如何：设置 Windows 窗体 ProgressBar 控件显示的值

更新：2007 年 11 月

重要说明：
ToolStripProgressBar 控件替换了 ProgressBar 控件并添加了功能；但是也可选择保留 ProgressBar 控件以备向后兼容和将来使用。

.NET Framework 使您可以通过几种不同的方法显示 ProgressBar 控件中的给定值。选择的方法将取决于您所要执行的任务或要解决的问题。下表说明了可以选择的方法。

方法	说明
直接设置 ProgressBar 控件的值。	如果您知道任务中涉及的测量项总数，此方法非常有用，例如从数据源中读取记录。此外，如果您只需要设置该值一次或两次，这将是实现该目的的简便方法。最后，如果您需要减小进度栏显示的值，请使用此方法。
使 ProgressBar 的显示值按固定值递增。	如果需要显示最小值和最大值之间的简单计数，此方法非常有用，例如运行时间或已知文件总数中已处理的文件数。
使 ProgressBar 的显示值按可变值递增。	如果需要多次以不同数量更改显示值，此方法非常有用。例如，显示将一系列文件写入磁盘时所占用的硬盘空间量。

设置进度栏的显示值的最直接方式是设置 Value 属性。该操作可以在设计时或运行时进行。

直接设置 ProgressBar 值

1. 设置 ProgressBar 控件的 Minimum 和 Maximum 值。

2. 在代码中，将该控件的 Value 属性设置为已设定的最小值与最大值之间的一个整数值。

   说明：
   如果将 Value 属性设置为 Minimum 和 Maximum 属性设定的边界之外的值，该控件将引发 ArgumentException 异常。

   下面的代码示例说明如何直接设置 ProgressBar 值。该代码从数据源中读取记录，并在每次读取数据记录时更新进度栏和标签。该示例要求窗体有一个 Label 控件、一个 ProgressBar 控件以及一个数据表，该数据表中名为 CustomerRow 的行具有 FirstName 和 Last Name 字段。

   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();
   }
   

   如果要显示按固定时间间隔增长的进度，则可以设置该值，然后调用方法，使 ProgressBar 控件的值按该时间间隔递增。对于计时器以及其他一些您无法以整体的百分比测量进度的方案，这是非常有用的。

使进度栏按固定值递增

1. 设置 ProgressBar 控件的 Minimum 和 Maximum 值。

2. 将控件的 Step 属性设置为一个整数，该整数代表进度栏的显示值递增的数量。

3. 调用 PerformStep 方法，使显示值按 Step 属性中设置的数量进行更改。

   下面的代码示例说明进度栏如何维护复制操作中的文件计数。

   在下面的示例中，当每个文件读入内存时，进度栏和标签都会相应地更新，以反映读取的文件总数。该示例要求窗体有一个 Label 控件和一个 ProgressBar 控件。

   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();
      }
   }
   

   最后，可以使进度栏的显示值每次递增的数量都是唯一的。这在您记录一系列唯一的操作时非常有用，例如将不同大小的文件写入硬盘，或者按整体的百分比测量进度。

使进度栏按动态值递增

1. 设置 ProgressBar 控件的 Minimum 和 Maximum 值。

2. 调用 Increment 方法，使显示值按指定的整数进行更改。

   下面的代码示例说明在复制操作期间，进度栏如何计算已使用的磁盘空间量。

   在下面的示例中，当每个文件写入硬盘时，进度栏和标签都会相应地更新，以反映可用的硬盘空间量。该示例要求窗体有一个 Label 控件和一个 ProgressBar 控件。

   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();
      }
   }
   

请参见

参考

ProgressBar 控件概述（Windows 窗体）

ProgressBar

ToolStripProgressBar

其他资源

ProgressBar 控件（Windows 窗体）