如何更改字符串数组vb.net中单个标签的文本

Question

所以我想在单个标签中显示一个字符串数组，该数组会随着时间的推移而更改内容，我试过所有的东西——计时器，后台工作程序，当我使用循环插入计时器时的问题——如果数组项目太多，启动的间隔应该很长，所以我试过后台工作程序但它不起作用
这是代码：

Dim array() As String = {"so", "nb", "de", "rty", "dcds"}
Private Sub Button1_Click(sender As Object, e As EventArgs) Handles Button1.Click
BackgroundWorker1.RunWorkerAsync()
End Sub
Private Sub Form1_Load(sender As Object, e As EventArgs) Handles MyBase.Load
Control.CheckForIllegalCrossThreadCalls = False
End Sub


Private Sub BackgroundWorker1_DoWork(sender As Object, e As DoWorkEventArgs) Handles BackgroundWorker1.DoWork
Dim worker As BackgroundWorker = CType(sender, BackgroundWorker)
Dim delay As Integer = 2000
Dim interval As Integer = 100
Dim elapsed As Integer = 0
Dim pos As Integer = array.Length
While Not worker.CancellationPending
If (elapsed >= delay) Then
worker.ReportProgress(pos)
' change label text in the Progress event handler
pos = (pos + 1)
elapsed = 0
If (pos = array.Length) Then
Exit While
End If
End If
Thread.Sleep(interval)
End While
End Sub
Private Sub BackgroundWorker1_ProgressChanged(sender As Object, e As ProgressChangedEventArgs) Handles BackgroundWorker1.ProgressChanged
Dim j As Integer
For j = 0 To array.Length
Label1.Text = array(j)
Next
End Sub

Answer 1

您的for循环在每次迭代中都会覆盖标签的.Text属性。您还会得到一个Index Out of Range异常，因为数组的索引是从零开始的。最高索引将比.Length.少1

Private arStr() As String = {"so", "nb", "de", "rty", "dcds"}
Private Sub Button1_Click(sender As Object, e As EventArgs) Handles Button1.Click
Dim LabelText = String.Join(Environment.NewLine, arStr)
Label1.Text = LabelText
End Sub

编辑

Private arStr() As String = {"so", "nb", "de", "rty", "dcds"}
Private Sub Button1_Click(sender As Object, e As EventArgs) Handles Button1.Click
Static index As Integer
If index < arStr.Length Then
Label1.Text &= arStr(index) & Environment.NewLine
index += 1
End If
End Sub

Answer 2

使用异步方法，您可以在没有BackgroundWorker和显式创建Timer的情况下一个接一个地显示数组值。

Private _values As New String() From {"so", "nb", "de", "rty", "dcds"}
Private Async Sub Button1_Click(sender As Object, e As EventArgs) Handles Button1.Click
For Each value In _values
await Task.Delay(2000)
Next
End Sub

使用异步方法，您可以像在同步代码中那样，在显示所有值之前防止单击按钮。

Private Async Sub Button1_Click(sender As Object, e As EventArgs) Handles Button1.Click
Dim button = DirectCast(sender, Button);
button.Enabled = False
For Each value In _values
await Task.Delay(2000)
Next
button.Enabled = True
End Sub