另一个java swing问题。我真的真的搜索了很多小时但我不能让我的代码工作..所以我希望你们能帮助我。我想我有一些基本的理解问题。
我必须扩展现有代码。 我的第一个任务是从mouseclick中画一条线来释放，我成功地实现了它。
现在我应该在RandomDrawer类中实现缺少的代码，通过单击JMenuItem来绘制圆圈。它们应该是随机的，但是现在这一点并不重要，我可以这样做，当我实际绘制时，看看我的形状：D。
我的问题是我根本无法画出任何东西。 我怎么能告诉他在画布上画画？ 它在Painter类中工作，当我以与RandomDrawer类相同的方式实现它时，它没有。 有人能帮助我吗？
到目前为止，这是我的代码：
package plotterpackage;
import java.awt.BorderLayout;
import java.awt.Color;
import java.awt.Dimension;
import java.awt.FlowLayout;
import java.awt.Graphics;
import java.awt.Graphics2D;
import java.awt.Point;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.awt.event.MouseAdapter;
import java.awt.event.MouseEvent;
import java.awt.geom.Line2D;
import javax.swing.JComponent;
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JMenu;
import javax.swing.JMenuBar;
import javax.swing.JMenuItem;
import javax.swing.JPanel;
import javax.swing.JTextField;
import javax.swing.WindowConstants;
import javax.swing.border.BevelBorder;
/
public class Main {
private JFrame frame;
private JPanel canvas;
private JPanel statusBar;
private JTextField status;
public Main() {
initialize();
}
public static void main(String[] args) {
Main app = new Main();
app.start();
}
protected void initialize() {
frame = new JFrame("Main");
frame.setDefaultCloseOperation(WindowConstants.EXIT_ON_CLOSE);
frame.setBounds(50,50, 50+640, 50+480);
frame.setBackground(Color.GREEN);
frame.setJMenuBar(createMenuBar());
frame.getContentPane().add(createContent(), BorderLayout.CENTER);
frame.getContentPane().add(createStatusBar(),BorderLayout.SOUTH);
}
public void start() {
// show the GUI
frame.setVisible(true);
status.setText("Application started");
}
protected JComponent createContent() {
canvas = new JPanel();
canvas.addMouseListener(new Painter());
canvas.setBackground(new Color(128,218,255));
canvas.setForeground(Color.RED);
canvas.setBorder(new BevelBorder(BevelBorder.LOWERED));
return canvas;
}
protected JComponent createStatusBar() {
FlowLayout layout = new FlowLayout(FlowLayout.LEFT);
layout.setHgap(5);
statusBar = new JPanel(layout);
statusBar.add(new JLabel("Status: "));
status = new JTextField();
status.setPreferredSize(new Dimension(400,25));
status.setEditable(false);
status.setBorder(new BevelBorder(BevelBorder.RAISED,Color.MAGENTA,Color.LIGHT_GRAY));
status.getInsets().set(2, 10, 2, 10);
statusBar.add(status);
return statusBar;
}
protected JMenuBar createMenuBar() {
JMenuBar mb = new JMenuBar();
JMenuItem item;
JMenu menu;
// Action menu
menu = new JMenu("Actions");
mb.add(menu);
item = new JMenuItem("Draw RandomCircle");
item.addActionListener(new RandomDrawer());
menu.add(item);
item = new JMenuItem("Draw RandomTriangle");
item.addActionListener(new RandomDrawer());
menu.add(item);
menu.addSeparator();
item = new JMenuItem("Exit");
item.addActionListener(new AppCloser());
menu.add(item);
// Color menu not used so far
menu = new JMenu("Colors");
mb.add(menu);
// Help menu not used so far
menu = new JMenu("Help");
mb.add(menu);
return mb;
}
class AppCloser implements ActionListener {
@Override
public void actionPerformed(ActionEvent e) {
System.out.printf("application finished, bye-bye... \n");
frame.setVisible(false);
frame.dispose();
System.exit(0);
}
}
class RandomDrawer extends JPanel implements ActionListener {
@Override
public void paintComponent(Graphics g) {
super.paintComponent(g);
g.drawOval(50, 50, 50, 50);
//repaint();
}
@Override
public void actionPerformed(ActionEvent e) {
double x = Math.random();
double y = Math.random();
status.setText(String.format("rnd draw x:%.3f y:%.3f",x,y));
//Graphics2D gg = (Graphics2D) canvas.getGraphics();
//paintComponent(gg);
//gg.draw(new Line2D.Double(0, 0, x, y));
//gg.drawLine(5, 5, 20, 20);
//gg.paintComponent();
}
}
class Painter extends MouseAdapter {
Point start, end;
int startX, startY;
@Override
public void mousePressed(MouseEvent e) {
start = e.getPoint();
startX = e.getX();
startY = e.getY();
status.setText(String.format("Mouse start: " + start));
}
@Override
public void mouseReleased(MouseEvent e) {
end = e.getPoint();
status.setText(String.format("Mouse end: " + end));
Graphics2D gc = (Graphics2D) canvas.getGraphics();
//gc.drawLine(0, 0, 80, 80);
gc.drawLine(startX, startY, e.getX(), e.getY());
//gc.drawOval(startX, startY, e.getX(), e.getY());
//gc.fillOval(startX, startY, e.getX(), e.getY());
}
}
}
非常感谢。
答案 0 :(得分：0)
您还需要在画布中包含MouseMotionListener。
Painter painter = new Painter();
canvas.addMouseListener(painter);
canvas.addMouseMotionListener(painter);
另外，要为您的矩形添加绘制效果，您需要更改Painter类，如下所示： 用此替换您的Painter类并运行应用程序，您可以根据绘图应用程序绘制矩形。了解我在课堂上的变化，如果有任何问题，请告诉我：
class Painter extends MouseAdapter implements MouseMotionListener
{
Point start, end;
Point oldStart, oldEnd;
int startX, startY, oldX, oldY, oldWidth, oldHeight;
public void mousePressed(MouseEvent e)
{
start = e.getPoint();
oldX = startX;
oldY = startY;
startX = e.getX();
startY = e.getY();
status.setText(String.format("Mouse start: " + start));
}
public void mouseDragged(MouseEvent e)
{
Graphics2D gc = (Graphics2D)canvas.getGraphics();
end = e.getPoint();
gc.setColor(new Color(128, 218, 255));
gc.drawOval(oldX, oldY, oldWidth, oldHeight);
oldX = startX;
oldY = startY;
oldWidth = e.getX();
oldHeight = e.getY();
gc.setColor(Color.BLACK);
gc.drawOval(startX, startY, e.getX(), e.getY());
}
public void mouseReleased(MouseEvent e)
{
end = e.getPoint();
status.setText(String.format("Mouse end: " + end));
Graphics2D gc = (Graphics2D)canvas.getGraphics();
oldX = 0;
oldY = 0;
oldWidth = 0;
oldHeight = 0;
}
}