xamarin/Xamarin.Forms

[Bug] Navigated event fired at startup for custom WebView on Android

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#8,954 opened on Dec 18, 2019

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a/customrenderera/webviewe/5 :clock5:help wantedin-progressp/Androidt/bug :bug:up-for-grabs

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Description

Description

If you create a custom renderer for Android WebView, the Navigated event is called during app startup. This results in behavior that Navigated event is called twice after launching the app.

  • The first call is when the app is starting - INCORRECT
  • The second call is when the page is loaded - CORRECT

Steps to Reproduce

  1. Download and open this project: App2.zip

  2. Put a breakpoint in this line in MainPage.xaml.cs

Debug.WriteLine("Navigated");
  1. Launch the app on Android.
  2. As you can see Navigated event is called twice. The first call is when the app is starting (during splash screen). Navigated event definitely should not be called at this moment.

Expected Behavior

Navigated event should be called only when the WebView page is loaded.

Actual Behavior

On Android Navigated event is also called during app startup.

Basic Information

  • Version with issue: 4.4.0.991265
  • IDE: Visual Studio 2019 16.4.1
  • Platform Target Frameworks:
    • Android: 9.0 (Pie)

Contributor guide

Research direction
Investigate the custom Android WebView renderer to determine why the Navigated event fires during app startup before page load. Trace the event lifecycle and check if there is an unintended invocation in the renderer's constructor or OnElementChanged method.
Tech stack
csharp
Domain
mobile
Issue type
Bug
DifficultyEstimated implementation difficulty for a new contributor, from 1 for very small changes to 5 for expert-level work.
2
Estimated timeA rough time range for an experienced contributor to investigate, implement, test, and prepare a pull request.
1-3 hours
Activity statusHow available the issue appears right now: fresh, active, stale, blocked, or waiting on maintainer input.
Active
ClarityHow clearly the issue explains the expected change, acceptance criteria, and next step.
Clear
Prerequisites
C#Xamarin.FormsAndroid
Newbie friendlinessA 1-100 score estimating how approachable this issue is for first-time contributors.
60