Question

我正在尝试为具有网格和刻度计数器的游戏制作一些代码，但网格只是尝试填充窗口而不是停止并且不显示刻度计数器。不断出现的错误是：

类型＆＃39; System.ObjectDisposedException＆＃39;的第一次机会异常。发生在System.Windows.Forms.dll
中

我不知道这意味着什么，我也不知道如何解决它。

继承我的代码：

Public Class Form1
    Dim G As Graphics
    Dim BBG As Graphics
    Dim BB As Bitmap
    Dim r As Rectangle

    Dim tSec As Integer = TimeOfDay.Second
    Dim tTicks As Integer = 0
    Dim MaxTicks As Integer = 0

    Dim IsRunning As Boolean = True

    Private Sub Form1_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load
        Me.Show()
        Me.Focus()

        G = Me.CreateGraphics
        BB = New Bitmap(Me.Width, Me.Height)

        StartGameLoop()
    End Sub

    Private Sub DrawGraphics()
        For X = 0 To 19
            For Y = 0 To 14
                r = New Rectangle(X * 32, Y * 32, 32, 32)

                G.FillRectangle(Brushes.BurlyWood, r)
                G.DrawRectangle(Pens.Black, r)
            Next
        Next
        G.DrawString("Ticks: " & tTicks & vbCrLf & _
                    "TPS: " & MaxTicks, Me.Font, Brushes.Black, 650, 0)

        G = Graphics.FromImage(BB)

        BBG = Me.CreateGraphics
        BBG.DrawImage(BB, 0, 0, Me.Width, Me.Height)

        G.Clear(Color.Wheat)
    End Sub

    Private Sub StartGameLoop()
        Do While IsRunning = True
            Application.DoEvents()



            DrawGraphics()

            TickCounter()
        Loop
    End Sub

    Private Sub TickCounter()
        If tSec = TimeOfDay.Second And IsRunning = True Then
            tTicks = tTicks + 1
        Else
            MaxTicks = tTicks
            tTicks = 0
            tSec = TimeOfDay.Second
        End If
    End Sub
End Class

Answer 1

你在这里利用了很多不好的做法......

首先，使用Me.CreateGraphics()是不好的，结果对象只能用一次绘制，这意味着你被迫多次调用它。连续调用它只会创建越来越多的图形对象，从而增加内存使用量。即使你在每次完成绘制时都要处理它们，它仍然是一个巨大的瓶颈，因为它会减慢处理速度。

其次，使用Application.DoEvents()是 非常糟糕的行为 ，并将像这样循环地刻录CPU。除非正确使用（您不会这样做），否则会导致意外和不可预测的行为。您获得的错误是这种意外行为的一个很好的例子。

我建议您阅读此MSDN博客，它解释了为什么 不应该 使用Application.DoEvents()：Keeping your UI Responsive and the Dangers of Application.DoEvents。

相反，为了正确执行此操作：

将Me.CreateGraphics()替换为您的表单Paint event，然后通过e.Graphics对象完成所有绘图。
用Timer替换游戏循环，不断调用Me.Invalidate()重绘表单。

例如：

Dim WithEvents GameTimer As New Timer() With {.Interval = 1}

Private Sub Form1_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load
    GameTimer.Start()
End Sub

Private GameTimer_Tick(sender As System.Object, e As System.EventArgs) Handles GameTimer.Tick
    Me.Invalidate() 'Redraw the form.
    TickCounter()
End Sub

Private Sub Form1_Paint(sender As System.Object, e As System.Windows.Forms.PaintEventArgs) Handles Me.Paint
    e.Graphics.Clear(Color.Wheat)

    For X = 0 To 19
        For Y = 0 To 14
            Dim r As New Rectangle(X * 32, Y * 32, 32, 32)

            e.Graphics.FillRectangle(Brushes.BurlyWood, r)
            e.Graphics.DrawRectangle(Pens.Black, r)
        Next
    Next

    e.Graphics.DrawString("Ticks: " & tTicks & vbCrLf & _
                          "TPS: " & MaxTicks, Me.Font, Brushes.Black, 650, 0)
End Sub

无法访问表单上的已处理对象

1 个答案: