教學課程：將參考變數和計時器控制項新增至您的配對遊戲 WinForms 應用程式

發行項
10/05/2023

在此系列四個教學課程中，您會建置配對遊戲，讓玩家在其中配對隱藏圖示。

您的配對遊戲程式需要追蹤玩家所選擇的 Label 控制項。在玩家選擇第一個標籤之後，程式應該會顯示圖示。在選擇第二個標籤之後，程式應該會短暫地顯示這兩個圖示。然後，其會隱藏這兩個圖示。

您的程式會使用「參考變數」，追蹤您選擇的第一個和第二個標籤。計時器會隱藏圖示，並控制顯示圖示多久時間

新增標籤參考。
新增計時器。

必要條件

本教學課程以先前的教學課程 (建立配對遊戲應用程式和將圖示新增至您的配對遊戲) 為基礎。請先完成這些教學課程。

新增標籤參考

在本節中，您會將兩個「參考變數」新增至您的程式碼。其會追蹤或參考 Label 物件。

使用下列程式碼，將標籤參考加入至您的表單。

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

使用此頁面右上方的程式設計語言控制項來檢視 C# 程式碼片段或 Visual Basic 程式碼片段。

Programming language control for Microsoft Learn

這些陳述式不會導致 Label 控制項出現在表單上，因為沒有 new 關鍵字。當程式啟動時，firstClicked 和 secondClicked 都會設定為 null (適用於 C#) 或設定為 Nothing (適用於 Visual Basic)。

修改 Click 事件處理常式，以使用新的 firstClicked 參考變數。移除 label1_Click() 事件處理常式方法 (clickedLabel.ForeColor = Color.Black;) 中的最後一個陳述式，並將其取代為 if 陳述式，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)
{
    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

儲存並執行您的程式。選擇其中一個 Label 控制項，其圖示就會出現。選擇一個 Label 控制項，並注意什麼事也沒發生。

只有第一個選擇的圖示才會出現。其他圖示會看不見。

程式已追蹤玩家選擇的第一個標籤。參考 firstClicked 不是 C# 中的 null 或 Visual Basic 中的 Nothing。當您的 if 陳述式發現 firstClicked 不等於 null 或 Nothing 時，其會執行陳述式。

新增計時器

配對遊戲應用程式會使用 Timer 控制項。計時器會等候，然後引發事件，稱為「刻度」。計時器可以啟動動作或定期重複動作。

在您的程式中，計時器可讓玩家選擇兩個圖示。如果圖示不符，其會在短時間內再次隱藏這兩個圖示。

選取 [工具箱] 索引標籤，然後在 [元件] 類別中，按兩下 [計時器] 元件或將其拖曳至表單。稱為 timer1 的計時器圖示會出現在表單下方的空白處。
選取 Timer1 圖示以選取計時器。在 [屬性] 視窗中，選取 [屬性] 按鈕來檢視屬性。
將 Interval 屬性設定為 750，也就是 750 毫秒。

Interval 屬性會告知計時器，當其觸發其 Tick 事件時，在「刻度」之間要等候多久的時間。在玩家選擇第二個標籤之後，您的程式會呼叫 Start() 方法，以啟動計時器。

選擇計時器控制項圖示，然後按 Enter 鍵或按兩下計時器。 IDE 會新增空的刻度事件處理常式。使用下列程式碼取代程式碼。

/// <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

刻度事件處理常式會執行下列三件事情：

其會呼叫 Stop() 方法來確定計時器並未執行。
其會使用兩個參考變數 firstClicked 和 secondClicked，確定玩家所選兩個標籤的圖示再次看不見。
其會將 firstClicked 和 secondClicked 參考變數重設為 Visual C# 中的 null 和 Visual Basic 中的 Nothing。

移至程式碼編輯器，並將程式碼新增至 label1_Click() 事件處理常式方法的頂端和底部。此程式碼會檢查計時器是否已啟用、設定 secondClicked 參考變數，以及啟動計時器。 label1_Click() 事件處理常式方法現在看起來如下所示：

/// <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

位於方法頂端的程式碼會檢查計時器是否藉由核取 [Enabled] 屬性的值來啟動。如果玩家選擇第一個和第二個 Label 控制項，且計時器啟動了，則選擇第三個標籤後並不會執行任何動作。
方法底部的程式碼會設定 secondClicked 參考變數，來追蹤第二個 Label 控制項。然後，其會將該標籤圖示顏色設定為黑色，使其看得見。然後，其會以一次性模式啟動計時器，因此會等待 750 毫秒，而後引發單一刻度。計時器的刻度事件處理常式會隱藏兩個圖示，並重設 firstClicked 和 secondClicked 參考變數。表單已準備好讓玩家選擇另一對圖示。

注意

如果您是透過複製並貼上 label1_Click() 程式碼區塊而非手動輸入程式碼，請務必取代現有的 label1_Click() 程式碼。否則，您將會產生重複的程式碼區塊。

儲存並執行您的程式。選取正方形，圖示就會看得見。選擇另一個正方形。圖示會短暫出現，然後這兩個圖示會消失。

您的程式現在會追蹤您選擇的第一個和第二個圖示。其會使用計時器暫停，再讓圖示消失。

下一步

前進到下一個教學課程，以了解如何完成您的配對遊戲。

為您的配對遊戲顯示恭喜訊息

共用方式為

教學課程：將參考變數和計時器控制項新增至您的配對遊戲 WinForms 應用程式

必要條件

新增標籤參考

新增計時器

下一步

意見反應

其他資源