本任务的内容
概要
本分步指南介绍了如何打印 RichTextBox 控件的内容。RichTextBox 控件没有提供任何打印 RichTextBox 内容的方法。您可以扩展 RichTextBox 类以使用 EM_FORMATRANGE 消息将 RichTextBox 控件的内容发送到一个输出设备(如打印机)。
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创建 RichTextBoxPrintCtrl 控件
下面的示例介绍了如何扩展 RichTextBox 类,以及如何使用 EM_FORMATRANGE 打印 RichTextBox 控件的内容。
- 在 Visual C# .NET 中,新建一个名为 RichTextBoxPrintCtrl 的类库项目。默认情况下创建 Class1.cs。
- 将 Class1.cs 的名称改为 RichTextBoxPrintCtrl.cs。
- 在解决方案资源管理器中,右键单击“引用”,然后单击“添加引用”。
- 在“添加引用”对话框中,双击“System.Drawing.dll”和“System.Windows.Forms.dll”,然后单击“确定”。
- 将 RichTextBoxPrintCtl.cs 中的现有代码替换为以下代码:
using System;
using System.Windows.Forms;
using System.Drawing;
using System.Runtime.InteropServices;
using System.Drawing.Printing; namespace RichTextBoxPrintCtrl
{
public class RichTextBoxPrintCtrl:RichTextBox
{
//Convert the unit used by the .NET framework (1/100 inch)
//and the unit used by Win32 API calls (twips 1/1440 inch)
private const double anInch = 14.4; [StructLayout(LayoutKind.Sequential)]
private struct RECT
{
public int Left;
public int Top;
public int Right;
public int Bottom;
} [StructLayout(LayoutKind.Sequential)]
private struct CHARRANGE
{
public int cpMin; //First character of range (0 for start of doc)
public int cpMax; //Last character of range (-1 for end of doc)
} [StructLayout(LayoutKind.Sequential)]
private struct FORMATRANGE
{
public IntPtr hdc; //Actual DC to draw on
public IntPtr hdcTarget; //Target DC for determining text formatting
public RECT rc; //Region of the DC to draw to (in twips)
public RECT rcPage; //Region of the whole DC (page size) (in twips)
public CHARRANGE chrg; //Range of text to draw (see earlier declaration)
} private const int WM_USER = 0x0400;
private const int EM_FORMATRANGE = WM_USER + 57; [DllImport("USER32.dll")]
private static extern IntPtr SendMessage (IntPtr hWnd , int msg , IntPtr wp, IntPtr lp); // Render the contents of the RichTextBox for printing
// Return the last character printed + 1 (printing start from this point for next page)
public int Print( int charFrom, int charTo,PrintPageEventArgs e)
{
//Calculate the area to render and print
RECT rectToPrint;
rectToPrint.Top = (int)(e.MarginBounds.Top * anInch);
rectToPrint.Bottom = (int)(e.MarginBounds.Bottom * anInch);
rectToPrint.Left = (int)(e.MarginBounds.Left * anInch);
rectToPrint.Right = (int)(e.MarginBounds.Right * anInch); //Calculate the size of the page
RECT rectPage;
rectPage.Top = (int)(e.PageBounds.Top * anInch);
rectPage.Bottom = (int)(e.PageBounds.Bottom * anInch);
rectPage.Left = (int)(e.PageBounds.Left * anInch);
rectPage.Right = (int)(e.PageBounds.Right * anInch); IntPtr hdc = e.Graphics.GetHdc(); FORMATRANGE fmtRange;
fmtRange.chrg.cpMax = charTo; //Indicate character from to character to
fmtRange.chrg.cpMin = charFrom;
fmtRange.hdc = hdc; //Use the same DC for measuring and rendering
fmtRange.hdcTarget = hdc; //Point at printer hDC
fmtRange.rc = rectToPrint; //Indicate the area on page to print
fmtRange.rcPage = rectPage; //Indicate size of page IntPtr res = IntPtr.Zero; IntPtr wparam = IntPtr.Zero;
wparam = new IntPtr(1); //Get the pointer to the FORMATRANGE structure in memory
IntPtr lparam= IntPtr.Zero;
lparam = Marshal.AllocCoTaskMem(Marshal.SizeOf(fmtRange));
Marshal.StructureToPtr(fmtRange, lparam, false); //Send the rendered data for printing
res = SendMessage(Handle, EM_FORMATRANGE, wparam, lparam); //Free the block of memory allocated
Marshal.FreeCoTaskMem(lparam); //Release the device context handle obtained by a previous call
e.Graphics.ReleaseHdc(hdc); //Return last + 1 character printer
return res.ToInt32();
} }
} - 在“生成”菜单中,单击“生成解决方案”以创建 RichTextBoxPrintCtrl.dll。
测试控件
- 在 Visual C# .NET 中创建一个新的 Windows 应用程序项目。默认情况下将创建出 Form1.cs。
- 将一个按钮控件从工具箱拖入 Form1。将 Name 属性更改为 btnPageSetup,并将 Text 属性更改为页面设置。
- 将另一个按钮控件从工具箱拖入 Form1。将 Name 属性更改为 btnPrintPreview,并将 Text 属性更改为打印预览。
- 将另一个按钮控件从工具箱拖入 Form1。将 Name 属性更改为 btnPrint,并将 Text 属性更改为打印。
- 在工具箱中,双击“PrintDialog”、“PrintPreviewDialog”、“PrintDocument”和“PageSetupDialog”以将这些控件添加到 Form1 中。
- 将 PrintDialog1、PrintPreviewDialog1 和 PageSetupDialog1 控件的 Document 属性修改为 PrintDocument1。
- 在“工具”菜单上,单击“自定义工具箱”。
- 在“.NET Framework 组件”选项卡上,单击“浏览”,单击以选中“RichTextBoxPrintCtrl.dll”,然后单击“确定”。
- 将 RichTextBoxPrintCtrl 从工具箱拖入 Form1。
- 在解决方案资源管理器中,右键单击 Form1.cs,然后单击查看代码。
- 将以下代码添加到 InitializeComponent 方法中:
this.printDocument1.BeginPrint += new System.Drawing.Printing.PrintEventHandler(this.printDocument1_BeginPrint);
this.printDocument1.PrintPage += new System.Drawing.Printing.PrintPageEventHandler(this.printDocument1_PrintPage);
this.btnPrint.Click += new System.EventHandler(this.btnPrint_Click);
this.btnPrintPreview.Click += new System.EventHandler(this.btnPrintPreview_Click);
this.btnPageSetup.Click += new System.EventHandler(this.btnPageSetup_Click); - 将下面的代码添加到 Form1 类:
private int checkPrint;
private void btnPageSetup_Click(object sender, System.EventArgs e)
{
pageSetupDialog1.ShowDialog();
} private void btnPrintPreview_Click(object sender, System.EventArgs e)
{
printPreviewDialog1.ShowDialog();
} private void btnPrint_Click(object sender, System.EventArgs e)
{
if (printDialog1.ShowDialog() == DialogResult.OK)
printDocument1.Print();
} private void printDocument1_BeginPrint(object sender, System.Drawing.Printing.PrintEventArgs e)
{
checkPrint = 0;
} private void printDocument1_PrintPage(object sender, System.Drawing.Printing.PrintPageEventArgs e)
{
// Print the content of RichTextBox. Store the last character printed.
checkPrint = richTextBoxPrintCtrl1.Print(checkPrint, richTextBoxPrintCtrl1.TextLength, e); // Check for more pages
if (checkPrint < richTextBoxPrintCtrl1.TextLength)
e.HasMorePages = true;
else
e.HasMorePages = false;
} - 在“调试”菜单上,单击“启动”以运行该应用程序。Form1 将显示出来。
- 在 RichTextBoxPrintCtrl 中键入一些文本。
- 单击“页面设置”以设置页面设置。
- 单击“打印预览”以查看页面的打印预览。
- 单击“打印”以打印“RichTextBoxPrintCtrl”的内容。