如何在 Android 上读取 MAUI/Xamarin 中的已部署文件

Question

I have a small MAUI app i'm testing with. Im trying to read a file that was part of the deployment. I have the code below, which works great in a Windows deploy of the MAUI app, but crashes in Android. What is the proper cross-platform way to do this?

        // TODO get from service or xml
        var path = AppDomain.CurrentDomain.BaseDirectory;
        //var path = System.IO.Path.GetDirectoryName(System.Reflection.Assembly.GetEntryAssembly().Location);
        var fullpath = Path.Combine(path, "Services\\questions.json");
        var json = File.ReadAllText(fullpath);

Answer 1

MAUI has a new way to access files included with the app: MauiAsset.

UPDATE: More detail in Resource Files section of Maui doc.

Early description in blog Announcing .NET MAUI Preview 4, Raw Assets:

.NET MAUI now makes it very easy to add other assets to your project and reference them directly while retaining platform-native performance. For example, if you want to display a static HTML file in a WebView you can add the file to your project and annotate it as a MauiAsset in the properties.

<MauiAsset Include="Resources\Raw\index.html" />

Tip: you can also use wildcards to enable all files in a directory:

... Include="Resources\Raw\*" ...

Then you can use it in your application by filename.

<WebView Source="index.html" />

MauiAssetPage.xaml:

<ContentPage xmlns="http://schemas.microsoft.com/dotnet/2021/maui"
             xmlns:x="http://schemas.microsoft.com/winfx/2009/xaml"
             x:Class="MauiTests.MauiAssetPage">
    <ContentPage.Content>
        <!-- By the time Maui is released, this is all you will need. -->
        <!-- The Init code-behind won't be needed. -->
        <WebView x:Name="MyWebView" Source="TestWeb.html" />
    </ContentPage.Content>
</ContentPage>

MauiAssetPage.xaml.cs:

using Microsoft.Maui.Controls;
using System.Threading.Tasks;

namespace MauiTests
{
    public partial class MauiAssetPage : ContentPage
    {
        public MauiAssetPage()
        {
            InitializeComponent();

            // *** Hopefully this block of code no longer needed for WebView Source. ***
            Device.BeginInvokeOnMainThread(async () =>
            {
                await InitAsync();
            });
        }


        // *** Hopefully this is no longer needed. ***
        private async Task InitAsync()
        {
            string filePath = "TestWeb.html";
            var stream = await FileSystem.OpenAppPackageFileAsync(filePath);

            if (stream != null)
            {
                string s = (new System.IO.StreamReader(stream)).ReadToEnd();
                this.MyWebView.Source = new HtmlWebViewSource { Html = s };
            }
        }
    }
}

TestWeb.html:

(whatever html you want)

In Solution Explorer, add TestWeb.html to your project. In its Properties, select Build Action = MauiAsset.