这是我的模特
public class Article { string Label{ get; set; } string Remark { get; set; } }
我的ViewModel
public class ArticleViewModel: MvxViewModel { public List<Article> Articles; .... }
我的layout.axml
…
<LinearLayout android:layout_width="0dip" android:layout_weight="6" android:layout_height="fill_parent" android:orientation="vertical" android:id="@+id/layoutArticleList"> <EditText android:layout_width="fill_parent" android:layout_height="wrap_content" android:id="@+id/editSearch" android:text="" android:singleLine="True" android:selectAllOnFocus="true" android:capitalize="characters" android:drawableLeft="@drawable/ic_search_24" local:MvxBind="{'Text':{'Path':'Filter','Mode':'TwoWay'}}" /> <Mvx.MvxBindableListView android:id="@+id/listviewArticle" android:choiceMode="singleChoice" android:layout_width="fill_parent" android:layout_height="fill_parent" android:orientation="vertical" local:MvxItemTemplate="@layout/article_rowlayout" local:MvxBind="{'ItemsSource':{'Path':'Articles'}}" /> </LinearLayout> ...
这就是我的问题,“article_rowlayout”
... <TableRow android:layout_width="wrap_content" android:layout_height="wrap_content" android:background="@color/blue"> <TextView android:id="@+id/rowArticleLabel" android:layout_width="0dip" android:layout_weight="14" android:layout_height="wrap_content" android:textSize="28dip" local:MvxBind="{'Text':{'Path':'Label'}}" /> <ImageButton android:src="@drawable/ic_modify" android:layout_width="0dip" android:layout_weight="1" android:layout_height="wrap_content" android:id="@+id/rowArticleButtonModify" android:background="@null" android:focusable="false" android:clickable="true" local:MvxBind="{'Click':{'Path':'MyTest'}}" /> ...
名为“MyTest”的“Click”命令链接在MvxBindableListView给出的项目上.换句话说,单击在我的模型“文章”中搜索命令“MyTest”,而不是我的ViewModel.如何更改该行为以链接我的ViewModel“ArticleViewModel”,它负责我的MvxBindableListView?
有什么建议?
解决方法
我通常采用两种方法:
>在列表上使用ItemClick
>继续使用Click但在ViewModel端进行一些重定向.
所以…… 1
本教程中的Main Menu有一个ViewModel,有点像:
public class MainMenuViewModel : MvxViewModel { public List<T> Items { get; set; } public IMvxCommand ShowItemCommand { get { return new MvxRelayCommand<T>((item) => /* do action with item */ ); } } }
这在axml中用作:
<Mvx.MvxBindableListView xmlns:android="http://schemas.android.com/apk/res/android" xmlns:local="http://schemas.android.com/apk/res/Tutorial.UI.Droid" android:layout_width="fill_parent" android:layout_height="fill_parent" local:MvxBind="{'ItemsSource':{'Path':'Items'},'ItemClick':{'Path':'ShowItemCommand'}}" local:MvxItemTemplate="@layout/listitem_viewmodel" />
这种方法只能对整个列表项中的ItemClick进行 – 而不是对列表项中的单个子视图进行.
还是… 2
由于我们在mvx中没有任何RelativeSource绑定指令,因此可以在ViewModel / Model代码中完成此类重定向.
这可以通过呈现Model对象的行为启用包装器而不是Model对象本身来完成 – 例如使用List< ActiveArticle>:
public ActiveArticle { Article _article; ArticleViewModel _parent; public WrappedArticle(Article article,ArticleViewModel parent) { /* assignment */ } public IMvxCommand TheCommand { get { return MvxRelayCommand(() -> _parent.DoStuff(_article)); } } public Article TheArticle { get { return _article; } } }
然后你的axml必须使用如下绑定:
<TextView ... local:MvxBind="{'Text':{'Path':'TheArticle.Label'}}" />
和
<ImageButton ... local:MvxBind="{'Click':{'Path':'TheCommand.MyTest'}}" />
这种方法的一个例子是使用WithCommand的会议样本
但请注意,使用WithCommand< T>时我们发现内存泄漏 – 基本上GarbageCollection拒绝收集嵌入式MvxRelayCommand – 这就是为什么WithCommand< T>是IDisposable,为什么BaseSessionListViewModel清除列表并在分离视图时处理WithCommand元素.
评论后更新:
如果您的数据列表很大 – 并且您的数据是固定的(您的文章是没有PropertyChanged的模型),并且您不希望产生创建大型List< WrappedArticle>的开销.那么解决这个问题的一种方法可能是使用WrappingList< T>类.
这与Microsoft代码中采用的方法非常相似 – 例如在WP7 / Silverlight – http://shawnoster.com/blog/post/Improving-ListBox-Performance-in-Silverlight-for-Windows-Phone-7-Data-Virtualization.aspx中的虚拟化列表中
对于您的文章,这可能是:
public class ArticleViewModel: MvxViewModel { public WrappingList<Article> Articles; // normal members... } public class Article { public string Label { get; set; } public string Remark { get; set; } } public class WrappingList<T> : IList<WrappingList<T>.Wrapped> { public class Wrapped { public IMvxCommand Command1 { get; set; } public IMvxCommand Command2 { get; set; } public IMvxCommand Command3 { get; set; } public IMvxCommand Command4 { get; set; } public T TheItem { get; set; } } private readonly List<T> _realList; private readonly Action<T>[] _realAction1; private readonly Action<T>[] _realAction2; private readonly Action<T>[] _realAction3; private readonly Action<T>[] _realAction4; public WrappingList(List<T> realList,Action<T> realAction) { _realList = realList; _realAction = realAction; } private Wrapped Wrap(T item) { return new Wrapped() { Command1 = new MvxRelayCommand(() => _realAction1(item)),Command2 = new MvxRelayCommand(() => _realAction2(item)),Command3 = new MvxRelayCommand(() => _realAction3(item)),Command4 = new MvxRelayCommand(() => _realAction4(item)),TheItem = item }; } #region Implementation of Key required methods public int Count { get { return _realList.Count; } } public Wrapped this[int index] { get { return Wrap(_realList[index]); } set { throw new NotImplementedException(); } } #endregion #region NonImplementation of other methods public IEnumerator<Wrapped> GetEnumerator() { throw new NotImplementedException(); } IEnumerator IEnumerable.GetEnumerator() { return GetEnumerator(); } public void Add(Wrapped item) { throw new NotImplementedException(); } public void Clear() { throw new NotImplementedException(); } public bool Contains(Wrapped item) { throw new NotImplementedException(); } public void CopyTo(Wrapped[] array,int arrayIndex) { throw new NotImplementedException(); } public bool Remove(Wrapped item) { throw new NotImplementedException(); } public bool IsReadOnly { get; private set; } #endregion #region Implementation of IList<DateFilter> public int IndexOf(Wrapped item) { throw new NotImplementedException(); } public void Insert(int index,Wrapped item) { throw new NotImplementedException(); } public void RemoveAt(int index) { throw new NotImplementedException(); } #endregion }