NET8 MAUI应用恢复时Plugin.Fingerprint生物验证无法终止问题

你在OnResume中使用async void调用指纹验证，且未配置取消机制，再加上应用恢复时UI上下文可能未完全就绪，导致验证弹窗无法响应取消操作，只能强制关闭应用。

1. 添加取消令牌控制验证生命周期 #

在App类中维护一个CancellationTokenSource实例，用于在应用再次进入后台时取消指纹验证请求：

private CancellationTokenSource _fingerprintCts;

protected override async void OnResume()
{
    base.OnResume(); // 务必调用基类方法

    _fingerprintCts?.Cancel(); // 取消之前未完成的请求
    _fingerprintCts = new CancellationTokenSource();

    var isAvailable = await CrossFingerprint.Current.IsAvailableAsync(true);
    if (isAvailable)
    {
        var request = new AuthenticationRequestConfiguration(
                                 "Login using biometrics", 
                                 "Confirm login with your biometrics")
        {
            AllowAlternativeAuthentication = true
        };

        try
        {
            var result = await CrossFingerprint.Current.AuthenticateAsync(request, _fingerprintCts.Token);
            Console.WriteLine(result.Status);
        }
        catch (OperationCanceledException)
        {
            // 处理取消逻辑
            Console.WriteLine("指纹验证已取消");
        }
    }
}

protected override void OnSleep()
{
    base.OnSleep();
    _fingerprintCts?.Cancel(); // 应用进入后台时取消验证
    _fingerprintCts?.Dispose();
    _fingerprintCts = null;
}

2. 绑定窗口Activated事件替代OnResume（可选更可靠方案） #

MAUI的OnResume可能在窗口完全激活前触发，导致指纹验证弹窗的UI上下文异常。可以改为监听窗口的Activated事件，确保UI就绪后再启动验证：

private CancellationTokenSource _fingerprintCts;

protected override void OnStart()
{
    base.OnStart();
    if (Application.Current.Windows.FirstOrDefault() is Window mainWindow)
    {
        mainWindow.Activated += MainWindow_Activated;
    }
}

private async void MainWindow_Activated(object sender, EventArgs e)
{
    _fingerprintCts?.Cancel();
    _fingerprintCts = new CancellationTokenSource();

    var isAvailable = await CrossFingerprint.Current.IsAvailableAsync(true);
    if (isAvailable)
    {
        var request = new AuthenticationRequestConfiguration(
                                 "Login using biometrics", 
                                 "Confirm login with your biometrics")
        {
            AllowAlternativeAuthentication = true
        };

        try
        {
            var result = await CrossFingerprint.Current.AuthenticateAsync(request, _fingerprintCts.Token);
            Console.WriteLine(result.Status);
        }
        catch (OperationCanceledException)
        {
            Console.WriteLine("指纹验证已取消");
        }
    }
}

protected override void OnSleep()
{
    base.OnSleep();
    _fingerprintCts?.Cancel();
    _fingerprintCts?.Dispose();
    _fingerprintCts = null;
}

关键注意点 #

• 必须在应用进入后台（OnSleep）时取消并释放CancellationTokenSource，避免内存泄漏和残留请求。
• 不要忽略OperationCanceledException，这是取消验证时的正常抛出，需要捕获处理。
• 调用base.OnResume()和base.OnSleep()确保MAUI生命周期的正常执行。

内容的提问来源于stack exchange，提问作者Enrico