NET中打印包含有格式的 RichTextBox 的內容
2024-07-21 02:25:12
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本文逐步說明如何打印 richtextbox 控件的內容。richtextbox 控件不提供打印其內容的方法。但是，您可以擴展 richtextbox 類以使用 em_formatrange 消息。然后，您可以將 richtextbox 的內容發送到某個輸出設備，例如打印機。
創建 richtextboxprintctrl 控件
要擴展 richtextbox 類并使用 em_formatrange 來打印 richtextbox 控件的內容，請按照下列步驟操作： 1. 使用 microsoft visual basic .net 新建一個名為 richtextboxprintctrl 的類庫項目。
默認情況下，將創建 class1.vb。
2. 將 class1.vb 文件的名稱更改為 richtextboxprintctrl.vb。
3. 在解決方案資源管理器中，右鍵單擊“引用”，然后單擊“添加引用”。
4. 在添加引用對話框中，雙擊“system.drawing.dll”，然后雙擊“system.windows.forms.dll”。
5. 要添加引用，請單擊“確定”。
6. 刪除“richtextboxprintctrl.vb”中的現有節點。
7. 將以下代碼復制到“richtextboxprintctrl.vb”中：
option explicit on
imports system
imports system.windows.forms
imports system.drawing
imports system.runtime.interopservices
imports system.drawing.printing
namespace richtextboxprintctrl
public class richtextboxprintctrl
inherits richtextbox
' convert the unit that is used by the .net framework (1/100 inch)
' and the unit that is used by win32 api calls (twips 1/1440 inch)
private const aninch as double = 14.4
<structlayout(layoutkind.sequential)> _
private structure rect
public left as integer
public top as integer
public right as integer
public bottom as integer
end structure
<structlayout(layoutkind.sequential)> _
private structure charrange
public cpmin as integer ' first character of range (0 for start of doc)
public cpmax as integer ' last character of range (-1 for end of doc)
end structure
<structlayout(layoutkind.sequential)> _
private structure formatrange
public hdc as intptr ' actual dc to draw on
public hdctarget as intptr ' target dc for determining text formatting
public rc as rect ' region of the dc to draw to (in twips)
public rcpage as rect ' region of the whole dc (page size) (in twips)
public chrg as charrange ' range of text to draw (see above declaration)
end structure
private const wm_user as integer = &h400
private const em_formatrange as integer = wm_user + 57
private declare function sendmessage lib "user32" alias "sendmessagea" (byval hwnd as intptr, byval msg as integer, byval wp as intptr, byval lp as intptr) as intptr
' render the contents of the richtextbox for printing
'return the last character printed + 1 (printing start from this point for next page)
public function print(byval charfrom as integer, byval charto as integer, byval e as printpageeventargs) as integer
' mark starting and ending character
dim crange as charrange
crange.cpmin = charfrom
crange.cpmax = charto
' calculate the area to render and print
dim recttoprint as rect
recttoprint.top = e.marginbounds.top * aninch
recttoprint.bottom = e.marginbounds.bottom * aninch
recttoprint.left = e.marginbounds.left * aninch
recttoprint.right = e.marginbounds.right * aninch
' calculate the size of the page
dim rectpage as rect
rectpage.top = e.pagebounds.top * aninch
rectpage.bottom = e.pagebounds.bottom * aninch
rectpage.left = e.pagebounds.left * aninch
rectpage.right = e.pagebounds.right * aninch
dim hdc as intptr = e.graphics.gethdc()
dim fmtrange as formatrange
fmtrange.chrg = crange ' indicate character from to character to
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 whole size of page
dim res as intptr = intptr.zero
dim wparam as intptr = intptr.zero
wparam = new intptr(1)
' move the pointer to the formatrange structure in memory
dim lparam as intptr = 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()
end function
end class
end namespace
8. 要創建“richtextboxprintctrl.dll”，請在“生成”菜單上單擊“生成解決方案”。
測試控件
要測試該控件，請按照下列步驟操作： 1. 使用 visual basic .net 新建一個 windows 應用程序項目。
默認情況下，將創建 form1.vb。
2. 從工具箱中，將一個按鈕拖到 form1 上。將名稱更改為 btnpagesetup，然后將“文本”更改為頁面設置。
3. 從工具箱中，將另一個按鈕拖到 form1 上。將名稱更改為 btnprintpreview，然后將“文本”更改為打印預覽。
4. 從工具箱中，將另一個按鈕拖到 form1 上。將名稱更改為 btnprint，然后將“文本”更改為打印。
5. 在工具箱中，依次雙擊“printdialog”、“printpreviewdialog”和“printdocument”，然后雙擊“pagesetupdialog”將這些控件添加到 form1 中。
6. 將“printdialog1”、“printpreviewdialog1”和“pagesetupdialog1”的 document 屬性修改為printdocument1。
7. 在“工具”菜單上，單擊“自定義工具箱”。
8. 單擊“.net framework 組件”，單擊“瀏覽”，單擊以選擇“richtextboxprintctrl.dll”，然后單擊“確定”。
9. 從工具箱中，將“richtextboxprintctrl”拖到 form1 上。
10. 在解決方案資源管理器中，右鍵單擊“form1.vb”，然后單擊“查看代碼”。
11. 將以下代碼添加到 form1 類中：
private checkprint as integer
private sub printdocument1_beginprint(byval sender as object, byval e as system.drawing.printing.printeventargs) handles printdocument1.beginprint
checkprint = 0
end sub
private sub printdocument1_printpage(byval sender as object, byval e as system.drawing.printing.printpageeventargs) handles printdocument1.printpage
' print the content of the richtextbox. store the last character printed.
checkprint = richtextboxprintctrl1.print(checkprint, richtextboxprintctrl1.textlength, e)
' look for more pages
if checkprint < richtextboxprintctrl1.textlength then
e.hasmorepages = true
else
e.hasmorepages = false
end if
end sub
private sub btnpagesetup_click(byval sender as system.object, byval e as system.eventargs) handles btnpagesetup.click.click
pagesetupdialog1.showdialog()
end sub
private sub btnprint_click(byval sender as system.object, byval e as system.eventargs) handles btnprint.click
if printdialog1.showdialog() = dialogresult.ok then
printdocument1.print()
end if
end sub
private sub btnprintpreview_click(byval sender as system.object, byval e as system.eventargs) handles btnprintpreview.click
printpreviewdialog1.showdialog()
end sub
12. 要運行該應用程序，請單擊“調試”菜單上的“開始”。
13. 在“richtextboxprintctrl”中鍵入文本。
14. 要設置頁面設置，請單擊“頁面設置”。
15. 要預覽該頁，請單擊“打印預覽”。
16. 要打印“richtextboxprintctrl”的內容，請單擊“打印”。
