Java, Swing

JLabel, Hintergrundfarbe setzen

JLabel label = new JLabel();
label.setOpaque(true);  // wichtig!
label.setBackground(Color.CYAN);

JLabel: Innenabstand zum Text setzen

import java.awt.Color; 
import java.awt.FlowLayout;

import javax.swing.BorderFactory;
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.border.EmptyBorder;
import javax.swing.border.LineBorder;

public class LabelPadding {

   public LabelPadding() {
      JFrame frame = new JFrame("JLabel mit Padding");

      initGUI(frame);

      frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
      frame.setLocationRelativeTo(null);
      frame.setVisible(true);
   }

   private void initGUI(JFrame frame) {
      JLabel label = new JLabel("Labeltext");
      EmptyBorder eBorder = new EmptyBorder(6, 6, 6, 6); // oben, rechts, unten, links
      LineBorder lBorder = new LineBorder(new Color(96, 96, 96));
      label.setBorder(BorderFactory.createCompoundBorder(lBorder, eBorder));
      frame.setLayout(new BorderLayout());
      frame.add(label, BorderLayout.CENTER);
   }

   public static void main(String[] args) {
      new LabelPadding();
   }
}

JTable, Bereich selektieren

JTable table = new JTable(4, 4);  // 4 rows, 4 columns
table.setColumnSelectionInterval(1, 2);  // Selektiert die mittleren beiden Spalten
table.setRowSelectionInterval(1, 2);  // Selektiert die mittleren beiden Zeilen

JTable, Focus-Rahmen auf Zelle beschränken (statt auf Zeile)

JTable table = new JTable(2, 2);  // 2 rows, 2 columns
table.setColumnSelectionAllowed(true);

KeyEvent, selber senden

JTable table = new JTable();

int key = KeyEvent.VK_DOWN;
Component target = table;

KeyEvent pressed = new KeyEvent(target, KeyEvent.KEY_PRESSED, System.currentTimeMillis(), 0, key, (char) key, 1);
KeyEvent typed = new KeyEvent(target, KeyEvent.KEY_TYPED, System.currentTimeMillis(), 0, 0, (char) key);
KeyEvent released = new KeyEvent(target, KeyEvent.KEY_RELEASED, System.currentTimeMillis(), 0, key, (char) key, 1);

EventQueue queue = Toolkit.getDefaultToolkit().getSystemEventQueue();
queue.postEvent(pressed);
queue.postEvent(typed);
queue.postEvent(released);

JTestField auf numerische Eingabe beschränken

package com.sowas.itwiki.snippets;
 
import javax.swing.text.BadLocationException;
import javax.swing.text.PlainDocument;
import javax.swing.text.AttributeSet;
import java.math.BigDecimal;
 
import javax.swing.*;
import java.awt.*;
import java.awt.event.*;
 
 
public class NumberDocument extends PlainDocument {
   @Override
   public void insertString (final int offset, final String text,
                             final AttributeSet attributeSet) throws BadLocationException {
      if (isNumber(text)){
         super.insertString (offset, text, attributeSet);
      }
   }
 
   protected boolean isNumber (final String text) {
      try {
         if (text.length() > 0){
            // Versuchen eine Zahl zu erzeugen:
            new BigDecimal(text);  
         }
         return true;
      }catch (final NumberFormatException e){
         // Hat nicht geklappt, also keine Zahl
      }
      return false;
   }
 
   public static void main (final String [] ignored){
      JFrame frame = new JFrame ("Numerisches JTextField");
      frame.getContentPane().setLayout (new BorderLayout (0,0));
      frame.getContentPane().add(new JTextField (new NumberDocument (), "", 0), BorderLayout.NORTH);
      frame.pack ();
      frame.setVisible (true);
   }
}

JTable, mit Zeilenbeschriftung

package com.sowas.javawiki.rowheadertable;
 
import java.awt.BorderLayout;
import java.awt.Component;
 
import javax.swing.AbstractListModel;
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JList;
import javax.swing.JScrollPane;
import javax.swing.JTable;
import javax.swing.ListCellRenderer;
import javax.swing.ListModel;
import javax.swing.UIManager;
import javax.swing.table.DefaultTableModel;
import javax.swing.table.JTableHeader;
 
public class RowHeaderTable extends JFrame {
   public RowHeaderTable(){
      super("Row Header Table");
 
      ListModel lm = new RowHeaderListModel();
 
      DefaultTableModel dtm = new DefaultTableModel(lm.getSize(), 4);
      JTable table = new JTable(dtm);
      table.setAutoResizeMode(JTable.AUTO_RESIZE_OFF);
 
      JList rowHeader = new JList(lm);
      rowHeader.setFixedCellWidth(30);
      rowHeader.setFixedCellHeight(table.getRowHeight());
      rowHeader.setCellRenderer(new RowHeaderRenderer(table));
 
      JScrollPane scroll = new JScrollPane(table);
      scroll.setRowHeaderView(rowHeader);
      getContentPane().add(scroll, BorderLayout.CENTER);
   }
 
   public static void main(String[] args){
      RowHeaderTable frame = new RowHeaderTable();
      frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
      frame.setVisible(true);
   }
}
 
class RowHeaderListModel extends AbstractListModel{
   String strRowHeaders[] = {"1", "2", "3", "4", "5", "6", "7"};
 
   public int getSize(){
      return strRowHeaders.length;
   }
 
   public Object getElementAt(int index){
      return strRowHeaders[index];
   }
}
 
class RowHeaderRenderer extends JLabel implements ListCellRenderer{
   RowHeaderRenderer(JTable table){
      JTableHeader tableHeader = table.getTableHeader();
      setBorder(UIManager.getBorder("TableHeader.cellBorder"));
      setHorizontalAlignment(CENTER);
      setForeground(tableHeader.getForeground());
      setOpaque(true);  // Damit der Hintergrund nicht verändert wird
      setFont(tableHeader.getFont());
   }
 
   public Component getListCellRendererComponent(JList list, Object value, int index, 
                                                 boolean fSelected, boolean fCellHasFocus){
      setText((value == null) ? "" : value.toString());
      return this;
   }
}

JTable, Spalten fixieren

JTable table = new JTable(10, 20);
table.getTableHeader().setReorderingAllowed(false);

JTable, Zelle zentrieren

public class MyCellRenderer extends JLabel implements TableCellRenderer {
   public Component getTableCellRendererComponent(JTable table, Object value, boolean isSelected, 
                                                  boolean hasFocus, int row, int column) {
      setHorizontalAlignment(DefaultTableCellRenderer.CENTER);
      return this;
   }
}

JTable table = new JTable(..
table.setDefaultRenderer(Object.class, new MyCellRenderer());

JTable, Spaltenbreite setzen

JTable table = new JTable(10, 20);
 
// Autoresizing abschalten, sonst sind alle Spalten gleich breit:
table.setAutoResizeMode(JTable.AUTO_RESIZE_OFF);
 
// Erste Spalte auf 100 Pixel Breite setzen:
final int INDEX_COLUMN1 = 0;
TableColumn col = table.getColumnModel().getColumn(INDEX_COLUMN1);
col.setPreferredWidth(100);