Question

我正在尝试制作一个应用程序，在硬币的头部标志和硬币的尾部图像之间切换。但是，每当我按下＆＃34; head＆＃34;按钮或＆＃34;尾巴＆＃34;按钮，发生错误。如何修复代码以便成功切换图像？

XAML：

<Window x:Class="HeadsOrTails.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:HeadsOrTails"
    mc:Ignorable="d"
    Title="MainWindow" Height="350" Width="525">
<Grid>
    <Image 
        x:Name="coinImage"
        HorizontalAlignment="Center"
        Height="100"
        Margin="43,10,374,209"
        VerticalAlignment="Center"
        Width="100"
        Loaded="Image_Loaded"/>
    <Button x:Name="tailsButton" Content="Show Tails" HorizontalAlignment="Center" Height="40" Margin="190,214,197,65" VerticalAlignment="Center" Width="130" Click="tailsButton_Click"/>
    <Button x:Name="headsButton" Content="Show Heads" HorizontalAlignment="Center" Height="40" Margin="43,214,344,65" VerticalAlignment="Center" Width="130" Click="headsButton_Click"/>
    <Button x:Name="exitButton" Content="Exit" HorizontalAlignment="Center" Height="40" Margin="339,214,48,65" VerticalAlignment="Center" Width="130" Click="exitButton_Click"/>

</Grid>
</Window>

C＃：

using System;
using System.Collections.Generic;
using System.Linq;
using System.Media;
using System.Text;
using System.Threading.Tasks;
using System.Windows;
using System.Windows.Controls;
using System.Windows.Data;
using System.Windows.Documents;
using System.Windows.Input;
using System.Windows.Media;
using System.Windows.Media.Imaging;
using System.Windows.Navigation;
using System.Windows.Shapes;

namespace HeadsOrTails
{
/// <summary>
/// Interaction logic for MainWindow.xaml
/// </summary>
public partial class MainWindow : Window
{
    public MainWindow()
    {
        InitializeComponent();
    }

    private void Image_Loaded(object sender, RoutedEventArgs e)
    {

    }

    private void tailsButton_Click(object sender, RoutedEventArgs e)
    {
        //create a second bitmap image (tails)
        BitmapImage c = new BitmapImage();
        c.BeginInit();
        c.UriSource = new Uri(@"C:\Users\Raymond\Documents\Visual Studio 2015\Projects\HeadsOrTails\tails.jpg");
        c.EndInit();

        var image = sender as Image;
        image.Source = c;
    }

    private void headsButton_Click(object sender, RoutedEventArgs e)
    {
        //create the new bitmap image (heads)
        BitmapImage b = new BitmapImage();
        b.BeginInit();
        b.UriSource = new Uri(@"C:\Users\Raymond\Documents\Visual Studio 2015\Projects\HeadsOrTails\heads.jpg");
        b.EndInit();

        var image = sender as Image;
        image.Source = b;
    }

    private void exitButton_Click(object sender, RoutedEventArgs e)
    {
        this.Close();
    }
}
}

Answer 1

你不能使用sender参数，因为那是Button，而不是Image控件。

请改为使用coinImage成员：

private void headsButton_Click(object sender, RoutedEventArgs e)
{
    coinImage.Source = new BitmapImage(new Uri(@"C:\Users\Raymond Karrenbauer\Documents\Visual Studio 2015\Projects\HeadsOrTails\heads.jpg"));
}

private void tailsButton_Click(object sender, RoutedEventArgs e)
{
    coinImage.Source = new BitmapImage(new Uri(@"C:\Users\Raymond Karrenbauer\Documents\Visual Studio 2015\Projects\HeadsOrTails\tails.jpg"));
}

除此之外，您应该将两个图像文件添加到Visual Studio项目中，将Build Action设置为Resource并通过Resource File Pack URI访问它们。这样您就不必处理绝对文件路径：

private void headsButton_Click(object sender, RoutedEventArgs e)
{
    coinImage.Source = new BitmapImage(new Uri("pack://application:,,,/heads.jpg"));
}

private void tailsButton_Click(object sender, RoutedEventArgs e)
{
    coinImage.Source = new BitmapImage(new Uri("pack://application:,,,/tails.jpg"));
}

然后，您还可以将BitmapImages添加为XAML资源：

<Window ...>
    <Window.Resources>
        <BitmapImage x:Key="heads" UriSource="heads.png"/>
        <BitmapImage x:Key="tails" UriSource="tails.png"/>
    </Window.Resources>
    ...
</Window>

并像这样使用它们：

private void headsButton_Click(object sender, RoutedEventArgs e)
{
    coinImage.Source = (ImageSource)Resources["heads"];
}

private void tailsButton_Click(object sender, RoutedEventArgs e)
{
    coinImage.Source = (ImageSource)Resources["tails"];
}

Answer 2

Clemens是绝对正确的，他的第二种选择远远优于它，因为每次翻转时它都不会重新加载位图。但是，如果我建议你做的更好的选择（恕我直言），而不是每次更改Source的{{1}}，你可能会想要有两个coinImage例如，Image和coinHeadsImage，并在这些coinTailsImage处理程序中翻转各自的Visibility属性。将Click包裹在他们自己的公共Image中，以便它们在可视树中重叠。我不是100％肯定，但我相信更改Grid的{{1}}比设置Visibility属性更有效率，无论哪种方式，都会更好体系结构，因为您可以使用适当的转换器将Images属性直接绑定到代码隐藏或视图模型中的假设Source属性。

此外，每次使用Visibility语法时，通常都应检查IsHeads的结果。与简单类型转换不同，如果在使用as时对象无法转换为所需类型，则不会出现异常。如果您检查了null，那么您会在那里发现错误。

如何在C＃WPF应用程序中切换图像？

2 个答案: