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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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原文地址:http://www.cnblogs.com/Coda/p/4579190.html