unoplatform/uno

Remove reflection to Uno.Toolkit

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#782 opened on Apr 17, 2019

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area/performance 📈difficulty/starter 🚀good first issuekind/enhancementlow-hanging-🍒no-repro

Description

I'm submitting a...

  • Feature request

Current behavior

Currently some classes in Uno.UI are using reflection to access classes in the toolkit and interact with them. This is not extensible, and in some cases the dependency can be inverted.

For instance Android's NativeFramePresenter seek for the CommandBarExtensions https://github.com/nventive/Uno/blob/master/src/Uno.UI/NativeFramePresenter.Android.cs#L28 in order to update the visibility of the back button (https://github.com/nventive/Uno/blob/master/src/Uno.UI/NativeFramePresenter.Android.cs#L81).

Expected behavior

No cross-layer dependencies.

For the example above, the CommandBar could instead walk the tree to discover the Frame and register to the history change events to update the visibility by itself.

Minimal reproduction of the problem with instructions

N/A

Environment

Nuget Package: Uno.UI Package Version(s): irrelevant

Affected platform(s):

  • iOS
  • Android
  • WebAssembly
  • Windows
  • Build tasks

Visual Studio: irrelevant Relevant plugins: none

Contributor guide

Tech stack
csharp
Domain
mobilefrontenddesktop
Issue type
refactor
DifficultyEstimated implementation difficulty for a new contributor, from 1 for very small changes to 5 for expert-level work.
4
Estimated timeA rough time range for an experienced contributor to investigate, implement, test, and prepare a pull request.
3-5 days
Activity statusHow available the issue appears right now: fresh, active, stale, blocked, or waiting on maintainer input.
stale
ClarityHow clearly the issue explains the expected change, acceptance criteria, and next step.
clear
Prerequisites
Uno.UI architectureC# reflectionXAML tree walking
Newbie friendlinessA 1-100 score estimating how approachable this issue is for first-time contributors.
15
Research direction
Examine the current reflection usage in NativeFramePresenter.Android.cs (lines 28 and 81) to interact with CommandBarExtensions. The goal is to invert the dependency: instead of the presenter using reflection, the CommandBar should walk the visual tree to find the Frame and register to history change events to update the back button visibility. Review the toolkit's CommandBarExtensions and how the CommandBar can listen to Frame navigation events. Consider implementing an interface or event pattern to decouple the layers.