java语言的科学与艺术-编程练习---10.5（简单的绘图程序）

创建一个简单的绘图程序，可以绘制矩形，椭圆和直线。

1.先生成程序界面：

创一个添加显示图片按钮的方法：

1 private JButton addButton(String str){
2         ImageIcon icon = new ImageIcon(str);//按钮图标
3         JButton button = new JButton(icon);
4         button.setContentAreaFilled(false);//按钮透明；
5         return button;
6     }

初始化界面：

 1 public void init(){
 2         setLayout(new BorderLayout(5,1)); //设置布局；
 3         JButton rectFilled = addButton("rectfilled.gif");
 4         rectFilled.setActionCommand("rectFilled");
 5         JButton rect = addButton("rect.gif");
 6         rect.setActionCommand("rect");
 7         JButton ovalFilled = addButton("ovalfilled.gif");
 8         ovalFilled.setActionCommand("ovalFilled");
 9         JButton oval = addButton("oval.gif");
10         oval.setActionCommand("oval");
11         JButton line = addButton("line.gif");
12         line.setActionCommand("line");
13         add(rectFilled, BorderLayout.WEST);
14         add(rect, BorderLayout.WEST);
15         add(ovalFilled, BorderLayout.WEST);
16         add(oval, BorderLayout.WEST);
17         add(line, BorderLayout.WEST);
18     }

 

2.创建按钮事件

点击按钮分别执行的事件；为了点击按钮画出相应的图形，我设置了5个boolean变量；

private boolean isDrawRectFilled = false, isDrawRect = false, isDrawOvalFilled = false, isDrawOval = false, isDrawLine = false;

按钮事件代码：

 1 public void actionPerformed(ActionEvent e){
 2         String cmd = e.getActionCommand();
 3         if(cmd.equals("rectFilled")){
 4             isDrawRectFilled = true;
 5             isDrawRect = false;
 6             isDrawOval = false;
 7             isDrawOvalFilled = false;
 8             isDrawLine = false;
 9         } else if (cmd.equals("rect")){
10             isDrawRect = true;
11             isDrawRectFilled = false;
12             isDrawOval = false;
13             isDrawOvalFilled = false;
14             isDrawLine = false;
15         } else if (cmd.equals("ovalFilled")){
16             isDrawRectFilled = false;
17             isDrawRect = false;
18             isDrawOval = false;
19             isDrawOvalFilled = true;
20             isDrawLine = false;
21         } else if (cmd.equals("oval")){
22             isDrawRectFilled = false;
23             isDrawRect = false;
24             isDrawOval = true;
25             isDrawOvalFilled = false;
26             isDrawLine = false;
27         } else if (cmd.equals("line")){
28             isDrawRectFilled = false;
29             isDrawRect = false;
30             isDrawOval = false;
31             isDrawOvalFilled = false;
32             isDrawLine = true;
33         }
34     }

分别将所需要画出的图形设为true，将其他设置为false；

3.主要的部分：鼠标点击和拖拽，画出相应的图形：

(1)先定义一个GPiont 变量用于储存鼠标按下的位置：

private GPoint press; //记录鼠标按下的点；

（2）分别创建储存相应图形的变量；

private GLine line;
private GRect rect;
private GOval oval;

（3）画矩形和画椭圆的代码类似；

分别设置他们的坐标和宽和高：

double x = press.getX();
double y = press.getY();
double width = e.getX() - press.getX();
double height = e.getY() - press.getY();

同时位置确保在每个方向都能画出图形，需要设置

//确保向左下方拖拽也能画出图形；
if(width < 0 ){
x = e.getX();
width = -width;
}
//确保向上方拖拽也能画出图形；
if(height < 0){
y = e.getY();
height = -height;
}

（4）画直线比较简单：

鼠标点击事件中加入一个：

line = new GLine(e.getX(), e.getY(),e.getX(), e.getY());

 在鼠标拖拽事件中设置终点：

line.setEndPoint(e.getX(),e.getY());

4.同时要允许可以拖动画出的图形：

设置一个GObject 变量，储存鼠标按下点的图形，如果不是null则拖动当前图形不是绘画。

1 if(gobj != null){
2             gobj.move(e.getX() - press.getX(), e.getY() - press.getY());
3             press = new GPoint(e.getPoint());
4 }

5.鼠标点击图形将其移动到最前

if(gobj != null){
gobj.sendToFront();
}

最后的效果：

完整代码：

  1 import acm.graphics.*;
  2 import acm.program.*;
  3 
  4 import java.awt.*;
  5 import java.awt.event.*;
  6 
  7 import acm.gui.*;
  8 import javax.swing.*;
  9 
 10 public class SimpleDraw extends GraphicsProgram {
 11     //初始化界面
 12     public void init(){
 13         setLayout(new BorderLayout(5,1)); //设置布局；
 14         JButton rectFilled = addButton("rectfilled.gif");
 15         rectFilled.setActionCommand("rectFilled");
 16         JButton rect = addButton("rect.gif");
 17         rect.setActionCommand("rect");
 18         JButton ovalFilled = addButton("ovalfilled.gif");
 19         ovalFilled.setActionCommand("ovalFilled");
 20         JButton oval = addButton("oval.gif");
 21         oval.setActionCommand("oval");
 22         JButton line = addButton("line.gif");
 23         line.setActionCommand("line");
 24         add(rectFilled, BorderLayout.WEST);
 25         add(rect, BorderLayout.WEST);
 26         add(ovalFilled, BorderLayout.WEST);
 27         add(oval, BorderLayout.WEST);
 28         add(line, BorderLayout.WEST);
 29         addActionListeners();
 30         addMouseListeners();
 31     }
 32     /*
 33      * 添加按钮方法，str 是显示的图片的路径；
 34      */
 35     private JButton addButton(String str){
 36         ImageIcon icon = new ImageIcon(str);//按钮图标
 37         JButton button = new JButton(icon);
 38         button.setContentAreaFilled(false);//按钮透明；
 39         return button;
 40     }
 41     /* 侦听的按钮事件*/
 42     public void actionPerformed(ActionEvent e){
 43         String cmd = e.getActionCommand();
 44         if(cmd.equals("rectFilled")){
 45             isDrawRectFilled = true;
 46             isDrawRect = false;
 47             isDrawOval = false;
 48             isDrawOvalFilled = false;
 49             isDrawLine = false;
 50         } else if (cmd.equals("rect")){
 51             isDrawRect = true;
 52             isDrawRectFilled = false;
 53             isDrawOval = false;
 54             isDrawOvalFilled = false;
 55             isDrawLine = false;
 56         } else if (cmd.equals("ovalFilled")){
 57             isDrawRectFilled = false;
 58             isDrawRect = false;
 59             isDrawOval = false;
 60             isDrawOvalFilled = true;
 61             isDrawLine = false;
 62         } else if (cmd.equals("oval")){
 63             isDrawRectFilled = false;
 64             isDrawRect = false;
 65             isDrawOval = true;
 66             isDrawOvalFilled = false;
 67             isDrawLine = false;
 68         } else if (cmd.equals("line")){
 69             isDrawRectFilled = false;
 70             isDrawRect = false;
 71             isDrawOval = false;
 72             isDrawOvalFilled = false;
 73             isDrawLine = true;
 74         }
 75     }
 76     public void mousePressed(MouseEvent e){
 77         press = new GPoint(e.getPoint());
 78         gobj = getElementAt(press);
 79         if(gobj != null){
 80             gobj.sendToFront();
 81         }
 82         line = new GLine(e.getX(), e.getY(),e.getX(), e.getY());
 83         rect = new GRect(0,0);
 84         oval = new GOval(0,0);
 85     }
 86     //鼠标拖拽事件
 87     public void mouseDragged(MouseEvent e){
 88         double x = press.getX();
 89         double y = press.getY();
 90         double width = e.getX() - press.getX();
 91         double height = e.getY() - press.getY();
 92         line.setEndPoint(e.getX(),e.getY());
 93         //确保向左下方拖拽也能画出图形；
 94         if(width < 0 ){
 95             x = e.getX();
 96             width = -width;
 97         }
 98         //确保向上方拖拽也能画出图形；
 99         if(height < 0){
100             y = e.getY();
101             height = -height;
102         }
103         rect.setSize(width, height);
104         oval.setSize(width, height);
105         if(gobj != null){
106             gobj.move(e.getX() - press.getX(), e.getY() - press.getY());
107             press = new GPoint(e.getPoint());
108         } else {
109             if(isDrawRectFilled == true){
110                 rect.setFilled(true);
111                 add(rect, x, y);
112             }
113             if(isDrawRect == true){
114                 add(rect, x, y);
115             }
116             if(isDrawOval == true){
117                 add(oval, x, y);
118             }
119             if(isDrawOvalFilled == true){
120                 oval.setFilled(true);
121                 add(oval, x, y);
122             }
123             if(isDrawLine == true){
124                 add(line);
125             }
126         }
127     }
128     
129     private boolean isDrawRectFilled = false, isDrawRect = false, isDrawOvalFilled = false, isDrawOval = false, isDrawLine = false;
130     private GLine line;
131     private GRect rect;
132     private GOval oval;
133     private GPoint press; //记录鼠标按下的点；
134     private GObject gobj; //记录鼠标按下点的图形；
135 }

 

posted on 2012-12-21 12:53  mybluecode  阅读(2188)  评论(0)  编辑  收藏  举报