[英]Xamarin.Android and Spinner binding with ReactiveUI
I'm trying to bind to a Spinner using ReactiveUI in a Xamarin.Android application. 我正在尝试在Xamarin.Android应用程序中使用ReactiveUI绑定到Spinner。 To add items to the Spinner
, I need to use ArrayAdapter
. 要将项目添加到Spinner
,我需要使用ArrayAdapter
。 But ArrayAdapter
needs Android.Content.Context
. 但是ArrayAdapter
需要Android.Content.Context
。 Should I pass it into the ViewModel? 我应该将其传递给ViewModel吗?
Anyone know about an application written in Xamarin.Android, which uses ReactiveUI, where I could look inspiration? 任何人都知道用Xamarin.Android编写的使用ReactiveUI的应用程序,在哪里可以找到灵感? The ReactiveUI documentation only has a reference to a sample application written for iOS. ReactiveUI文档仅引用了为iOS编写的示例应用程序。
<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="fill_parent"
android:layout_height="fill_parent">
<TextView
android:id="@+id/Label"
android:text="Zařízení:"
android:layout_width="wrap_content"
android:layout_height="wrap_content"/>
<Spinner
android:id="@+id/Devices"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_toRightOf="@id/Label"/>
<Button
android:id="@+id/EditCommand"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_toRightOf="@+id/Devices"
android:text="Edit"/>
</RelativeLayout>
namespace Test.Droid
{
[Activity(Label = "Test.Droid", MainLauncher = true)]
public class MainActivity : ReactiveActivity, IViewFor<MainViewModel>
{
public Spinner Devices { get; private set; }
protected override void OnCreate(Bundle savedInstanceState)
{
base.OnCreate(savedInstanceState);
SetContentView(Resource.Layout.Main);
ViewModel = new MainViewModel();
this.WireUpControls();
// Bindings
this.Bind(this.ViewModel, ) // ?
}
private MainViewModel _viewModel;
public MainViewModel ViewModel
{ get => _viewModel; set { this.RaiseAndSetIfChanged(ref _viewModel, value); } }
object IViewFor.ViewModel
{ get => ViewModel; set { ViewModel = (MainViewModel)value; } }
}
}
namespace Test.Droid.ViewModels
{
public class MainViewModel : ReactiveObject
{
// How to databind Spinner Devices ?
public MainViewModel()
{
}
}
}
I haven't done any Xamarin.Android development, but in general you don't want to pass details about the view into the ViewModel - it should not know anything about the view. 我还没有做过Xamarin.Android开发,但是总的来说,您不想将有关视图的详细信息传递给ViewModel-它不应该对视图有任何了解。
I would expose the list of items as a collection (eg IList<Item>
) and use a converter on the binding to create an ArrayAdapter
: 我将项目列表作为集合公开(例如IList<Item>
),并在绑定上使用转换器创建ArrayAdapter
:
this.OneWayBind(this.ViewModel.Devices, this.View.Property, devices => new ArrayAdapter(devices));
this.View.Property
should refer to the property that changes whenever the list of devices changes. this.View.Property
应该引用每当设备列表更改时更改的属性。 The third parameter ( devices => new ArrayAdapter()
) receives the property from the ViewModel as an argument, you then return a value that can be set on the this.View.Property
. 第三个参数( devices => new ArrayAdapter()
)从ViewModel接收属性作为参数,然后返回可以在this.View.Property
上设置的this.View.Property
。
For example: 例如:
ViewModel.Count
is astring
ViewModel.Count
是一个string
View.Property
is anint
View.Property
是一个int
Bind like this: 像这样绑定:
this.OneWayBind(this.ViewModel.Count, this.View.Property, count => int.Parse(count));
The third parameter can be a function or lambda that accepts an argument of the type of the ViewModel property and returns a value of the type of the view property. 第三个参数可以是接受ViewModel属性类型的参数并返回view属性类型的值的函数或lambda。
I'd said I'd given in providing any feedback on Stackoverflow but anyway... we have a collection of binding extensions, one of which is for a Spinner. 我说过我会提供有关Stackoverflow的任何反馈,但是无论如何...我们有一系列绑定扩展,其中一个是Spinner。 in typical usage it looks like this 在典型用法中,它看起来像这样
// bind the options for the distance
this.BindSpinner(ViewModel,
vm => vm.TravelLimitSelected,
vm => vm.CurrentTravelLimit,
vm => vm.TravelLimitChoices.Distances,
f => f.travelLimitSpinner,
(items) =>
new ActionSpinnerAdapter<DistanceChoiceModel>((c, p) => new DistanceLimitViewHost(c, p), items));
where in this case, the extension method looks like 在这种情况下,扩展方法看起来像
public static IDisposable BindSpinner<TView, TViewModel, TCommandProp, TSpinnerViewModel>(
this TView view,
TViewModel viewModel,
Expression<Func<TViewModel, TCommandProp>> viewModelCommandName,
Expression<Func<TViewModel, int>> viewModelSelectedPropertyName,
Expression<Func<TViewModel, IList<TSpinnerViewModel>>> viewModelSourceItemsName,
Expression<Func<TView, Spinner>> spinnerControl, Func<IList<TSpinnerViewModel>, ISpinnerAdapter> adapterFactory) where TViewModel : RxViewModel
where TCommandProp : ICommand
where TView : class, IViewFor<TViewModel>
where TSpinnerViewModel : class
{
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