MvvmCross：ShowViewModel是否总是构造新实例？

When are new instances of the ViewModel and View created versus looked up and retrieved from a cache somewhere?

从不 – 对于新导航,默认行为始终是创建新实例.

if… how do I show my cached ViewModel instance?

如果出于某种原因想要覆盖ViewModel位置/创建,那么可以获得有关覆盖App.cs中的DefaultViewModelLocator的信息：

> MVVMCross Passing values to ViewModel that has 2 constructors
> http://slodge.blogspot.co.uk/2013/01/navigating-between-viewmodels-by-more.html

简而言之,实现您的代码：

public class MyViewModelLocator
  : MvxDefaultViewModelLocator
{
    public override bool TryLoad(Type viewModelType,IDictionary<string,string> parameterValueLookup,out IMvxViewModel model)
    {
        // your implementation
    }
}

然后在App.cs中返回它：

protected override IMvxViewModelLocator CreateDefaultViewModelLocator()
{
    return new MyViewModelLocator();
}

请注意,像How to replace MvxDefaultViewModelLocator in MVVMCross application这样的旧帖子仍然在概念上兼容 – 但这些旧帖子中的详细信息现已过时.