1. MVVM 模式基礎
   • 視圖模型（ViewModel）：MainViewModel類作為視圖模型，封裝了與視圖相關的屬性和命令。它實現了INotifyPropertyChanged接口，當屬性值發生改變時，通過OnPropertyChanged方法通知視圖進行更新，確保視圖與數據的一致性。
   • 視圖（View）：在 XAML 文件中定義，通過數據綁定將Button的Width和Height屬性與視圖模型的ButtonWidth和ButtonHeight屬性關聯起來，實現視圖對數據的展示。同時，將按鈕的點擊事件綁定到視圖模型的ResizeButtonCommand命令，使視圖的交互操作能觸發視圖模型中的邏輯。
2. 動畫創建與管理
   • Storyboard 初始化：在視圖模型的InitializeStoryboard方法中，創建了一個Storyboard對象_resizeStoryboard，用于管理和協調多個動畫。
   • DoubleAnimation 創建：為按鈕的寬度和高度變化分別創建了DoubleAnimation對象。這些動畫定義了從初始值（From屬性）到目標值（To屬性）的過渡，這里目標值是初始值的 1.5 倍。動畫的持續時間由Duration屬性設置為 0.5 秒，AutoReverse屬性設置為true，使動畫在到達目標值后自動反向播放，RepeatBehavior屬性設置為RepeatBehavior.Forever，讓動畫無限循環。
3. 命令綁定與參數傳遞
   • MyCommand 實現：定義了MyCommand類來實現ICommand接口，該類允許將一個Action<object>作為參數傳遞給構造函數，在按鈕點擊時執行相應的邏輯。
   • 命令綁定：在視圖模型的構造函數中，將ResizeButtonCommand初始化為MyCommand的實例，并關聯到ExecuteResizeButtonCommand方法，該方法處理按鈕點擊后的邏輯。
   • 參數傳遞：在視圖中，通過CommandParameter="{Binding ElementName=PART_Button}"將按鈕自身作為參數傳遞給命令。在視圖模型的ExecuteResizeButtonCommand方法中，通過判斷參數類型來獲取按鈕實例，以便正確設置動畫目標和啟動動畫。
4. 事件處理與狀態管理
   • 點擊事件處理：ExecuteResizeButtonCommand方法負責處理按鈕的點擊事件。它根據_isAnimating標志判斷當前動畫狀態，若正在動畫，則停止動畫并將按鈕大小恢復到初始值；若未動畫，則啟動動畫。每次點擊按鈕時，都會切換_isAnimating標志的值，以記錄動畫狀態。

? ? ? 5.代碼

MainWindow.xaml

<Window x:Class="WpfAppButtonResize.MainWindow"xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"xmlns:d="http://schemas.microsoft.com/expression/blend/2008"xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"xmlns:local="clr-namespace:WpfAppButtonResize"xmlns:local2="clr-namespace:WpfAppButtonResize.ViewModel"mc:Ignorable="d"Title="MainWindow" Height="350" Width="525"><Window.DataContext><local2:MainWindowViewModel/></Window.DataContext><Grid><Button Content="點擊我" Width="{Binding ButtonWidth}" Height="{Binding ButtonHeight}" Command="{Binding ResizeButtonCommand}"CommandParameter="{Binding ElementName=PART_Button}"Name="PART_Button"/></Grid>
</Window>

MainWindowViewModel.cs

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Windows;
using System.Windows.Controls;
using System.Windows.Input;
using System.Windows.Media.Animation;namespace WpfAppButtonResize.ViewModel
{public class MainWindowViewModel:Notify{private double _buttonWidth = 100;private double _buttonHeight = 50;private bool _isAnimating = false;private Storyboard _resizeStoryboard;public double ButtonWidth{get { return _buttonWidth; }set{_buttonWidth = value;OnPropertyChanged();}}public double ButtonHeight{get { return _buttonHeight; }set{_buttonHeight = value;OnPropertyChanged();}}public ICommand ResizeButtonCommand { get; private set; }public MainWindowViewModel(){ResizeButtonCommand = new MyCommand(ExecuteResizeButtonCommand);InitializeStoryboard();}private void InitializeStoryboard(){_resizeStoryboard = new Storyboard();// 寬度動畫DoubleAnimation widthAnimation = new DoubleAnimation{From = _buttonWidth,To = _buttonWidth * 1.5,Duration = TimeSpan.FromSeconds(0.5),AutoReverse = true,RepeatBehavior = RepeatBehavior.Forever};// 這里后續在設置目標時會修正_resizeStoryboard.Children.Add(widthAnimation);// 高度動畫DoubleAnimation heightAnimation = new DoubleAnimation{From = _buttonHeight,To = _buttonHeight * 1.5,Duration = TimeSpan.FromSeconds(0.5),AutoReverse = true,RepeatBehavior = RepeatBehavior.Forever};_resizeStoryboard.Children.Add(heightAnimation);}private void ExecuteResizeButtonCommand(object parameter){if (parameter is Button button){if (_isAnimating){_resizeStoryboard.Stop();ButtonWidth = 100;ButtonHeight = 50;}else{// 設置寬度動畫的目標和屬性路徑Storyboard.SetTarget(_resizeStoryboard.Children[0] as DoubleAnimation, button);Storyboard.SetTargetProperty(_resizeStoryboard.Children[0] as DoubleAnimation, new PropertyPath("(FrameworkElement.Width)"));// 設置高度動畫的目標和屬性路徑Storyboard.SetTarget(_resizeStoryboard.Children[1] as DoubleAnimation, button);Storyboard.SetTargetProperty(_resizeStoryboard.Children[1] as DoubleAnimation, new PropertyPath("(FrameworkElement.Height)"));_resizeStoryboard.Begin();}_isAnimating = !_isAnimating;}}}
}

MyCommand.cs

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Windows.Input;namespace WpfAppButtonResize
{public class MyCommand : ICommand{private readonly Action _execute;private readonly Action<object> _execute2;private readonly Func<bool> _canExecute;public MyCommand(Action<object> execute){_execute2 = execute;}public MyCommand(Action execute, Func<bool> canExecute = null){_execute = execute;_canExecute = canExecute;}public event EventHandler CanExecuteChanged{add { CommandManager.RequerySuggested += value; }remove { CommandManager.RequerySuggested -= value; }}public bool CanExecute(object parameter){return _canExecute == null || _canExecute();}public void Execute(object parameter){if (_execute != null){_execute();}else if (_execute2 != null){_execute2(parameter);}}}
}

Notify.cs

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Linq;
using System.Runtime.CompilerServices;
using System.Text;
using System.Threading.Tasks;namespace WpfAppButtonResize
{public abstract class Notify : INotifyPropertyChanged{public event PropertyChangedEventHandler PropertyChanged;public void OnPropertyChanged([CallerMemberName] string name = null){PropertyChanged?.Invoke(this, new PropertyChangedEventArgs(name));}}
}