使用ProgressBar和組合框

Question

我遇到了MarqueeProgressBar問題。我需要執行一個方法（refreshList()）以獲得List<string>。然後我將這List分配到ComboBox，所以ComboBox刷新與新的Items。由於refreshList()需要3或4秒，我想運行一個MarqueeProgressBar。但我不能。 ProgressBar是好的，但是ComboBox不會加載新的Items。

我refreshList()方法：

private void refreshList(List<string> list) 
{ 
    albumList.DataSource = null; 
    albumList.DataSource = list; 
} 

我有下面的代碼，它工作正常：

private void changeDirectoryToolStripMenuItem_Click(object sender, EventArgs e) 
{ 
    fbd.RootFolder  = Environment.SpecialFolder.MyComputer; 
    folderPath = ""; 
    if (fbd.ShowDialog() == System.Windows.Forms.DialogResult.OK) 
    { 
     folderPath  = fbd.SelectedPath; 
     refreshList(N.getList(folderPath)); 

    } 
} 

但我添加了一個ProgressBar寫了這樣的代碼：

private void changeDirectoryToolStripMenuItem_Click(object sender, EventArgs e) 
{ 
    fbd.RootFolder  = Environment.SpecialFolder.MyComputer; 
    folderPath = ""; 
    if (fbd.ShowDialog() == System.Windows.Forms.DialogResult.OK) 
    { 
     folderPath  = fbd.SelectedPath; 
     bgWorker.WorkerReportsProgress = true; 
     bgWorker.RunWorkerAsync(); 

    } 
} 

而且我把refreshList()放在doWork()方法：

private void bgWorker_DoWork(object sender, DoWorkEventArgs e) 
{ 
    refreshList(N.getList(folderPath)); 
} 

但不幸的是，這是行不通的。任何人都可以幫我解決這個問題嗎？提前致謝。

Answer 1

您可以使用ProgressBar控件的MarqueeAnimationSpeed和Value屬性來停止和啓動選取框。沒有必要使用WorkerReportsProgress *，因爲您沒有增加正常的進度條 - 只是想「旋轉」選取框。

你可以做類似如下：

public Form1() 
    { 
     InitializeComponent(); 
     //Stop the progress bar to begin with 
     progressBar1.MarqueeAnimationSpeed = 0;    
     //If you wire up the event handler in the Designer, then you don't need 
     //the following line of code (the designer adds it to InitializeComponent) 
     //backgroundWorker1.RunWorkerCompleted += backgroundWorker1_RunWorkerCompleted; 
    } 

    private void changeDirectoryToolStripMenuItem_Click(object sender, EventArgs e) 
    { 
     fbd.RootFolder = Environment.SpecialFolder.MyComputer; 
     folderPath = ""; 
     if (fbd.ShowDialog() == System.Windows.Forms.DialogResult.OK) 
     { 
      folderPath = fbd.SelectedPath; 
      //This line effectively starts the progress bar 
      progressBar1.MarqueeAnimationSpeed = 10;     
      bgWorker.RunWorkerAsync(); //Calls the DoWork event 

     } 
    } 

    private void backgroundWorker1_DoWork(object sender, DoWorkEventArgs e) 
    { 
     e.Result = N.getList(folderPath); //Technically this is the only work you need to do in the background 
    } 

    private void backgroundWorker1_RunWorkerCompleted(object sender, RunWorkerCompletedEventArgs e) 
    { 
     //these two lines effectively stop the progress bar 
     progressBar1.Value = 0; 
     progressBar1.MarqueeAnimationSpeed = 0; 
     //Now update the list with the result from the work done on the background thread 
     RefreshList(e.Result as List<String>); 
    } 


    private void RefreshList(List<String> results) 
    { 
     albumList.DataSource = null; //You don't need this line but there is no real harm. 
     albumList.DataSource = list; 
    } 

記住通過屬性欄要連接的RunWorkerCompleted事件backgroundWorker1_RunWorkerCompleted，在設計活動部分。

首先，我們通過將MarqueeAnimationSpeed屬性設置爲一個非零的正數來啓動ProgressBar的動畫，作爲成功的文件夾選擇的一部分。

然後，在調用RunWorkerAsync之後，代碼將在DoWork方法中構建您的列表，然後將結果分配給DoWorkEventArgs，DoWorkEventArgs將傳遞給RunWorkerCompleted事件（DoWork完成時觸發）。

在backgroundWorker1_RunWorkerCompleted方法中，我們停止進度條（並將其值設置爲零以有效地將其返回到原始狀態），然後我們將該列表傳遞給refreshList方法以對其進行數據綁定並填充組合框。

使用VS2012，Windows窗體，.NET 4.0（用了Thread.Sleep效仿採取N.getList時間）

* WorkerReportsProgress，以及相關的ReportProgress方法/事件進行測試時，要使用增加進度條 - 你可以告訴GUI你完成10％，完成20％，完成50％等等。