如何创建加载窗口？

Question

好的，在我的应用程序中，有时加载 DataGridView 可能需要一两分钟。我想要做的是以无边框的形式显示 GIF 直到它到达加载函数的末尾。但是，如果我这样做：

Views.Loading ldw = new Views.Loading();
ldw.Show();
...
ldw.Close();

...它实际上从未将其绘制到屏幕上，而且我看不到它。如果我执行 ShowDialog()，它会显示窗口，但永远不会超过该行代码。我有一种感觉，这是因为它不是后台工作者，或者因为处理过程中焦点被设置回父级......我不知道。

我的表单是一个空白表单，添加了一个图片框，在图片框中添加了一个gif，并让FormBorderStyle = none。感谢任何和所有的帮助。

更新：当前（非工作）代码

        private void InitializeBackgroundWorker()
        {
            //Defines the DoWork Event Handler for _backgroundWorker.
            _bgWorkerReports.DoWork += new DoWorkEventHandler(bgWorkerReports_DoWork);
            //Defines the RunWorkCompleted Event Handler for _backgroundWorker.
            _bgWorkerReports.RunWorkerCompleted += new RunWorkerCompletedEventHandler(bgWorkerReports_RunWorkerCompleted);
        }

        private void bgWorkerReports_DoWork(object sender, DoWorkEventArgs e)
        {
            ldw.Show();
            try
            {                   
                string strFilter = "";

                if (!_strSearchFilter.Equals(""))
                {
                    strFilter += strFilter.Equals("") ? " " + _strSearchFilter : "  and " + _strSearchFilter;
                }

                if (tvFigure.Nodes.Count > 0)
                {
                    if (_strFigureFilter == "ALL")
                    {
                        strFilter += " " + Constants.GetColumnName("Figure") + " LIKE '%%' ";
                    }
                    else if (!_strFigureFilter.Equals("") && !_strFigureFilter.Equals(tvFigure.TopNode.Name))
                    {
                        if (_strSearchFilter.Equals("") || !cbCurrentFigure.Checked)
                        {
                            strFilter += strFilter.Equals("") ? " " + Constants.GetColumnName("Figure") + "='" + _strFigureFilter + "'" : " and " + Constants.GetColumnName("Figure") + "='" + _strFigureFilter + "'";
                        }
                    }
                }

                if (!_strIndentureFilter.Equals(""))
                {
                    strFilter += strFilter.Equals("") ? " " + _strIndentureFilter : "  and " + _strIndentureFilter;
                }

                if (!_strReportFilter.Equals(""))
                {
                    strFilter += (!strFilter.Equals("") ? " and" : "") + " part_id in (" + _strReportFilter + ")";
                }

                if (strFilter.Length > 0)
                {
                    BindingSource bSource = new BindingSource();
                    bSource.DataSource = _dataController.PopulateDataGrid(_nViewMode, strFilter).Tables[0];

                    //Set DataSource to bindingSource for DataGridView.
                    if (_lstValidationResults.Count > 0)
                    {
                        dgvParts.DataSource = _lstValidationResults;
                        foreach (DataGridViewColumn dc in dgvParts.Columns)
                        {
                            dc.DataPropertyName = "ErrorMessage";
                            dc.Visible = true;
                            dc.SortMode = DataGridViewColumnSortMode.Programmatic;
                            dc.AutoSizeMode = DataGridViewAutoSizeColumnMode.ColumnHeader;
                        }
                        dgvParts.AutoResizeColumns();
                        return;
                    }
                    else if (!string.IsNullOrEmpty(_strFigureFilter))
                    {
                        dgvParts.DataSource = bSource;
                        dgvParts.Columns[0].Visible = false;
                        dgvParts.Columns["Description"].Resizable = DataGridViewTriState.False;
                        dgvParts.Columns["Description"].Width = 750;
                    }

                    // Automatically resize the visible rows.
                    foreach (DataGridViewColumn col in dgvParts.Columns)
                    {
                        col.SortMode = DataGridViewColumnSortMode.Automatic;
                        if (col.Name != "Description")
                        {
                            dgvParts.AutoResizeColumn(col.Index);
                        }
                    }
                    dgvParts.AutoSizeRowsMode = DataGridViewAutoSizeRowsMode.DisplayedCells;

                    // Hide the ToolTips for all the cells - redisplay if there is a report.
                    dgvParts.ShowCellToolTips = true;

                    // Set the dataGridView control's border.
                    dgvParts.BorderStyle = BorderStyle.Fixed3D;

                    // Get and set the ipb_number to the label.
                    string ipb_number = _dataController.IPBNumber;
                }
            }
            catch (Exception ex)
            {
                MessageBox.Show(ex.Message);
            }
        }

        private void bgWorkerReports_RunWorkerCompleted(object sender, RunWorkerCompletedEventArgs e)
        {
            ldw.Close();
            this.Cursor = Cursors.Default; //Throws error (Cross-thread)

            FormatCells();
            BuildColumnsComboBox();

            int nTotalCount = 0;

            foreach (ListViewItem lvi in listView1.Items)
            {
                int nCount = _lstReportRecords.Where(rr => lvi.Text.Contains(rr.Description)).Count();
                nTotalCount += nCount;
                lvi.Text = (lvi.Text.Contains("(") ? lvi.Text.Substring(0, lvi.Text.IndexOf("(") + 1) : lvi.Text.Trim() + " (") + nCount.ToString() + ")";
            }

            rbAllReports.Text = (rbAllReports.Text.Contains("(") ? rbAllReports.Text.Substring(0, rbAllReports.Text.IndexOf("(") + 1) : rbAllReports.Text + " (") + nTotalCount.ToString() + ")";
            int nTaggedCount = _lstReportRecords.Where(rr => rr.Description.Contains("Tagged")).Count();
            rbTaggedRecords.Text = (rbTaggedRecords.Text.Contains("(") ? rbTaggedRecords.Text.Substring(0, rbTaggedRecords.Text.IndexOf("(") + 1) : rbTaggedRecords.Text + " (") + nTaggedCount.ToString() + ")";
        }

Answer 1

您必须在另一个线程上运行代码来填充网格。像这样的东西：

// Set the picturebox loading state, resize the form etc.
PictureBox.SetLoadingImage();

// Initialize a new thread
Thread t = new Thread(new ThreadStart(() =>
{
    // Fill the gridview here
    GridView1.DataSource = FillWithData();
    GridView1.DataBind();

    // When finished, reset the picturebox on it's own thread
    PictureBox.Invoke((MethodInvoker)(()=> PictureBox.ClearLoadingImage() ));
}));

// Run the thread.
t.Start();

Answer 2

理想情况下，您应该有两个线程：GUI 线程和工作线程（可以是 BackgroundWorker）。在 GUI 线程中创建并显示窗口。处理 BackgroundWorker 的 DoWork 事件中的加载。加载完成后，您可以通过 RunWorkerCompleted 事件在加载窗口上调用 Close() 并释放它。

LoadWindow loadWindow = new LoadWindow();
loadWindow.TopMost = true;  // make sure it doesn't get created behind other forms
loadWindow.Show();

BackgroundWorker worker = new BackgroundWorker();
worker.DoWork += new DoWorkEventHandler(worker_DoWork);
worker.RunWorkerCompleted += new RunWorkerCompletedEventHandler(worker_RunWorkerCompleted);
worker.RunWorkerAsync();

void worker_DoWork(object sender, DoWorkEventArgs e)
{
    // do your loading here
}

void worker_RunWorkerCompleted(object sender, RunWorkerCompletedEventArgs e)
{
    // set DataGridView datasource here
    ...

    // close loading window
    loadWindow.Close();
}

显示窗口时可能遇到的问题可能来自 TopMost 属性，该属性必须设置为 true。您还可以在创建并显示加载窗口后尝试在加载窗口上调用 BringToFront()。

Answer 3

是的，BackgroundWorker 正是用于此类目的。需要添加几件事：

1. 不要在worker_DoWork 事件中与UI 交互，因为它在后台线程上运行。完成后设置 e.Result，您可以从 RunWorkerCompleted 事件中检查该结果 - 或使用表单级变量。
2. 让任何异常在worker_DoWork事件中失败，您将在e.Error的worker_RunWorkerCompleted事件中看到它们。
3. 如果您需要取消负载的能力，请在 DoWork 事件中设置worker.WorkerSupportsCancellation 并检查 e.Cancel，然后您可以在 RunWorkerCompleted 事件中检查 e.Cancelled。
4. 完成后，您应该在您的BackgroundWorker 上调用.Dispose()。