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WPF实现主题更换的简单DEMO

WPF实现主题更换的简单DEMO

实现主题更换功能主要是三个知识点:

    动态资源 ( DynamicResource )INotifyPropertyChanged 接口界面元素与数据模型的绑定 (MVVM中的ViewModel)

Demo 代码地址:GITHUB

下面开门见山,直奔主题

一、准备主题资源

在项目 (怎么建项目就不说了,百度上多得是) 下面新建一个文件夹 Themes,主题资源都放在这里面,这里我就简单实现了两个主题 Light /Dark,主题只包含背景颜色一个属性。

1. Themes

    Theme.Dark.xaml

<ResourceDictionary xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation" xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml" xmlns:local="clr-namespace:ModernUI.Example.Theme.Themes"> <Color x:Key="WindowBackgroundColor">#333</Color></ResourceDictionary>

    Theme.Light.xaml

<ResourceDictionary xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation" xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml" xmlns:local="clr-namespace:ModernUI.Example.Theme.Themes"> <Color x:Key="WindowBackgroundColor">#ffffff</Color></ResourceDictionary>

然后在程序的App.xaml中添加一个默认的主题不同意义的资源最好分开到单独的文件里面,最后Merge到App.xaml里面,这样方便管理和搜索。

    App.xaml

<Application x:Class="ModernUI.Example.Theme.App" xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation" xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml" xmlns:local="clr-namespace:ModernUI.Example.Theme" StartupUri="MainWindow.xaml"> <Application.Resources> <ResourceDictionary> <ResourceDictionary.MergedDictionaries> <ResourceDictionary Source="Themes/Theme.Light.xaml"/> </ResourceDictionary.MergedDictionaries> </ResourceDictionary> </Application.Resources></Application>

二、实现视图模型 (ViewModel)

界面上我模仿 ModernUI ,使用ComboBox 控件来更换主题,所以这边需要实现一个视图模型用来被 ComboBox 绑定。

新建一个文件夹 Prensentation ,存放所有的数据模型类文件

1. NotifyPropertyChanged 类

NotifyPropertyChanged 类实现 INotifyPropertyChanged 接口,是所有视图模型的基类,主要用于实现数据绑定功能。

abstract class NotifyPropertyChanged : INotifyPropertyChanged{ public event PropertyChangedEventHandler PropertyChanged; protected virtual void OnPropertyChanged([CallerMemberName]string propertyName = "") { PropertyChanged?.Invoke(this, new PropertyChangedEventArgs(propertyName)); }}

这里面用到了一个 [CallerMemberName] Attribute ,这个是.net 4.5里面的新特性,可以实现形参的自动填充,以后在属性中调用 OnPropertyChanged 方法就不用在输入形参了,这样更利于重构,不会因为更改属性名称后,忘记更改 OnPropertyChanged 的输入参数而导致出现BUG。具体可以参考 C# in depth (第五版) 16.2 节 的内容

2. Displayable 类

Displayable 用来实现界面呈现的数据,ComboBox Item上显示的字符串就是 DisplayName 这个属性

class Displayable : NotifyPropertyChanged{ private string _displayName { get; set; } /// <summary> /// name to display on ui /// </summary> public string DisplayName { get => _displayName; set { if (_displayName != value) { _displayName = value; OnPropertyChanged(); } } }}

3. Link 类

Link 类继承自 Displayable ,主要用于保存界面上显示的主题名称(DisplayName),以及主题资源的路径(Source)

class Link : Displayable{ private Uri _source = null; /// <summary> /// resource uri /// </summary> public Uri Source { get => _source; set { _source = value; OnPropertyChanged(); } }}

4. LinkCollection 类

LinkCollection 继承自 ObservableCollection<Link>,被 ComboBoxItemsSource 绑定,当集合内的元素发生变化时,ComboBoxItems 也会一起变化。

class LinkCollection : ObservableCollection<Link>{ /// <summary> /// Initializes a new instance of the <see cref="LinkCollection"/> class. /// </summary> public LinkCollection() { } /// <summary> /// Initializes a new instance of the <see cref="LinkCollection"/> class that contains specified links. /// </summary> /// <param name="links">The links that are copied to this collection.</param> public LinkCollection(IEnumerable<Link> links) { if (links == null) { throw new ArgumentNullException("links"); } foreach (var link in links) { Add(link); } }}

5.ThemeManager 类

ThemeManager 类用于管理当前正在使用的主题资源,使用单例模式 (Singleton) 实现。

class ThemeManager : NotifyPropertyChanged{ #region singletion private static ThemeManager _current = null; private static readonly object _lock = new object(); public static ThemeManager Current { get { if (_current == null) { lock (_lock) { if (_current == null) { _current = new ThemeManager(); } } } return _current; } } #endregion /// <summary> /// get current theme resource dictionary /// </summary> /// <returns></returns> private ResourceDictionary GetThemeResourceDictionary() { return (from dictionary in Application.Current.Resources.MergedDictionaries where dictionary.Contains("WindowBackgroundColor") select dictionary).FirstOrDefault(); } /// <summary> /// get source uri of current theme resource /// </summary> /// <returns>resource uri</returns> private Uri GetThemeSource() { var theme = GetThemeResourceDictionary(); if (theme == null) return null; return theme.Source; } /// <summary> /// set the current theme source /// </summary> /// <param name="source"></param> public void SetThemeSource(Uri source) { var oldTheme = GetThemeResourceDictionary(); var dictionaries = Application.Current.Resources.MergedDictionaries; dictionaries.Add(new ResourceDictionary { Source = source }); if (oldTheme != null) { dictionaries.Remove(oldTheme); } } /// <summary> /// current theme source /// </summary> public Uri ThemeSource { get => GetThemeSource(); set { if (value != null) { SetThemeSource(value); OnPropertyChanged(); } } }}

6. SettingsViewModel 类

SettingsViewModel 类用于绑定到 ComboBoxDataContext 属性,构造器中会初始化 Themes 属性,并将我们预先定义的主题资源添加进去。

ComboBox.SelectedItem -> SettingsViewModel.SelectedTheme

ComboBox.ItemsSource -> SettingsViewModel.Themes

class SettingsViewModel : NotifyPropertyChanged{ public LinkCollection Themes { get; private set; } private Link _selectedTheme = null; public Link SelectedTheme { get => _selectedTheme; set { if (value == null) return; if (_selectedTheme != value) _selectedTheme = value; ThemeManager.Current.ThemeSource = value.Source; OnPropertyChanged(); } } public SettingsViewModel() { Themes = new LinkCollection() { new Link { DisplayName = "Light", Source = new Uri(@"Themes/Theme.Light.xaml" , UriKind.Relative) } , new Link { DisplayName = "Dark", Source = new Uri(@"Themes/Theme.Dark.xaml" , UriKind.Relative) } }; SelectedTheme = Themes.FirstOrDefault(dcts => dcts.Source.Equals(ThemeManager.Current.ThemeSource)); }}

三、实现视图(View)

1.MainWindwo.xaml

主窗口使用 Border 控件来控制背景颜色,BorderBackground.Color 指向到动态资源 WindowBackgroundColor ,这个 WindowBackgroundColor 就是我们在主题资源中定义好的 Color 的 Key,因为需要动态更换主题,所以需要用DynamicResource 实现。

Border 背景动画比较简单,就是更改 SolidColorBrushColor 属性。

ComboBox 控件绑定了三个属性 :

    ItemsSource="{Binding Themes }" -> SettingsViewModel.ThemesSelectedItem="{Binding SelectedTheme , Mode=TwoWay}" -> SettingsViewModel.SelectedThemeDisplayMemberPath="DisplayName" -> SettingsViewModel.SelectedTheme.DisplayName

<Window ...> <Grid> <Border x:Name="Border"> <Border.Background> <SolidColorBrush x:Name="WindowBackground" Color="{DynamicResource WindowBackgroundColor}"/> </Border.Background> <Border.Resources> <Storyboard x:Key="BorderBackcolorAnimation"> <ColorAnimation Storyboard.TargetName="WindowBackground" Storyboard.TargetProperty="Color" To="{DynamicResource WindowBackgroundColor}" Duration="0:0:0.5" AutoReverse="False"> </ColorAnimation> </Storyboard> </Border.Resources> <ComboBox x:Name="ThemeComboBox" VerticalAlignment="Top" HorizontalAlignment="Left" Margin="30,10,0,0" Width="150" DisplayMemberPath="DisplayName" ItemsSource="{Binding Themes }" SelectedItem="{Binding SelectedTheme , Mode=TwoWay}" > </ComboBox> </Border> </Grid></Window>

2. MainWindow.cs

后台代码将 ComboBox.DataContext 引用到 SettingsViewModel ,实现数据绑定,同时监听 ThemeManager.Current.PropertyChanged 事件,触发背景动画

public partial class MainWindow : Window{ private Storyboard _backcolorStopyboard = null; public MainWindow() { InitializeComponent(); ThemeComboBox.DataContext = new Presentation.SettingsViewModel(); Presentation.ThemeManager.Current.PropertyChanged += AppearanceManager_PropertyChanged; } private void AppearanceManager_PropertyChanged(object sender, System.ComponentModel.PropertyChangedEventArgs e) { if (_backcolorStopyboard != null) { _backcolorStopyboard.Begin(); } } public override void OnApplyTemplate() { base.OnApplyTemplate(); if (Border != null) { _backcolorStopyboard = Border.Resources["BorderBackcolorAnimation"] as Storyboard; } }}

四、总结

关键点:

    绑定 ComboBox(View层)ItemsSourceSelectedItem 两个属性到 SettingsViewModel (ViewModel层)ComboBoxSelectedItem 被更改后,会触发 ThemeManager 替换当前正在使用的主题资源(ThemeSource属性)视图模型需要实现 INotifyPropertyChanged 接口来通知 WPF 框架属性被更改使用 DynamicResource 引用 会改变的 资源,实现主题更换。

另外写的比较啰嗦,主要是给自己回过头来复习看的。。。这年头WPF也没什么市场了,估计也没什么人看吧 o(╥﹏╥)o

欢迎阅读本文章: 李雨遥

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