Question

我正在研究xamarin。单击加载时的选项卡式页面。我想在后台通过api加载数据并显示加载指示器。

protected override void OnAppearing()
{
    base.OnAppearing();

    if (!_appeared)
    {
        // Want this to be run behind
        ProductViewData productViewData = new ProductViewData();
        products = productViewData.GetProductList("10");
        count = 10;

        productListView.ItemsSource = products;

        _appeared = true;
    }
}

感谢您的帮助。

Answer 1

您可以使方法异步并等待您的响应。您不应该从另一个线程更新UI线程，因此使用Task.Run是一个坏主意。 Take a look at Async Programming if you need more details

protected override async void OnAppearing()
{
    base.OnAppearing();

    if (!_appeared)
    {
        try
        {
            ProductViewData productViewData = new ProductViewData();
            // make the method asynchronous
            products = productViewData.GetProductListAsync("10");
            count = 10;

            productListView.ItemsSource = products;

            _appeared = true;
        }
        catch(Exception exception)
        {
            // good idea to catch any network exceptions
        }
    }
}

Answer 2

只需将Task.Run放入其中即可使用

protected override void OnAppearing()
    {
        base.OnAppearing();

        if (!_appeared) // Avoid repeat loding
        {
            activity.IsEnabled = true;
            activity.IsRunning = true;
            activity.IsVisible = true;

            var task = Task.Run(() =>
            {
                ProductViewData productViewData = new ProductViewData();
                products = productViewData.GetProductList("10");
                count = 10;
                productListView.ItemsSource = products;
            });

            _appeared = true;
        }
    }

如何在后台使用另一个线程运行代码

2 个答案: