JavaSwing_5.3: 事件处理

秒速五厘米 2021-09-22 09:28 256阅读 0赞

本文链接: [http://blog.csdn.net/xietansheng/article/details/78389255][http_blog.csdn.net_xietansheng_article_details_78389255]

[Java Swing 图形界面开发（目录）][Java Swing]

前面介绍每个组件时，几乎都已经介绍了相应事件的使用，这里仅对常用的事件做一个小整理。

### 1. 动作监听器 — ActionListener ###

动作监听器的动作通常为“点击动作”，常用的组件基本都支持该事件。如果有多个组件都需要设置动作监听器，可以为它们设置同一个实例，再为组件绑定不同的动作命令（ActionCommand）来区分当前触发事件的组件。

final String COMMAND_OK = "OK";
    final String COMMAND_CANCEL = "Cancel";
    
    JButton okBtn = new JButton("OK");
    okBtn.setActionCommand(COMMAND_OK);             // 按钮绑定动作命令
    
    JButton cancelBtn = new JButton("Cancel");
    cancelBtn.setActionCommand(COMMAND_CANCEL);     // 按钮绑定动作命令
    
    // 创建一个动作监听器实例
    ActionListener listener = new ActionListener() { 
        @Override
        public void actionPerformed(ActionEvent e) { 
            // 获取事件源，即触发事件的组件（按钮）本身
            // e.getSource();
        
            // 获取动作命令
            String command = e.getActionCommand();
            
            // 根据动作命令区分被点击的按钮
            if (COMMAND_OK.equals(command)) { 
                System.out.println("OK 按钮被点击");
                
            } else if (COMMAND_CANCEL.equals(command)) { 
                System.out.println("Cancel 按钮被点击");
            }
        }
    };
    
    // 设置两个按钮的动作监听器（使用同一个监听器实例）
    okBtn.addActionListener(listener);
    cancelBtn.addActionListener(listener);

### 2. 焦点监听器 — FocusListener ###

一个窗口内的所有组件（包括窗口本身）同一时间只能有一个组件获得焦点。

JButton btn = new JButton("OK");
    btn.addFocusListener(new FocusListener() { 
        @Override
        public void focusGained(FocusEvent e) { 
            System.out.println("获得焦点: " + e.getSource());
        }
        @Override
        public void focusLost(FocusEvent e) { 
            System.out.println("失去焦点: " + e.getSource());
        }
    });
    
    JTextField textField = new JTextField(10);
    textField.addFocusListener(new FocusListener() { 
        @Override
        public void focusGained(FocusEvent e) { 
            System.out.println("获得焦点: " + e.getSource());
        }
        @Override
        public void focusLost(FocusEvent e) { 
            System.out.println("失去焦点: " + e.getSource());
        }
    });

### 3. 鼠标监听器 — MouseListener ###

JPanel panel = new JPanel();
    
    panel.addMouseListener(new MouseListener() { 
        @Override
        public void mouseEntered(MouseEvent e) { 
            System.out.println("鼠标进入组件区域");
        }
    
        @Override
        public void mouseExited(MouseEvent e) { 
            System.out.println("鼠标离开组建区域");
        }
    
        @Override
        public void mousePressed(MouseEvent e) { 
            // 获取按下的坐标（相对于组件）
            e.getPoint();
            e.getX();
            e.getY();
    
            // 获取按下的坐标（相对于屏幕）
            e.getLocationOnScreen();
            e.getXOnScreen();
            e.getYOnScreen();
    
            // 判断按下的是否是鼠标右键
            e.isMetaDown();
    
            System.out.println("鼠标按下");
        }
    
        @Override
        public void mouseReleased(MouseEvent e) { 
            System.out.println("鼠标释放");
        }
    
        @Override
        public void mouseClicked(MouseEvent e) { 
            // 鼠标在组件区域内按下并释放（中间没有移动光标）才识别为被点击
            System.out.println("鼠标点击");
        }
    });

### 4. 鼠标移动/拖动监听器 — MouseMotionListener ###

JPanel panel = new JPanel();
    
    panel.addMouseMotionListener(new MouseMotionListener() { 
        @Override
        public void mouseDragged(MouseEvent e) { 
            // 鼠标保持按下状态移动即为拖动
            System.out.println("鼠标拖动");
        }
        @Override
        public void mouseMoved(MouseEvent e) { 
            System.out.println("鼠标移动");
        }
    });

### 5. 鼠标滚轮监听器 — MouseWheelListener ###

JPanel panel = new JPanel();
    
    panel.addMouseWheelListener(new MouseWheelListener() { 
        @Override
        public void mouseWheelMoved(MouseWheelEvent e) { 
            // e.getWheelRotation() 为滚轮滚动多少的度量
            System.out.println("mouseWheelMoved: " + e.getWheelRotation());
        }
    });

### 6. 键盘监听器 — KeyListener ###

组件监听键盘的按键，该组件必须要获取到焦点。

如果一个窗口内没有可获取焦点的组件，一般打开窗口后焦点为窗口所有，可以把键盘监听器设置到窗口（JFrame）身上。

如果窗口内还有其他组件可获取焦点（例如按钮、文本框），窗口打开后焦点会被内部组件获得，如果想要在窗口打开期间都能监听键盘按键，可以为所有可获得焦点的组件都设置一个键盘监听器。

JFrame jf = new JFrame();
    
    jf.addKeyListener(new KeyListener() { 
        @Override
        public void keyPressed(KeyEvent e) { 
            // 获取键值，和 KeyEvent.VK_XXXX 常量比较确定所按下的按键
            int keyCode = e.getKeyCode();
            System.out.println("按下: " + e.getKeyCode());
        }
        
        @Override
        public void keyTyped(KeyEvent e) { 
            // e.getKeyChar() 获取键入的字符
            System.out.println("键入: " + e.getKeyChar());
        }
        
        @Override
        public void keyReleased(KeyEvent e) { 
            System.out.println("释放: " + e.getKeyCode());
        }
    });

### 7. 窗口监听器 — WindowListener ###

窗口监听器只有窗口类组件支持，例如 JFrame、JDialog。

JFrame jf = new JFrame();
    
    jf.addWindowListener(new WindowListener() { 
        @Override
        public void windowOpened(WindowEvent e) { 
            System.out.println("windowOpened: 窗口首次变为可见时调用");
        }
    
        @Override
        public void windowClosing(WindowEvent e) { 
            System.out.println("windowClosing: 用户试图从窗口的系统菜单中关闭窗口时调用");
        }
    
        @Override
        public void windowClosed(WindowEvent e) { 
            System.out.println("windowClosed: 窗口调用 dispose 而将其关闭时调用");
        }
    
        @Override
        public void windowIconified(WindowEvent e) { 
            System.out.println("windowIconified: 窗口从正常状态变为最小化状态时调用");
        }
    
        @Override
        public void windowDeiconified(WindowEvent e) { 
            System.out.println("windowDeiconified: 窗口从最小化状态变为正常状态时调用");
        }
    
        @Override
        public void windowActivated(WindowEvent e) { 
            System.out.println("windowActivated: 窗口变为活动状态时调用");
        }
    
        @Override
        public void windowDeactivated(WindowEvent e) { 
            System.out.println("windowDeactivated: 窗口变为不再是活动状态时调用");
        }
    });
    
    // 窗口焦点监听器
    jf.addWindowFocusListener(new WindowFocusListener() { 
        @Override
        public void windowGainedFocus(WindowEvent e) { 
            System.out.println("windowGainedFocus: 窗口得到焦点");
        }
    
        @Override
        public void windowLostFocus(WindowEvent e) { 
            System.out.println("windowLostFocus: 窗口失去焦点");
        }
    });
    
    // 窗口状态监听器
    jf.addWindowStateListener(new WindowStateListener() { 
        @Override
        public void windowStateChanged(WindowEvent e) { 
            System.out.println("windowStateChanged: " + e.getNewState());
        }
    });

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[http_blog.csdn.net_xietansheng_article_details_78389255]: http://blog.csdn.net/xietansheng/article/details/78389255
[Java Swing]: http://blog.csdn.net/xietansheng/article/details/72814492