Java图形绘制
public void paintComponent(Graphics g)
{
Graphics2D g2=(Graphics2D) g; //这行代码是什么意思,为什么在一些代码中可有可无???
/**
public class Geom extends JFrame{
public Geom(){
super("draw");
}
public void paint(Graphics g){
g.setColor(Color.red);
g.drawOval(50, 50, 10, 10);
}
public static void main(String[] args){
Geom kj=new Geom();
kj.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
kj.setSize(500, 400);
kj.setVisible(true);
}
}
*/
/**
class GeomFrame extends JComponent
{
private static final int DEFAULT_WIDTH = 400;
private static final int DEFAULT_HEIGHT = 400;
public void paintComponent(Graphics g)
{
Graphics2D g2=(Graphics2D) g;
double leftX = 100;
double topY = 100;
double width = 200;
double height = 150;
Rectangle2D rect = new Rectangle2D.Double(leftX, topY, width, height);
g2.draw(rect);
Ellipse2D ellipse =new Ellipse2D.Double();
ellipse.setFrame(rect);
g2.draw(ellipse);
g2.draw(new Line2D.Double(leftX, topY, width, height));
double centerX = rect.getCenterX();
double centerY = rect.getCenterY();
double radius = 150;
Ellipse2D circle = new Ellipse2D.Double();
circle.setFrameFromCenter(centerX, centerY, centerX + radius, centerY + radius);
g2.draw(circle);
}
public Dimension getPreferredSize(){
return new Dimension(DEFAULT_WIDTH, DEFAULT_HEIGHT);
}
}
*/