从可移植类库更新UI线程 [英] Update UI thread from portable class library

问题描述

我有一个运行在Windows Phone 8上的MVVM Cross应用程序，我最近将其移植到了使用可移植类库的地方.

I have an MVVM Cross application running on Windows Phone 8 which I recently ported across to using Portable Class Libraries.

视图模型位于可移植类库中，并且其中之一公开了一个属性，该属性通过数据绑定从Silverlight for WP工具包启用和禁用PerformanceProgressBar.

The view models are within the portable class library and one of them exposes a property which enables and disables a PerformanceProgressBar from the Silverlight for WP toolkit through data binding.

当用户按下按钮时，RelayCommand将启动一个后台进程，该进程将属性设置为true，这将启用进度条并进行后台处理.

When the user presses a button a RelayCommand kicks off a background process which sets the property to true which should enable the progress bar and does the background processing.

在将其移植到PCL之前，我能够从UI线程调用更改以确保启用进度条，但是Dispatcher对象在PCL中不可用.我该如何解决?

Before I ported it to a PCL I was able to invoke the change from the UI thread to ensure the progress bar got enabled, but the Dispatcher object isn't available in a PCL. How can I work around this?

谢谢

丹

推荐答案

如果您无权访问Dispatcher，则可以将BeginInvoke方法的委托传递给您的类:

If you don't have access to the Dispatcher, you can just pass a delegate of the BeginInvoke method to your class:

public class YourViewModel
{
    public YourViewModel(Action<Action> beginInvoke)
    {
        this.BeginInvoke = beginInvoke;
    }

    protected Action<Action> BeginInvoke { get; private set; }

    private void SomeMethod()
    {
        this.BeginInvoke(() => DoSomething());
    }
}

然后实例化(从可以访问调度程序的类中进行实例化):

Then to instanciate it (from a class that has access to the dispatcher):

var dispatcherDelegate = action => Dispatcher.BeginInvoke(action);

var viewModel = new YourViewModel(dispatcherDelegate);

---

或者您也可以在调度程序周围创建包装器.

---

Or you can also create a wrapper around your dispatcher.

首先，在您的可移植类库中定义一个IDispatcher接口:

First, define a IDispatcher interface in your portable class library:

public interface IDispatcher
{
    void BeginInvoke(Action action);
}

然后，在有权访问调度程序的项目中，实现接口:

Then, in the project who has access to the dispatcher, implement the interface:

public class DispatcherWrapper : IDispatcher
{
    public DispatcherWrapper(Dispatcher dispatcher)
    {
        this.Dispatcher = dispatcher;
    }

    protected Dispatcher Dispatcher { get; private set; }

    public void BeginInvoke(Action action)
    {
        this.Dispatcher.BeginInvoke(action);
    }
}

然后，您可以将该对象作为IDispatcher实例传递给您的可移植类库.

Then you can just pass this object as a IDispatcher instance to your portable class library.

这篇关于从可移植类库更新UI线程的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！