123 lines
2.9 KiB
Java
123 lines
2.9 KiB
Java
import java.awt.Font;
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import java.awt.Rectangle;
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import java.awt.Color;
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import java.awt.Graphics;
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import javax.swing.JScrollPane;
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import javax.swing.JTextArea;
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import javax.swing.JScrollBar;
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/** A message area displays text in a scrollable text widget. It is a
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singleton. Other objects can access it directly to display messages.
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*/
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public class MessageArea
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extends JScrollPane
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{
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public static synchronized MessageArea Instance ()
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{
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if (saInstance == null)
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saInstance = new MessageArea ();
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return saInstance;
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}
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/** Create a new message area. This method is private because the class is
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a singleton and may therefore not be instanciated from the outside.
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*/
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private MessageArea ()
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{
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maText = new JTextArea();
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maText.setBackground (new Color (255,250,240));
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maText.setFont (new Font ("Helvetica", Font.PLAIN, 9));
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setViewportView (maText);
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setVerticalScrollBarPolicy (JScrollPane.VERTICAL_SCROLLBAR_ALWAYS);
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setHorizontalScrollBarPolicy (JScrollPane.HORIZONTAL_SCROLLBAR_ALWAYS);
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printMessage (
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"class path is " + System.getProperty ("java.class.path") + "\n");
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}
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/** Show the given string at the end of the message area and scroll to make
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it visible.
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*/
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public static synchronized void print (String aMessage)
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{
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print (0, aMessage);
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}
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/** Show the given string at the end of the message area and scroll to make
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it visible. Indent the string as requested.
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*/
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public static synchronized void print (int nIndentation, String aMessage)
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{
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while (nIndentation-- > 0)
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aMessage = " " + aMessage;
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Instance().printMessage(aMessage);
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}
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/** Show the given string at the end of the message area and scroll to make
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it visible.
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*/
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public static void println (String aMessage)
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{
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println (0, aMessage);
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}
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/** Show the given string at the end of the message area and scroll to make
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it visible.
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*/
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public static void println (int nIndentation, String aMessage)
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{
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print (nIndentation, aMessage+"\n");
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}
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public void paintComponent (Graphics g)
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{
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synchronized (g)
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{
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JScrollBar sb = getVerticalScrollBar();
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if (sb != null)
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{
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int nScrollBarValue = sb.getMaximum() - sb.getVisibleAmount() - 1;
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sb.setValue (nScrollBarValue);
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}
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super.paintComponent (g);
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}
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}
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/** Append the given string to the end of the text and scroll so that it
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becomes visible. This is an internal method. Use one of the static
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and public ones.
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*/
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private synchronized void printMessage (String aMessage)
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{
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maText.append (aMessage);
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}
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private static MessageArea saInstance = null;
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private JTextArea maText;
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}
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