编写一个简单画板，要求能够绘制直线、矩形、圆形、圆角矩形及三角形。
效果图如下：
##################################分割线##################################
import java.awt.BorderLayout;
import java.awt.Color;
import java.awt.Dimension;
import java.awt.Graphics;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JPanel;
public class DrawingBoard extends JFrame{
/**
* @param args
*/
public static void main(String[] args) {
DrawingBoard db = new DrawingBoard();
db.initUI();
}
//画板类的属性值
private String shape="line";
//构造方法
public DrawingBoard() {
}
//获得按钮所指示的形状的方法
public String getShapes(){
return shape;
}
//初始化界面的方法
public void initUI() {
this.setTitle("简单画板");
this.setSize(600, 500);
this.setDefaultCloseOperation(3);
this.setLocationRelativeTo(rootPane);
JPanel northPanel =new JPanel();
//创建按钮组件并设置大小
JButton line =new JButton("直线");
line.setActionCommand("line");
JButton rect =new JButton("矩形");
rect.setActionCommand("rect");
JButton oval =new JButton("圆形");
oval.setActionCommand("oval");
JButton roundrect =new JButton("圆角矩形");
roundrect.setActionCommand("roundrect");
JButton triangle =new JButton("三角形");
triangle.setActionCommand("triangle");
line.setPreferredSize(new Dimension(90,40));
rect.setPreferredSize(new Dimension(90,40));
oval.setPreferredSize(new Dimension(90,40));
roundrect.setPreferredSize(new Dimension(90,40));
triangle.setPreferredSize(new Dimension(90,40));
//匿名内部类直接“实例化”一个接口
ActionListener al = new ActionListener(){
//事件处理方法
public void actionPerformed(ActionEvent e) {
//获取按钮的动作命令
shape = e.getActionCommand();
System.out.println("shape = "+shape);
}
};
//为各个按钮组件添加监听器方法并绑定事件处理类对象
line.addActionListener(al);
oval.addActionListener(al);
rect.addActionListener(al);
roundrect.addActionListener(al);
triangle.addActionListener(al);
//将各个按钮组件添加到南部面板上
northPanel.add(line);
northPanel.add(rect);
northPanel.add(oval);
northPanel.add(roundrect);
northPanel.add(triangle);
//将南部面板添加到窗体的南部
this.add(northPanel,BorderLayout.NORTH);
//创建中部面板
JPanel centerPanel = new JPanel();
//设置背景色为白色
centerPanel.setBackground(Color.WHITE);
//将中部面板添加到窗体的中部
this.add(centerPanel,BorderLayout.CENTER);
this.setVisible(true);
//画图形必须在setVisible之后
//
Graphics g=centerPanel.getGraphics();
//创建一个鼠标事件处理类对象
DrawingListener dl = new DrawingListener(this,g);
//为中部面板添加监听器方法并绑定处理类对象
centerPanel.addMouseListener(dl);
}
}