Como imprimir nos Windows Forms usando Visualização de Impressão

É muito comum na programação do Windows Forms oferecer a visualização de impressão além dos serviços de impressão. Uma maneira fácil de adicionar serviços de visualização de impressão ao seu aplicativo é usar um controle em combinação com a PrintPage lógica de manipulação de eventos para imprimir um PrintPreviewDialog arquivo.

Visualizar um documento de texto com um controle PrintPreviewDialog

1. Adicione um PrintPreviewDialog, PrintDocumente duas cadeias de caracteres ao formulário.

   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
   

2. Defina a propriedade para o documento que você deseja imprimir e abra e leia o conteúdo do documento para a DocumentName cadeia de caracteres adicionada anteriormente.

   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
   

3. Como faria para imprimir o documento, no PrintPage manipulador de eventos, use a Graphics PrintPageEventArgs propriedade da classe e o conteúdo do arquivo para calcular linhas por página e renderizar o conteúdo do documento. Depois que cada página for desenhada, verifique se é a última página e defina a HasMorePages PrintPageEventArgs propriedade do correspondente. O PrintPage evento é levantado até HasMorePages que seja false. Após a renderização do documento ser concluída, redefina a cadeia de caracteres a ser renderizada. Além disso, verifique se o PrintPage evento está associado ao seu método de manipulação de eventos.

   Observação

   Você poderá já ter concluído as etapas 2 e 3 se tiver implementado a impressão em seu aplicativo.

   No exemplo de código a seguir, o manipulador de eventos é usado para imprimir o arquivo “testPage.txt” na mesma fonte usada no formulário.

   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
   

4. Defina a Document PrintPreviewDialog propriedade do controle para o PrintDocument componente no formulário.

   printPreviewDialog1.Document = printDocument1;
   

   printPreviewDialog1.Document = printDocument1
   

5. Chame PrintPreviewDialog o ShowDialog método no controle. Normalmente, você chamaria ShowDialog a partir do Click método de manipulação de eventos de um botão. A chamada ShowDialog gera o evento e renderiza a saída para o PrintPreviewDialog PrintPage controle. Quando o usuário clica no ícone de impressão na caixa de diálogo, o PrintPage evento é gerado novamente, enviando a saída para a impressora em vez da caixa de diálogo de visualização. É por isso a cadeia de caracteres é redefinida no final do processo de renderização na etapa 3.

   O exemplo de código a seguir mostra o Click método de manipulação de eventos para um botão no formulário. Esse método de manipulação de eventos chama os métodos para ler o documento e mostrar a caixa de diálogo de visualização de impressão.

   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
   

Exemplo

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 

Compilando o código

Este exemplo requer:

• Referências aos assemblies System, System.Windows.Forms e System.Drawing.

Confira também

• Como: imprimir um arquivo de texto de várias páginas nos Windows Forms
• Suporte à impressão nos Windows Forms
• Impressão mais segura nos Windows Forms