Java知多少(93)鼠标事件

鼠标事件的事件源往往与容器相关,当鼠标进入容器、离开容器,或者在容器中单击鼠标、拖动鼠标时都会发生鼠标事件。java语言为处理鼠标事件提供两个接口:MouseListener,MouseMotionListener接口。

MouseListener接口

MouseListener接口能处理5种鼠标事件:按下鼠标,释放鼠标,点击鼠标、鼠标进入、鼠标退出。相应的方法有:
(1) getX():鼠标的X坐标
(2) getY():鼠标的Y坐标
(3) getModifiers():获取鼠标的左键或右键。
(4) getClickCount():鼠标被点击的次数。
(5) getSource():获取发生鼠标的事件源。
(6) addMouseListener(监视器):加放监视器。
(7) removeMouseListener(监视器):移去监视器。

要实现的MouseListener接口的方法有:
(1) mousePressed(MouseEvent e);
(2) mouseReleased(MouseEvent e);
(3) mouseEntered(MouseEvent e);
(4) mouseExited(MouseEvent e);
(5) mouseClicked(MouseEvent e);

【例 11-18】小应用程序设置了一个文本区,用于记录一系列鼠标事件。当鼠标进入小应用程序窗口时,文本区显示“鼠标进来”;当鼠标离开 窗口时,文本区显示“鼠标走开”;当鼠标被按下时,文本区显示“鼠标按下”,当鼠标被双击时,文本区显示“鼠标双击”;并显示鼠标的坐标。程序还显示一个红色的圆,当点击鼠标时,圆的半径会不断地变大。

 1 import java.applet.*;
 2 import javax.swing.*;
 3 import java.awt.*;
 4 import java.awt.event.*;
 5 class MyPanel extends JPanel{
 6     public void print(int r){
 7         Graphics g = getGraphics();
 8         g.clearRect(0,0,this.getWidth(),this.getHeight());
 9         g.setColor(Color.red);
10         g.fillOval(10,10,r,r);
11     }
12 }
13 class MyWindow extends JFrame implements MouseListener{
14     JTextArea text;
15     MyPanel panel;
16     int x,y,r =10;
17     int mouseFlg=0;
18     static String mouseStates[]={"鼠标键按下","鼠标松开","鼠标进来","鼠标走开","鼠标双击"};
19     MyWindow(String s){
20         super(s);
21         Container con = this.getContentPane();
22         con.setLayout(new GridLayout(2,1));
23         this.setSize(200,300);
24         this.setLocation(100,100);
25         panel = new MyPanel();
26         con.add(panel);
27         text = new JTextArea(10,20);
28         text.setBackground(Color.blue);
29         con.add(text);
30         addMouseListener(this);
31         this.setVisible(true);
32         this.pack();
33     }
34     public void paint(Graphics g){
35         r = r+4;
36         if(r>80){
37             r=10;
38         }
39         text.append(mouseStates[mouseFlg]+"了,位置是:" +x+","+y+"\n");
40         panel.print(r);
41     }
42     public void mousePressed(MouseEvent e){
43         x = e.getX();
44         y = e.getY();
45         mouseFlg = 0;
46         repaint();
47     }
48     public void mouseRelease(MouseEvent e){
49         x = e.getX();
50         y = e.getY();
51         mouseFlg = 1;
52         repaint();
53     }
54     public void mouseEntered(MouseEvent e){
55         x = e.getX();
56         y = e.getY();
57         mouseFlg = 2;
58         repaint();
59     }
60     public void mouseExited(MouseEvent e){
61         x = e.getX();
62         y = e.getY();
63         mouseFlg = 3;
64         repaint();
65     }
66     public void mouseClicked(MouseEvent e){
67         if(e.getClickCount()==2){
68             x = e.getX();
69             y = e.getY();
70             mouseFlg = 4;
71             repaint();
72         }
73         else{}
74     }
75 }
76 public class Example6_8 extends Applet{
77     public void init(){
78         MyWindow myWnd = new MyWindow("鼠标事件示意程序");
79     }
80 }

任何组件上都可以发生鼠标事件:鼠标进入、鼠标退出、按下鼠标等。例如,在上述程序中添加一个按钮,并给按钮对象添加鼠标监视器,将上述程序中的init()方法修改成如下形式,即能示意按钮上的所有鼠标事件。

1 JButton button;
2 public void init(){
3     button = new JButton(“按钮也能发生鼠标事件”);
4     r = 10;
5     text = new JTextArea(15,20);
6     add(button);
7     add(text);
8     button.addMouseListener(this);
9 }

如果程序希望进一步知道按下或点击的是鼠标左键或右键,鼠标的左键或右键可用InputEvent类中的常量BUTTON1_MASK和BUTTON3_MASK来判定。例如,以下表达式判断是否按下或点击了鼠标右键:

    e.getModifiers()==InputEvent. BUTTON3_MASK

MouseMotionListener接口

MouseMotionListener接口处理拖动鼠标和鼠标移动两种事件。

注册监视器的方法是:
    addMouseMotionListener(监视器)
要实现的的接口方法有两个:
(1) mouseDragged(MouseEvent e)
(2) mouseMoved(MouseEvent e)

【例 11-19】一个滚动条与显示窗口同步变化的应用程序。窗口有一个方块,用鼠标拖运方块,或用鼠标点击窗口,方块改变显示位置,相应水平和垂直滚动条的滑块也会改变它们在滚动条中的位置。反之,移动滚动条的滑块,方块在窗口中的显示位置也会改变。

 1 import java.applet.*;
 2 import javax.swing.*;
 3 import java.awt.*;
 4 import java.awt.event.*;
 5 class MyPanel extends JPanel{
 6     public void print(int r){
 7         Graphics g = getGraphics();
 8         g.clearRect(0,0,this.getWidth(),this.getHeight());
 9         g.setColor(Color.red);
10         g.fillOval(10,10,r,r);
11     }
12 }
13 class MyWindow extends JFrame implements MouseListener{
14     JTextArea text;
15     MyPanel panel;
16     int x,y,r =10;
17     int mouseFlg=0;
18     static String mouseStates[]={"鼠标键按下","鼠标松开","鼠标进来","鼠标走开","鼠标双击"};
19     MyWindow(String s){
20         super(s);
21         Container con = this.getContentPane();
22         con.setLayout(new GridLayout(2,1));
23         this.setSize(200,300);
24         this.setLocation(100,100);
25         panel = new MyPanel();
26         con.add(panel);
27         text = new JTextArea(10,20);
28         text.setBackground(Color.blue);
29         con.add(text);
30         addMouseListener(this);
31         this.setVisible(true);
32         this.pack();
33     }
34     public void paint(Graphics g){
35         r = r+4;
36         if(r>80){
37             r=10;
38         }
39         text.append(mouseStates[mouseFlg]+"了,位置是:" +x+","+y+"\n");
40         panel.print(r);
41     }
42     public void mousePressed(MouseEvent e){
43         x = e.getX();
44         y = e.getY();
45         mouseFlg = 0;
46         repaint();
47     }
48     public void mouseRelease(MouseEvent e){
49         x = e.getX();
50         y = e.getY();
51         mouseFlg = 1;
52         repaint();
53     }
54     public void mouseEntered(MouseEvent e){
55         x = e.getX();
56         y = e.getY();
57         mouseFlg = 2;
58         repaint();
59     }
60     public void mouseExited(MouseEvent e){
61         x = e.getX();
62         y = e.getY();
63         mouseFlg = 3;
64         repaint();
65     }
66     public void mouseClicked(MouseEvent e){
67         if(e.getClickCount()==2){
68             x = e.getX();
69             y = e.getY();
70             mouseFlg = 4;
71             repaint();
72         }
73         else{}
74     }
75 }
76 public class Example6_8 extends Applet{
77     public void init(){
78         MyWindow myWnd = new MyWindow("鼠标事件示意程序");
79     }
80 }

上述例子中,如果只要求通过滑动滑块,改变内容的显示位置,可以简单地使用滚动面板JScrollPane。如果是这样,关于滚动条的创建和控制都可以免去,直接由JScrollPane内部实现。参见以下修改后的MyWindow的定义:

 1 class MyWindow extends JFrame{
 2     public MyWindow(String s){
 3         super(s);
 4         Container con = this.getContentPane();
 5         con.setLayout(new BorderLayout());
 6         this.setLocaltion(100,100);
 7         MyListener listener = new MyListener();
 8         listener.setPreferredSize(new Dimension(700,700));
 9         JScrollPane scrolledCanvas = new JScrollPane(listener);
10         this.add(scrolledCanvas,BorderLayout.CENTER);
11         this.setVisible(true);
12         this.pack();
13     }
14     public Dimension getPreferredSize(){
15         return new Dimension(400,400);
16     }
17 }

鼠标指针形状也能由程序控制 ,setCursor()方法能设置鼠标指针形状。例如,代码setCursor(Cursor.getPredefinedCursor(cursor.WAIT_CURSOR))。

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posted @ 2015-06-15 20:54  Coda  阅读(...)  评论(... 编辑 收藏