用java编写一个三角形程序

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用java编写一个三角形程序

>不要从顶级容器(如JFrame)扩展,你不会添加任何有益的东西.

>避免油漆到顶层容器.而是使用像JPanel这样的东西.

>避免覆盖绘画,改为使用paintComponent.有关详细信息,请参见

Performing Custom Painting

这不是绘画的工作方式(我不会尝试重写你的代码来制作它).

当重绘系统决定需要更新UI的一部分或全部时,将调用Paint来响应许多事件.绘制是破坏性的,也就是说,当调用paint时,Graphics将被完全刷新,需要您从头开始“重建”输出.

代替.

编写一个递归算法,可以绘制到像BufferedImage这样的东西,然后在paintComponent中绘制…

更新

Swing中的绘画由RepaintManager控制,它有责任确定重绘屏幕的内容和时间.你似乎认为油漆是你可以控制的东西,当它不是时.

您需要准备好完全重新绘制UI或准备好可以根据需要绘制到UI上的缓冲区.

import java.awt.BorderLayout;

import java.awt.Dimension;

import java.awt.EventQueue;

import java.awt.Graphics;

import java.awt.Graphics2D;

import java.awt.Rectangle;

import java.awt.geom.AffineTransform;

import java.awt.geom.Path2D;

import javax.swing.JFrame;

import javax.swing.JPanel;

import javax.swing.UIManager;

import javax.swing.UnsupportedLookAndFeelException;

public class SierpinskisGasket {

public static void main(String[] args) {

new SierpinskisGasket();

}

public SierpinskisGasket() {

EventQueue.invokeLater(new Runnable() {

@Override

public void run() {

try {

UIManager.setLookAndFeel(UIManager.getSystemLookAndFeelClassName());

} catch (ClassNotFoundException | InstantiationException | IllegalAccessException | UnsupportedLookAndFeelException ex) {

}

JFrame frame = new JFrame("Testing");

frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);

frame.setLayout(new BorderLayout());

frame.add(new TestPane());

frame.pack();

frame.setLocationRelativeTo(null);

frame.setVisible(true);

}

});

}

public class TestPane extends JPanel {

public TestPane() {

}

@Override

public Dimension getPreferredSize() {

return new Dimension(200, 200);

}

@Override

protected void paintComponent(Graphics g) {

super.paintComponent(g);

Graphics2D g2d = (Graphics2D) g.create();

BaseShape base = new BaseShape(Math.min(getWidth(), getHeight()));

Rectangle bounds = base.getBounds();

int x = (getWidth() - bounds.width) / 2;

int y = (getHeight() - bounds.height) / 2;

base.transform(AffineTransform.getTranslateInstance(x, y));

g2d.fill(base);

g2d.dispose();

}

}

public class BaseShape extends Path2D.Float {

public BaseShape(float size) {

float subSize = size / 2f;

Triangle top = new Triangle(subSize);

top.transform(AffineTransform.getTranslateInstance((size - subSize) / 2, 0));

append(top, false);

Triangle left = new Triangle(subSize);

left.transform(AffineTransform.getTranslateInstance(0, subSize));

append(left, false);

Triangle right = new Triangle(subSize);

right.transform(AffineTransform.getTranslateInstance(subSize, subSize));

append(right, false);

}

}

public class Triangle extends Path2D.Float {

public Triangle(float size) {

moveTo(size / 2f, 0);

lineTo(size, size);

lineTo(0, size);

closePath();

}

}

}

你永远不应该从可以改变UI状态并触发另一个重绘的paint中调用任何东西,否则你将最终在重绘的最终循环中最终消耗你的CPU.