's not copacetic to fail to return promptly to that method, to introduce new user interface elements, etc.
If you really, really need the "save" vs. "cancel" user interface, then that lends itself to more of a modal interface (or push a new view controller that you have to pop off to return to your tab bar view controller) with save and cancel buttons rather than a tab bar interface. E.g. your tab bar view could show current values, you tap on an "edit" button, which pushes new view with save and cancel buttons. We don't know enough about your app to be able to advise whether this is logical in your case or not. (For another approach, see enabling edit mode in view controller.)
You can't stop the view from disappearing once the app has progressed to the point where viewWillDisappear: has been called. The thing to do would be to create a function like:
- (void)saveAndClose {
//Display sheet asking user what they want to do
}
- (void)dismissWithClickedButtonIndex:(NSInteger)buttonIndex animated:(BOOL)animated
{
if (buttonIndex == 0) // 0 or whatever the index of your save button is
{
// Perform save functions
}
[self dismissModalViewControllerAnimated:YES]; // or pop the view controller if appropriate
}
Related
My app contains TabBar controller with 5 viewcontrollers. It is possible to click on a button in each of viewcontrollers which will popup another view in which user can choose a setting. The button (which was clicked) is supposed to change its background according to chosen setting in each viewcontroller. So if the user clicks on button in VC1 and chooses the setting, this information should spread into all of the other VCs so that the button has the same background.
I am using storyboards, and I know that this is easily possible between 2VCs using segues, protocols, closures... I cannot find a proper way to spread information to more than 2VCs.
The only solution I can think of is usage of UserDefaults. I would save an information about a button setting and then call ViewWillAppear in each VC, where the background of the button would be set according to the value in UserDefaults. Is there a better solution, please?
EDIT:
As #cora mentioned in the comments, I was able to solve this using Notification Center.
You have several options, including:
Pass an array of the tab controllers to your "popup settings" controller and call a "settingSelected" func in each one directly.
Using Protocol / Delegate pattern, you could create an array of delegates in your "popup settings" controller.
You can use Notification Center.
You could subclass the button and use UIAppearance proxy.
Which approach to use will depend on a number of factors, based on exactly what all you need to do (are there other "settings"? or only that button background?)
You may want to search for swift using themes to see various different approaches.
“Is there a better solution, please?”
Not necessarily. Is this in fact a user default, to be preserved between launches? Then this is exactly what user defaults are for.
If not, then at least you need some central location where information about the current button color can be stored. An obvious candidate here is the tab bar controller itself. It gets notified every time there is a tab bar item switch, so it’s a perfect candidate.
Since you have mentioned you are using a UITabbarController, you can use an instance of UITabbarController and then access .viewControllers property of it and call their added public methods to get them triggered on events that you add. Additionally, using Notification Center makes more sense to me since your code will be more readable. Sometimes Notifications can just get a little confusing for new developers who are working on your code.
I want to build some analytics into my app and I would like to send some data when user leaves current screen, though there are multiple ways he can do so (back button, other button, sidebar menu, etc). Is there any efficient way to do this? I really don't feel like implementing it to every possible button that can lead the user to different screen.
You should call your function inside viewWillDisappear, which is called every time the current view controller is about to disappear from screen. See the documentation of viewWillDisappear
Also see the view controller life cycle (thanks #Paolo for the tip) below (documentation).
I want a button that will become available at, say, 8 AM. I know how to check if the button is available when the view is loaded, but, if the user is looking at the button as the clock turns to 8 AM, how do I get the button to become active without loading the view?
The button should always be present. Use its hidden to hide and show it as necessary. Or you can use its enabled to enable or disable it as necessary, but this can require more work, because a disabled button might not automatically look disabled so the user won't understand that it isn't truly "available".
Thus we have three cases to deal with:
The user moves to this view controller, the view controller loads its view, and your code decides about the button state / visibility now. You've already handled this one.
The view controller is already present and the view is visible, and the availability-change moment comes. In this case you will need previously to have set up a notification to prompt the view controller to take action now. Do not loop perpetually watching the time. Use an NSTimer or similar (a local notification is also worth considering).
The view controller is covered by another view controller and then uncovered. Perhaps the state needs to have changed in the meantime. So you will also want to do this check generally in viewWillAppear:, not just in viewDidLoad.
In the XCode IDE, at the bottom of the view controller in the MainStoryboard editor, are two boxes: First Responder, and Exit.
I know what a firstResponder is programatically within the code, but in the storyboard editor, I can't seem to do anything useful by it.
Am I able to use the first responder in this area to somehow set the first responder of the view? I'd like the first textfield to be active on load and I have tried right+click and dragging to no avail. I know I can set it programatically in the viewDidLoad method, but is there some way of doing it here?
And what is the green Exit for?
There are no good answer for this question, so I am posting my answer:
From here:
Note: You probably won’t be using the First Responder very much. This is a proxy object that refers to whatever object has first responder status at any given time. It was also present in your nibs and you probably never had a need to use it then either. As an example, you can hook up the Touch Up Inside event from a button to First Responder’s cut: selector. If at some point a text field has input focus then you can press that button to make the text field, which is now the first responder, cut its text to the pasteboard.
Edit:
1) First Responder is very useful if you are using text fields with keyboard notifications. I use it to make keyboard disappear, make an outlet to variable currentFirstResponder of your class, and in viewWillDisappear:
[self.currentFirstResponder resignFirstResponder];
2) You can read about unwind segues ("Exit" box) here
I've never used it and probably never will but you can assign an object to be the first in line to receive the events from the UI.
I suppose you could be creating a UIView subclass and add it in to a UIViewController but you actually want some other object to receive and process the events other than the UIViewController you are adding it to.
I found this link which kind of explains it a bit better.
First Responder: The First Responder icon stands for the object that the user is currently interacting with. When a user works with an iOS application, multiple objects could potentially respond to the various gestures or keystrokes that the user creates. The first responder is the object currently in control and interacting with the user. A text field that the user is typing into, for example, would be the first responder until the user moves to another field or control.
Exit: The Exit icon serves a very specific purpose that will come into play only in multiscene applications. When you are creating an app that moves the user between a series of screens, the Exit icon provides a visual means of jumping back to a previous screen. If you have built five scenes that link from one to another and you want to quickly return to the first scene from the fifth, you’ll link from the fifth scene to the first scene’s Exit icon.
More here
You don't see this very often, where a deleted answer is actually correct, and the comment (likely influencing its deletion) on it is totally wrong! I'll try and improve on it.
Usually the IBAction you want to hook up to a button is in the view controller containing the button. However if the IBAction is in a different controller, e.g. a parent controller then drag from the button to the First Responder object and you are able to select the IBAction in the parent controller!
As the hidden answer states, how this is implemented is the action is sent to nil, which has the effect of the responder chain (i.e. view hierarchy) being searched for the action, as follows:
[UIApplication.sharedApplication sendAction:#selector(nextObject:) to:nil from:self forEvent:nil];
An example is a custom UITableViewCell. Add a UIButton to the cell but you want the action to go up to a View Controller that has an embed segue to a UITableViewController. Drag the touch up instead action to the First Responder and select the action in the container view controller. In the action to find the indexPath simply loop the visibleCells and check if the sender is isDescendantOfView:
- (IBAction)cellButtonTapped:(id)sender{
for(UITableViewCell *cell in self.tableViewController.tableView.visibleCells){
if([sender isDescendantOfView:cell]){
NSIndexPath *indexPath = [self.tableViewController.tableView indexPathForCell:cell];
NSLog(#"tapped %#", indexPath);
}
}
}
Another example could be a reload button: say your first view controller shows an downloaded item with an IBAction to reload it to get the latest data, then your child controller shows some detail, but you also want them to be able to reload the main item from within the detail, just add a button in the detail and drag its action to First Responder and select the reload IBAction in the parent controller. This allows you to hook up buttons to parent actions with no additional code like delegate methods!
For this to work the action needs to be in the responder chain hierarchy or it won't be found, you can read how the chain is built up in the docs. Also note if called from code the view needs to have appeared, viewWillAppear is too soon.
i'm working on my first app and the problem a have is that the application interface design is quite customised, (even though it is a tab bar based app). now in one of the view controllers i need to present the user with the print interaction controller to print images. the thing is i don't use a navigation bar or a toolbar system or otherwise. i have managed to attach a target action method to a custom button. however, apple states that the printing interface should be presented by a system button (the one that looks like an arrow, kind of). question is: is there any way of putting a system icon inside a button that is not inside a (bar)?, or would it be ok to somehow tell the user (with an overlay or something) that tapping the button i'm using (the button is a red ribbon coming down from a picture frame) they will get the printing options?
Apple says:
Although the print button can be any
custom button, it is recommended that
you use the system item-action button
shown in Figure 6-1.
I'd interpret that to mean that you can use your own button if you want to.
You might want to consider having a toolbar at the top of the view for this particular tab. Just appearing on this tab. This would make the issue moot.
You could also, have the tool bar "slide in" and "slide out" from the top to provide access to this (and other?) actions. A single or double tap could instigate such an action.
Unfortunately, Apple doesn't expose the images for the custom bar button items in any reasonable manner. If you'd like access to them, I suggest using the bug reporter system at Apple's developer site to request that.