从零开始编写一个办公软件（二、自适应窗口）

桌面开发通常需要面对因为屏幕大小不同产生的视觉过大或过小的问题，基本都会被要求做大小自适应处理。网上一般介绍的是ViewBox，简单方便，但不仅面临性能的问题，部分情况下还会出现UI失真。我这里介绍下更繁琐但实用的方法，虽然开发起来麻烦不少，但运行效果会好很多。
首先建立一个资源字典，把所有和尺寸相关的数值都放进这个字典文件中，举个例子：

<ResourceDictionary xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"xmlns:sys="clr-namespace:System;assembly=netstandard" xmlns:m="http://schemas.microsoft.com/netfx/2009/xaml/presentation"><!--#region Double--><sys:Double x:Key="D_1d5">1.5</sys:Double><sys:Double x:Key="D_2">2</sys:Double><sys:Double x:Key="D_8">8</sys:Double><sys:Double x:Key="D_30">30</sys:Double><sys:Double x:Key="D_45">45</sys:Double><sys:Double x:Key="D_48">48</sys:Double><sys:Double x:Key="D_640">640</sys:Double><sys:Double x:Key="D_960">960</sys:Double><!--#endregion--><!--#region Thickness--><m:Thickness x:Key="T_1d5">1.5</m:Thickness><m:Thickness x:Key="T_2">2</m:Thickness><m:Thickness x:Key="T_7">7</m:Thickness><m:Thickness x:Key="T_0_48_0_0">0 48 0 0</m:Thickness><!--#endregion--><!--#region Geometry--><m:Geometry x:Key="MinimizeButtonGeometry">M0,0 12,0</m:Geometry><m:Geometry x:Key="MaximizeButtonGeometry1">M0,0 12,0 12,10 0,10 z</m:Geometry><m:Geometry x:Key="MaximizeButtonGeometry2">M0,3 0,12 9,12 9,3 z M3,3 3,0 12,0 12,9 9,9</m:Geometry><m:Geometry x:Key="CloseButtonGeometry">M0,0 12,12 M12,0 0,12</m:Geometry><!--#endregion--><!--#region CornerRadius--><m:CornerRadius x:Key="CR_8">8</m:CornerRadius><!--#endregion-->
</ResourceDictionary>

然后是重点，千万不要在xaml里引用这个字典！
考虑到开发过程当中的设计问题，可以这么写：

<Window x:Class="LkWork.WPF.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:LkWork.WPF"mc:Ignorable="d" WindowStartupLocation="CenterScreen"Title="MainWindow" Height="{DynamicResource D_640}" Width="{DynamicResource D_960}"><Window.Resources><ResourceDictionary><ResourceDictionary.MergedDictionaries><d:ResourceDictionary Source="pack://application:,,,/LkWork.WPF;component/Resources/Styles/WindowSizeStyles.xaml"/></ResourceDictionary.MergedDictionaries></ResourceDictionary></Window.Resources><Grid></Grid>
</Window>

在ResourceDictionary前面加上d:，既不影响使用，又比较方便开发。

然后开始使用了，打开App.xaml.cs文件，替换代码

using Microsoft.Win32;
using System.Configuration;
using System.Data;
using System.Windows;
using System.Windows.Media;
using System.Windows.Threading;namespace LkWork.WPF
{/// <summary>/// Interaction logic for App.xaml/// </summary>public partial class App : Application{protected override void OnStartup(StartupEventArgs e){//监听显示设置变化事件SystemEvents.DisplaySettingsChanging += SystemEvents_DisplaySettingsChanging;InitializeAppSize();base.OnStartup(e);}private double WindowScale = 1;private void SystemEvents_DisplaySettingsChanging(object? sender, EventArgs e){InitializeAppSize();}private void InitializeAppSize(){ResourceDictionary resource = new ResourceDictionary() { Source = new Uri("pack://application:,,,/LkWork.WPF;component/Resources/Styles/WindowSizeStyles.xaml", UriKind.Absolute) };var firstKey = resource.Keys.Cast<string>().First();double scale = Math.Max(SystemParameters.PrimaryScreenWidth / 1920, SystemParameters.PrimaryScreenHeight / 1080);if (firstKey is not null){if (Math.Abs(scale - WindowScale) > 0.1) return; //缩放比例没有变化则不处理var old = this.Resources.MergedDictionaries.Where(x => x.Contains(firstKey)).FirstOrDefault();if (old is not null) this.Resources.MergedDictionaries.Remove(old);}//缩放比例有比较明显的变化，需要调整资源中的数值if (Math.Abs(scale - WindowScale) > 0.1){foreach (var key in resource.Keys.Cast<string>()){var value = resource[key];if (value is double d){resource.Remove(key);resource.Add(key, d * scale);}else if (value is Thickness t){resource.Remove(key);resource.Add(key, new Thickness(t.Left * scale, t.Top * scale, t.Right * scale, t.Bottom * scale));}else if (value is CornerRadius c){resource.Remove(key);resource.Add(key, new CornerRadius(c.TopLeft * scale, c.TopRight * scale, c.BottomRight * scale, c.BottomLeft * scale));}else if(value is Geometry g){g = g.Clone();g.Transform = new ScaleTransform(scale, scale, 0, 0);g.Freeze();resource.Remove(key);resource.Add(key, g);}}//窗口大小需要额外调整foreach (Window window in this.Windows){if (!double.IsNaN(window.Width)) window.Width *= scale / WindowScale;if (!double.IsNaN(window.Height)) window.Height *= scale / WindowScale;}}this.Resources.MergedDictionaries.Add(resource);WindowScale = scale;}}}

运行代码，调整显示缩放查看效果

我这里是成功更改大小了的，收工。