HOW TO：設定 Windows Form ProgressBar 控制項顯示的值

更新：2007 年 11 月

重要事項：
ToolStripProgressBar 控制項會取代並且將功能加入至 ProgressBar 控制項；不過，不過您也可以選擇保留 ProgressBar 控制項，以提供回溯相容性 (Backward Compatibility) 以及供未來使用。

.NET Framework 對於在 ProgressBar 控制項內部顯示特定值方面，提供數種不同的方式。您所選擇的方法，端視手邊的工作或正在解決的問題而定。下表顯示了您可選擇的形式：

處理方式	說明
直接設定 ProgressBar 控制項的值。	對於已知道所含測量項目總數的工作，例如從資料來源讀取記錄而言，這個方法就很實用。此外，如果只需要設定值一次或兩次，這個方法也很容易。最後，如果需要降低進度列所顯示的值，也請使用這個處理序。
以固定值增加 ProgressBar 顯示。	在最小和最大之間顯示簡單計數時，例如已耗用時間或已知總數中已處理的檔案數，這個方法就很實用。
以變化值增加 ProgressBar 顯示。	需要數次以不同數量變更顯示值時，這個方法就很有用。稍後會提供範例，說明將一系列檔案寫入磁碟時所耗用的硬碟空間量。

由進度列顯示該值最直接的方法就是設定 Value 屬性。您可以在設計階段或執行階段執行此作業。

若要直接設定 ProgressBar 值

1. 設定 ProgressBar 控制項的 Minimum 和 Maximum 的值。

2. 在程式碼中，將控制項的 Value 屬性設定為介於已建立的最小和最大值之間的整數值。

   注意事項：
   如果您在由 Minimum 和 Maximum 屬性建立的界限之外，設定 Value 屬性，此控制項會擲回 ArgumentException 例外狀況。

   下列程式碼範例說明如何直接設定 ProgressBar 值。程式碼會從資料來源讀取記錄，然後在每次讀取資料記錄時更新進度列和標籤。這個範例需要您的表單具有 Label 控制項、ProgressBar 控制項，以及具有稱為 CustomerRow 的資料列 (其中包含 FirstName 和 Last Name 欄位) 的資料表。

   Public Sub CreateNewRecords()
      ' Sets the progress bar's Maximum property to
      ' the total number of records to be created.
      ProgressBar1.Maximum = 20
   
      ' Creates a new record in the dataset.
      ' NOTE: The code below will not compile, it merely
      ' illustrates how the progress bar would be used.
      Dim anyRow As CustomerRow = DatasetName.ExistingTable.NewRow
      anyRow.FirstName = "Stephen"
      anyRow.LastName = "James"
      ExistingTable.Rows.Add(anyRow)
   
      ' Increases the value displayed by the progress bar.
      ProgressBar1.Value += 1
      ' Updates the label to show that a record was read.
      Label1.Text = "Records Read = " & ProgressBar1.Value.ToString()
   End Sub
   

   public void createNewRecords()
   {
      // Sets the progress bar's Maximum property to
      // the total number of records to be created.
      progressBar1.Maximum = 20;
   
      // Creates a new record in the dataset.
      // NOTE: The code below will not compile, it merely
      // illustrates how the progress bar would be used.
      CustomerRow anyRow = DatasetName.ExistingTable.NewRow();
      anyRow.FirstName = "Stephen";
      anyRow.LastName = "James";
      ExistingTable.Rows.Add(anyRow);
   
      // Increases the value displayed by the progress bar.
      progressBar1.Value += 1;
      // Updates the label to show that a record was read.
      label1.Text = "Records Read = " + progressBar1.Value.ToString();
   }
   

   如果顯示的進度是以固定間隔進行，則可設定該值，然後呼叫方法，以該間隔增加 ProgressBar 控制項的值。對於計時器和未以整體百分比測量進度的其他案例而言，這個方法很有用。

若要以固定值增加進度列

1. 設定 ProgressBar 控制項的 Minimum 和 Maximum 的值。

2. 將控制項的 Step 屬性設定為整數，表示增加進度列顯示值的數量。

3. 呼叫 PerformStep 方法，依在 Step 屬性中設定的數量變更顯示值。

   下列程式碼範例說明進度列如何在複製作業中維持檔案計數。

   在下列範例中，當每個檔案讀取至記憶體時，系統會更新進度列和標籤，以反映讀取的檔案總數。在這個範例中，您的表單必須有 Label 控制項和 ProgressBar 控制項。

   Public Sub LoadFiles()
      ' Sets the progress bar's minimum value to a number representing
      ' no operations complete -- in this case, no files read.
      ProgressBar1.Minimum = 0
      ' Sets the progress bar's maximum value to a number representing
      ' all operations complete -- in this case, all five files read.
      ProgressBar1.Maximum = 5
      ' Sets the Step property to amount to increase with each iteration.
      ' In this case, it will increase by one with every file read.
      ProgressBar1.Step = 1
   
      ' Dimensions a counter variable.
      Dim i As Integer
      ' Uses a For...Next loop to iterate through the operations to be
      ' completed. In this case, five files are to be copied into memory,
      ' so the loop will execute 5 times.
      For i = 0 To 4
         ' Insert code to copy a file
         ProgressBar1.PerformStep()
         ' Update the label to show that a file was read.
         Label1.Text = "# of Files Read = " & ProgressBar1.Value.ToString
      Next i
   End Sub
   

   public void loadFiles()
   {
      // Sets the progress bar's minimum value to a number representing
      // no operations complete -- in this case, no files read.
      progressBar1.Minimum = 0;
      // Sets the progress bar's maximum value to a number representing
      // all operations complete -- in this case, all five files read.
      progressBar1.Maximum = 5;
      // Sets the Step property to amount to increase with each iteration.
      // In this case, it will increase by one with every file read.
      progressBar1.Step = 1;
   
      // Uses a for loop to iterate through the operations to be
      // completed. In this case, five files are to be copied into memory,
      // so the loop will execute 5 times.
      for (int i = 0; i <= 4; i++)
      {
         // Inserts code to copy a file
         progressBar1.PerformStep();
         // Updates the label to show that a file was read.
         label1.Text = "# of Files Read = " + progressBar1.Value.ToString();
      }
   }
   

   最後，您可以增加進度列的顯示值，如此一來每次增加的數量都是唯一的。在追蹤一系列唯一作業時，例如將不同大小的檔案寫入磁碟，或是以整體百分比測量進度時，這個方法就很有用。

若要以動態值增加進度列

1. 設定 ProgressBar 控制項的 Minimum 和 Maximum 的值。

2. 呼叫 Increment 方法，依您指定的整數變更顯示值。

   下列程式碼範例說明進度列如何計算複製作業期間，已經使用的磁碟空間有多少。

   在下列範例中，當每個檔案寫入硬碟時，進度列和標籤會進行更新，以反映可用的硬碟空間量。在這個範例中，您的表單必須有 Label 控制項和 ProgressBar 控制項。

   Public Sub ReadFiles()
      ' Sets the progress bar's minimum value to a number 
      ' representing the hard disk space before the files are read in.
      ' You will most likely have to set this using a system call.
      ' NOTE: The code below is meant to be an example and
      ' will not compile.
      ProgressBar1.Minimum = AvailableDiskSpace()
      ' Sets the progress bar's maximum value to a number 
      ' representing the total hard disk space.
      ' You will most likely have to set this using a system call.
      ' NOTE: The code below is meant to be an example 
      ' and will not compile.
      ProgressBar1.Maximum = TotalDiskSpace()
   
      ' Dimension a counter variable.
      Dim i As Integer
      ' Uses a For...Next loop to iterate through the operations to be
      ' completed. In this case, five files are to be written to the disk,
      ' so it will execute the loop 5 times.
      For i = 1 To 5
         ' Insert code to read a file into memory and update file size.
         ' Increases the progress bar's value based on the size of 
         ' the file currently being written.
         ProgressBar1.Increment(FileSize)
         ' Updates the label to show available drive space.
         Label1.Text = "Current Disk Space Used = " &_ 
         ProgressBar1.Value.ToString()
      Next i
   End Sub
   

   public void readFiles()
   {
      // Sets the progress bar's minimum value to a number 
      // representing the hard disk space before the files are read in.
      // You will most likely have to set this using a system call.
      // NOTE: The code below is meant to be an example and 
      // will not compile.
      progressBar1.Minimum = AvailableDiskSpace();
      // Sets the progress bar's maximum value to a number 
      // representing the total hard disk space.
      // You will most likely have to set this using a system call.
      // NOTE: The code below is meant to be an example 
      // and will not compile.
      progressBar1.Maximum = TotalDiskSpace();
   
      // Uses a for loop to iterate through the operations to be
      // completed. In this case, five files are to be written
      // to the disk, so it will execute the loop 5 times.
      for (int i = 1; i<= 5; i++)
      {
         // Insert code to read a file into memory and update file size.
         // Increases the progress bar's value based on the size of 
         // the file currently being written.
         progressBar1.Increment(FileSize);
         // Updates the label to show available drive space.
         label1.Text = "Current Disk Space Used = " + progressBar1.Value.ToString();
      }
   }
   

請參閱

參考

ProgressBar 控制項概觀 (Windows Form)

ProgressBar

ToolStripProgressBar

其他資源

ProgressBar 控制項 (Windows Form)