主观题：使用按钮选择绘制不同图形

编写一个程序，实现如下的界面，当点击不同按钮时绘制相应的图形。点击“椭圆”，绘制一个椭圆形；点击“矩形”，绘制一个矩形；点击“直线”，绘制一条直线。实现图形绘制即可，图形位置和大小自定。








答案：import java.awt.BorderLayout;
import java.awt.EventQueue;
import java.awt.Graphics;
import java.awt.Graphics2D;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.awt.geom.Ellipse2D;
import java.awt.geom.Line2D;
import java.awt.geom.Rectangle2D;

import javax.swing.JButton;
import javax.swing.JComponent;
import javax.swing.JFrame;
import javax.swing.JPanel;

public class ChangeImage {
public static void main(String[] args) {
EventQueue.invokeLater(new Runnable() {
public void run() {
ChangeGraphFrame frame = new ChangeGraphFrame();
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
frame.setVisible(true);
}
});
}
}

class ChangeGraphFrame extends JFrame {
private GraphComponent graphComponent;

public ChangeGraphFrame() {
setSize(250, 200);
setTitle("绘制图形");

graphComponent = new GraphComponent();
add(graphComponent, BorderLayout.CENTER);

JButton elipseButton = new JButton("椭圆");
elipseButton.addActionListener(new ChangeGraphAction(1));
JButton rectButton = new JButton("矩形");
rectButton.addActionListener(new ChangeGraphAction(2));
JButton lineButton = new JButton("直线");
lineButton.addActionListener(new ChangeGraphAction(3));

JPanel buttonPanel = new JPanel();
buttonPanel.add(elipseButton);
buttonPanel.add(rectButton);
buttonPanel.add(lineButton);
add(buttonPanel, BorderLayout.SOUTH);
}

private class ChangeGraphAction implements ActionListener {
private int choice;

public ChangeGraphAction(int choice) {
this.choice = choice;
}

public void actionPerformed(ActionEvent event) {
graphComponent.setGraphChoice(choice);
repaint();
}
}
}

class GraphComponent extends JComponent {
private int graphChoice = 0;

public int getGraphChoice() {
return graphChoice;
}

public void setGraphChoice(int graphChoice) {
this.graphChoice = graphChoice;
}

public void paintComponent(Graphics g) {
Graphics2D g2 = (Graphics2D) g;

Ellipse2D elipse = new Ellipse2D.Double(70, 10, 100, 100);
Rectangle2D rect = new Rectangle2D.Double(70, 10, 100, 100);
Line2D line = new Line2D.Double(10, 10, 200, 100);

switch (graphChoice) {
case 1:
g2.draw(elipse);
break;
case 2:
g2.draw(rect);
break;
case 3:
g2.draw(line);
break;
}
}

}