我想用Java2D來做一些簡單的圖形編程。我開始很簡單,只是試圖在JFrame中顯示幾個圓圈。我成功地顯示了一個圓圈,但是當添加第二個圓圈時,僅顯示添加到JFrame的最後一個圓圈。我使用Circle類來定義我的圓並重寫用於顯示它的paintComponent方法。任何關於我可能會做錯的建議將不勝感激。下面提供了我的班級Circle和DancingCircles的代碼以供參考。用Java2D繪製多個圓圈
import java.awt.*;
import javax.swing.*;
import java.awt.geom.*;
/**
*
* @author Paul
*/
public class Circle extends JPanel {
// Data members for Circle center and radius
private double centerX, centerY;
private double radius;
// No-argument constructor
Circle() {
centerX = 200;
centerY = 200;
radius = 10;
}
// Full-argument constructor
Circle(double x, double y, double r) {
centerX = x;
centerY = y;
radius = r;
}
// Draw a Circle
protected void paintComponent(Graphics g) {
super.paintComponent(g);
//Convert to Java2D Object
Graphics2D g2 = (Graphics2D) g;
// Create the circle
Ellipse2D circle = new Ellipse2D.Double();
circle.setFrameFromCenter(centerX, centerY, centerX + radius, centerY + radius);
// Draw it
g2.draw(circle);
}// end paintComponent
// Get/set data members
public void setCenterX(double x){this.centerX = x;}
public void setCenterY(double y){this.centerY = y;}
public void setRadius(double r){radius = r;}
public double getCenterX(){return centerX;}
public double getCenterY(){return centerY;}
public double getRadius(){return radius;}
}// end class Circle
import java.awt.*;
import javax.swing.*;
/**
*
* @author Paul
*/
public class DancingCircles extends JFrame{
// Display Dimensions
public static final int DEFAULT_WIDTH = 400;
public static final int DEFAULT_HEIGHT = 400;
// Default constructor
private DancingCircles() {
setTitle("Dancing Circles");
setSize(DEFAULT_WIDTH, DEFAULT_HEIGHT);
// Add Circles to JFrame
Circle myCircle = new Circle(200.0, 200.0, 20.0);
add(myCircle); // Add circle to frame
Circle myCircle2 = new Circle(100.0, 100.0, 30.0);
add(myCircle2); // Add circle to frame
}// end DancingCircles
public static void main(String[] args) {
EventQueue.invokeLater(new Runnable()
{
public void run()
{
DancingCircles dc = new DancingCircles();
dc.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
dc.setVisible(true);
}
});
}// end main
}
謝謝!
Paul
感謝您的解釋。現在有道理! Paul – Paul 2010-01-07 22:27:33