爲什麼我在System.Drawing.dll中得到System.ArgumentException

Question

有人能幫我嗎？我試圖繪製圖像，我得到這個錯誤：

An unhandled exception of type 'System.ArgumentException' occurred in System.Drawing.dll"

有以下功能：被點擊的按鈕之前

Dim x, y, xlatime, ylungime As Integer 
Dim myImage As Image 
Dim folder As String 

Sub PictureBox1_Paint(sender1 As Object, er As PaintEventArgs) 
    Dim r As New Rectangle(x, y, xlatime, ylungime) 
    er.Graphics.DrawImage(myImage, r) 
End Sub 

Private Function deseneaza(ByVal poza As String, ByRef x_perm As Integer, ByRef y_perm As Integer, ByRef lungime As Integer, ByRef latime As Integer) 
    myImage = Image.FromFile(poza) 
    x = x_perm 
    y = y_perm 
    xlatime = latime 
    ylungime = lungime 
    Refresh() 
    Return Nothing 
End Function 

Private Sub joaca_buton_Click(sender As Object, e As EventArgs) Handles joaca_buton.Click 
    Timer1.Stop() 
    nor.Hide() 
    nor_mic.Hide() 
    logo.Hide() 
    exit_buton.Hide() 
    joaca_buton.Hide() 
    continua_buton.Hide() 
    optiuni_buton.Hide() 
    BackgroundImage.Dispose() 
    deseneaza(folder + "\incarcare1.png", 0, 0, 729, 1008) 
End Sub 

Answer 1

在PictureBox的Paint事件將被調用。在這種情況下，MyImage將是Nothing，因此在您嘗試繪製時會導致異常。更改油漆事件，包括檢查：

Sub PictureBox1_Paint(sender1 As Object, er As PaintEventArgs) 
    If myImage IsNot Nothing Then  
     Dim r As New Rectangle(x, y, xlatime, ylungime) 
     er.Graphics.DrawImage(myImage, r) 
    End If 
End Sub 

，並強制重繪，添加Picturebox1.Invalidate()到Sub joaca_buton_Click末。

Private Sub joaca_buton_Click(sender As Object, e As EventArgs) Handles joaca_buton.Click 
    'The rest of the sub here 
    deseneaza(folder + "\incarcare1.png", 0, 0, 729, 1008) 
    PictureBox1.Invalidate() 
End Sub