如何使用VisualStateManager而不是DataTrigger来实现动态绑定？

Question

我试图实现DataTrigger,根据在视图中切换的切换按钮执行动态绑定.但在搜索问题之后,WinRT中的DataTrigger？看起来这在Windows Universal应用程序中不可用,而应该使用VisualStateManager.

我的问题是,如何使用VisualStateManager实现以下代码的等效代码？或者从视图模型后面的代码中的属性设置动态绑定的任何其他替代方法.

这是我打算使用的XAML,直到我遇到这个问题,其中默认绑定是OrdinaryGradePointKV,当切换按钮切换时,绑定更改为HigherGradePointKV:

<ComboBox
     Grid.Row="1"
     Grid.Column="0"
     Grid.ColumnSpan="2"
     Width="60"
     HorizontalAlignment="Right"
     DisplayMemberPath="Key">
     <ComboBox.Style>
         <Style>
             <Setter Property="ComboBox.ItemsSource" Value="{Binding OrdinaryGradePointKV}"></Setter>
             <Style.Triggers>
                 <DataTrigger Binding="{Binding IsHigherToggled}" Value="True">
                     <Setter Property="ComboBox.ItemsSource"
                         Value="{Binding HigherGradePointKV}" />
                 </DataTrigger>
             </Style.Triggers>
         </Style>
     </ComboBox.Style>
 </ComboBox>

VM的精简版本如下所示,显示了绑定的属性:

namespace LC_Points.ViewModel
{

    public class MainViewModel : ViewModelBase
    {

        /// <summary>
        /// Initializes a new instance of the MainViewModel class.
        /// </summary>
        public MainViewModel()
        {
            //call methods to initialize list data
            GetSubjectTypes();
            GetOrdinaryGradePairs();
            GetHigherGradePairs();
        }


        public List<Score> Subjects { get; set; }
        public List<StringKeyValue> HigherGradePointKV { get; set; }
        public List<StringKeyValue> OrdinaryGradePointKV { get; set; }


        //ordinary toggle button bool
        private bool _isOrdinaryToggled;
        public bool IsOrdinaryToggled
        {
            get
            {
                return _isOrdinaryToggled;
            }
            set
            {
                _isOrdinaryToggled = value;
                RaisePropertyChanged("IsOrdinaryToggled");
            }
        }

        //Higher toggle button bool property
        private bool _isHigherToggled;
        public bool IsHigherToggled
        {
            get
            {
                return _isHigherToggled;
            }
            set
            {
                _isHigherToggled = value;
                RaisePropertyChanged("IsHigherToggled");
            }
        }




        public class StringKeyValue
        {
            public string Key { get; set; }
            public int Value { get; set; }
        }


        public void GetOrdinaryGradePairs()
        {

            List<StringKeyValue> ordianryGradePointKVTemp = new List<StringKeyValue>();


            ordianryGradePointKVTemp.Add(new StringKeyValue { Key = "A1", Value = 60 });
            ordianryGradePointKVTemp.Add(new StringKeyValue { Key = "A2", Value = 50 });
            ordianryGradePointKVTemp.Add(new StringKeyValue { Key = "B1", Value = 45 });
            ordianryGradePointKVTemp.Add(new StringKeyValue { Key = "B2", Value = 40 });
            ordianryGradePointKVTemp.Add(new StringKeyValue { Key = "B3", Value = 35 });
            ordianryGradePointKVTemp.Add(new StringKeyValue { Key = "C1", Value = 30 });
            ordianryGradePointKVTemp.Add(new StringKeyValue { Key = "C2", Value = 25 });
            ordianryGradePointKVTemp.Add(new StringKeyValue { Key = "C3", Value = 20 });
            ordianryGradePointKVTemp.Add(new StringKeyValue { Key = "D1", Value = 15 });
            ordianryGradePointKVTemp.Add(new StringKeyValue { Key = "D2", Value = 10 });
            ordianryGradePointKVTemp.Add(new StringKeyValue { Key = "D3", Value = 5 });
            ordianryGradePointKVTemp.Add(new StringKeyValue { Key = "E,F,NG", Value = 0 });
            ordianryGradePointKVTemp.Add(new StringKeyValue { Key = "Pass", Value = 30 });
            ordianryGradePointKVTemp.Add(new StringKeyValue { Key = "Merit", Value = 50 });
            ordianryGradePointKVTemp.Add(new StringKeyValue { Key = "Distinction", Value = 70 });


            OrdinaryGradePointKV = ordianryGradePointKVTemp;

        }


        public void GetHigherGradePairs()
        {

            List<StringKeyValue> higherGradePointKVTemp = new List<StringKeyValue>();


            higherGradePointKVTemp.Add(new StringKeyValue { Key = "A1", Value = 100 });
            higherGradePointKVTemp.Add(new StringKeyValue { Key = "A2", Value = 90 });
            higherGradePointKVTemp.Add(new StringKeyValue { Key = "B1", Value = 85 });
            higherGradePointKVTemp.Add(new StringKeyValue { Key = "B2", Value = 80 });
            higherGradePointKVTemp.Add(new StringKeyValue { Key = "B3", Value = 75 });
            higherGradePointKVTemp.Add(new StringKeyValue { Key = "C1", Value = 70 });
            higherGradePointKVTemp.Add(new StringKeyValue { Key = "C2", Value = 65 });
            higherGradePointKVTemp.Add(new StringKeyValue { Key = "C3", Value = 60 });
            higherGradePointKVTemp.Add(new StringKeyValue { Key = "D1", Value = 55 });
            higherGradePointKVTemp.Add(new StringKeyValue { Key = "D2", Value = 50 });
            higherGradePointKVTemp.Add(new StringKeyValue { Key = "D3", Value = 45 });
            higherGradePointKVTemp.Add(new StringKeyValue { Key = "E,F,NG", Value = 0 });
            higherGradePointKVTemp.Add(new StringKeyValue { Key = "Pass", Value = 30 });
            higherGradePointKVTemp.Add(new StringKeyValue { Key = "Merit", Value = 50 });
            higherGradePointKVTemp.Add(new StringKeyValue { Key = "Distinction", Value = 70 });


            HigherGradePointKV = higherGradePointKVTemp;
        }



        public void GetSubjectTypes()
        {
            List<Score> subjectList = new List<Score>();

            // Adding Subjects to List
            subjectList.Add(new Score { Subject = "Biology" });
            subjectList.Add(new Score { Subject = "Business" });
            subjectList.Add(new Score { Subject = "Business Group" });
            subjectList.Add(new Score { Subject = "Chemistry" });
            subjectList.Add(new Score { Subject = "Classical Studies" });

            Subjects = subjectList;

        }

    }
}

Answer 1

如果您想坚持使用DataTriggers,可以使用Microsoft.Xaml.Interactions.Core命名空间中的DataTriggerBehavior.添加行为的最简单方法是在Blend中打开项目并从资产窗格中添加它们.Blend会自动将BehaviorsXamlSDKManaged引用添加到项目中.

<ComboBox>
    <Interactivity:Interaction.Behaviors>
        <Core:DataTriggerBehavior Value="True" Binding="{Binding IsChecked, ElementName=toggleButton}">
            <Core:ChangePropertyAction PropertyName="ItemsSource" Value="{Binding OrdinaryGradePointKV}"/>
        </Core:DataTriggerBehavior>
        <Core:DataTriggerBehavior Value="False" Binding="{Binding IsChecked, ElementName=toggleButton}">
            <Core:ChangePropertyAction PropertyName="ItemsSource" Value="{Binding HighGradePointKV}"/>
        </Core:DataTriggerBehavior>
    </Interactivity:Interaction.Behaviors>
</ComboBox>

这可能比使用Visual States更适合您在这里使用.

如果要移动到Visual States,则可以为普通和高级状态的页面添加可视状态,并使这些状态为ComboBox的ItemsSource设置动画.假设默认绑定是普通的,你的VisualStateGroup看起来像这样:

<VisualStateGroup x:Name="GradePointStates">
    <VisualState x:Name="Higher">
        <Storyboard>
            <ObjectAnimationUsingKeyFrames Storyboard.TargetProperty="(ItemsControl.ItemsSource)" Storyboard.TargetName="comboBox">
                <DiscreteObjectKeyFrame KeyTime="0" Value="{Binding HigherGradePointKV}" />
            </ObjectAnimationUsingKeyFrames>
        </Storyboard>
    </VisualState>
    <VisualState x:Name="Ordinary">
    </VisualState>
</VisualStateGroup>

您可以从代码触发VisualState,也可以使用Behavior触发GoToStateAction:

<ToggleButton Content="ToggleButton">
    <Interactivity:Interaction.Behaviors>
        <Core:EventTriggerBehavior EventName="Checked">
            <Core:GoToStateAction StateName="Higher"/>
        </Core:EventTriggerBehavior>
        <Core:EventTriggerBehavior EventName="Unchecked">
            <Core:GoToStateAction StateName="Ordinary"/>
        </Core:EventTriggerBehavior>
    </Interactivity:Interaction.Behaviors>
</ToggleButton>