Question

我是mahapps.metro主题的新人。当我使用ThemeManager时它只工作一次然后在第二次使用时它会引发一个空引用异常。例如，首先我选择它可以工作的蓝色主题，但在此之后我选择绿色主题它不起作用，并提出一个空参考例外。这是一个示例代码：

ThemeManager.ChangeAppStyle(Application.Current,
                                    ThemeManager.GetAccent("Blue"),
                                    ThemeManager.GetAppTheme("BaseDark"));
 ThemeManager.ChangeAppStyle(Application.Current,
                                    ThemeManager.GetAccent("Green"),
                                    ThemeManager.GetAppTheme("BaseDark"));

出了什么问题？

Answer 1

这一行应该在App.xaml代码的后面或在你的主Window构造函数中工作。

using System.Windows;
using MahApps.Metro;

namespace MetroDemo
{
    /// <summary>
    /// Interaction logic for App.xaml
    /// </summary>
    public partial class App : Application
    {
        protected override void OnStartup(StartupEventArgs e)
        {
            base.OnStartup(e);
            ThemeManager.ChangeAppStyle(Application.Current,
                                        ThemeManager.GetAccent("Blue"),
                                        ThemeManager.GetAppTheme("BaseDark"));
            ThemeManager.ChangeAppStyle(Application.Current,
                                        ThemeManager.GetAccent("Green"),
                                        ThemeManager.GetAppTheme("BaseDark"));
        }
    }
}

确保您要向App.xaml添加必要的资源，因为您想要更改应用程序的资源！

<Application x:Class="MetroDemo.App"
             xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
             xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
             StartupUri="MainWindow.xaml">
  <Application.Resources>
    <ResourceDictionary>
      <ResourceDictionary.MergedDictionaries>
        <!-- MahApps.Metro resource dictionaries. Make sure that all file names are Case Sensitive! -->
        <ResourceDictionary Source="pack://application:,,,/MahApps.Metro;component/Styles/Controls.xaml" />
        <ResourceDictionary Source="pack://application:,,,/MahApps.Metro;component/Styles/Fonts.xaml" />
        <ResourceDictionary Source="pack://application:,,,/MahApps.Metro;component/Styles/Colors.xaml" />
        <!-- Accent and AppTheme setting -->
        <ResourceDictionary Source="pack://application:,,,/MahApps.Metro;component/Styles/Accents/Blue.xaml" />
        <ResourceDictionary Source="pack://application:,,,/MahApps.Metro;component/Styles/Accents/BaseLight.xaml" />
      </ResourceDictionary.MergedDictionaries>
    </ResourceDictionary>
  </Application.Resources>
</Application>

希望这有帮助。

如何在代码behinde中使用ThemeManager

1 个答案: