在后台代码中动态生成pivot项并设置EventTrigger和Action的绑定

最近在做今日头条WP的过程中，遇到需要动态生成Pivot项的问题。第一个版本是把几个频道写死在xaml里了，事件绑定也写在xaml里，每个频道绑定一个ObservableCollection<ArticleItem>。xaml中一个Pivot项的代码大体如下：

<phone:PivotItem Header="热点">
                <Grid Margin="12,0,0,0" >
                    <Grid.RowDefinitions>
                        <RowDefinition Height="*" />
                        <RowDefinition Height="Auto"/>
                        <RowDefinition Height="Auto"/>
                    </Grid.RowDefinitions>
                    <telerikPrimitives:RadDataBoundListBox

                UseOptimizedManipulationRouting="False"
                       DataVirtualizationMode="OnDemandAutomatic"
                IsPullToRefreshEnabled="True"
                EmptyContent=""
                IsAsyncBalanceEnabled="True"
                x:Name="radListBoxHot"
                Margin="0"
                CacheMode="BitmapCache"

                ItemsSource="{Binding ArticleItemListHot}"

                telerikCore:InteractionEffectManager.IsInteractionEnabled="True" ItemTemplate="{StaticResource ArticleItemDataTemplate}"   >
                        <i:Interaction.Triggers>
                            <i:EventTrigger EventName="ItemTap">
                                <i:InvokeCommandAction Command="{Binding CommandNavToArticleDetail}" CommandParameter="{Binding SelectedItem, ElementName=radListBoxHot}" />
                            </i:EventTrigger>
                            <i:EventTrigger EventName="DataRequested">
                                <i:InvokeCommandAction Command="{Binding CommandDataRequestedArticle}" CommandParameter="Hot"/>
                            </i:EventTrigger>
                            <i:EventTrigger EventName="RefreshRequested" >
                                <i:InvokeCommandAction Command="{Binding CommandRefreshRequestedArticle}" CommandParameter="Hot"/>
                            </i:EventTrigger>
                            <ec:PropertyChangedTrigger Binding="{Binding IsUIBusy}">
                                <i:Interaction.Behaviors>
                                    <ec:ConditionBehavior>
                                        <ec:ConditionalExpression>
                                            <ec:ComparisonCondition LeftOperand="{Binding IsUIBusy}" RightOperand="False"/>
                                        </ec:ConditionalExpression>
                                    </ec:ConditionBehavior>
                                </i:Interaction.Behaviors>
                                <action:StopPullToRefreshLoadingAction TargetObject="{Binding ElementName=radListBoxHot}"/>
                            </ec:PropertyChangedTrigger>
                        </i:Interaction.Triggers>

                        <telerikPrimitives:RadDataBoundListBox.ItemAddedAnimation>
                            <telerikCore:RadFadeAnimation StartOpacity="0" InitialDelay="0:0:0.3" EndOpacity="1"
                        Duration="0:0:0.9">
                                <telerikCore:RadFadeAnimation.Easing>
                                    <CubicEase EasingMode="EaseOut" />
                                </telerikCore:RadFadeAnimation.Easing>
                            </telerikCore:RadFadeAnimation>
                        </telerikPrimitives:RadDataBoundListBox.ItemAddedAnimation>
                        <telerikPrimitives:RadDataBoundListBox.ItemLoadingTemplate>
                            <DataTemplate>
                                <telerikPrimitives:RadBusyIndicator AnimationStyle="AnimationStyle9" IsRunning="{Binding IsUIBusy}" Content="努力加载ing..."/>
                            </DataTemplate>
                        </telerikPrimitives:RadDataBoundListBox.ItemLoadingTemplate>
                        <telerikPrimitives:RadDataBoundListBox.VirtualizationStrategyDefinition>
                            <telerikPrimitives:StackVirtualizationStrategyDefinition Orientation="Vertical"
                        />
                        </telerikPrimitives:RadDataBoundListBox.VirtualizationStrategyDefinition>
                    </telerikPrimitives:RadDataBoundListBox>

                </Grid>
            </phone:PivotItem>

ViewModel中要绑定几个command，实现点击项、下拉刷新、自动加载更多等，具体代码就不贴了，主要是根据CommandParameter来区分是触发哪个列表的事件。

这样实现的话，ViewModel中需要有n个ObservableCollection<ArticleItem>，代码重复的太多。

后来用户要求根据设置自定义首页频道，于是要改成后台代码生成的方式。因为首页枢轴里还有几个Pivot项不是文章列表，所以想在Page_Loaded事件中动态去生成所需的Pivot项，并手动设置绑定。

自定义频道的实体类：

    /// <summary>
    /// 用户固定在首页的自定义频道信息
    /// </summary>
    public class UserCategoryItem : BindableBase<UserCategoryItem>
    {

        public UserCategoryItem()
        {
            ArticleItemList = new ObservableCollection<ArticleListItem>();
            TempArticleItemList = new List<ArticleListItem>();
        }

        /// <summary>
        /// 频道
        /// </summary>
        public CategoryItem CurrentCategoryItem
        {
            get { return _CurrentCategoryItemLocator(this).Value; }
            set { _CurrentCategoryItemLocator(this).SetValueAndTryNotify(value); }
        }
        #region Property CategoryItem CurrentCategoryItem Setup
        protected Property<CategoryItem> _CurrentCategoryItem = new Property<CategoryItem> { LocatorFunc = _CurrentCategoryItemLocator };
        static Func<BindableBase, ValueContainer<CategoryItem>> _CurrentCategoryItemLocator = RegisterContainerLocator<CategoryItem>("CurrentCategoryItem", model => model.Initialize("CurrentCategoryItem", ref model._CurrentCategoryItem, ref _CurrentCategoryItemLocator, _CurrentCategoryItemDefaultValueFactory));
        static Func<CategoryItem> _CurrentCategoryItemDefaultValueFactory = () => { return default(CategoryItem); };
        #endregion

        /// <summary>
        /// 上次获取数据最大时间
        /// </summary>
        public string MaxBehotTime
        {
            get { return _MaxBehotTimeLocator(this).Value; }
            set { _MaxBehotTimeLocator(this).SetValueAndTryNotify(value); }
        }
        #region Property string MaxBehotTime Setup
        protected Property<string> _MaxBehotTime = new Property<string> { LocatorFunc = _MaxBehotTimeLocator };
        static Func<BindableBase, ValueContainer<string>> _MaxBehotTimeLocator = RegisterContainerLocator<string>("MaxBehotTime", model => model.Initialize("MaxBehotTime", ref model._MaxBehotTime, ref _MaxBehotTimeLocator, _MaxBehotTimeDefaultValueFactory));
        static Func<string> _MaxBehotTimeDefaultValueFactory = () => { return default(string); };
        #endregion

        /// <summary>
        /// 最小获取时间
        /// </summary>
        public string MinBehotTime
        {
            get { return _MinBehotTimeLocator(this).Value; }
            set { _MinBehotTimeLocator(this).SetValueAndTryNotify(value); }
        }
        #region Property string MinBehotTime Setup
        protected Property<string> _MinBehotTime = new Property<string> { LocatorFunc = _MinBehotTimeLocator };
        static Func<BindableBase, ValueContainer<string>> _MinBehotTimeLocator = RegisterContainerLocator<string>("MinBehotTime", model => model.Initialize("MinBehotTime", ref model._MinBehotTime, ref _MinBehotTimeLocator, _MinBehotTimeDefaultValueFactory));
        static Func<string> _MinBehotTimeDefaultValueFactory = () => { return default(string); };
        #endregion

        /// <summary>
        /// 文章内容
        /// </summary>
        public ObservableCollection<ArticleListItem> ArticleItemList
        {
            get { return _ArticleItemListLocator(this).Value; }
            set { _ArticleItemListLocator(this).SetValueAndTryNotify(value); }
        }
        #region Property ObservableCollection<ArticleListItem> ArticleItemList Setup
        protected Property<ObservableCollection<ArticleListItem>> _ArticleItemList = new Property<ObservableCollection<ArticleListItem>> { LocatorFunc = _ArticleItemListLocator };
        static Func<BindableBase, ValueContainer<ObservableCollection<ArticleListItem>>> _ArticleItemListLocator = RegisterContainerLocator<ObservableCollection<ArticleListItem>>("ArticleItemList", model => model.Initialize("ArticleItemList", ref model._ArticleItemList, ref _ArticleItemListLocator, _ArticleItemListDefaultValueFactory));
        static Func<ObservableCollection<ArticleListItem>> _ArticleItemListDefaultValueFactory = () => { return new ObservableCollection<ArticleListItem>(); };
        #endregion

        /// <summary>
        /// 排序
        /// </summary>
        public int SortOrder
        {
            get { return _SortOrderLocator(this).Value; }
            set { _SortOrderLocator(this).SetValueAndTryNotify(value); }
        }
        #region Property int SortOrder Setup
        protected Property<int> _SortOrder = new Property<int> { LocatorFunc = _SortOrderLocator };
        static Func<BindableBase, ValueContainer<int>> _SortOrderLocator = RegisterContainerLocator<int>("SortOrder", model => model.Initialize("SortOrder", ref model._SortOrder, ref _SortOrderLocator, _SortOrderDefaultValueFactory));
        static Func<int> _SortOrderDefaultValueFactory = () => { return default(int); };
        #endregion

    }

在程序首次运行时，如果用户还没有自定义频道，则自动添加默认的，否则从存储中读取，代码写在MainPage.xaml.cs里：

        private void MVVMPage_Loaded(object sender, RoutedEventArgs e)
        {
            if (pivotMain.Items.Count < )
            {
                MainPage_Model vm = this.LayoutRoot.DataContext as MainPage_Model;
                if (vm != null)
                {
                    vm.IsUIBusy = true;
                    List<UserCategoryItem> listLocal = FileHelper.Open<List<UserCategoryItem>>(Constants.UserCategoryItemListDataFileName);
                    if(listLocal.Any())
                    {
                        listLocal.ForEach(x => vm.UserCategoryItemList.Add(x));
                    }
                    if(!vm.UserCategoryItemList.Any())
                    {
                        UserCategoryItem item1 = new UserCategoryItem { CurrentCategoryItem = new CategoryItem { Name = "推荐", Category = "" }, SortOrder =  };
                        vm.UserCategoryItemList.Add(item1);
                        UserCategoryItem item2 = new UserCategoryItem { CurrentCategoryItem = new CategoryItem { Name = "热点", Category = "news_hot" }, SortOrder =  };
                        vm.UserCategoryItemList.Add(item2);
                        UserCategoryItem item3 = new UserCategoryItem { CurrentCategoryItem = new CategoryItem { Name = "社会", Category = "news_society" }, SortOrder =  };
                        vm.UserCategoryItemList.Add(item3);
                        UserCategoryItem item4 = new UserCategoryItem { CurrentCategoryItem = new CategoryItem { Name = "娱乐", Category = "news_entertainment" }, SortOrder =  };
                        vm.UserCategoryItemList.Add(item4);
                        UserCategoryItem item5 = new UserCategoryItem { CurrentCategoryItem = new CategoryItem { Name = "体育", Category = "news_sports" }, SortOrder =  };
                        vm.UserCategoryItemList.Add(item5);
                        FileHelper.Save<List<UserCategoryItem>>(Constants.UserCategoryItemListDataFileName, vm.UserCategoryItemList.ToList());
                    }

                    for (int i = ; i < vm.UserCategoryItemList.Count; i++)
                    {
                        UserCategoryItem item = vm.UserCategoryItemList[i];
                        //userCategoryItem.CurrentCategoryItem = new CategoryItem { Category = "", Name = "推荐" };
                        //vm.UserCategoryItemList.Add(userCategoryItem);
                        //手工添加pivot项
                        PivotItem pivot = new PivotItem();
                        pivot.Header = item.CurrentCategoryItem.Name;
                        Grid grid = new Grid();
                        grid.Margin = new Thickness(, -, , );
                        pivot.Content = grid;
                        RadDataBoundListBox listBox = new RadDataBoundListBox();
                        listBox.Name = string.Format("listBox{0}", i);
                        listBox.UseOptimizedManipulationRouting = false;
                        listBox.DataVirtualizationMode = DataVirtualizationMode.OnDemandAutomatic;
                        listBox.IsPullToRefreshEnabled = true;
                        listBox.IsAsyncBalanceEnabled = true;
                        listBox.ItemsSource = item.ArticleItemList;
                        listBox.ItemTemplate = App.Current.Resources["ArticleItemDataTemplate"] as DataTemplate;
                        listBox.ItemLoadingTemplate = App.Current.Resources["CommonItemLoadingDataTemplate"] as DataTemplate;
                        //listBox.ListHeaderTemplate = App.Current.Resources["CommonListHeaderDataTemplate"] as DataTemplate;
                        listBox.SetValue(InteractionEffectManager.IsInteractionEnabledProperty, true);
                        //listBox.ItemAddedAnimation = App.Current.Resources["CommonItemAddesAnimation"] as RadAnimation;
                        listBox.VirtualizationStrategyDefinition = new StackVirtualizationStrategyDefinition { Orientation = System.Windows.Controls.Orientation.Vertical };
                        listBox.Margin = new Thickness(, , , );
                        listBox.EmptyContentTemplate = App.Current.Resources["CommonEmptyDataTemplate"] as DataTemplate;
                        //手动添加EventTrigger

                        //设置目标属性
                        //BindingOperations.SetBinding(selectedItem, TextBlock.TextProperty, binding);
                        //var invokeCommandAction = new InvokeCommandAction { CommandParameter = "btnAdd" };

                        var triggers = Interaction.GetTriggers(listBox);

                        //添加ItemTap事件绑定
                        //#region ItemTap

                        //var itemTapInvokeCommandAction = new InvokeCommandAction();

                        //// create the command action and bind the command to it
                        //Binding itemTapParameterBinding = new Binding();
                        ////设置源对象
                        //itemTapParameterBinding.Source = listBox;
                        ////设置源属性
                        //itemTapParameterBinding.Path = new PropertyPath("SelectedItem");
                        ////ElementName与Source只能用一个
                        ////itemTapParameterBinding.ElementName = listBox.Name;
                        //BindingOperations.SetBinding(itemTapInvokeCommandAction, InvokeCommandAction.CommandParameterProperty, itemTapParameterBinding);

                        //var itemTapEventBinding = new Binding { Path = new PropertyPath("CommandNavToArticleDetail") };
                        //BindingOperations.SetBinding(itemTapInvokeCommandAction, InvokeCommandAction.CommandProperty, itemTapEventBinding);

                        //// create the event trigger and add the command action to it
                        //var itemTapEventTrigger = new System.Windows.Interactivity.EventTrigger { EventName = "ItemTap" };
                        //itemTapEventTrigger.Actions.Add(itemTapInvokeCommandAction);

                        //// attach the trigger to the control
                        //triggers.Add(itemTapEventTrigger);
                        //#endregion

                        //添加DataRequested事件绑定
                        #region DataRequested

                        var dataRequestedInvokeCommandAction = new InvokeCommandAction();

                        // create the command action and bind the command to it
                        Binding dataRequestedParameterBinding = new Binding();
                        //设置源对象
                        dataRequestedParameterBinding.Source = item;
                        //设置源属性
                        dataRequestedParameterBinding.Path = new PropertyPath("CurrentCategoryItem");
                        //dataRequestedParameterBinding.ElementName = listBox.Name;
                        BindingOperations.SetBinding(dataRequestedInvokeCommandAction, InvokeCommandAction.CommandParameterProperty, dataRequestedParameterBinding);

                        var dataRequestedEventBinding = new Binding { Path = new PropertyPath("CommandDataRequestedArticle") };
                        BindingOperations.SetBinding(dataRequestedInvokeCommandAction, InvokeCommandAction.CommandProperty, dataRequestedEventBinding);

                        // create the event trigger and add the command action to it
                        var dataRequestedEventTrigger = new System.Windows.Interactivity.EventTrigger { EventName = "DataRequested" };
                        dataRequestedEventTrigger.Actions.Add(dataRequestedInvokeCommandAction);

                        // attach the trigger to the control
                        triggers.Add(dataRequestedEventTrigger);
                        #endregion

                        //添加RefreshRequested事件绑定
                        #region RefreshRequested

                        var refreshRequestedInvokeCommandAction = new InvokeCommandAction();

                        // create the command action and bind the command to it
                        Binding refreshRequestedParameterBinding = new Binding();
                        //设置源对象
                        refreshRequestedParameterBinding.Source = item;
                        //设置源属性
                        refreshRequestedParameterBinding.Path = new PropertyPath("CurrentCategoryItem");
                        //refreshRequestedParameterBinding.ElementName = listBox.Name;
                        BindingOperations.SetBinding(refreshRequestedInvokeCommandAction, InvokeCommandAction.CommandParameterProperty, refreshRequestedParameterBinding);

                        var refreshRequestedEventBinding = new Binding { Path = new PropertyPath("CommandRefreshRequestedArticle") };
                        BindingOperations.SetBinding(refreshRequestedInvokeCommandAction, InvokeCommandAction.CommandProperty, refreshRequestedEventBinding);

                        // create the event trigger and add the command action to it
                        var refreshRequestedEventTrigger = new System.Windows.Interactivity.EventTrigger { EventName = "RefreshRequested" };
                        refreshRequestedEventTrigger.Actions.Add(refreshRequestedInvokeCommandAction);

                        // attach the trigger to the control
                        triggers.Add(refreshRequestedEventTrigger);
                        #endregion

                        #region 下拉刷新完成后停止
                        PropertyChangedTrigger stopPullToRefreshTrigger = new PropertyChangedTrigger();

                        Binding pullToRefreshBinding = new Binding();
                        pullToRefreshBinding.Path = new PropertyPath("IsUIBusy");
                        //stopPullToRefreshTrigger.SetValue(PropertyChangedTrigger.BindingProperty, pullToRefreshBinding);
                        //用下面这句不管用
                        BindingOperations.SetBinding(stopPullToRefreshTrigger, PropertyChangedTrigger.BindingProperty, pullToRefreshBinding);

                        StopPullToRefreshLoadingAction stopPullToRefreshLoadingAction = new StopPullToRefreshLoadingAction();
                        Binding stopPullToRefreshTargetObjectBinding = new Binding();
                        stopPullToRefreshTargetObjectBinding.ElementName = listBox.Name;
                        //stopPullToRefreshLoadingAction.SetValue(StopPullToRefreshLoadingAction.TargetObjectProperty, stopPullToRefreshTargetObjectBinding);
                        //用下面这句不管用
                        BindingOperations.SetBinding(stopPullToRefreshLoadingAction, StopPullToRefreshLoadingAction.TargetObjectProperty, stopPullToRefreshTargetObjectBinding);

                        stopPullToRefreshTrigger.Actions.Add(stopPullToRefreshLoadingAction);

                        Binding pullToRefreshBinding2 = new Binding();
                        pullToRefreshBinding2.Path = new PropertyPath("IsUIBusy");
                        ComparisonCondition condition = new ComparisonCondition();
                        BindingOperations.SetBinding(condition, ComparisonCondition.LeftOperandProperty, pullToRefreshBinding2);
                        condition.RightOperand = false;
                        condition.Operator = ComparisonConditionType.Equal;
                        ConditionalExpression expression = new ConditionalExpression();
                        expression.Conditions.Add(condition);
                        expression.ForwardChaining = ForwardChaining.And;
                        ConditionBehavior conditionBehavior = new ConditionBehavior();
                        conditionBehavior.Condition = expression;
                        conditionBehavior.Attach(stopPullToRefreshTrigger);

                        triggers.Add(stopPullToRefreshTrigger);

                        #endregion

                        grid.Children.Add(listBox);
                        this.pivotMain.Items.Insert(i, pivot);
                    }
                    vm.IsUIBusy = false;

                }
            }
        }

这里主要是用到了在代码中设置绑定的方法，一般要先初始化一个Binding,设置其Path、ElementName、Source等属性，然后调用BindingOperations.SetBinding()方法来进行绑定。主要麻烦的部分是设置EventTrigger的绑定，上面的代码基本是xaml里的绑定用后台代码翻译了一遍。

但这种方式仍然不太好，下个版本再修改一下，改成全部Pivot项都用绑定的方式。