简单的Java 2D图形：绘制一个矩形？

Question

我想要得到一个Java 2D图形“你好世界”去，我发现它奇怪的困难（即，我是Googling“java你好世界的例子”的变种，并且空来）。任何人都可以用最简单的世界例子来帮助我吗？

编辑

这是一个很好的起点，虽然，"The Java Tutorials: Performing Custom Painting"。

Answer 1

要绘制在Swing一个矩形，你应该：

所有的

• 首先，直接在JFrame中或其他顶级窗口永远不会画。
• 而是绘制一个JPanel，JComponent或其他最终从JComponent继承的类。
• 您应该重写paintComponent(Graphics g)方法。
• 您应该确保调用超级方法
• 您应该使用JVM为该方法提供的Graphics对象绘制矩形。
• 您应该阅读Swing教程中的绘画。

清除？

例如，

import java.awt.Dimension; 
import java.awt.Graphics; 
import javax.swing.*; 

public class DrawRect extends JPanel { 
    private static final int RECT_X = 20; 
    private static final int RECT_Y = RECT_X; 
    private static final int RECT_WIDTH = 100; 
    private static final int RECT_HEIGHT = RECT_WIDTH; 

    @Override 
    protected void paintComponent(Graphics g) { 
     super.paintComponent(g); 
     // draw the rectangle here 
     g.drawRect(RECT_X, RECT_Y, RECT_WIDTH, RECT_HEIGHT); 
    } 

    @Override 
    public Dimension getPreferredSize() { 
     // so that our GUI is big enough 
     return new Dimension(RECT_WIDTH + 2 * RECT_X, RECT_HEIGHT + 2 * RECT_Y); 
    } 

    // create the GUI explicitly on the Swing event thread 
    private static void createAndShowGui() { 
     DrawRect mainPanel = new DrawRect(); 

     JFrame frame = new JFrame("DrawRect"); 
     frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE); 
     frame.getContentPane().add(mainPanel); 
     frame.pack(); 
     frame.setLocationByPlatform(true); 
     frame.setVisible(true); 
    } 

    public static void main(String[] args) { 
     SwingUtilities.invokeLater(new Runnable() { 
     public void run() { 
      createAndShowGui(); 
     } 
     }); 
    } 
} 

Answer 2

您需要创建一个从JComponent延伸（或它的子类中的一个，如在JPanel下面的例子），并覆盖paintComponent(Graphics g)的类。这里有一个例子：

class MyPanel extends JPanel { 

    private int squareX = 50; 
    private int squareY = 50; 
    private int squareW = 20; 
    private int squareH = 20; 

    protected void paintComponent(Graphics g) { 
     super.paintComponent(g); // do your superclass's painting routine first, and then paint on top of it. 
     g.setColor(Color.RED); 
     g.fillRect(squareX,squareY,squareW,squareH); 
    } 
} 

Answer 3

class JCanvas extends JComponent 
    { 
     public void paintComponent(Graphics g) 
     { 

     Graphics2D g2 = (Graphics2D) g; 
      super.paintComponent(g); 
      g2.setColor(Color.red); 
      g2.drawRect(10,10,100,100); 


     } 
     }