在全局窗口之間傳遞值

Question

所以我嘗試使用公共變量將數據從Form1發送到Form2。我沒有得到任何錯誤，但字符串「另一個測試」沒有出現在Form1的文本框中。我這是做這件事的正確方法？

' ### Form1 ### 
Public Class Form1 
    Public MyData As String 

    Private Sub Form1_Load(ByVal sender As Object, ByVal e As System.EventArgs) Handles Me.Load 
     MyData = "test" 
    End Sub 
End Class 

' ### Form2 ### 
Public Class Form2 
    ' Form1 
    Private Form1 As New Form1 

    Private Sub Form2_Load(ByVal sender As Object, ByVal e As System.EventArgs) Handles Me.Load 
     If Form1.MyData = "test" Then 
      Form1.Textbox1.text = "another test" 
     End If 
    End Sub 
End Class 

Answer 1

這將是更好地設置MyData = "test"在Form1的構造函數，而不是在onload事件。更好的辦法是通過它的構造函數傳遞你想讓Form2知道的值。這使得它更清楚它的依賴者是誰而不是從靜態/全局狀態拉動。如果它確實需要使用Form1然後傳遞表單，如果它只需要字符串，然後只傳遞字符串。總是給班級最低限度的他們需要做他們的工作。這使得它們更加鬆散耦合，並且更容易測試和使用。

---

如果首先加載form1，這將是一種方法。原因是它可以讓你將現有的form1傳遞給form2的構造函數。否則，你要創建一個新的Form1中，我不認爲這是你想要做

Public Class Form2 
    Form Form1 

    Sub New(ByVal form1 as Form)  
     Form1 = form 
    EndSub 

    Private Sub Form2_Load(ByVal sender As Object, ByVal e As System.EventArgs) Handles Me.Load 
     If Form1.Data = "test" Then 
      Form1.Textbox1.text = "another test" 
     End If 
    End Sub 
End Class 

---

Public Class App 
    Sub Main 
     Form1 f1 = new Form1(); 
     // display f1 
     Form2 f2 = new Form2(f1); 
     // display f2 
    End Sub 
End Class 

Answer 2

的問題是，你正在創建2個Form1中clases，例如一個屬於yourproject什麼。 Form1上，第二個是yourproject.form2.form1，那becasue要創建屬於類形式2.

Public Class Form2 
' Form1 
Private Form1 As New Form1 ' in this line you are creating a new form1 class that belongs to form2 

Private Sub Form2_Load(ByVal sender As Object, ByVal e As System.EventArgs) Handles Me.Load 
    If Form1.MyData = "test" Then 
     Form1.Textbox1.text = "another test" 
    End If 
End Sub 
End Class 

一種新的形式，你有兩個選擇：

1. 刪除Private Form1 As New Form1。

2. 更改此行Form1.Textbox1爲nameofyourproject.form1，因此vb知道你正在談論的形式1。

希望它可以幫助

Answer 3

1）中提到的命名問題。如果VB不是困惑，我是

2）你做一個新的表單（新），但從不顯示它。 NEW運行如此，你可以在構造函數中傳遞信息。否則，您需要顯示Load中要執行的代碼的表單。

Public Class Form1 
Public MyData As String 

Private Sub Form1_Load(ByVal sender As Object, ByVal e As System.EventArgs) 
     Handles Me.Load 
    MyData = "test" 
End Sub 
End Class 

' ### Form2 ### 
Public Class Form2 
    ' Form1 
    ' really bad naming 
    'Private Form1 As New Form1 
    Private frm1 As New Form1   ' only a little better 

    Private Sub Form2_Load(ByVal sender As Object, ByVal e As System.EventArgs) 
     Handles Me.Load 

     frm1.Show ' SHOW form1 so the LOAD runs, not just NEW 

     If frm1 .MyData = "test" Then 
      frm1 .Textbox1.text = "another test" 
     End If 
    End Sub 
End Class 

Bravo用於實例化表單，但一般形式不應該與其他表單的控件混淆。換句話說，使用構造函數，但在這種情況下不行。如果你想讓Form2從Form1中獲取一些文本 - 誰創建了他。 Form1中：

Dim frm2 As New Form2("some data to pass") 

在窗口2：

Public Sub New(txt As String) 

    ' NEVER add code before the InitializeComponent call 
    ' This call is required by the Windows Form Designer. 
    InitializeComponent() 

    ' Add any initialization after the InitializeComponent() call. 
    Label1.Text = txt 

End Sub 

Answer 4

這可能是你想要什麼：

' --------- 
Public Class Form1 

    Private innerData As String 
    Public Property MyData() As String 
     Get 
      Return innerData 
     End Get 
     Set(ByVal value As String) 
      innerData = value 
     End Set 
    End Property 

    Public Property TextData() As String 
     Get 
      Return TextBox1.Text 
     End Get 
     Set(ByVal value As String) 
      TextBox1.Text = value 
     End Set 
    End Property 

End Class 

' --------- 
Public Class Form2 

    Private frm1 As New Form1 

    Protected Overrides Sub OnLoad(ByVal e As System.EventArgs) 
     MyBase.OnLoad(e) 

     If frm1 IsNot Nothing Then 
      frm1.Show() 
     End If 
    End Sub 

    Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click 
     frm1.MyData = "test" 
     frm1.TextData = "another test" 
    End Sub 
End Class