Xamarin 表单 - 异步 ContentPage

Question

我有以下内容页面，我想在其中加载 Steema Teechart，但我不能，因为我无法使 MainPage 异步：

我的主页：

public class MainPage : ContentPage
{
    public MainPage (bool chart)
    {           
        ChartView chartView = new ChartView 
        { 
            VerticalOptions = LayoutOptions.FillAndExpand, 
            HorizontalOptions = LayoutOptions.FillAndExpand,
            HeightRequest = 300,
            WidthRequest = 400
        }; 

        LineModel test1 = new LineModel();
        chartView.Model = await test1.GetModel(); 

        //put the chartView in a grid and other stuff

        Content = new StackLayout { 
            HorizontalOptions = LayoutOptions.FillAndExpand,
            VerticalOptions = LayoutOptions.FillAndExpand,
            Children = {
                    grid
            }
        };
    }
}

我的线模型Class:

public class LineModel
{
        public async Task<Steema.TeeChart.Chart> GetModel ()
        { //some stuff happens here }
}

如何使 MainPage 异步以便 chartView.Model = await test1.GetModel(); 可以工作？我试过 "async MainPage" 但我收到错误。

Answer 1

不，你不能。 Constructor can't be async in C#;典型的解决方法是使用异步工厂方法。

public class MainPage : ContentPage
{
    public MainPage (bool chart)
    {           
        ChartView chartView = new ChartView 
        { 
            VerticalOptions = LayoutOptions.FillAndExpand, 
            HorizontalOptions = LayoutOptions.FillAndExpand,
            HeightRequest = 300,
            WidthRequest = 400
        };    
    }

    public static async Task<MainPage> CreateMainPageAsync(bool chart)
    {
         MainPage page = new MainPage();

        LineModel test1 = new LineModel();
        chartView.Model = await test1.GetModelAsync(); 
        page.Content = whatever;

        return page;
    }
}

然后用作

MainPage page = await MainPage.CreateMainPageAsync(true);

请注意，我已将 "Async" 后缀添加到方法 GetModel，这是用于异步方法的通用约定。

Xamarin 表单 - 异步 ContentPage

Xamarin Forms - async ContentPage

c#

asynchronous

async-await

xamarin.forms