thanks.I has solved it.The following source is sample./* * This code is based on an example provided by John Vella, * a tutorial reader. */import javax.swing.*; import javax.swing.event.MouseInputAdapter; import java.awt.*; import java.awt.event.*; import java.util.*;/* ScrollDemo2.java is a 1.4 application that requires no other files. */ public class ScrollDemo2 extends JPanel implements MouseListener { private Dimension area; //indicates area taken up by graphics private Vector circles; //coordinates used to draw graphics private JPanel drawingPane; private final Color colors[] = { Color.red, Color.blue, Color.green, Color.orange, Color.cyan, Color.magenta, Color.darkGray, Color.yellow}; private final int color_n = colors.length; public ScrollDemo2() { super(new BorderLayout()); area = new Dimension(0,0); circles = new Vector(); //Set up the instructions. JLabel instructionsLeft = new JLabel( "Click left mouse button to place a circle."); JLabel instructionsRight = new JLabel( "Click right mouse button to clear drawing area."); JPanel instructionPanel = new JPanel(new GridLayout(0,1)); instructionPanel.add(instructionsLeft); instructionPanel.add(instructionsRight); //Set up the drawing area. drawingPane = new DrawingPane(); drawingPane.setBackground(Color.white); drawingPane.addMouseListener(this); //Put the drawing area in a scroll pane. JScrollPane scroller = new JScrollPane(drawingPane); scroller.setPreferredSize(new Dimension(200,200)); //Lay out this demo. add(instructionPanel, BorderLayout.PAGE_START); add(scroller, BorderLayout.CENTER); } /** The component inside the scroll pane. */ public class DrawingPane extends JPanel { protected void paintComponent(Graphics g) { super.paintComponent(g); Rectangle rect; for (int i = 0; i < circles.size(); i++) { rect = (Rectangle)circles.elementAt(i); g.setColor(colors[(i % color_n)]); g.fillOval(rect.x, rect.y, rect.width, rect.height); } } } //Handle mouse events. public void mouseReleased(MouseEvent e) { final int W = 100; final int H = 100; boolean changed = false; if (SwingUtilities.isRightMouseButton(e)) { //This will clear the graphic objects. circles.removeAllElements(); area.width=0; area.height=0; changed = true; } else { int x = e.getX() - W/2; int y = e.getY() - H/2; if (x < 0) x = 0; if (y < 0) y = 0; Rectangle rect = new Rectangle(x, y, W, H); circles.addElement(rect); drawingPane.scrollRectToVisible(rect); int this_width = (x + W + 2); if (this_width > area.width) { area.width = this_width; changed=true; } int this_height = (y + H + 2); if (this_height > area.height) { area.height = this_height; changed=true; } } if (changed) { //Update client's preferred size because //the area taken up by the graphics has //gotten larger or smaller (if cleared). drawingPane.setPreferredSize(area); //Let the scroll pane know to update itself //and its scrollbars. drawingPane.revalidate(); } drawingPane.repaint(); } public void mouseClicked(MouseEvent e){} public void mouseEntered(MouseEvent e){} public void mouseExited(MouseEvent e){} public void mousePressed(MouseEvent e){} /** * Create the GUI and show it. For thread safety, * this method should be invoked from the * event-dispatching thread. */ private static void createAndShowGUI() { //Make sure we have nice window decorations. JFrame.setDefaultLookAndFeelDecorated(true); //Create and set up the window. JFrame frame = new JFrame("ScrollDemo2"); frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE); //Create and set up the content pane. JComponent newContentPane = new ScrollDemo2(); newContentPane.setOpaque(true); //content panes must be opaque frame.setContentPane(newContentPane); //Display the window. frame.pack(); frame.setVisible(true); } public static void main(String[] args) { //Schedule a job for the event-dispatching thread: //creating and showing this application's GUI. javax.swing.SwingUtilities.invokeLater(new Runnable() { public void run() { createAndShowGUI(); } }); } }
我现在需要的是鼠标到了边界自动扩充
自己试过也可以,现在只能提醒一下书名
叫《java专业编程》
* This code is based on an example provided by John Vella,
* a tutorial reader.
*/import javax.swing.*;
import javax.swing.event.MouseInputAdapter;
import java.awt.*;
import java.awt.event.*;
import java.util.*;/* ScrollDemo2.java is a 1.4 application that requires no other files. */
public class ScrollDemo2 extends JPanel
implements MouseListener {
private Dimension area; //indicates area taken up by graphics
private Vector circles; //coordinates used to draw graphics
private JPanel drawingPane; private final Color colors[] = {
Color.red, Color.blue, Color.green, Color.orange,
Color.cyan, Color.magenta, Color.darkGray, Color.yellow};
private final int color_n = colors.length; public ScrollDemo2() {
super(new BorderLayout()); area = new Dimension(0,0);
circles = new Vector(); //Set up the instructions.
JLabel instructionsLeft = new JLabel(
"Click left mouse button to place a circle.");
JLabel instructionsRight = new JLabel(
"Click right mouse button to clear drawing area.");
JPanel instructionPanel = new JPanel(new GridLayout(0,1));
instructionPanel.add(instructionsLeft);
instructionPanel.add(instructionsRight); //Set up the drawing area.
drawingPane = new DrawingPane();
drawingPane.setBackground(Color.white);
drawingPane.addMouseListener(this); //Put the drawing area in a scroll pane.
JScrollPane scroller = new JScrollPane(drawingPane);
scroller.setPreferredSize(new Dimension(200,200)); //Lay out this demo.
add(instructionPanel, BorderLayout.PAGE_START);
add(scroller, BorderLayout.CENTER);
} /** The component inside the scroll pane. */
public class DrawingPane extends JPanel {
protected void paintComponent(Graphics g) {
super.paintComponent(g); Rectangle rect;
for (int i = 0; i < circles.size(); i++) {
rect = (Rectangle)circles.elementAt(i);
g.setColor(colors[(i % color_n)]);
g.fillOval(rect.x, rect.y, rect.width, rect.height);
}
}
} //Handle mouse events.
public void mouseReleased(MouseEvent e) {
final int W = 100;
final int H = 100;
boolean changed = false;
if (SwingUtilities.isRightMouseButton(e)) {
//This will clear the graphic objects.
circles.removeAllElements();
area.width=0;
area.height=0;
changed = true;
} else {
int x = e.getX() - W/2;
int y = e.getY() - H/2;
if (x < 0) x = 0;
if (y < 0) y = 0;
Rectangle rect = new Rectangle(x, y, W, H);
circles.addElement(rect);
drawingPane.scrollRectToVisible(rect); int this_width = (x + W + 2);
if (this_width > area.width) {
area.width = this_width; changed=true;
} int this_height = (y + H + 2);
if (this_height > area.height) {
area.height = this_height; changed=true;
}
}
if (changed) {
//Update client's preferred size because
//the area taken up by the graphics has
//gotten larger or smaller (if cleared).
drawingPane.setPreferredSize(area); //Let the scroll pane know to update itself
//and its scrollbars.
drawingPane.revalidate();
}
drawingPane.repaint();
}
public void mouseClicked(MouseEvent e){}
public void mouseEntered(MouseEvent e){}
public void mouseExited(MouseEvent e){}
public void mousePressed(MouseEvent e){} /**
* Create the GUI and show it. For thread safety,
* this method should be invoked from the
* event-dispatching thread.
*/
private static void createAndShowGUI() {
//Make sure we have nice window decorations.
JFrame.setDefaultLookAndFeelDecorated(true); //Create and set up the window.
JFrame frame = new JFrame("ScrollDemo2");
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE); //Create and set up the content pane.
JComponent newContentPane = new ScrollDemo2();
newContentPane.setOpaque(true); //content panes must be opaque
frame.setContentPane(newContentPane); //Display the window.
frame.pack();
frame.setVisible(true);
} public static void main(String[] args) {
//Schedule a job for the event-dispatching thread:
//creating and showing this application's GUI.
javax.swing.SwingUtilities.invokeLater(new Runnable() {
public void run() {
createAndShowGUI();
}
});
}
}