简单的 Java 2D 图形：绘制一个矩形？
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Simple Java 2D graphics: draw a rectangle?
提问by McGarnagle
I'm trying to get a Java 2D graphics "hello world" going, and am finding it strangely difficult (ie, I'm Googling variations of "java hello world example" and coming up empty). Can anyone help me with a minimal hellow world example?
我试图让 Java 2D 图形“hello world”运行起来，但我发现它出奇地困难（即，我在谷歌上搜索“java hello world example”的变体，结果却是空的）。任何人都可以用一个最小的地狱世界示例来帮助我吗？
Edit
编辑
This is a good starting point though, "The Java Tutorials: Performing Custom Painting".
不过，这是一个很好的起点，“Java 教程：执行自定义绘画”。
采纳答案by Hovercraft Full Of Eels
To draw a rectangle in Swing you should:
要在 Swing 中绘制矩形，您应该：
- First of all, never draw directly in the JFrame or other top-level window.
- Instead draw in a JPanel, JComponent or other class that eventually extends from JComponent.
- You should override the
paintComponent(Graphics g)method. - You should be sure to call the super method
- You should draw your rectangle with the Graphics object provided to the method by the JVM.
- You should read the painting in Swing tutorial.
- 首先，永远不要直接在 JFrame 或其他顶级窗口中绘制。
- 而是绘制 JPanel、JComponent 或其他最终从 JComponent 扩展的类。
- 您应该覆盖该
paintComponent(Graphics g)方法。 - 一定要调用super方法
- 您应该使用 JVM 提供给该方法的 Graphics 对象绘制矩形。
- 您应该阅读 Swing 教程中的绘画。
Clear?
清除？
e.g.,
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();
}
});
}
}
回答by ArtOfWarfare
You need to create a class that extends from JComponent(or one of its subclasses, like JPanelin the below example) and overrides paintComponent(Graphics g). Here's an example:
您需要创建一个从JComponent（或其子类JPanel之一，如下例所示）扩展并覆盖的类paintComponent(Graphics g)。下面是一个例子：
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);
}
}
回答by Benjamin
public void paintComponent(Graphics g) {
Graphics2D g2 = (Graphics2D) g;
super.paintComponent(g);
g2.setColor(Color.red);
g2.drawRect(10, 10, 100, 100);
}
