How to hide the iOS 8 Today Widget when there is nothing to display? - objective-c

Question

I'm using the today widget for iOS8 to display information relevant to the current day. The problem is I don't want to display the widget/section at all if there are no relevant messages to show.
I know it must be possible as the BA app does it (it only shows the widget when there is a flight, the rest of the time its not visible at all). I just cant figure out a way to achieve this behaviour.
Does anyone know how this can be done?

Answer 1

I found the way to do this is using the NCWidgetController. This allows you to easily specify when the today widget should be displayed based on whatever criteria you see fit.
Simply add the following into your viewDidLoad method (or anywhere that will be called when the widget reloads) in the today widget view controller and it will work:
BOOL hasDataToDisplay = NO;
NCWidgetController *widgetController = [NCWidgetController widgetController];
[widgetController setHasContent:hasDataToDisplay forWidgetWithBundleIdentifier:#"com.my-company.my-app.my-widget"];
Apple Docs: https://developer.apple.com/library/ios/documentation/NotificationCenter/Reference/NCWidgetController_Class/index.html#//apple_ref/occ/cl/NCWidgetController
WARNING: The NCWidgetController cannot be reset from the widget itself once you have set there is no content to display. In other words once you set it to NO then there is no going back unless you trigger it from the parent/containing app.

Answer 2

In the widget's ViewController's viewDidLoad method add the following:
BOOL DisplayWidget = NO;
[[NCWidgetController widgetController] setHasContent:DisplayWidget
forWidgetWithBundleIdentifier:#"<widget's bunder identifier>"];
This will disable the widget from showing.
To enable it again, you must do that from the containing app using the same line passing YES to setHasContent parameter. Make sure to add the necessary imports to the containing app in the ViewController which will re-enable the widget:
#import <NotificationCenter/NotificationCenter.h>
#interface ViewController () <NCWidgetProviding> {...}
[Check out page 41 of the documentations for widgets
https://developer.apple.com/library/ios/documentation/General/Conceptual/ExtensibilityPG/ExtensibilityPG.pdf ]

Answer 3

The approach which I used, though not perfect and has a small remnant in Notification Center, but worked for me:
In viewDidLoad() set preferred content size height to 1:
override func viewDidLoad() {
super.viewDidLoad()
// Do any additional setup after loading the view from its nib.
preferredContentSize = CGSizeMake(0, 1)
view.setNeedsLayout()
}
then when widget updates, gets real height and set it:
var data: NSData?
func updateData() {
// fetch data
if let data = data {
let viewHeight: CGFloat
// UI preperation and initialize viewHeight var
preferredContentSize = CGSizeMake(0, viewHeight);
} else {
preferredContentSize = CGSizeMake(0, 1);
}
}
func widgetPerformUpdateWithCompletionHandler(completionHandler: ((NCUpdateResult) -> Void)) {
// Perform any setup necessary in order to update the view.
// If an error is encountered, use NCUpdateResult.Failed
// If there's no update required, use NCUpdateResult.NoData
// If there's an update, use NCUpdateResult.NewData
updateData()
completionHandler(data != nil ? NCUpdateResult.NewData : NCUpdateResult.NoData)
}

Answer 4

It is better use
+ (instancetype)widgetController
then call
- (void)setHasContent:(BOOL)flag forWidgetWithBundleIdentifier:(NSString *)bundleID