java-GUI实现简单画笔小画板

GUI学习记录(2)

在一块画板上实现鼠标点击画图案的功能, (本文未实现拖动划线功能, 可见后续文章)

思路

与java设计GUI的大体思路一致, 先设置Frame类作为框架, 其中添加组件类作为功能补充. 该设计中需要设置鼠标监听类, 给frame加上组件

this.addMouseListener(new MyMouseListener());

并自己实现一个监听类, implements需要重写所有方法, 所以使用适配器

private class MyMouseListener extends MouseAdapter

给全局一个points数组变量, 保存所有点击的点的信息, 然后重写frame类的paint方法时改成迭代器依次画数组中的点

    @Override
    public void paint(Graphics g) {
     
        // paint listen on mouse event
        Iterator iterator = points.iterator();
        while (iterator.hasNext()){
     
            Point point = (Point) iterator.next();
            g.setColor(Color.GREEN);
            g.fillOval(point.x, point.y, 10, 10);
        }
    }

完整代码

import java.awt.*;
import java.awt.event.MouseAdapter;
import java.awt.event.MouseEvent;
import java.util.ArrayList;
import java.util.Iterator;

public class testmousepaint {
     
    public static void main(String[] args) {
     
        MyFrame myFrame = new MyFrame("IDEA");
    }
}

class MyFrame extends Frame{
     

    ArrayList points;

    public MyFrame(String title) {
     
        super(title);
        setBounds(200, 200, 400, 400);
        this.addMouseListener(new MyMouseListener());
        setVisible(true);
        setBounds(200,200,400,400);
        setBackground(Color.white);
        points = new ArrayList<>();
    }

    @Override
    public void paint(Graphics g) {
     
        // paint listen on mouse event
        Iterator iterator = points.iterator();
        while (iterator.hasNext()){
     
            Point point = (Point) iterator.next();
            g.setColor(Color.GREEN);
            g.fillOval(point.x, point.y, 10, 10);
        }
    }

    public void addpoint(Point point){
     
        points.add(point);
    }

    private class MyMouseListener extends MouseAdapter{
     
        @Override
        public void mousePressed(MouseEvent e) {
     
            MyFrame frame = (MyFrame) e.getSource();
            frame.addpoint(new Point(e.getX(), e.getY()));

            // click and paint every time
            frame.repaint();

        }
    }

}

实现效果