Java学习笔记----事件驱动程序设计

时间：2022-07-03 19:21:22

监听器

import javax.swing.JPanel;
import javax.swing.JFrame;
import javax.swing.JButton;
import java.awt.Color;
import java.awt.Graphics;
import java.awt.BorderLayout;
import java.awt.event.*;

public class ControlCircle extends JFrame{
private JButton jbtEnlarge = new JButton("Enlarge");
private JButton jbtShrink = new JButton("Shrink");
private CirclePanel circle = new CirclePanel();

public ControlCircle()
    {
        jbtEnlarge.addActionListener(new EnlargeListener());//为按钮安装监听器,监听该按钮的触发事件
        jbtShrink.addActionListener(new ShrinkListener());
        JPanel panel = new JPanel();
        panel.add(jbtEnlarge);
        panel.add(jbtShrink);
this.add(circle,BorderLayout.CENTER);
this.add(panel,BorderLayout.SOUTH);
    }

    class EnlargeListener implements ActionListener 
/*
 * 1.如果某个类只是被某一类使用,最好写成嵌套类.分为内部类和外部类
 * 2.每一个触发事件,都有属于它的监听器.
 * 如: ActionEvent 的监听器为: ActionListener
 */
    {
public void actionPerformed(ActionEvent e)
        {
            circle.enlarge();//内部类可以直接使用外部类的数据域,包括 private数据域
        }
    }

    class ShrinkListener implements ActionListener 
    {
public void actionPerformed(ActionEvent e)
        {
            circle.shrink();
        }
    }

public static void main(String[] args)
    {
        JFrame frame = new ControlCircle();
        frame.setSize(300, 300);
        frame.setTitle("Control Circle");
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        frame.setLocationRelativeTo(null);
        frame.setVisible(true);
    }

}

class CirclePanel extends JPanel
{
private int radius = 50;
protected void paintComponent(Graphics g)
    {

this.setBackground(Color.GRAY);
super.paintComponent(g);
        g.setColor(Color.WHITE);
        g.fillOval(this.getWidth()/2 - this.radius, this.getHeight()/2 - this.radius, this.radius*2, this.radius*2);

    }

void enlarge()
    {
this.radius += 5;
this.repaint(); //重新调用一次 paintComponent() 方法
    }

void shrink()
    {
this.radius -= 5;
this.repaint();
    }
}

鼠标事件(鼠标监听器接口适配器)

判断鼠标是否在圆内

*
 * 鼠标事件
 * 监听器接口适配器
 * MouseListener接口中的方法都是抽象的,即使不关注某些事件,还是必须实现所有抽象方法
 * MouseAdapter适配器提供了所有监听器中所有方法的默认实现方法,使用适配器代替监听器则可以只关注自己想要实现的方法
 */

import java.awt.*;
import java.awt.event.MouseAdapter;
import java.awt.event.MouseEvent;
import javax.swing.*;

public class Exercise16_19 extends JFrame{
    Exercise16_19()
    {
this.add(new Circle1());
    }

public static void main(String[] args)
    {
        JFrame frame = new Exercise16_19();
        frame.setSize(300, 200);
        frame.setLocationRelativeTo(null);
        frame.setTitle("Exercise16_19");
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        frame.setVisible(true);
    }
}

class Circle1 extends JPanel
{
private int stringY = -100;
private int panelWidth;private int panelHeight;//由于panel的长宽必须在图形布局后才能获得，所以在paint()方法中动态获得panel的长宽
protected void paintComponent(Graphics g)
    {       
        panelWidth = getWidth();panelHeight = getHeight();
super.paintComponent(g);//每次绘画之前，清楚前一次绘画的结果
        g.setColor(Color.BLUE);
        g.drawOval(panelWidth/2-50, panelHeight/2-50, 100, 100);
        g.setColor(Color.RED);
        g.drawString("The mouse is in the circle", panelWidth/2-50, stringY);
    }
    Circle1()
    {

this.addMouseMotionListener(new MouseAdapter() //MouseMotionListener接口处理拖动和移动鼠标事件
        {
@Override
public void mouseMoved(MouseEvent e) 
            {
// TODO Auto-generated method stub
double x = e.getX();
double y = e.getY();
if ((Math.abs((x-panelWidth/2))<50) && (Math.abs(y-panelHeight/2)<50))
                {
                     stringY = panelHeight/2;
                     repaint();
                }
else
                {
                    stringY = -100;
                    repaint();
                }
            };
        });

this.addMouseListener(new MouseAdapter() //MouseListener接口处理鼠标建按下,释放,点击,输入和退出事件
        {
@Override
public void mousePressed(MouseEvent e) 
                {
// TODO Auto-generated method stub
                    stringY += 10;
                    repaint();
                }
        });
    }
}

键盘事件(键盘接口接听器接口适配器)

方向键控制字符串的移动，其他键改变字符串的内容

其他

import java.awt.*;
import javax.swing.*;
import java.awt.event.*;

public class KeyEventDemo extends JFrame{

static class KeyboardPanel extends JPanel
    {
private int charX = 100;private int charY = 100;
private char keyChar = 'A';
        KeyboardPanel()
        {
            addKeyListener(new KeyAdapter()
                    {
@Override
public void keyPressed(KeyEvent e) 
                        {
switch(e.getKeyCode())//getKeyCode()返回按键定义在KeyEvent表中的值
                            {
//KeyEvent类封装了关于案件事件的信息
case KeyEvent.VK_DOWN:charY += 10;break;
case KeyEvent.VK_UP:charY -= 10;break;
case KeyEvent.VK_LEFT:charX -=10;break;
case KeyEvent.VK_RIGHT:charX += 10;break;
default: keyChar = e.getKeyChar();//getKeyChar()返回输入的字符
                            }
                            repaint();
                        }
                    });
        }

protected void paintComponent(Graphics g)
        {
super.paintComponent(g);
            g.setColor(Color.CYAN);
            g.setFont(new Font("TimesRoman",Font.PLAIN,24));
            g.drawString(String.valueOf(keyChar), charX, charY);
        }
    }


    KeyEventDemo()
    {
        KeyboardPanel keyPanel = new KeyboardPanel();
        add(keyPanel);
        keyPanel.setFocusable(true);//仅有一个焦点的组件才能够接收KeyEvent.所以要将组件设为聚焦的
    }

public static void main(String[] args)
    {
        JFrame frame = new KeyEventDemo();
        frame.setSize(300, 200);
        frame.setLocationRelativeTo(null);
        frame.setTitle("KEYEVENTDEMO");
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        frame.setVisible(true);
    }
}

Timer类

触边反弹的小球

import java.awt.*;
import javax.swing.*;
import java.awt.event.*;

public class BounceBall extends JFrame 
{
static class Ball extends JPanel
 {
private int circleX = 100;private int circleY = 100;private int circleRadius = 80;
private int moveX = 1;private int moveY = 1;
        Ball()
        {
            Timer timer = new Timer(1,new TimerListener());//没1毫秒触发一次接听器
            timer.start();
this.setBackground(Color.BLACK);
        }

protected void paintComponent(Graphics g)
        {
super.paintComponent(g);
            g.setColor(Color.GRAY);
            g.fillOval(circleX, circleY, circleRadius*2, circleRadius*2);
            circleX += moveX;circleY += moveY;
if((circleX <= 0)||(circleX >= (getWidth()-circleRadius*2)))//触边反弹
                moveX = -moveX;
if((circleY <= 0)||(circleY >= (getHeight()-circleRadius*2)))
                moveY = -moveY;
        }

class TimerListener implements ActionListener
 {
public void actionPerformed(ActionEvent e)
            {
                repaint();
            }
        }
    }

    BounceBall()
    {
        add(new Ball());        

    }

public static void main(String[] args)
    {
        JFrame frame = new BounceBall();
        frame.setTitle("BounceBall");
        frame.setSize(600, 400);
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        frame.setLocationRelativeTo(null);
        frame.setVisible(true);
    }
}

实例：按紧q键在画布上画圆

public class DrawCircle extends JFrame{
public DrawCircle()
    {
        add(new circlePanel());
    }

public static void main(String[] args)
    {
        JFrame frame = new DrawCircle();
        frame.setTitle("DrawCircle");
        frame.setSize(400, 300);
        frame.setLocationRelativeTo(null);
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        frame.setVisible(true);
    }
static class circlePanel extends JPanel
    {
private int circleX=-10000000;//圆的初始位置在画布以外
private int circleY=-10000000;
private int circleWidth;
private int circleHeight;
private int startX; 
private int startY;
private boolean canPaint;
protected void paintComponent(Graphics g)
        {
super.paintComponent(g);
            g.setColor(Color.GRAY);
            g.fillOval(circleX, circleY, circleWidth, circleHeight);
        }

        circlePanel() 
        {
this.setFocusable(true);//仅有一个焦点的组件可以接受KeyEvent
this.setBackground(Color.BLACK);
            addKeyListener(new KeyAdapter() 
            {
public void keyPressed(KeyEvent e) 
                {
if(e.getKeyCode() == KeyEvent.VK_Q)
                    {
                        canPaint = true;
                    }
                }
public void keyReleased(KeyEvent e)
                {
if(e.getKeyCode() == KeyEvent.VK_Q)
                    {
                        canPaint = false;
                    }
                }
            });

            addMouseMotionListener(new MouseMotionAdapter() 
            {
@Override
public void mouseDragged(MouseEvent e)
                {
if(circleX == -10000000)
                    {
                        circleX = e.getX();
                        circleY = e.getY();
                        startX = circleX;
                        startY = circleY;
                    }
                    circleWidth = e.getX() - startX;
                    circleHeight = e.getY() - startY;
if (circleWidth<0) //如果圆往左或往上画时，圆的起点座标也需要跟着像左或右移动
                    {
                        circleWidth = -circleWidth;
                        circleX = startX - circleWidth;
                    }
if(circleHeight<0)
                    {
                        circleHeight = -circleHeight;
                        circleY = startY - circleHeight;
                    }
if (canPaint)
                        repaint();
                }
            });

            addMouseListener(new MouseAdapter()
            {
@Override
public void mouseReleased(MouseEvent e) {
                    circleX = -10000000;
                    circleY = -10000000;
                    repaint();
                }

            });     
        }
    }
}
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