教程：向匹配游戏 WinForms 应用中添加引用变量和计时器控件

项目
01/13/2024

在这四个教程系列中，你将构建一个匹配游戏，玩家在其中匹配隐藏的图标对。

匹配游戏程序需要跟踪玩家选择了哪些标签控件。在玩家选择第一个标签后，该程序应显示图标。在选择第二个标签后，该程序应短暂显示两个图标。然后隐藏这两个图标。

程序通过引用变量跟踪第一次和第二次分别选择的标签控件。计时器隐藏图标并控制显示图标的时间长度

添加标签引用。
添加计时器。

必备条件

本教程基于前面的教程，即创建匹配游戏应用程序和向匹配游戏中添加图标。请先完成这些教程的学习。

添加标签引用

本部分将向代码添加两个引用变量。它们跟踪或引用标签对象。

通过使用下面的代码向窗体中添加标签引用。

public partial class Form1 : Form
{
    // firstClicked points to the first Label control 
    // that the player clicks, but it will be null 
    // if the player hasn't clicked a label yet
    Label firstClicked = null;

    // secondClicked points to the second Label control 
    // that the player clicks
    Label secondClicked = null;

Public Class Form1

    ' firstClicked points to the first Label control 
    ' that the player clicks, but it will be Nothing 
    ' if the player hasn't clicked a label yet
    Private firstClicked As Label = Nothing

    ' secondClicked points to the second Label control 
    ' that the player clicks
    Private secondClicked As Label = Nothing

重要

使用此页右上角的编程语言控件查看 C# 代码片段或 Visual Basic 代码片段。

Programming language control for Microsoft Learn

这些语句不会导致窗体中显示标签控件，因为没有 new 关键字。当程序启动时，firstClicked 和 secondClicked 都设置为 null（对于 C#）或 Nothing（对于 Visual Basic）。

修改 Click 事件处理程序，以使用新的 firstClicked 引用变量。移除 label1_Click() 事件处理程序方法中的最后一个语句 (clickedLabel.ForeColor = Color.Black;)，并将它替换为下面的 if 语句。

/// <summary>
/// Every label's Click event is handled by this event handler
/// </summary>
/// <param name="sender">The label that was clicked</param>
/// <param name="e"></param>
private void label1_Click(object sender, EventArgs e)
{
    Label clickedLabel = sender as Label;

    if (clickedLabel != null)
    {
        // If the clicked label is black, the player clicked
        // an icon that's already been revealed --
        // ignore the click
        if (clickedLabel.ForeColor == Color.Black)
            return;

        // If firstClicked is null, this is the first icon 
        // in the pair that the player clicked,
        // so set firstClicked to the label that the player 
        // clicked, change its color to black, and return
        if (firstClicked == null)
        {
            firstClicked = clickedLabel;
            firstClicked.ForeColor = Color.Black;

            return;
        }
    }
}

''' <summary>
''' Every label's Click event is handled by this event handler
''' </summary>
''' <param name="sender">The label that was clicked</param>
''' <param name="e"></param>
''' <remarks></remarks>
Private Sub label_Click(ByVal sender As System.Object, 
                        ByVal e As System.EventArgs) Handles Label9.Click, 
    Label8.Click, Label7.Click, Label6.Click, Label5.Click, Label4.Click, 
    Label3.Click, Label2.Click, Label16.Click, Label15.Click, Label14.Click, 
    Label13.Click, Label12.Click, Label11.Click, Label10.Click, Label1.Click

    Dim clickedLabel = TryCast(sender, Label)

    If clickedLabel IsNot Nothing Then

        ' If the clicked label is black, the player clicked
        ' an icon that's already been revealed --
        ' ignore the click
        If clickedLabel.ForeColor = Color.Black Then Exit Sub

        ' If firstClicked is Nothing, this is the first icon 
        ' in the pair that the player clicked, 
        ' so set firstClicked to the label that the player
        ' clicked, change its color to black, and return
        If firstClicked Is Nothing Then
            firstClicked = clickedLabel
            firstClicked.ForeColor = Color.Black
            Exit Sub
        End If
    End If

End Sub

保存并运行程序。选择其中一个标签控件，它的图标将显示。选择下一个标签控件，发现没有任何反应。

只有选择的第一个图标会出现。其他图标是不可见的。

该程序已跟踪玩家选择的第一个标签。引用 firstClicked 不是 C# 中的 null 或 Visual Basic 中的 Nothing。当 if 语句发现 firstClicked 不等于 null 或 Nothing 时，会运行这些语句。

添加计时器

匹配游戏应用使用 Timer 控件。计时器等待后，触发一个称为“Tick”的事件。计时器可以启动操作或定期重复操作。

在程序中，计时器允许玩家选择两个图标。如果图标不匹配，则在短暂时间后再次隐藏这两个图标。

选择“工具箱”选项卡，在“组件”类别中，双击“计时器”组件或将其拖到窗体中。该计时器图标名为“timer1”，显示在窗体下的空间中。
选择“Timer1”图标以选中该计时器。在“属性”窗口中，选择“属性”按钮以查看属性。
将“间隔”属性设置为“750”，即 750 毫秒。

“间隔”属性将通知计时器两个时钟周期之间的等待时长，或何时触发 Tick 事件。在玩家选择第二个标签后，程序调用 Start() 方法启动计时器。

选择计时器控件图标，然后按 Enter，或双击计时器。 IDE 添加空的 Tick 事件处理程序。将代码替换为以下代码。

/// <summary>
/// This timer is started when the player clicks 
/// two icons that don't match,
/// so it counts three quarters of a second 
/// and then turns itself off and hides both icons
/// </summary>
/// <param name="sender"></param>
/// <param name="e"></param>
private void timer1_Tick(object sender, EventArgs e)
{
    // Stop the timer
    timer1.Stop();

    // Hide both icons
    firstClicked.ForeColor = firstClicked.BackColor;
    secondClicked.ForeColor = secondClicked.BackColor;

    // Reset firstClicked and secondClicked 
    // so the next time a label is
    // clicked, the program knows it's the first click
    firstClicked = null;
    secondClicked = null;
}

''' <summary>
''' This timer is started when the player clicks 
''' two icons that don't match,
''' so it counts three quarters of a second 
''' and then turns itself off and hides both icons
''' </summary>
''' <remarks></remarks>
Private Sub Timer1_Tick() Handles Timer1.Tick

    ' Stop the timer
    Timer1.Stop()

    ' Hide both icons
    firstClicked.ForeColor = firstClicked.BackColor
    secondClicked.ForeColor = secondClicked.BackColor

    ' Reset firstClicked and secondClicked 
    ' so the next time a label is
    ' clicked, the program knows it's the first click
    firstClicked = Nothing
    secondClicked = Nothing

End Sub

Tick 事件处理程序将执行三项操作：

通过调用 Stop() 方法确保计时器没有运行。
它使用两个引用变量 firstClicked 和 secondClicked，使得玩家选择的两个标签的图标再次不可见。
它将 firstClicked 和 secondClicked 引用变量重置为 null（C# 中）或 Nothing（Visual Basic 中）。

转至代码编辑器，将代码添加到 label1_Click() 事件处理程序方法的顶部和底部。此代码将检查计时器是否已启用，设置 secondClicked 引用变量，并启动计时器。 label1_Click() 事件处理程序方法现在如下所示：

/// <summary>
/// Every label's Click event is handled by this event handler
/// </summary>
/// <param name="sender">The label that was clicked</param>
/// <param name="e"></param>
private void label1_Click(object sender, EventArgs e)
{
    // The timer is only on after two non-matching 
    // icons have been shown to the player, 
    // so ignore any clicks if the timer is running
    if (timer1.Enabled == true)
        return;

    Label clickedLabel = sender as Label;

    if (clickedLabel != null)
    {
        // If the clicked label is black, the player clicked
        // an icon that's already been revealed --
        // ignore the click
        if (clickedLabel.ForeColor == Color.Black)
            return;

        // If firstClicked is null, this is the first icon
        // in the pair that the player clicked, 
        // so set firstClicked to the label that the player 
        // clicked, change its color to black, and return
        if (firstClicked == null)
        {
            firstClicked = clickedLabel;
            firstClicked.ForeColor = Color.Black;
            return;
        }

        // If the player gets this far, the timer isn't
        // running and firstClicked isn't null,
        // so this must be the second icon the player clicked
        // Set its color to black
        secondClicked = clickedLabel;
        secondClicked.ForeColor = Color.Black;

        // If the player gets this far, the player 
        // clicked two different icons, so start the 
        // timer (which will wait three quarters of 
        // a second, and then hide the icons)
        timer1.Start();
    }
}

''' <summary>
''' Every label's Click event is handled by this event handler
''' </summary>
''' <param name="sender">The label that was clicked</param>
''' <param name="e"></param>
''' <remarks></remarks>
Private Sub label_Click(ByVal sender As System.Object, 
                        ByVal e As System.EventArgs) Handles Label9.Click, 
    Label8.Click, Label7.Click, Label6.Click, Label5.Click, Label4.Click,  
    Label3.Click, Label2.Click, Label16.Click, Label15.Click, Label14.Click, 
    Label13.Click, Label12.Click, Label11.Click, Label10.Click, Label1.Click

    ' The timer is only on after two non-matching 
    ' icons have been shown to the player, 
    ' so ignore any clicks if the timer is running
    If Timer1.Enabled Then Exit Sub

    Dim clickedLabel = TryCast(sender, Label)

    If clickedLabel IsNot Nothing Then
        ' If the clicked label is black, the player clicked
        ' an icon that's already been revealed --
        ' ignore the click
        If clickedLabel.ForeColor = Color.Black Then Exit Sub

        ' If firstClicked is Nothing, this is the first icon 
        ' in the pair that the player clicked, 
        ' so set firstClicked to the label that the player 
        ' clicked, change its color to black, and return
        If firstClicked Is Nothing Then
            firstClicked = clickedLabel
            firstClicked.ForeColor = Color.Black
            Exit Sub
        End If

        ' If the player gets this far, the timer isn't 
        ' running and firstClicked isn't Nothing, 
        ' so this must be the second icon the player clicked
        ' Set its color to black
        secondClicked = clickedLabel
        secondClicked.ForeColor = Color.Black

        ' If the player gets this far, the player 
        ' clicked two different icons, so start the 
        ' timer (which will wait three quarters of 
        ' a second, and then hide the icons)
        Timer1.Start()
    End If

End Sub

该方法顶部的代码通过检查 Enabled 属性的值来检查计时器是否已启动。如果玩家选择第一个和第二个标签控件，且计时器启动，则选择第三个控件将不会执行任何操作。
该方法底部的代码将 secondClicked 引用变量设置为跟踪第二个标签控件。然后将该标签的图标颜色设置为黑色以使其可见。然后，它在单触发模式下启动计时器，以便在等待 750 毫秒后触发单个 Tick。计时器的 Tick 事件处理程序会隐藏这两个图标，并重置 firstClicked 和 secondClicked 引用变量。窗体准备就绪供玩家选择另一对图标。

注意

如果你复制和粘贴 label1_Click() 代码块，而不是手动输入代码，请确保替换现有的 label1_Click() 代码。否则，你将得到重复的代码块。

保存并运行程序。选择一个正方形，图标将变得可见。选择另一个正方形。图标会短暂显示，然后两个图标都消失。

程序现在跟踪你选择的第一个和第二个图标。它使用计时器在使图标消失之前暂停。

后续步骤

请继续阅读下一篇教程，了解如何完成匹配游戏。

为匹配游戏显示祝贺消息

通过

教程：向匹配游戏 WinForms 应用中添加引用变量和计时器控件

必备条件

添加标签引用

添加计时器

后续步骤

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