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WPF實現主題更換的簡單DEMO

handle lock except protect -name 綁定 一個 space 更換

WPF實現主題更換的簡單DEMO

實現主題更換功能主要是三個知識點:

  1. 動態資源 ( DynamicResource )
  2. INotifyPropertyChanged 接口
  3. 界面元素與數據模型的綁定 (MVVM中的ViewModel)

Demo 代碼地址:GITHUB

下面開門見山,直奔主題

一、準備主題資源

在項目 (怎麽建項目就不說了,百度上多得是) 下面新建一個文件夾 Themes,主題資源都放在這裏面,這裏我就簡單實現了兩個主題 Light /Dark,主題只包含背景顏色一個屬性。

1. Themes

  1. 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>
  1. 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>

然後在程序的App.xaml中添加一個默認的主題
不同意義的資源最好分開到單獨的文件裏面,最後Merge到App.xaml裏面,這樣方便管理和搜索。

  1. 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、實現視圖模型 (ViewModel)

界面上我模仿 ModernUI ,使用ComboBox 控件來更換主題,所以這邊需要實現一個視圖模型用來被 ComboBox 綁定。

新建一個文件夾 Prensentation ,存放所有的數據模型類文件

1. NotifyPropertyChanged 類

NotifyPropertyChanged 類實現 INotifyPropertyChanged 接口,是所有視圖模型的基類,主要用於實現數據綁定功能。

abstract class NotifyPropertyChanged : INotifyPropertyChanged
{
    public event PropertyChangedEventHandler PropertyChanged;

    protected virtual void OnPropertyChanged([CallerMemberName]string propertyName = "")
    {
        PropertyChanged?.Invoke(this, new PropertyChangedEventArgs(propertyName));
    }
}

這裏面用到了一個 [CallerMemberName] Attribute ,這個是.net 4.5裏面的新特性,可以實現形參的自動填充,以後在屬性中調用 OnPropertyChanged 方法就不用在輸入形參了,這樣更利於重構,不會因為更改屬性名稱後,忘記更改 OnPropertyChanged 的輸入參數而導致出現BUG。具體可以參考 C# in depth (第五版) 16.2 節 的內容

2. Displayable 類

Displayable 用來實現界面呈現的數據,ComboBox Item上顯示的字符串就是 DisplayName 這個屬性

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();
            }
        }
    }
}

Link 類繼承自 Displayable ,主要用於保存界面上顯示的主題名稱(DisplayName),以及主題資源的路徑(Source)

class Link : Displayable
{
    private Uri _source = null;

    /// <summary>
    /// resource uri
    /// </summary>
    public Uri Source
    {
        get => _source;
        set
        {
            _source = value;
            OnPropertyChanged();
        }
    }
}

4. LinkCollection 類

LinkCollection 繼承自 ObservableCollection<Link>,被 ComboBoxItemsSource 綁定,當集合內的元素發生變化時,ComboBoxItems 也會一起變化。

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 類

ThemeManager 類用於管理當前正在使用的主題資源,使用單例模式 (Singleton) 實現。

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 類

SettingsViewModel 類用於綁定到 ComboBoxDataContext 屬性,構造器中會初始化 Themes 屬性,並將我們預先定義的主題資源添加進去。

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、實現視圖(View)

1.MainWindwo.xaml

主窗口使用 Border 控件來控制背景顏色,BorderBackground.Color 指向到動態資源 WindowBackgroundColor ,這個 WindowBackgroundColor 就是我們在主題資源中定義好的 Color 的 Key,因為需要動態更換主題,所以需要用DynamicResource 實現。

Border 背景動畫比較簡單,就是更改 SolidColorBrushColor 屬性。

ComboBox 控件綁定了三個屬性 :

  1. ItemsSource="{Binding Themes }" -> SettingsViewModel.Themes
  2. SelectedItem="{Binding SelectedTheme , Mode=TwoWay}" -> SettingsViewModel.SelectedTheme
  3. DisplayMemberPath="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

後臺代碼將 ComboBox.DataContext 引用到 SettingsViewModel ,實現數據綁定,同時監聽 ThemeManager.Current.PropertyChanged 事件,觸發背景動畫

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、總結

關鍵點:

  1. 綁定 ComboBox(View層)ItemsSourceSelectedItem 兩個屬性到 SettingsViewModel (ViewModel層)
  2. ComboBoxSelectedItem 被更改後,會觸發 ThemeManager 替換當前正在使用的主題資源(ThemeSource屬性)
  3. 視圖模型需要實現 INotifyPropertyChanged 接口來通知 WPF 框架屬性被更改
  4. 使用 DynamicResource 引用 會改變的 資源,實現主題更換。

另外寫的比較啰嗦,主要是給自己回過頭來復習看的。。。這年頭WPF也沒什麽市場了,估計也沒什麽人看吧 o(╥﹏╥)o

WPF實現主題更換的簡單DEMO