android–MVVMCross从MvxBindableListView获取SelectedItem

概述我的Android应用程序的问题很小,我不知道如何使用MVVMCross解决它.这是我的ViewModel：publicclassAddressesShowViewModel:MvxViewModel{publicList<Address>Addresses{get;set;}publicAddressesShowViewModel(stringaddressesForListView){

我的Android应用程序的问题很小,我不知道如何使用MVVM Cross解决它.

这是我的viewmodel：

public class AddressesShowviewmodel : Mvxviewmodel{    public List<Address> Addresses { get; set; }    public AddressesShowviewmodel(string addressesForListVIEw)    {        Addresses = JsonConvert.DeserializeObject<List<Address>>(addressesForListVIEw);    }    public IMvxCommand Showitemcommand    {        get        {            //return new MvxRelayCommand<Type>((type) => this.RequestNavigate(type));            return new MvxRelayCommand(DoShowContact);        }    }    private Address selectedItem;    public Address SelectedItem    {        get { return selectedItem; }        set { selectedItem = value; FirePropertyChanged(() => SelectedItem); }    }    private voID DoShowContact()    {        RequestNavigate<AddressShowviewmodel>();    }}

我的AddressesShow.axml

<?xml version="1.0" enCoding="utf-8"?><FrameLayout    xmlns:androID="http://schemas.androID.com/apk/res/androID"    xmlns:local="http://schemas.androID.com/apk/res/INMobileCRM4AndroID.INMobileCRM4AndroID"    androID:layout_wIDth="fill_parent"    androID:layout_height="fill_parent"    ><Mvx.MvxBindableListVIEw    androID:layout_wIDth="fill_parent"    androID:layout_height="fill_parent"    local:MvxBind="{'ItemsSource':{'Path':'Addresses'},'ItemClick':{'Path':'Showitemcommand'}, 'SelectedItem':{'Path':'SelectedItem'}}"    local:MvxItemTemplate="@layout/addressListitem"  /></FrameLayout>

我想知道,我如何从AddressesShow.axml中的ListVIEw获取SelectedItem ..我试图创建一个Property’SelectedItem’..但它在开始时被调用,当viewmodel被创建时(显然正在返回) null),而不是单击Item时..它的btw是一种Address,而不仅仅是String或者什么……也许有什么建议吗？

解决方法:

Dir的SelectedItem缺乏在上周为DanIEl在Build的演讲做准备时被确定为一个问题.

要解决它,有几个快速的答案：

1您可以使用SelectedItemposition进行绑定 – 这是一个int

2您可以使用Click ICommand / IMvxCommand绑定而不是使用SelectedItem – 在您的示例中,这将是相同的axml但

public IMvxCommand Showitemcommand{    get    {        return new MvxRelayCommand<Address>(address => DoShowContact(address));    }}

要明确这个上面的点击选项就是我要用的.

如果确实需要SelectedItem ……

然后,为了得到一个完整的答案,DanIEl和我制作了一个新的绑定原型.使用以下方式注册此绑定：

        registry.RegisterFactory(new MvxCustomBindingFactory<MvxBindableListVIEw>("SelectedItem", adapterVIEw => new MvxAdapterVIEwSelectedItemTargetBinding(adapterVIEw)));

并包含逻辑：

using System;using AndroID.Widget;using CirrIoUs.MvvmCross.Binding.DroID.VIEws;using CirrIoUs.MvvmCross.Binding.Interfaces;using CirrIoUs.MvvmCross.Interfaces.Platform.Diagnostics;namespace CirrIoUs.MvvmCross.Binding.DroID.Target{#warning This needs to be redone for all adaptervIEws not just List vIEw!#warning The use of ItemClick instead of ItemSelected needs to be reinvestigated here!    public class MvxAdapterVIEwSelectedItemTargetBinding : MvxBaseandroidTargetBinding    {        private Readonly MvxBindableListVIEw _vIEw;        private object _currentValue;        public MvxAdapterVIEwSelectedItemTargetBinding(MvxBindableListVIEw vIEw)        {            _vIEw = vIEw;            ((ListVIEw)_vIEw).ItemClick += OnItemClick;        }        private voID OnItemClick(object sender, AdapterVIEw.ItemClickEventArgs itemClickEventArgs)        {            var container = (_vIEw.GetItemAtposition(itemClickEventArgs.position) as MvxJavaContainer);            if (container == null)            {                MvxBindingTrace.Trace(MvxTraceLevel.Warning, "Missing MvxJavaContainer in MvxAdapterVIEwSelectedItemTargetBinding");                return;            }            var newValue = container.Object;            if (!newValue.Equals(_currentValue))            {                _currentValue = newValue;                FireValueChanged(newValue);            }        }        public overrIDe voID SetValue(object value)        {#warning Sort out Equals test here            if (value != null && value != _currentValue)            {                var index = _vIEw.Adapter.Getposition(value);                if (index < 0)                {                    MvxBindingTrace.Trace(MvxTraceLevel.Warning, "Value not found for spinner {0}", value.ToString());                    return;                }                _currentValue = value;                _vIEw.SetSelection(index);            }        }        public overrIDe MvxBindingMode DefaultMode        {            get { return MvxBindingMode.TwoWay; }        }        public overrIDe Type targettype        {            get { return typeof(object); }        }        protected overrIDe voID dispose(bool isdisposing)        {            if (isdisposing)            {                ((ListVIEw)_vIEw).ItemClick -= OnItemClick;            }            base.dispose(isdisposing);        }    }}

为了测试这个工作,我使用Tutorial PullToRefresh代码改编使用：

<Mvx.MvxBindableListVIEw         androID:ID="@androID:ID/List"         androID:layout_wIDth="fill_parent"    androID:layout_height="fill_parent"    local:MvxBind="{'ItemsSource':{'Path':'Emails'},'ItemClick':{'Path':'Showitemcommand'},'SelectedItem':{'Path':'TheSelectedEmail'}}"    local:MvxItemTemplate="@layout/Listitem_email"/>

和：

    public class SimpleEmail    {        public string From { get; set; }            public string header { get; set; }            public string Message { get; set; }        }    private ObservableCollection<SimpleEmail> _emails;    public ObservableCollection<SimpleEmail> Emails    {        get { return _emails; }        private set { _emails = value; RaisePropertyChanged(() => Emails); }    }    private SimpleEmail _email;    public SimpleEmail TheSelectedEmail    {        get { return _email; }        set        {            _email = value;            MvxTrace.Trace(MvxTraceLevel.Error, "HELLO {0} ", value == null ? "null" : value.From);        }    }

在所有这些工作中要注意的一件事是AndroID中的列表视图选定项与Silverlight / wp中的列表框选定项略有不同 – 例如在androID中获取ListvIEw以突出当前选择可能会非常困难,并且很难让ListvIEw生成选择更改事件.

注意：我已将DroID SelectedItem上的问题记录到https://github.com/slodge/MvvmCross/issues/52 – 我将确保在不久的将来将绑定添加到核心库中

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