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  • Java之事件处理

    监听器

    ActionListener接口 ——通常用自己创建的新类implements接口

    建议使用匿名内部类实现，因为内部类可以访问类内的变量，而匿名类可以大大简化代码，不需要构造函数。

    实例：处理按钮点击事件

     1 package button;
 2 
 3 import java.awt.*;
 4 import java.awt.event.*;
 5 import javax.swing.*;
 6 
 7 /**
 8  * A frame with a button panel
 9  */
10 public class ButtonFrame extends JFrame
11 {
12    private JPanel buttonPanel;
13    private static final int DEFAULT_WIDTH = 300;
14    private static final int DEFAULT_HEIGHT = 200;
15 
16    public ButtonFrame()
17    {      
18       setSize(DEFAULT_WIDTH, DEFAULT_HEIGHT);
19 
20       // create buttons
21       JButton yellowButton = new JButton("Yellow");
22       JButton blueButton = new JButton("Blue");
23       JButton redButton = new JButton("Red");
24 
25       buttonPanel = new JPanel();
26 
27       // add buttons to panel
28       buttonPanel.add(yellowButton);
29       buttonPanel.add(blueButton);
30       buttonPanel.add(redButton);
31 
32       // add panel to frame
33       add(buttonPanel);
34 
35       // create button actions
36       ColorAction yellowAction = new ColorAction(Color.YELLOW);
37       ColorAction blueAction = new ColorAction(Color.BLUE);
38       ColorAction redAction = new ColorAction(Color.RED);
39 
40       // associate actions with buttons
41       yellowButton.addActionListener(yellowAction);
42       blueButton.addActionListener(blueAction);
43       redButton.addActionListener(redAction);
44    }
45 
46    /**
47     * An action listener that sets the panel's background color.
48     */
49    private class ColorAction implements ActionListener
50    {
51       private Color backgroundColor;
52 
53       public ColorAction(Color c)
54       {
55          backgroundColor = c;
56       }
57 
58       public void actionPerformed(ActionEvent event)
59       {
60          buttonPanel.setBackground(backgroundColor);
61       }
62    }
63 }
    View Code

    实例：改变观感

     1 package plaf;
 2 
 3 import java.awt.event.*;
 4 import javax.swing.*;
 5 
 6 /**
 7  * A frame with a button panel for changing look and feel
 8  */
 9 public class PlafFrame extends JFrame
10 {
11    private JPanel buttonPanel;
12    public PlafFrame()
13    {
14       buttonPanel = new JPanel();
15       
16       UIManager.LookAndFeelInfo[] infos = UIManager.getInstalledLookAndFeels();
17       for (UIManager.LookAndFeelInfo info : infos)
18          makeButton(info.getName(), info.getClassName());
19       
20       add(buttonPanel);
21       pack();
22    }
23 
24    /**
25     * Makes a button to change the pluggable look and feel.
26     * @param name the button name
27     * @param plafName the name of the look and feel class
28     */
29    void makeButton(String name, final String plafName)
30    {
31       // add button to panel
32 
33       JButton button = new JButton(name);
34       buttonPanel.add(button);
35 
36       // set button action
37 
38       button.addActionListener(new ActionListener()
39          {
40             public void actionPerformed(ActionEvent event)
41             {
42                // button action: switch to the new look and feel
43                try
44                {
45                   UIManager.setLookAndFeel(plafName);
46                   SwingUtilities.updateComponentTreeUI(PlafFrame.this);
47                   pack();
48                }
49                catch (Exception e)
50                {
51                   e.printStackTrace();
52                }
53             }
54          });
55    }  
56 }
    View Code

    适配器

    由WindowAdapter类实现的WindowListener接口中的众多方法

    由于ActionListener接口只有一个方法所以不需要提供适配器类

    动作

    Action接口 由AbstractAction类实现 包含以下方法：

    void actionPerformed(ActionEvent event); //扩展于ActionListener接口
void setEnabled(boolean b); //启用或禁用这个这个动作
boolean isEnabled(); //检查动作是否启用
void putValue(String key, Object value); //存储名/值对到动作对象中
Object getvalue(String key); //检索动作对象中的任意名/值对
void addPropertyChangeListener(PropertyChangeListener listener);
void remove PropertyChangeListener(PropertyChangeListener listener); 
    //最后两个方法能够让其他对象在动作对象的属性发生变化时得到通告
    预定义的动作表名称
    名称 值
    NAME 动作名称，显示在按钮和菜单上
    SMALL_ICON 存储小图标的地方；显示在按钮、菜单项或工具栏中
    SHORT_DESCRIPTION 图标的简要说明；显示在工具提示中
    LONG_DESCRIPTION 图标的详细说明；显示在在线帮助中。没有Swing组件使用这个值
    MNEMONIC_KEY 快捷键缩写；显示在菜单项中
    ACCELERATOR_KEY 存储加速击键的地方；Swing组件不使用这个值
    ACTION_COMMAND_KEY 历史遗留；仅在旧版本的registerKeyboardAction方法中使用
    DEFAULT 常用的综合属性；Swing组件不使用这个值

     

     

     

     

     

     

    键盘事件

    KeyStroke类将击键与动作相关联

    每个组件可以有三个输入映射InputMap和一个动作映射ActionMap 用get获取 put改变

    输入映射条件
    标志 激活动作
    WHEN_FOCUSED 当这个组件拥有键盘焦点时
    WHEN_ANCESTOR_OF_FOCUSED_COMPONENT 当这个组件包含了拥有键盘焦点的组件时
    WHEN_IN_FOCUSED_WINDOW 当这个组件被包含在一个拥有键盘焦点组件的窗口中时

     

     

     

    动作实例：

     1 package action;
 2 
 3 import java.awt.*;
 4 import java.awt.event.*;
 5 import javax.swing.*;
 6 
 7 /**
 8  * A frame with a panel that demonstrates color change actions.
 9  */
10 public class ActionFrame extends JFrame
11 {
12    private JPanel buttonPanel;
13    private static final int DEFAULT_WIDTH = 300;
14    private static final int DEFAULT_HEIGHT = 200;
15 
16    public ActionFrame()
17    {
18       setSize(DEFAULT_WIDTH, DEFAULT_HEIGHT);
19 
20       buttonPanel = new JPanel();
21 
22       // define actions
23       Action yellowAction = new ColorAction("Yellow", new ImageIcon("yellow-ball.gif"),
24             Color.YELLOW);
25       Action blueAction = new ColorAction("Blue", new ImageIcon("blue-ball.gif"), Color.BLUE);
26       Action redAction = new ColorAction("Red", new ImageIcon("red-ball.gif"), Color.RED);
27 
28       // add buttons for these actions
29       buttonPanel.add(new JButton(yellowAction));
30       buttonPanel.add(new JButton(blueAction));
31       buttonPanel.add(new JButton(redAction));
32 
33       // add panel to frame
34       add(buttonPanel);
35 
36       // associate the Y, B, and R keys with names
37       InputMap imap = buttonPanel.getInputMap(JComponent.WHEN_ANCESTOR_OF_FOCUSED_COMPONENT);
38       imap.put(KeyStroke.getKeyStroke("ctrl Y"), "panel.yellow");
39       imap.put(KeyStroke.getKeyStroke("ctrl B"), "panel.blue");
40       imap.put(KeyStroke.getKeyStroke("ctrl R"), "panel.red");
41 
42       // associate the names with actions
43       ActionMap amap = buttonPanel.getActionMap();
44       amap.put("panel.yellow", yellowAction);
45       amap.put("panel.blue", blueAction);
46       amap.put("panel.red", redAction);
47    }
48    
49    public class ColorAction extends AbstractAction
50    {
51       /**
52        * Constructs a color action.
53        * @param name the name to show on the button
54        * @param icon the icon to display on the button
55        * @param c the background color
56        */
57       public ColorAction(String name, Icon icon, Color c)
58       {
59          putValue(Action.NAME, name);
60          putValue(Action.SMALL_ICON, icon);
61          putValue(Action.SHORT_DESCRIPTION, "Set panel color to " + name.toLowerCase());
62          putValue("color", c);
63       }
64 
65       public void actionPerformed(ActionEvent event)
66       {
67          Color c = (Color) getValue("color");
68          buttonPanel.setBackground(c);
69       }
70    }
71 }
    View Code

    鼠标事件

    如果只希望用户点击按钮或菜单，则不需要显式地处理鼠标事件。然而，如果希望用户使用鼠标画图，就需要捕获鼠标移动点击和拖动事件。

    鼠标点击事件：

    MouseHandler类 extends MouseAdapter类 implement MouseListener接口

    鼠标第一次被按下时，调用mouse Pressed方法；鼠标被释放时调用mouseReleased方法；最后调用mouseClicked方法。如果只对最终的点击事件感兴趣，可以忽略前两个方法。

    扩展——getModifiersEx方法能够准确地报告鼠标事件的鼠标按钮和键盘修饰符。有下列掩码

    　　BUTTON1_DOWN_MASK

    　　BUTTON2_DOWN_MASK

    　　BUTTON3_DOWN_MASK

    　　SHIFT_DOWN_MASK

    　　CTRL_DOWN_MASK

    　　ALT_DOWN_MASK

    　　ALT_GRAPH_DOWN_MASK

    　　META_DOWN_MASK

    鼠标移动与拖动事件：

    MouseMotionHandler类 implement MouseMotionListener接口

    鼠标移动调用mouseMoved方法，鼠标拖动调用mouseDragged方法。

    鼠标光标可以参考Cursor类的getPredefinedCursor方法。

      1 package mouse;
  2 
  3 import java.awt.*;
  4 import java.awt.event.*;
  5 import java.awt.geom.*;
  6 import java.util.*;
  7 import javax.swing.*;
  8 
  9 /**
 10  * A component with mouse operations for adding and removing squares.
 11  */
 12 public class MouseComponent extends JComponent
 13 {
 14    private static final int DEFAULT_WIDTH = 300;
 15    private static final int DEFAULT_HEIGHT = 200;
 16 
 17    private static final int SIDELENGTH = 10;
 18    private ArrayList<Rectangle2D> squares;
 19    private Rectangle2D current; // the square containing the mouse cursor
 20 
 21    public MouseComponent()
 22    {
 23       squares = new ArrayList<>();
 24       current = null;
 25 
 26       addMouseListener(new MouseHandler());
 27       addMouseMotionListener(new MouseMotionHandler());
 28    }
 29 
 30    public void paintComponent(Graphics g)
 31    {
 32       Graphics2D g2 = (Graphics2D) g;
 33 
 34       // draw all squares
 35       for (Rectangle2D r : squares)
 36          g2.draw(r);
 37    }
 38 
 39    /**
 40     * Finds the first square containing a point.
 41     * @param p a point
 42     * @return the first square that contains p
 43     */
 44    public Rectangle2D find(Point2D p)
 45    {
 46       for (Rectangle2D r : squares)
 47       {
 48          if (r.contains(p)) return r;
 49       }
 50       return null;
 51    }
 52 
 53    /**
 54     * Adds a square to the collection.
 55     * @param p the center of the square
 56     */
 57    public void add(Point2D p)
 58    {
 59       double x = p.getX();
 60       double y = p.getY();
 61 
 62       current = new Rectangle2D.Double(x - SIDELENGTH / 2, y - SIDELENGTH / 2, SIDELENGTH,
 63             SIDELENGTH);
 64       squares.add(current);
 65       repaint();
 66    }
 67 
 68    /**
 69     * Removes a square from the collection.
 70     * @param s the square to remove
 71     */
 72    public void remove(Rectangle2D s)
 73    {
 74       if (s == null) return;
 75       if (s == current) current = null;
 76       squares.remove(s);
 77       repaint();
 78    }
 79 
 80    private class MouseHandler extends MouseAdapter
 81    {
 82       public void mousePressed(MouseEvent event)
 83       {
 84          // add a new square if the cursor isn't inside a square
 85          current = find(event.getPoint());
 86          if (current == null) add(event.getPoint());
 87       }
 88 
 89       public void mouseClicked(MouseEvent event)
 90       {
 91          // remove the current square if double clicked
 92          current = find(event.getPoint());
 93          if (current != null && event.getClickCount() >= 2) remove(current);
 94       }
 95    }
 96 
 97    private class MouseMotionHandler implements MouseMotionListener
 98    {
 99       public void mouseMoved(MouseEvent event)
100       {
101          // set the mouse cursor to cross hairs if it is inside
102          // a rectangle
103 
104          if (find(event.getPoint()) == null) setCursor(Cursor.getDefaultCursor());
105          else setCursor(Cursor.getPredefinedCursor(Cursor.CROSSHAIR_CURSOR));
106       }
107 
108       public void mouseDragged(MouseEvent event)
109       {
110          if (current != null)
111          {
112             int x = event.getX();
113             int y = event.getY();
114 
115             // drag the current rectangle to center it at (x, y)
116             current.setFrame(x - SIDELENGTH / 2, y - SIDELENGTH / 2, SIDELENGTH, SIDELENGTH);
117             repaint();
118          }
119       }
120    }
121    
122    public Dimension getPreferredSize() { return new Dimension(DEFAULT_WIDTH, DEFAULT_HEIGHT); }
123 }
    View Code

    AWT事件继承层次

     AWT事件类的继承关系

    事件处理总结
    事件 接口 方法 访问方法 事件源
    语义事件类 ActionEvent ActionListener actionPerformed

    getActionCommand

    getModifiers

    AbstractButton

    JComboBox

    JTextField

    Timer
    AdjustmentEvent AdjustmentListener adjustmentValueChanged

    getAdjustable

    getAdjustmentType

    getValue

    		 JScrollbar
    ItemEvent ItemListener itemStateChanged

    getIten

    getItemSelectable

    getStateChange

    AbstractButton

    JComboBox
    低级事件类 FocusEvent FocusListener

    focusGained

    focusLost

    		 isTemporary Component
    KeyEvent KeyListener

    keyPressed

    keyReleased

    keyTyped

    getKeyChar

    getKeyCode

    getKeyModifiersText

    getKeyText

    isActionKey

    		 Component
    MouseEvent MouseListener

    mousePressed

    mouseReleased

    mouseEntered

    mouseExited

    mouseClicked

    getClickCount

    getX

    getY

    getPoint

    translatePoint

    		 Component
    MouseEvent MouseMotionListener

    mouseDragged

    mouseMoved

    		   Component
    MouseWheelEvent MouseWheelListener mouseWheelMoved

    getWheelRotation

    getScrollAmount

    		 Component
    WindowEvent WindowListener

    windowClosing

    windowOpened

    windowIconified

    windowDeiconified

    windowClosed

    windowActivated

    windowDeactivated

    getWindow

    		 Window
    WindowEvent WindowFocusListener

    windowGainFocus

    windowLostFocus

    		 getOppositeWindow Window
    WindowEvent WindowStateListener windowStateChanged

    getOldState

    getNewState

    		 Window
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  • 原文地址：https://www.cnblogs.com/fr-ruiyang/p/8796837.html
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