Can I return a PDF file from a BlazorWebView in a .NET MAUI wrapper?

Question

I'm building an APP which need to be published in both the IOS & Play Store.

Tech Stack

.NET MAUI Blazor project, the entire app is rendered inside a BlazorWebView. All data is retrieved via an API.

Problem statement

I have a page which contains multiple PDF downloads. I want the app to open the default PDF app installed on that device. Is this possible?

My attempts

I've tried the classic Blazor WASM way by using a javascript function (this works without MAUI wrapper), but it's not working in the current setup. No error, the app just doesn't return a file. Any tips from the MAUI / Blazor community are very welcome. I want to avoid having to write native code.

I'm sharing my current approach (which works in WASM without the MAUI wrapper)

C#

public async Task<File> DownloadPdf(string url, string name)
{
    using (HttpClient client = new HttpClient())
    {
        HttpResponseMessage response = await client.GetAsync(url);

        if (response.IsSuccessStatusCode)
        {
            var file = await response.Content.ReadAsByteArrayAsync();
            await JS.InvokeVoidAsync("BlazorDownloadFile", $"update.pdf", "application/pdf", file);
        }
    }
}

Javascript

window.BlazorDownloadFile = (filename, contentType, content) => {
        // Create the URL
        const file = new File([content], filename, { type: contentType });
        const exportUrl = URL.createObjectURL(file);

        // Create the <a> element and click on it
        const a = document.createElement("a");
        document.body.appendChild(a);
        a.href = exportUrl;
        a.download = filename;
        a.target = "_self";
        a.click();

        // We don't need to keep the object URL, let's release the memory
        // On older versions of Safari, it seems you need to comment this line...
        URL.revokeObjectURL(exportUrl);
    }

Opi · Accepted Answer · 2023-05-10 14:41:24Z

2

I have solved it with the information found here: https://learn.microsoft.com/en-us/dotnet/maui/platform-integration/appmodel/launcher?tabs=android

If anyone needs it, this is my adjusted code which opens the PDF in the correct app!

        if (response.IsSuccessStatusCode)
        {
            IsDownloading = true;

            var pdfByteArray = await response.Content.ReadAsByteArrayAsync();

            // cache the file
            string file = System.IO.Path.Combine(FileSystem.CacheDirectory, $"{name.Replace(" ", "-")}.pdf");
            await System.IO.File.WriteAllBytesAsync(file, pdfByteArray);

            IsDownloading = false;
            await Launcher.Default.OpenAsync(new OpenFileRequest(name, new ReadOnlyFile(file)));
        }

answered May 10, 2023 at 14:41

Opi

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