Java将矩形添加到ArrayList，然后绘制它们

Question

我真的需要你们的帮助。 我尝试将矩形添加到 ArrayList，然后循环遍历列表以将它们全部绘制出来。我不确定我是否使用了正确的方法，但这是我目前的代码。

编辑：代码不会绘制我添加到 ArrayList 的矩形。我什至不知道它们是否以正确的方式添加，或者以正确的方式通过 for 循环访问。

在测试程序中

import java.awt.BorderLayout;
import java.awt.Graphics;
import java.util.ArrayList;
import javax.swing.JFrame;


public class TestProgram extends JFrame {
    private ShapeRectangle rectangle;
    public ArrayList<Shapes> list = new ArrayList<Shapes>();


    public TestProgram(String title) {
        super(title);
        setLayout(new BorderLayout());
        setDefaultCloseOperation(EXIT_ON_CLOSE);
        setLocationRelativeTo(null);
        initComponents();
        setSize(500, 700);
        setVisible(true);
  }

    private void initComponents() {
        rectangle = new ShapeRectangle();    
        add(rectangle, BorderLayout.CENTER);

        list.add(rectangle);        
        Graphics g = getGraphics();
        for (int i = 0; i < list.size(); i++) {
            rectangle.draw(g);
        }
  }

    public static void main(String args[]) {
        new TestProgram("Drawing program");
    }
}

在 ShapeRectangles 类中：

import java.awt.Graphics;

public class ShapeRectangle extends Shapes {

    public ShapeRectangle() {}    

    @Override
    public void paintComponent(Graphics g) {
        super.paintComponents(g);
        draw(g);        
    }

    @Override
    public void draw(Graphics g) {
       g.drawLine(20,20,60,60);
       g.drawLine(130,30,80,11);
       g.drawRect(200,30,20,140);        
   }
}

在形状类中：

import java.awt.Graphics;
import javax.swing.JPanel;

public abstract class Shapes extends JPanel {

    abstract public void draw(Graphics g); 

}

Answer 1

首先查看2D Graphics，尤其是Working with Geometry

2D 图形 API 定义了一个 Shape API，其中包括一个 Rectangle 类

例如...

import java.awt.Dimension;
import java.awt.EventQueue;
import java.awt.Graphics;
import java.awt.Graphics2D;
import java.awt.Rectangle;
import java.util.ArrayList;
import java.util.List;
import java.util.Random;
import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.UIManager;
import javax.swing.UnsupportedLookAndFeelException;

public class TestRectangles {

    public static void main(String[] args) {
        new TestRectangles();
    }

    public TestRectangles() {
        EventQueue.invokeLater(new Runnable() {
            @Override
            public void run() {
                try {
                    UIManager.setLookAndFeel(UIManager.getSystemLookAndFeelClassName());
                } catch (ClassNotFoundException | InstantiationException | IllegalAccessException | UnsupportedLookAndFeelException ex) {
                    ex.printStackTrace();
                }

                JFrame frame = new JFrame("Testing");
                frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
                frame.add(new TestPane());
                frame.pack();
                frame.setLocationRelativeTo(null);
                frame.setVisible(true);
            }
        });
    }

    public class TestPane extends JPanel {

        private List<Rectangle> rectangles;

        public TestPane() {
            rectangles = new ArrayList<>(25);
            Random ran = new Random();

            for (int index = 0; index < 10; index++) {
                int x = ran.nextInt(200 - 10);
                int y = ran.nextInt(200 - 10);
                int width = ran.nextInt(200 - x);
                int height = ran.nextInt(200 - y);
                rectangles.add(new Rectangle(
                        x, 
                        y, 
                        width, 
                        height));
            }
        }

        @Override
        public Dimension getPreferredSize() {
            return new Dimension(200, 200);
        }

        @Override
        protected void paintComponent(Graphics g) {
            super.paintComponent(g);
            Graphics2D g2d = (Graphics2D) g.create();
            for (Rectangle rect : rectangles) {
                g2d.draw(rect);
            }
            g2d.dispose();
        }

    }

}

Answer 2

不要把Shapes 变成JPanel。也取出它的paintComponent 方法。

取而代之的是一个JPanel 类，它是主要的绘图表面。在课堂上保留List<Shapes>。遍历该类的paintComponent方法中的列表，调用每个Shapes的draw方法

class DrawingPanel extends JPanel {
    List<Shapes> shapes;
    // add shapes

    protected void paintComponent(Graphics g) {
        super.paintComponent(g);
        for (Shapes shape: shapes) {
            shape.draw(g);
        }
    }
}

然后将该面板添加到框架中。

请记住，所有绘制都应使用传递给paintComponent 方法的 Graphics 上下文来完成。我们不使用getGraphics 进行自定义绘画。

此外，您可能希望在 Shapes 类中存储一些状态，以便您可以更改 x/y/width/height 状态。现在，您正在为所有形状使用相同的硬编码值。

abstract class Shapes {
    int x, y;
    public Shapes(int x, int y) {
        this.x = x; this.y = y;
    }
    protected abstract void draw(Graphics g);
}
class RectangleShape extends Shape {
    int width, height;
    public RectangleShape(int x, int y, int width, int height) {
        super(x, y);
        this.width = width; this.height = height;
    }
    @Override   
    public void draw(Graphics g) {
        g.fillRect(x, y, width, height);
    }
}

查看complete example with more complex objects with animation

Answer 3

这个不好，你要么想把它添加为一个绝对定位的组件，要么你想画它，选择一个。

this.add(rectangle, BorderLayout.CENTER); // Add as component of the panel.
list.add(rectangle);                      // Add as method of drawing on the panel.

后者会更好，因为您正在绘图。如果需要拖放，请将其添加为子项，但将绘图添加到子项。

你可以在JFrame上调用repaint()来更新矩形的坐标和大小后的图形。

绘制形状

import java.awt.BorderLayout;
import java.awt.Graphics;
import java.util.ArrayList;

import javax.swing.JFrame;
import javax.swing.SwingUtilities;

public class DrawShapes extends JFrame {
    public ArrayList<Shape> shapeList = new ArrayList<Shape>();

    public DrawShapes(String title) {
        super(title);

        this.setLayout(new BorderLayout());
        this.setDefaultCloseOperation(EXIT_ON_CLOSE);
        this.setSize(500, 700);
        this.setLocationRelativeTo(null);

        this.initComponents();
    }

    private void initComponents() {
        shapeList.add(new RectangleShape(20, 20, 60, 60));
        shapeList.add(new RectangleShape(130, 30, 80, 11));
        shapeList.add(new RectangleShape(200, 30, 20, 140));
    }

    @Override
    public void paint(Graphics g) {
        for (Shape s : shapeList) {
            s.draw(g);
        }
    }

    public static void main(String args[]) {
        SwingUtilities.invokeLater(new Runnable() {
            @Override
            public void run() {
                DrawShapes d = new DrawShapes("Drawing program");
                d.setVisible(true);
            }
        });
    }
}

矩形形状

import java.awt.Graphics;

public class RectangleShape extends Shape {
    public RectangleShape(int x, int y, int width, int height) {
        super(x, y, width, height);
    }

    public RectangleShape() {
        super();
    }

    @Override
    public void draw(Graphics g) {
        g.drawRect(getX(), getY(), getWidth(), getHeight());
    }
}

形状

import java.awt.Graphics;

public abstract class Shape {
    private int x;
    private int y;
    private int width;
    private int height;

    public Shape() {
        this(0, 0, 1, 1);
    }

    public Shape(int x, int y, int width, int height) {
        this.x = x;
        this.y = y;
        this.width = width;
        this.height = height;
    }

    public abstract void draw(Graphics g);

    public int getX() {
        return x;
    }

    public void setX(int x) {
        this.x = x;
    }

    public int getY() {
        return y;
    }

    public void setY(int y) {
        this.y = y;
    }

    public int getWidth() {
        return width;
    }

    public void setWidth(int width) {
        this.width = width;
    }

    public int getHeight() {
        return height;
    }

    public void setHeight(int height) {
        this.height = height;
    }
}