[Win8]Windows8开发笔记（十）：FlipView和自定义值转换器

新建一个项目叫做TestFlip，拖动一个FlipView到MainPage.xaml上面。

和前面说到的控件ListView一样，我们可以在代码中设置FlipView控件的元素格式和内容。

完整的xaml代码如下：

<Page    x:Class="TestFlip.MainPage"    xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"    xmlns:local="using:TestFlip"    xmlns:d="http://schemas.microsoft.com/expression/blend/2008"    xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"    mc:Ignorable="d">    <Grid Background="{StaticResource ApplicationPageBackgroundThemeBrush}">        <FlipView x:Name="myFlip" HorizontalAlignment="Center" VerticalAlignment="Center" Width="600" Height="400">            <FlipView.ItemTemplate>                <DataTemplate>                    <TextBlock Text="{Binding}"/>                </DataTemplate>            </FlipView.ItemTemplate>        </FlipView>    </Grid></Page>

接下来跳转到后台的代码处进行设置。

先将几张图片添加到项目中。新建一个文件夹：Images，然后将图片添加进去。

然后在后台代码里添加字符串数组用来存储这些图片的路径。

using System;using System.Collections.Generic;using System.IO;using System.Linq;using Windows.Foundation;using Windows.Foundation.Collections;using Windows.UI.Xaml;using Windows.UI.Xaml.Controls;using Windows.UI.Xaml.Controls.Primitives;using Windows.UI.Xaml.Data;using Windows.UI.Xaml.Input;using Windows.UI.Xaml.Media;using Windows.UI.Xaml.Navigation;// “空白页”项模板在 http://go.microsoft.com/fwlink/?LinkId=234238 上有介绍namespace TestFlip{    /// <summary>    /// 可用于自身或导航至 Frame 内部的空白页。    /// </summary>    public sealed partial class MainPage : Page    {        public MainPage()        {            this.InitializeComponent();        }        /// <summary>        /// 在此页将要在 Frame 中显示时进行调用。        /// </summary>        /// <param name="e">描述如何访问此页的事件数据。Parameter        /// 属性通常用于配置页。</param>        protected override void OnNavigatedTo(NavigationEventArgs e)        {            if (e.NavigationMode == NavigationMode.New)            {                string[] myString = new string[] {                     "ms-appx:///Images/1.jpg",                    "ms-appx:///Images/2.jpg",                    "ms-appx:///Images/3.jpg",                    "ms-appx:///Images/4.jpg",                    "ms-appx:///Images/5.jpg",                    "ms-appx:///Images/6.jpg",                };                myFlip.ItemsSource = myString;            }        }    }}

这样可以看到在FlipView中会显示相应的路径，并且有按钮可以切换。

接下来我们要把这些图片在FlipView中显示出来。

新建一个类叫做Person.cs文件用来存储人物姓名和图片路径：

using System;using System.Collections.Generic;using System.ComponentModel;using System.Linq;using System.Text;using System.Threading.Tasks;namespace TestFlip{    class Person : INotifyPropertyChanged    {        private string _name;        public string Name        {            get            {                return _name;            }            set            {                _name = value;                FirePropertyChanged("Name");            }        }        private string _imgPath;        public string ImgPath        {            get            {                return _imgPath;            }            set            {                _imgPath = value;                FirePropertyChanged("ImgPath");            }        }        private void FirePropertyChanged(string propName)        {            if (PropertyChanged != null)            {                PropertyChanged(this, new PropertyChangedEventArgs(propName));            }        }        public event PropertyChangedEventHandler PropertyChanged;    }}

接下来到MainPage.xaml.cs文件里进行如下修改：

using System;using System.Collections.Generic;using System.IO;using System.Linq;using Windows.Foundation;using Windows.Foundation.Collections;using Windows.UI.Xaml;using Windows.UI.Xaml.Controls;using Windows.UI.Xaml.Controls.Primitives;using Windows.UI.Xaml.Data;using Windows.UI.Xaml.Input;using Windows.UI.Xaml.Media;using Windows.UI.Xaml.Navigation;// “空白页”项模板在 http://go.microsoft.com/fwlink/?LinkId=234238 上有介绍namespace TestFlip{    /// <summary>    /// 可用于自身或导航至 Frame 内部的空白页。    /// </summary>    public sealed partial class MainPage : Page    {        public MainPage()        {            this.InitializeComponent();        }        /// <summary>        /// 在此页将要在 Frame 中显示时进行调用。        /// </summary>        /// <param name="e">描述如何访问此页的事件数据。Parameter        /// 属性通常用于配置页。</param>        protected override void OnNavigatedTo(NavigationEventArgs e)        {            if (e.NavigationMode == NavigationMode.New)            {                List<Person> people = new List<Person>();                people.Add(new Person() { Name = "Why1", ImgPath = "ms-appx:///Images/1.jpg" });                people.Add(new Person() { Name = "Why2", ImgPath = "ms-appx:///Images/2.jpg" });                people.Add(new Person() { Name = "Why3", ImgPath = "ms-appx:///Images/3.jpg" });                people.Add(new Person() { Name = "Why4", ImgPath = "ms-appx:///Images/4.jpg" });                people.Add(new Person() { Name = "Why5", ImgPath = "ms-appx:///Images/5.jpg" });                myFlip.ItemsSource = people;            }        }    }}

最后到xaml页面设置一下显示的内容：

<Page    x:Class="TestFlip.MainPage"    xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"    xmlns:local="using:TestFlip"    xmlns:d="http://schemas.microsoft.com/expression/blend/2008"    xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"    mc:Ignorable="d">    <Grid Background="{StaticResource ApplicationPageBackgroundThemeBrush}">        <FlipView x:Name="myFlip" HorizontalAlignment="Center" VerticalAlignment="Center" Width="600" Height="400">            <FlipView.ItemTemplate>                <DataTemplate>                    <Grid Background="DarkGray">                        <Grid.RowDefinitions>                            <RowDefinition></RowDefinition>                            <RowDefinition></RowDefinition>                        </Grid.RowDefinitions>                        <TextBlock Grid.Row="0" Text="{Binding Name}" FontSize="40" TextAlignment="Center"></TextBlock>                        <Image Source="{Binding ImagePath}" Grid.Row="1"></Image>                    </Grid>                </DataTemplate>            </FlipView.ItemTemplate>        </FlipView>    </Grid></Page>

便可以看到FlipView的效果了：

但是有一个问题，比如一个TextBox的Text可以显示int类型的Age数值，一个Image的ImageSource属性也可以用一个string来赋值，

但是如果是一个bool类型的值，想绑定在Visibility属性（枚举）上怎么办呢？

这时我们需要做一个数据转换。

我们在Person类里面添加一个属性：ShowImage来判断是否展现图片。

using System;using System.Collections.Generic;using System.ComponentModel;using System.Linq;using System.Text;using System.Threading.Tasks;namespace TestFlip{    class Person : INotifyPropertyChanged    {        private string _name;        public string Name        {            get            {                return _name;            }            set            {                _name = value;                FirePropertyChanged("Name");            }        }        private string _imagePath;        public string ImagePath        {            get            {                return _imagePath;            }            set            {                _imagePath = value;                FirePropertyChanged("ImgPath");            }        }        private bool _showImage;        public bool ShowImage        {            get            {                return _showImage;            }            set            {                _showImage = value;                FirePropertyChanged("ShowImage");            }        }        private void FirePropertyChanged(string propName)        {            if (PropertyChanged != null)            {                PropertyChanged(this, new PropertyChangedEventArgs(propName));            }        }        public event PropertyChangedEventHandler PropertyChanged;    }}

此时如果直接将其绑定到image的Visibility上是不可以的，因为Visibility是枚举类型：

这个时候我们就需要一个转换器。

xx-xx转换器，也就是Model-UI的转换。

新建一个类，命名为：BoolVisibilityConverter.cs。

using System;using System.Collections.Generic;using System.Linq;using System.Text;using System.Threading.Tasks;using Windows.UI.Xaml;using Windows.UI.Xaml.Data;namespace TestFlip{    class BoolVisibilityConverter : IValueConverter    {        public object Convert(object value, Type targetType, object parameter, string language)        {            //value是model中的数据，返回值是转换后UI中的数据            bool b = (bool)value;            return b ? Visibility.Visible : Visibility.Collapsed;        }        public object ConvertBack(object value, Type targetType, object parameter, string language)        {            //TwoWay绑定            Visibility v = (Visibility)value;            return v == Visibility.Visible;        }    }}

接下来到xaml界面中继续设置一下：

<Page    x:Class="TestFlip.MainPage"    xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"    xmlns:local="using:TestFlip"    xmlns:d="http://schemas.microsoft.com/expression/blend/2008"    xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"    mc:Ignorable="d">    <Page.Resources>        <local:BoolVisibilityConverter x:Key="BoolVisibilityConverter" />    </Page.Resources>        <Grid Background="{StaticResource ApplicationPageBackgroundThemeBrush}">        <FlipView x:Name="myFlip" HorizontalAlignment="Center" VerticalAlignment="Center" Width="600" Height="400">            <FlipView.ItemTemplate>                <DataTemplate>                    <Grid Background="DarkGray">                        <Grid.RowDefinitions>                            <RowDefinition></RowDefinition>                            <RowDefinition></RowDefinition>                        </Grid.RowDefinitions>                        <TextBlock Grid.Row="0" Text="{Binding Name}" FontSize="40" TextAlignment="Center"></TextBlock>                        <Image Source="{Binding ImagePath}" Visibility="{Binding ShowImage,Converter={StaticResource BoolVisibilityConverter}}" Grid.Row="1"></Image>                    </Grid>                </DataTemplate>            </FlipView.ItemTemplate>        </FlipView>    </Grid></Page>

这样就可以实现用bool值控制Visibility了。