printtextexample.java

Eclipse从入门到精通源代码/第二篇 SWT_JFace篇(6-16章)

/**
 * @作者：陈刚
 * @Email：[e-mail]
 * @Blog：http://blog.csdn.net/glchengang
 */
package jface.dialog.other;

import java.io.BufferedReader;
import java.io.FileNotFoundException;
import java.io.FileReader;
import java.io.IOException;

import org.eclipse.swt.SWT;
import org.eclipse.swt.graphics.GC;
import org.eclipse.swt.graphics.Point;
import org.eclipse.swt.graphics.Rectangle;
import org.eclipse.swt.printing.PrintDialog;
import org.eclipse.swt.printing.Printer;
import org.eclipse.swt.printing.PrinterData;
import org.eclipse.swt.widgets.Display;
import org.eclipse.swt.widgets.FileDialog;
import org.eclipse.swt.widgets.Shell;

public class PrintTextExample {

    public static void main(String[] args) {
        try {
            PrintTextExample window = new PrintTextExample();
            window.open();
        } catch (Exception e) {
            e.printStackTrace();
        }
    }

    public void open() {
        final Display display = Display.getDefault();
        final Shell shell = new Shell();
        //用文件选择对话框取得一个文件名字符串
        FileDialog fileDlg = new FileDialog(shell, SWT.OPEN);
        String fileName = fileDlg.open();
        if (fileName != null) {
            //用打印对话框取得一个打印对话printer
            PrintDialog printDlg = new PrintDialog(shell);
            PrinterData printerData = printDlg.open();
            if (printerData != null) {
                Printer printer = new Printer(printerData);
                //打印文件
                try {
                    String contents = getFileContents(fileName);//取出文件内容
                    MyPrinter p = new MyPrinter(printer, fileName, contents);
                    p.print();
                } catch (java.lang.Exception e) {
                    e.printStackTrace();
                }
                printer.dispose();//printer对象没用后要手动dispose掉
            }
        }
        display.dispose();
    }

    /**
     * 取出文件内容的方法
     */
    private String getFileContents(String fileName) throws FileNotFoundException, IOException {
        StringBuffer contents = new StringBuffer();
        BufferedReader reader = null;
        try {
            reader = new BufferedReader(new FileReader(fileName));
            while (reader.ready()) {
                contents.append(reader.readLine());
                contents.append("\n"); //每读完一行，换行一次
            }
        } finally {
            if (reader != null)
                try {
                    reader.close();
                } catch (IOException e) {
                }
        }
        return contents.toString();
    }

    /**
     * 自定义的打印实现类，将所需参数传入，调用print方法即可打印
     */
    private class MyPrinter {
        private Printer printer; // 打印对象

        private String fileName; //文件名（带路径）

        private String contents; //文件名对应的文件内容

        private GC gc; //一个GC对象

        private int xPos, yPos; //打印对象printer用的坐标

        private Rectangle bounds; //打印空间

        private StringBuffer buf; // Holds a word at a time

        private int lineHeight; // The height of a line of text

        /**
         * 构造函数
         */
        public MyPrinter(Printer printer, String fileName, String contents) {
            this.printer = printer;
            this.fileName = fileName;
            this.contents = contents;
        }

        /**
         * 打印文件的方法
         */
        public void print() {
            if (printer.startJob(fileName)) {//开始打印任务
                //设定打印空间
                bounds = computePrintArea(printer);
                xPos = bounds.x;
                yPos = bounds.y;
                //创建GC对象
                gc = new GC(printer);
                //设定线的高度
                lineHeight = gc.getFontMetrics().getHeight();
                //设定tab键的空格数
                int tabWidth = gc.stringExtent(" ").x;
                //开始打印
                printer.startPage();
                buf = new StringBuffer();
                char c;
                for (int i = 0, n = contents.length(); i < n; i++) {
                    //得到文件内容的字符
                    c = contents.charAt(i);
                    //如果读到\n，调用printBuffer方法将buf中的字符打印，并换行
                    if (c == '\n') {
                        printBuffer();
                        printNewline();
                    }
                    //如果读到\t，表示要跳过一定的空格
                    else if (c == '\t') {
                        xPos += tabWidth;
                    } else {
                        buf.append(c);//将字符添加进buf变量
                        //检查是否有空间，如果则打印
                        if (Character.isWhitespace(c))
                            printBuffer();

                    }
                }
                printer.endPage();
                printer.endJob();
                gc.dispose();
            }
        }

        /**
         * 打印缓存buf变量中的字符
         */
        private void printBuffer() {
            //取得缓存中的字符宽度
            int width = gc.stringExtent(buf.toString()).x;
            //如果宽度不够，则换行
            if (xPos + width > bounds.x + bounds.width)
                printNewline();
            //打印缓存buf变量中的字符
            gc.drawString(buf.toString(), xPos, yPos, false);
            xPos += width;
            buf.setLength(0);
        }

        /**
         * 打印换行的方法
         */
        private void printNewline() {
            //重设新行的坐标
            xPos = bounds.x;
            yPos += lineHeight;
            //如果超过页长度，则换一页打印
            if (yPos > bounds.y + bounds.height) {
                yPos = bounds.y;
                printer.endPage();
                printer.startPage();
            }
        }

        /**
         * 计算打印空间的方法
         */
        private Rectangle computePrintArea(Printer printer) {
            //取得打印空间
            Rectangle rect = printer.getClientArea();
            Rectangle trim = printer.computeTrim(0, 0, 0, 0);
            //取得打印机的DPI（DPI：表示每英寸的点数,即通常说的打印机的分辨率）
            Point dpi = printer.getDPI();
            // 计算可打印空间
            int left = trim.x + dpi.x;
            if (left < rect.x)
                left = rect.x;
            int right = (rect.width + trim.x + trim.width) - dpi.x;
            if (right > rect.width)
                right = rect.width;
            int top = trim.y + dpi.y;
            if (top < rect.y)
                top = rect.y;
            int bottom = (rect.height + trim.y + trim.height) - dpi.y;
            if (bottom > rect.height)
                bottom = rect.height;
            return new Rectangle(left, top, right - left, bottom - top);
        }
    }
}