java可打印文件无法正常工作
我有一个系统，用户可以注册学生、科目和每个科目的学生成绩，以及主题和日期。您可以通过输入学生代码并从组合框中选择科目来搜索特定科目中的特定学生成绩。如果搜索它，这些内容将显示在jTable1中
然后，我有一个打印按钮。当用户单击“打印”按钮时，jTable1中显示的内容将转到jTable2，这两个表之间的区别在于jTable1显示学生的姓名和科目的名称，但jTable2不显示。为了更好地理解，这里有一张图片：
http://i.stack.imgur.com/37SNh.png
因此，当用户单击按钮打印jTable2时，我在这里使用了以下代码：
MessageFormat header = new MessageFormat("Ficha Pedagógica - "+jComboBox1.getSelectedItem());
MessageFormat footer = new MessageFormat("Página {0,number,integer}");
try{
jTable2.print(JTable.PrintMode.NORMAL, header, null);
}
catch(java.awt.print.PrinterException e){
System.out.println("error");
}
事实上，我想打印两个标题，但使用内置的打印功能无法实现这一点。因此，在堆栈溢出中，我找到了以下主题：
How to print multiple header lines with MessageFormat using a JTable
在我找到这个之后，我尝试使用那里给出的代码。因为我是一个初学者，即使代码中有所有的注释，我也不能完全理解它。所以，我试图实现它，但现在，当我点击“打印”按钮时，什么都没有发生。这是我的打印按钮代码：
private void jButton4ActionPerformed(java.awt.event.ActionEvent evt) {
// TODO add your handling code here:
try{
Class.forName(driver);
con = DriverManager.getConnection(str_conn,usuario,senha);
stmt = con.createStatement();
sql = "select topico, nota, datanota from notas where notas.cod_aluno ="+jTextField1.getText()+" and notas.cod_curso ="+jTextField2.getText()+" order by notas.datanota";
rs = stmt.executeQuery(sql);
if(rs == null){
return;
}
ResultSetMetaData rsmd;
rsmd = rs.getMetaData();
Vector vetColuna = new Vector();
for(int i = 0;i<rsmd.getColumnCount();i++){
vetColuna.add(rsmd.getColumnLabel(i+1));
}
Vector vetLinhas = new Vector();
while(rs.next()){
Vector vetLinha = new Vector();
for(int i = 0;i<rsmd.getColumnCount();i++){
vetLinha.add(rs.getObject(i+1));
}
vetLinhas.add(vetLinha);
jTable2.setModel(new DefaultTableModel(vetLinhas,vetColuna));
}
}catch(ClassNotFoundException ex){
JOptionPane.showMessageDialog(null,"Erro\nNão foi possível carregar o driver.");
System.out.println("Nao foi possivel carregar o driver");
ex.printStackTrace();
}catch(SQLException ex){
JOptionPane.showMessageDialog(null,"Erro\nCertifique-se de que todos os\ncampos estejam preenchidos corretamente.");
System.out.println("Problema com o SQL");
ex.printStackTrace();
}
/*MessageFormat header = new MessageFormat("Ficha Pedagógica - "+jComboBox1.getSelectedItem());
MessageFormat footer = new MessageFormat("Página {0,number,integer}");
try{
jTable2.print(JTable.PrintMode.NORMAL, header, null);
}
catch(java.awt.print.PrinterException e){
System.out.println("gsgd");
}*/
DefaultTableModel dtm = new DefaultTableModel(new String[] { "Column 1" }, 1);
JTable jTable2 = new JTable(dtm) {
@Override
public Printable getPrintable(PrintMode printMode, MessageFormat headerFormat, MessageFormat footerFormat) {
return new TablePrintable(this, printMode, headerFormat, footerFormat);
}
};
}
“TablePrintable”类的代码如下所示：
static class TablePrintable implements Printable {
private final JTable table;
private final JTableHeader header;
private final TableColumnModel colModel;
private final int totalColWidth;
private final JTable.PrintMode printMode;
private final MessageFormat headerFormat;
private final MessageFormat footerFormat;
private int last = -1;
private int row = 0;
private int col = 0;
private final Rectangle clip = new Rectangle(0, 0, 0, 0);
private final Rectangle hclip = new Rectangle(0, 0, 0, 0);
private final Rectangle tempRect = new Rectangle(0, 0, 0, 0);
private static final int H_F_SPACE = 8;
private static final float HEADER_FONT_SIZE = 18.0f;
private static final float FOOTER_FONT_SIZE = 12.0f;
private final Font headerFont;
private final Font footerFont;
public TablePrintable(JTable table, JTable.PrintMode printMode, MessageFormat headerFormat,
MessageFormat footerFormat) {
this.table = table;
header = table.getTableHeader();
colModel = table.getColumnModel();
totalColWidth = colModel.getTotalColumnWidth();
if (header != null) {
// the header clip height can be set once since it's unchanging
hclip.height = header.getHeight();
}
this.printMode = printMode;
this.headerFormat = headerFormat;
this.footerFormat = footerFormat;
// derive the header and footer font from the table's font
headerFont = table.getFont().deriveFont(Font.BOLD, HEADER_FONT_SIZE);
footerFont = table.getFont().deriveFont(Font.PLAIN, FOOTER_FONT_SIZE);
}
@Override
public int print(Graphics graphics, PageFormat pageFormat, int pageIndex) throws PrinterException {
// for easy access to these values
final int imgWidth = (int) pageFormat.getImageableWidth();
final int imgHeight = (int) pageFormat.getImageableHeight();
if (imgWidth <= 0) {
throw new PrinterException("Width of printable area is too small.");
}
// to pass the page number when formatting the header and footer
// text
Object[] pageNumber = new Object[] { Integer.valueOf(pageIndex + 1) };
// fetch the formatted header text, if any
String headerText = null;
if (headerFormat != null) {
headerText = headerFormat.format(pageNumber);
}
// fetch the formatted footer text, if any
String footerText = null;
if (footerFormat != null) {
footerText = footerFormat.format(pageNumber);
}
// to store the bounds of the header and footer text
Rectangle2D hRect = null;
Rectangle2D fRect = null;
// the amount of vertical space needed for the header and footer
// text
int headerTextSpace = 0;
int footerTextSpace = 0;
// the amount of vertical space available for printing the table
int availableSpace = imgHeight;
// if there's header text, find out how much space is needed for it
// and subtract that from the available space
if (headerText != null) {
graphics.setFont(headerFont);
int nbLines = headerText.split("\n").length;
hRect = graphics.getFontMetrics().getStringBounds(headerText, graphics);
hRect = new Rectangle2D.Double(hRect.getX(), Math.abs(hRect.getY()), hRect.getWidth(),
hRect.getHeight() * nbLines);
headerTextSpace = (int) Math.ceil(hRect.getHeight() * nbLines);
availableSpace -= headerTextSpace + H_F_SPACE;
}
// if there's footer text, find out how much space is needed for it
// and subtract that from the available space
if (footerText != null) {
graphics.setFont(footerFont);
fRect = graphics.getFontMetrics().getStringBounds(footerText, graphics);
footerTextSpace = (int) Math.ceil(fRect.getHeight());
availableSpace -= footerTextSpace + H_F_SPACE;
}
if (availableSpace <= 0) {
throw new PrinterException("Height of printable area is too small.");
}
// depending on the print mode, we may need a scale factor to
// fit the table's entire width on the page
double sf = 1.0D;
if (printMode == JTable.PrintMode.FIT_WIDTH && totalColWidth > imgWidth) {
// if not, we would have thrown an acception previously
assert imgWidth > 0;
// it must be, according to the if-condition, since imgWidth > 0
assert totalColWidth > 1;
sf = (double) imgWidth / (double) totalColWidth;
}
// dictated by the previous two assertions
assert sf > 0;
// This is in a loop for two reasons:
// First, it allows us to catch up in case we're called starting
// with a non-zero pageIndex. Second, we know that we can be called
// for the same page multiple times. The condition of this while
// loop acts as a check, ensuring that we don't attempt to do the
// calculations again when we are called subsequent times for the
// same page.
while (last < pageIndex) {
// if we are finished all columns in all rows
if (row >= table.getRowCount() && col == 0) {
return NO_SUCH_PAGE;
}
// rather than multiplying every row and column by the scale
// factor
// in findNextClip, just pass a width and height that have
// already
// been divided by it
int scaledWidth = (int) (imgWidth / sf);
int scaledHeight = (int) ((availableSpace - hclip.height) / sf);
// calculate the area of the table to be printed for this page
findNextClip(scaledWidth, scaledHeight);
last++;
}
// create a copy of the graphics so we don't affect the one given to
// us
Graphics2D g2d = (Graphics2D) graphics.create();
// translate into the co-ordinate system of the pageFormat
g2d.translate(pageFormat.getImageableX(), pageFormat.getImageableY());
// to save and store the transform
AffineTransform oldTrans;
// if there's footer text, print it at the bottom of the imageable
// area
if (footerText != null) {
oldTrans = g2d.getTransform();
g2d.translate(0, imgHeight - footerTextSpace);
String[] lines = footerText.split("\n");
printText(g2d, lines, fRect, footerFont, imgWidth);
g2d.setTransform(oldTrans);
}
// if there's header text, print it at the top of the imageable area
// and then translate downwards
if (headerText != null) {
String[] lines = headerText.split("\n");
printText(g2d, lines, hRect, headerFont, imgWidth);
g2d.translate(0, headerTextSpace + H_F_SPACE);
}
// constrain the table output to the available space
tempRect.x = 0;
tempRect.y = 0;
tempRect.width = imgWidth;
tempRect.height = availableSpace;
g2d.clip(tempRect);
// if we have a scale factor, scale the graphics object to fit
// the entire width
if (sf != 1.0D) {
g2d.scale(sf, sf);
// otherwise, ensure that the current portion of the table is
// centered horizontally
} else {
int diff = (imgWidth - clip.width) / 2;
g2d.translate(diff, 0);
}
// store the old transform and clip for later restoration
oldTrans = g2d.getTransform();
Shape oldClip = g2d.getClip();
// if there's a table header, print the current section and
// then translate downwards
if (header != null) {
hclip.x = clip.x;
hclip.width = clip.width;
g2d.translate(-hclip.x, 0);
g2d.clip(hclip);
header.print(g2d);
// restore the original transform and clip
g2d.setTransform(oldTrans);
g2d.setClip(oldClip);
// translate downwards
g2d.translate(0, hclip.height);
}
// print the current section of the table
g2d.translate(-clip.x, -clip.y);
g2d.clip(clip);
table.print(g2d);
// restore the original transform and clip
g2d.setTransform(oldTrans);
g2d.setClip(oldClip);
// draw a box around the table
g2d.setColor(Color.BLACK);
g2d.drawRect(0, 0, clip.width, hclip.height + clip.height);
// dispose the graphics copy
g2d.dispose();
return PAGE_EXISTS;
}
private void printText(Graphics2D g2d, String[] lines, Rectangle2D rect, Font font, int imgWidth) {
g2d.setColor(Color.BLACK);
g2d.setFont(font);
for (int i = 0; i < lines.length; i++) {
int tx;
// if the text is small enough to fit, center it
if (rect.getWidth() < imgWidth) {
tx = (int) (imgWidth / 2 - g2d.getFontMetrics().getStringBounds(lines[i], g2d).getWidth() / 2);
// otherwise, if the table is LTR, ensure the left side of
// the text shows; the right can be clipped
} else if (table.getComponentOrientation().isLeftToRight()) {
tx = 0;
// otherwise, ensure the right side of the text shows
} else {
tx = -(int) (Math.ceil(rect.getWidth()) - imgWidth);
}
int ty = (int) Math.ceil(Math.abs(rect.getY() + i * rect.getHeight() / lines.length));
g2d.drawString(lines[i], tx, ty);
}
}
private void findNextClip(int pw, int ph) {
final boolean ltr = table.getComponentOrientation().isLeftToRight();
// if we're ready to start a new set of rows
if (col == 0) {
if (ltr) {
// adjust clip to the left of the first column
clip.x = 0;
} else {
// adjust clip to the right of the first column
clip.x = totalColWidth;
}
// adjust clip to the top of the next set of rows
clip.y += clip.height;
// adjust clip width and height to be zero
clip.width = 0;
clip.height = 0;
// fit as many rows as possible, and at least one
int rowCount = table.getRowCount();
int rowHeight = table.getRowHeight(row);
do {
clip.height += rowHeight;
if (++row >= rowCount) {
break;
}
rowHeight = table.getRowHeight(row);
} while (clip.height + rowHeight <= ph);
}
// we can short-circuit for JTable.PrintMode.FIT_WIDTH since
// we'll always fit all columns on the page
if (printMode == JTable.PrintMode.FIT_WIDTH) {
clip.x = 0;
clip.width = totalColWidth;
return;
}
if (ltr) {
// adjust clip to the left of the next set of columns
clip.x += clip.width;
}
// adjust clip width to be zero
clip.width = 0;
// fit as many columns as possible, and at least one
int colCount = table.getColumnCount();
int colWidth = colModel.getColumn(col).getWidth();
do {
clip.width += colWidth;
if (!ltr) {
clip.x -= colWidth;
}
if (++col >= colCount) {
// reset col to 0 to indicate we're finished all columns
col = 0;
break;
}
colWidth = colModel.getColumn(col).getWidth();
} while (clip.width + colWidth <= pw);
}
}
但是，就像我说的，当我点击“打印”按钮时，什么也没发生。出了什么问题
# 1 楼答案
对于新修改的
JTable，您只需要调用它的print方法因为您已经重写了
getPrintable方法来返回自己的实现，所以这将用于物理打印表更新
标题文本需要用
\n分隔，例如它可以产生
更新
据我所知，在无法完全运行代码的情况下，您的打印代码应该看起来像