Question

这是Visual Basic中的嵌套循环，循环遍历数组中的数字。

For x As Integer = 0 To test.Length - 1
            Console.WriteLine(test(x))
            For y As Integer = 0 To test.Length - 1
                Console.WriteLine(test(x) & test(y))
                 Next
               Next

我想通过单击按钮来终止循环。由于所有处理能力都进入循环，因此按钮显示为灰色。我该怎么办？

Answer 1

您必须使用类似System.Threading.Tasks.Task或System.ComponentModel.BackgroundWorker的内容，并检查每次循环迭代时是否已取消任务/工作程序。多线程是一个相当广泛的主题，但this page或this page应该可以帮助您入门。

Answer 2

首先添加一个布尔值

Dim done As Boolean

现在向表单添加后台工作程序。双击backgroundWorker并在backgroundWorker

下添加以下代码

 Private Sub BackgroundWorker1_DoWork(ByVal sender As System.Object, ByVal e As        System.ComponentModel.DoWorkEventArgs) Handles BackgroundWorker1.DoWork


For x As Integer = 0 To test.Length - 1
        Console.WriteLine(test(x))
        For y As Integer = 0 To test.Length - 1
            Console.WriteLine(test(x) & test(y))
             Next
            If done = true then exit sub
           Next
         If done = true then exit sub
End Sub

现在添加一个按钮来启动循环。此按钮将布尔值设置为false并运行backgroundWorker。

Private Sub ButtonStart_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button2.Click
done = False 
BackgroundWorker1.RunWorkerAsync()
End Sub

最后添加一个按钮来停止循环。此按钮将布尔值设置为true。

Private Sub ButtonStop_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click
done = True
End SUb

如何通过单击按钮来终止嵌套的for循环？

2 个答案: