MvxCommand中间的UI操作 [英] UI action in middle of MvxCommand
问题描述
我正在使用MvvmCross，但这可能是常规命令绑定.
I am using MvvmCross, but this may be general command binding.
当用户单击按钮时，应用程序需要额外的输入数据，然后才能继续执行我想在实际命令中执行的操作.我无法在ViewModel的中间调用UI操作的问题，因此仅绑定MvxCommand(或任何ICommand)将无法工作.
When user click a button, the application require an extra input data before proceed to what I want to do in the actual command. The problem that I cannot call an UI action in middle of ViewModel, so just binding MvxCommand (or any ICommand) would not work.
一个人可能会问为什么: 1)我没有在用户界面上输入任何内容，用户可以在单击按钮之前输入数据->我没有空间. 2)设置默认数据，然后让用户稍后进行更改->虽然这是我的第一个操作，但用户往往忘记稍后进行更改！
One may ask why: 1) I don't put an input on the UI and user can enter data before click button -> I don't have space. 2) Make default data, and let user change it later -> This my first though, but user tend to forget to change it later!!
那么有人可以提出解决方案吗?我唯一能想到的就是忘记命令绑定，并在后面的代码中弹出ui以获取更多数据，然后在视图模型中调用方法！
So can someone come up with a solution? The only thing I can think of is forgetting command binding, and have code behind pop the ui for extra data, then call a method in view model!
谢谢
推荐答案
有几种方法可以做到这一点.
There are several ways to do this.
我个人首选的方式是使用交互请求"，这是我从Microsoft模式和实践的Prism框架中学到的.
My personal preferred way is to use an "Interaction Request" - something that I learnt from the Prism framework from Microsoft patterns and practices.
在Mvx中，可以使用ViewModel上的IMvxInteraction属性来执行此操作. https://github中显示了一个示例. com/slodge/BindingTalk/blob/master/BindingTalk.Core/ViewModels/QuestionViewModel.cs
In Mvx, you can do this using an IMvxInteraction property on your ViewModel. An example of this is shown in https://github.com/slodge/BindingTalk/blob/master/BindingTalk.Core/ViewModels/QuestionViewModel.cs
每次请求交互时，ViewModel都会为View提供一个对象-在本例中为YesNoQuestion:
Each time an interaction is requested, the ViewModel provides an object to the View - in this case a YesNoQuestion:
public class YesNoQuestion
{
public Action YesAction { get; set; }
public Action NoAction { get; set; }
public string QuestionText { get; set; }
public YesNoQuestion()
{
YesAction = () => { };
NoAction = () => { };
}
}
ViewModel使用IMvxInteraction<TQuestion>属性公开请求者:
The ViewModel exposes the requester using an IMvxInteraction<TQuestion> property:
public class QuestionViewModel
: MvxViewModel
{
private MvxInteraction<YesNoQuestion> _confirm = new MvxInteraction<YesNoQuestion>();
public IMvxInteraction<YesNoQuestion> Confirm
{
get { return _confirm; }
}
public IMvxCommand GoCommand
{
get
{
return new MvxCommand(() =>
{
var question = new YesNoQuestion()
{
QuestionText = "Close me now?",
YesAction = () => Close(this),
};
_confirm.Raise(question);
});
}
}
}
然后，每个平台上的视图都可以绑定并订阅交互请求属性.这有点奇怪-因为它使用弱引用来防止内存泄漏-特别是在iOS上，但在其他平台上也可能.
The view on each platform can then bind and subscribe to the interaction request property. This is a little fiddly - because it uses weak references to prevent memory leaks - especially on iOS, but also possible on other platforms too.
为此提供了一些示例Droid代码:
Some example Droid code for this is in:
- https: //github.com/slodge/BindingTalk/blob/master/BindingTalk.Droid/Views/2%20%20More%20Controls/QuestionView.cs
- 在
- https://github.com/slodge/BindingTalk/blob/master/BindingTalk.Droid/Views/2%20%20More%20Controls/QuestionView.cs
- with AXML in https://github.com/slodge/BindingTalk/blob/master/BindingTalk.Droid/Resources/Layout/QuestionView.axml
很抱歉，这里的ConfirmationView和QuestionView名称混乱-第一个是Android View，第二个是Mvvm View和Android Activity.
Sorry for the confusing ConfirmationView and QuestionView names here - the first is an Android View, the second is an Mvvm View and an Android Activity.
另外，请注意，在Android中实现对话框时，您需要注意屏幕旋转-因为Android的Activity生命周期可能会使这里的事情混乱-最简单的机制(我发现)是您自己处理屏幕旋转，而不是允许Android处理它.
Also, please note that when implementing Dialogs in Android, then you need to be careful about screen rotation - as Android's Activity lifecycle can very much confuse things here - easiest mecahnism (I find) is to just handle screen rotation yourself rather than allowing Android to handle it.
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