Bug 22317 - Subscribing using MessagingCenter causes duplicate messages
Summary: Subscribing using MessagingCenter causes duplicate messages
Alias: None
Product: Forms
Classification: Xamarin
Component: Forms ()
Version: 1.2.3
Hardware: PC Mac OS
: Normal normal
Target Milestone: ---
Assignee: Bugzilla
Depends on:
Reported: 2014-08-22 18:31 UTC by John Miller [MSFT]
Modified: 2015-07-21 04:37 UTC (History)
7 users (show)

Is this bug a regression?: ---
Last known good build:

Test Case (3.11 MB, application/zip)
2014-08-22 18:31 UTC, John Miller [MSFT]

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Description John Miller [MSFT] 2014-08-22 18:31:22 UTC
Created attachment 7778 [details]
Test Case


   The attached example subscribes to a message from a view model. The message callback is fired once for each time that the page is pushed. 

**Steps to Reproduce:**

   1. Run the test app on a simulator.
   2. Touch the button to push the child page. 
   3. Touch the Perform Activity button. 
   4. Notice that the message handler in ChildPage.cs is fired once.
   5. Press the Back button and repeat steps 2-4. 

**Actual Results:**

   Message callback is fired multiple times.

**Expected Results:**

   Message callback is fired once. 

**Build Date & Platform:**

   XF 1.2.3

**Additional Information:**

   It is unclear if this is an implementation issue. If so, it is unclear where to unsubscribe to a message properly. OnDissapearing and OnAppearing are not consistent between platforms, so the messaging is not constant.
Comment 1 Mohit Kheterpal 2014-08-25 12:13:33 UTC
I have checked this issue and getting same behavior as mentioned in bud description. Screencast for the same :http://screencast.com/t/iv2kkoTZ

IDE Logs : https://gist.github.com/Mohit-Kheterpal/6271be621a95cd3ec8a5

Environment info :
=== Xamarin Studio ===

Version 5.3 (build 434)
Installation UUID: 449f40dd-b3f1-4028-9a6b-cca0d1a2307d
	Mono 3.8.0 ((no/62a857e)
	GTK+ 2.24.23 (Raleigh theme)

	Package version: 308000007

=== Apple Developer Tools ===

Xcode 5.1.1 (5085)
Build 5B1008

=== Xamarin.Mac ===

Version: (Starter Edition)

=== Xamarin.Android ===

Version: 4.16.0 (Trial Edition)
Android SDK: /Users/360logicaxamarinmacmini/Desktop/android-sdk-macosx_AndÃsdk
	Supported Android versions:
		1.6    (API level 4)
		2.1    (API level 7)
		2.2    (API level 8)
		2.3    (API level 10)
		3.1    (API level 12)
		3.2    (API level 13)
		4.0    (API level 14)
		4.0.3  (API level 15)
		4.1    (API level 16)
		4.2    (API level 17)
		4.3    (API level 18)
		4.4    (API level 19)
		4.4.87 (API level 20)
		4.5    (API level 21)
Java SDK: /usr
java version "1.7.0_65"
Java(TM) SE Runtime Environment (build 1.7.0_65-b17)
Java HotSpot(TM) 64-Bit Server VM (build 24.65-b04, mixed mode)

=== Xamarin.iOS ===

Version: (Trial Edition)
Hash: 3991e99
Build date: 2014-08-22 13:09:34-0400

=== Build Information ===

Release ID: 503000434
Git revision: 9b508e2173c6a211fa020d9743a86b484b5ed0d2
Build date: 2014-08-21 12:41:28-04
Xamarin addins: 69708b283b171ea053d0edfbf09d98457d21fbee

=== Operating System ===

Mac OS X 10.8.4
Darwin 360Logicas-Mac-mini.local 12.4.0 Darwin Kernel Version 12.4.0
    Sun Mar 10 18:01:10 PDT 2013
    root:xnu-2050.24.6~1/RELEASE_X86_64 x86_64
Comment 2 Michael 2015-05-20 18:05:45 UTC
I have checked and verified that this is working with Xamarin.Forms 1.4.2
The MessagingCenter only fires once.
Comment 3 Maarten 2015-07-21 04:37:31 UTC
Is broken in 1.4.3 , please fix! MessagingCenter is not getting cleared