如何使用打印预览在 Windows 窗体中打印

项目
12/18/2024

除了打印服务之外，Windows 窗体编程中也非常常见地提供打印预览。向应用程序添加打印预览服务的一种简单方法是将 PrintPreviewDialog 控件与用于打印文件的 PrintPage 事件处理逻辑结合使用。

使用 PrintPreviewDialog 控件预览文本文档

向窗体添加 PrintPreviewDialog、PrintDocument和两个字符串。

private PrintPreviewDialog printPreviewDialog1 = new PrintPreviewDialog();
private PrintDocument printDocument1 = new PrintDocument();

// Declare a string to hold the entire document contents.
private string documentContents;

// Declare a variable to hold the portion of the document that
// is not printed.
private string stringToPrint;

Private printPreviewDialog1 As New PrintPreviewDialog()
Private WithEvents printDocument1 As New PrintDocument()

' Declare a string to hold the entire document contents.
Private documentContents As String

' Declare a variable to hold the portion of the document that
' is not printed.
Private stringToPrint As String

将 DocumentName 属性设置为要打印的文档，然后打开文档并将其内容读取到之前添加的字符串中。

private void ReadDocument()
{
    string docName = "testPage.txt";
    string docPath = @"c:\";
    printDocument1.DocumentName = docName;
    using (FileStream stream = new FileStream(docPath + docName, FileMode.Open))
    using (StreamReader reader = new StreamReader(stream))
    {
        documentContents = reader.ReadToEnd();
    }
    stringToPrint = documentContents;
}

Private Sub ReadDocument() 
    Dim docName As String = "testPage.txt"
    Dim docPath As String = "c:\"
    printDocument1.DocumentName = docName
    Dim stream As New FileStream(docPath + docName, FileMode.Open)
    Try
        Dim reader As New StreamReader(stream)
        Try
            documentContents = reader.ReadToEnd()
        Finally
            reader.Dispose()
        End Try
    Finally
        stream.Dispose()
    End Try
    stringToPrint = documentContents

End Sub

与打印文档一样，在 PrintPage 事件处理程序中，使用 PrintPageEventArgs 类的 Graphics 属性和文件内容来计算每页的行数并呈现文档的内容。绘制每个页面后，检查每一页是否为最后一页，并相应地设置 PrintPageEventArgs 的 HasMorePages 属性。将引发 PrintPage 事件，直到 HasMorePagesfalse。文档完成呈现后，重置要呈现的字符串。此外，请确保 PrintPage 事件与其事件处理方法相关联。

注意

如果已在应用程序中实现打印，则可能已完成步骤 2 和 3。

在下面的代码示例中，事件处理程序用于以窗体上所用的同一字体打印“testPage.txt”文件。

void printDocument1_PrintPage(object sender, PrintPageEventArgs e)
{
    int charactersOnPage = 0;
    int linesPerPage = 0;

    // Sets the value of charactersOnPage to the number of characters
    // of stringToPrint that will fit within the bounds of the page.
    e.Graphics.MeasureString(stringToPrint, this.Font,
        e.MarginBounds.Size, StringFormat.GenericTypographic,
        out charactersOnPage, out linesPerPage);

    // Draws the string within the bounds of the page.
    e.Graphics.DrawString(stringToPrint, this.Font, Brushes.Black,
    e.MarginBounds, StringFormat.GenericTypographic);

    // Remove the portion of the string that has been printed.
    stringToPrint = stringToPrint.Substring(charactersOnPage);

    // Check to see if more pages are to be printed.
    e.HasMorePages = (stringToPrint.Length > 0);

    // If there are no more pages, reset the string to be printed.
    if (!e.HasMorePages)
        stringToPrint = documentContents;
}

Sub printDocument1_PrintPage(ByVal sender As Object, _
    ByVal e As PrintPageEventArgs) Handles printDocument1.PrintPage

    Dim charactersOnPage As Integer = 0
    Dim linesPerPage As Integer = 0

    ' Sets the value of charactersOnPage to the number of characters 
    ' of stringToPrint that will fit within the bounds of the page.
    e.Graphics.MeasureString(stringToPrint, Me.Font, e.MarginBounds.Size, _
        StringFormat.GenericTypographic, charactersOnPage, linesPerPage)

    ' Draws the string within the bounds of the page.
    e.Graphics.DrawString(stringToPrint, Me.Font, Brushes.Black, _
        e.MarginBounds, StringFormat.GenericTypographic)

    ' Remove the portion of the string that has been printed.
    stringToPrint = stringToPrint.Substring(charactersOnPage)

    ' Check to see if more pages are to be printed.
    e.HasMorePages = stringToPrint.Length > 0

    ' If there are no more pages, reset the string to be printed.
    If Not e.HasMorePages Then
        stringToPrint = documentContents
    End If

End Sub

将 PrintPreviewDialog 控件的 Document 属性设置为窗体上的 PrintDocument 组件。

printPreviewDialog1.Document = printDocument1;

printPreviewDialog1.Document = printDocument1

对 PrintPreviewDialog 控件调用 ShowDialog 方法。通常，您会从按钮的 Click 事件处理方法中调用 ShowDialog。调用 ShowDialog 将引发 PrintPage 事件，并将输出呈现到 PrintPreviewDialog 控件。当用户单击对话框上的打印图标时，将再次引发 PrintPage 事件，将输出发送到打印机而不是预览对话框。这就是在步骤 3 中呈现过程结束时重置字符串的原因。

下面的代码示例显示了窗体上按钮的 Click 事件处理方法。此事件处理方法调用方法读取文档并显示打印预览对话框。
```
private void printPreviewButton_Click(object sender, EventArgs e)
{
    ReadDocument();
    printPreviewDialog1.Document = printDocument1;
printPreviewDialog1.ShowDialog();
}
```
```
Private Sub printPreviewButton_Click(ByVal sender As Object, _
    ByVal e As EventArgs) Handles printPreviewButton.Click

    ReadDocument()
    printPreviewDialog1.Document = printDocument1
    printPreviewDialog1.ShowDialog()
End Sub
```

例

using System;
using System.Drawing;
using System.IO;
using System.Drawing.Printing;
using System.Windows.Forms;

namespace PrintPreviewApp
{
    public partial class Form1 : Form
    {
        private Button printPreviewButton;

        private PrintPreviewDialog printPreviewDialog1 = new PrintPreviewDialog();
        private PrintDocument printDocument1 = new PrintDocument();

        // Declare a string to hold the entire document contents.
        private string documentContents;

        // Declare a variable to hold the portion of the document that
        // is not printed.
        private string stringToPrint;

        public Form1()
        {
            this.printPreviewButton = new System.Windows.Forms.Button();
            this.printPreviewButton.Location = new System.Drawing.Point(12, 12);
            this.printPreviewButton.Size = new System.Drawing.Size(125, 23);
            this.printPreviewButton.Text = "Print Preview";
            this.printPreviewButton.Click += new System.EventHandler(this.printPreviewButton_Click);
            this.ClientSize = new System.Drawing.Size(292, 266);
            this.Controls.Add(this.printPreviewButton);
            printDocument1.PrintPage +=
                new PrintPageEventHandler(printDocument1_PrintPage);
        }
        private void ReadDocument()
        {
            string docName = "testPage.txt";
            string docPath = @"c:\";
            printDocument1.DocumentName = docName;
            using (FileStream stream = new FileStream(docPath + docName, FileMode.Open))
            using (StreamReader reader = new StreamReader(stream))
            {
                documentContents = reader.ReadToEnd();
            }
            stringToPrint = documentContents;
        }

        void printDocument1_PrintPage(object sender, PrintPageEventArgs e)
        {
            int charactersOnPage = 0;
            int linesPerPage = 0;

            // Sets the value of charactersOnPage to the number of characters
            // of stringToPrint that will fit within the bounds of the page.
            e.Graphics.MeasureString(stringToPrint, this.Font,
                e.MarginBounds.Size, StringFormat.GenericTypographic,
                out charactersOnPage, out linesPerPage);

            // Draws the string within the bounds of the page.
            e.Graphics.DrawString(stringToPrint, this.Font, Brushes.Black,
            e.MarginBounds, StringFormat.GenericTypographic);

            // Remove the portion of the string that has been printed.
            stringToPrint = stringToPrint.Substring(charactersOnPage);

            // Check to see if more pages are to be printed.
            e.HasMorePages = (stringToPrint.Length > 0);

            // If there are no more pages, reset the string to be printed.
            if (!e.HasMorePages)
                stringToPrint = documentContents;
        }
        private void printPreviewButton_Click(object sender, EventArgs e)
        {
            ReadDocument();
            printPreviewDialog1.Document = printDocument1;
        printPreviewDialog1.ShowDialog();
        }

        [STAThread]
        static void Main()
        {
            Application.EnableVisualStyles();
            Application.SetCompatibleTextRenderingDefault(false);
            Application.Run(new Form1());
        }
    }
}

Imports System.Drawing
Imports System.IO
Imports System.Drawing.Printing
Imports System.Windows.Forms



Class Form1
    Inherits Form

    Private WithEvents printPreviewButton As Button
    
    Private printPreviewDialog1 As New PrintPreviewDialog()
    Private WithEvents printDocument1 As New PrintDocument()
    
    ' Declare a string to hold the entire document contents.
    Private documentContents As String
    
    ' Declare a variable to hold the portion of the document that
    ' is not printed.
    Private stringToPrint As String

    Public Sub New() 
        Me.printPreviewButton = New System.Windows.Forms.Button()
        Me.printPreviewButton.Location = New System.Drawing.Point(12, 12)
        Me.printPreviewButton.Size = New System.Drawing.Size(125, 23)
        Me.printPreviewButton.Text = "Print Preview"
        Me.ClientSize = New System.Drawing.Size(292, 266)
        Me.Controls.Add(Me.printPreviewButton)

    End Sub
    
    Private Sub ReadDocument() 
        Dim docName As String = "testPage.txt"
        Dim docPath As String = "c:\"
        printDocument1.DocumentName = docName
        Dim stream As New FileStream(docPath + docName, FileMode.Open)
        Try
            Dim reader As New StreamReader(stream)
            Try
                documentContents = reader.ReadToEnd()
            Finally
                reader.Dispose()
            End Try
        Finally
            stream.Dispose()
        End Try
        stringToPrint = documentContents
    
    End Sub

    Sub printDocument1_PrintPage(ByVal sender As Object, _
        ByVal e As PrintPageEventArgs) Handles printDocument1.PrintPage

        Dim charactersOnPage As Integer = 0
        Dim linesPerPage As Integer = 0

        ' Sets the value of charactersOnPage to the number of characters 
        ' of stringToPrint that will fit within the bounds of the page.
        e.Graphics.MeasureString(stringToPrint, Me.Font, e.MarginBounds.Size, _
            StringFormat.GenericTypographic, charactersOnPage, linesPerPage)

        ' Draws the string within the bounds of the page.
        e.Graphics.DrawString(stringToPrint, Me.Font, Brushes.Black, _
            e.MarginBounds, StringFormat.GenericTypographic)

        ' Remove the portion of the string that has been printed.
        stringToPrint = stringToPrint.Substring(charactersOnPage)

        ' Check to see if more pages are to be printed.
        e.HasMorePages = stringToPrint.Length > 0

        ' If there are no more pages, reset the string to be printed.
        If Not e.HasMorePages Then
            stringToPrint = documentContents
        End If

    End Sub

    Private Sub printPreviewButton_Click(ByVal sender As Object, _
        ByVal e As EventArgs) Handles printPreviewButton.Click

        ReadDocument()
        printPreviewDialog1.Document = printDocument1
        printPreviewDialog1.ShowDialog()
    End Sub

    <STAThread()>  _
    Shared Sub Main() 
        Application.EnableVisualStyles()
        Application.SetCompatibleTextRenderingDefault(False)
        Application.Run(New Form1())
    
    End Sub
End Class

编译代码

此示例需要：

对 System、System.Windows.Forms、System.Drawing 程序集的引用。

通过

如何使用打印预览在 Windows 窗体中打印

使用 PrintPreviewDialog 控件预览文本文档

例

编译代码

另请参阅

其他资源