Forum› Xamarin.iOS
Update Status Bar Menu title
DanBol
USMember ✭✭
USMember ✭✭
in Xamarin.iOS
I am trying to figure out how to update the Status bar menu title property from a timer type item.
This is what I have tried so far without success.
`
NSStatusItem _item;
public AppDelegate()
{
}
public override void DidFinishLaunching(NSNotification notification)
{
NSStatusBar _statusBar = NSStatusBar.SystemStatusBar;
Random _rand = new Random();
_item = _statusBar.CreateStatusItem(NSStatusItemLength.Variable);
_item.Title = $"Text {_rand.Next(1, 100).ToString()}";
Timer _timer = new Timer(2000);
_timer.Elapsed += ATimer_Elapsed;
_timer.Start();
}
void ATimer_Elapsed(object sender, System.Timers.ElapsedEventArgs e)
{
_item.Title = $" NEW Text";
}
`
I have used the Action on the menu item, but I do not want it to be a event based item.
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Best Answers
-
ChrisHamons
USForum Administrator, Xamarin Team Xamurai
The root problem is that your Timer proc is not on the UI thread when called:
MenuTimer.AppDelegate.ATimer_Elapsed(System.Timers.Timer sender, System.Timers.ElapsedEventArgs e) in /Users/donblas/Projects/MenuTimer/AppDelegate.cs:34 System.Timers.Timer.MyTimerCallback(object state) in /Library/Frameworks/Xamarin.Mac.framework/Versions/4.0.0.214/src/mono/mcs/class/referencesource/System/services/timers/system/timers/Timer.cs:324 System.Threading.Timer.Scheduler.TimerCB(System.Threading.Timer o) in /Library/Frameworks/Xamarin.Mac.framework/Versions/4.0.0.214/src/mono/mcs/class/corlib/System.Threading/Timer.cs:327 System.Threading.QueueUserWorkItemCallback.System.Threading.IThreadPoolWorkItem.ExecuteWorkItem() in /Library/Frameworks/Xamarin.Mac.framework/Versions/4.0.0.214/src/mono/mcs/class/referencesource/mscorlib/system/threading/threadpool.cs:1279 System.Threading.ThreadPoolWorkQueue.Dispatch() in /Library/Frameworks/Xamarin.Mac.framework/Versions/4.0.0.214/src/mono/mcs/class/referencesource/mscorlib/system/threading/threadpool.cs:856 ObjCRuntime.Runtime.ThreadPoolDispatcher(System.Func<bool> callback) in /Users/builder/data/lanes/5489/c4240f3f/source/xamarin-macios/src/ObjCRuntime/Runtime.cs:244 System.Threading._ThreadPoolWaitCallback.PerformWaitCallback() in /Library/Frameworks/Xamarin.Mac.framework/Versions/4.0.0.214/src/mono/mcs/class/referencesource/mscorlib/system/threading/threadpool.cs:1208
so you need to invoke back to the UI thread:
void ATimer_Elapsed (object sender, System.Timers.ElapsedEventArgs e) { BeginInvokeOnMainThread (() => { _item.Title = $" NEW Text"; }); }As noted in the Apple documentation here unless specified in documentation it is not safe to invoke UI objects from non-UI threads. BeginInvokeOnMainThread forces that code to invoke on the correct thread.
However, a better way of structuring this in my opinion is to use the underlying NSTimer APIs, which do exactly what you want here:
NSStatusItem StatusItem; public override void DidFinishLaunching (NSNotification notification) { Random rand = new Random (); StatusItem = NSStatusBar.SystemStatusBar.CreateStatusItem (NSStatusItemLength.Variable); StatusItem.Title = $"Text {rand.Next (1, 100).ToString ()}"; NSTimer.CreateScheduledTimer (2, (obj) => { StatusItem.Title = $" NEW Text"; }); }5
Answers
The root problem is that your Timer proc is not on the UI thread when called:
so you need to invoke back to the UI thread:
void ATimer_Elapsed (object sender, System.Timers.ElapsedEventArgs e) { BeginInvokeOnMainThread (() => { _item.Title = $" NEW Text"; }); }As noted in the Apple documentation here unless specified in documentation it is not safe to invoke UI objects from non-UI threads. BeginInvokeOnMainThread forces that code to invoke on the correct thread.
However, a better way of structuring this in my opinion is to use the underlying NSTimer APIs, which do exactly what you want here:
NSStatusItem StatusItem; public override void DidFinishLaunching (NSNotification notification) { Random rand = new Random (); StatusItem = NSStatusBar.SystemStatusBar.CreateStatusItem (NSStatusItemLength.Variable); StatusItem.Title = $"Text {rand.Next (1, 100).ToString ()}"; NSTimer.CreateScheduledTimer (2, (obj) => { StatusItem.Title = $" NEW Text"; }); }Thank you ChrisHamons. Made perfect sense after you explained it.