Question

我正在制作搜索工具并使用BackgroundWorker进行搜索。我希望一旦找到第一个结果，就会打开一个新窗口，其中ListBox显示第一个元素。现在，我希望在找到后续结果后，ListBox应该使用这些结果进行更新我认为的方法是在找到结果后立即报告进度，并将“新”和“更新”作为userState传递给方法。
根据{{1}}，我可以决定是创建新的userState还是更新现有的。{ 这是代码： -

Form

我在变量private void backgroundWorker1_ProgressChanged(object sender, ProgressChangedEventArgs e) { if (e.UserState.ToString() == "New") { Form ResultForm = new Form(); ResultForm.Name = "ResultForm" + i.ToString(); LastFormName = ResultForm.Name; ListBox ResultListBox = new ListBox(); ResultListBox.DataSource = SearchList; ResultListBox.Name = "ResultListBox" + i.ToString(); LastListName = ResultListBox.Name ; ResultForm.Container.Add(ResultListBox); ResultListBox.Show(); ResultForm.Show(); i++; } else { ; } }和'LastListName'中存储了Last open Form和它的ListBox的名称。我无法理解在else条件下放入什么内容，以便更新LastFormName。

Answer 1

我要做的是在弹出窗体上公开一些属性，以便您可以判断它是否已打开并且可以访问列表框。

    public partial class Popup : Form
    {
     public bool isOpen;
     public ListBox PopupListBox;

     public Popup()
     {
        InitializeComponent();
     }

     void Popup_FormClosing(object sender, FormClosingEventArgs e)
     {
        isOpen = false;
     }

     private void Popup_Load(object sender, EventArgs e)
     {
        this.FormClosing += Popup_FormClosing;
        PopupListBox = popupListBox;
     }
 }

然后在调用表单上，我将订阅ProcessedChanged事件并使用您通过ProcessedChangedEventArgs传递的数据更新列表框。这是调用表单的代码

public partial class Form1 : Form
{
    Popup popupForm = new Popup();
    BackgroundWorker backgroundWorker = new BackgroundWorker();

    public Form1()
    {
        InitializeComponent();
    }

    private void Form1_Load(object sender, EventArgs e)
    {
        backgroundWorker.WorkerSupportsCancellation = true;
        backgroundWorker.WorkerReportsProgress = true;
        backgroundWorker.DoWork += backgroundWorkerDoWork;
        backgroundWorker.ProgressChanged += backgroundWorkerProgressChanged;
        backgroundWorker.RunWorkerCompleted += backgroundWorkerRunWorkerCompleted;
    }

    void backgroundWorkerRunWorkerCompleted(object sender, RunWorkerCompletedEventArgs e)
    {
        if ((e.Cancelled == true))
        {
            //What do you want to do if Cancelled?
        }

        else if (!(e.Error == null))
        {
            //What do you want to do if there is an error?
        }
        else
        {
            //What do you want to do when it is done?
        }
    }

    void backgroundWorkerProgressChanged(object sender, ProgressChangedEventArgs e)
    {
        if (!popupForm.isOpen || popupForm == null)
        {
            popupForm = new Popup();
            popupForm.Show();
            popupForm.isOpen = true;
        }
        else
        {
            popupForm.Activate();
            popupForm.WindowState = FormWindowState.Normal;
        }

        popupForm.PopupListBox.Items.Add(e.ProgressPercentage.ToString() + "%");
    }

    void backgroundWorkerDoWork(object sender, DoWorkEventArgs e)
    {
        BackgroundWorker worker = sender as BackgroundWorker;

        for (int i = 1; (i <= 10); i++)
        {
            if ((worker.CancellationPending == true))
            {
                e.Cancel = true;
                break;
            }
            else
            {
                // Perform a time consuming operation and report progress.
                System.Threading.Thread.Sleep(500);
                worker.ReportProgress((i * 10));
            }
        }
    }

    private void buttonStart_Click(object sender, EventArgs e)
    {
        if (backgroundWorker.IsBusy != true)
        {
            backgroundWorker.RunWorkerAsync();
        }
    }

    private void buttonCancel_Click(object sender, EventArgs e)
    {
        if (backgroundWorker.WorkerSupportsCancellation == true)
        {
            backgroundWorker.CancelAsync();
        }
    }
}

Answer 2

您不应该在ProgressChanged事件处理程序

中工作

您将无法访问结果，因为它只传递了一个int用于进度和用户状态
这是在UI线程上。完整的一点是在后台线程上进行处理
名称DoWork事件处理程序很清楚，这是您应该进行处理的地方。

回答你的问题。由于您在事件处理程序中创建了ListBox，因此它超出了if语句之外的范围。您需要在更全局的范围内创建它。然后添加到ResultListBox.Items.Add("ResultListBox" + i.ToString());

如何动态更新列表框？

2 个答案: