我正在尝试将Rectangle
绘制到JPanel
的中心。我已经编写了这段代码,但是当我运行它时,该矩形不会出现在面板中。如果尝试使用JFrame
,则会出现矩形。有人可以帮我吗?
RectangleTester
package eventi5;
import javax.swing.JFrame;
import javax.swing.JPanel;
public class RectangleTester {
public static void main(String[] args) {
JFrame frame = new JFrame("Rectangle");
frame.setSize(250, 250);
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
final RectangleComponent component = new RectangleComponent();
frame.setVisible(true);
JPanel panel=new JPanel();
panel.add(component);
frame.add(panel);
}
}
RectangleComponent
import java.awt.Color;
import java.awt.Graphics;
import java.awt.Graphics2D;
import java.awt.Rectangle;
import javax.swing.JPanel;
public class RectangleComponent extends JPanel{
private Rectangle box;
public RectangleComponent(){
box=new Rectangle(10,20,30,40);
}
public void paintComponent(Graphics g){
Graphics2D g2=(Graphics2D) g;
g2.draw(box);
g2.setColor(Color.BLUE);
g2.fill(box);
}
}
1)您需要像下面一样覆盖getPreferredSize()
的RectangleComponent
:
@Override
public Dimension getPreferredSize() {
return new Dimension(box.width+box.x*2,box.height+box.y*2);
}
2)在自定义之前调用super()
(paintComponent()
)的super.paintComponent(g);
方法。
编辑:
public class RectangleComponent extends JPanel {
private List<Rectangle> boxes;
private int width = 30;
private int height = 40;
private int startX = 10;
private int startY = 20;
public RectangleComponent() {
boxes = new ArrayList<Rectangle>();
for (int i = 0; i < 3; i++){
boxes.add(new Rectangle(startX+(width+startX)*i, startY, width, height));
}
}
public void paintComponent(Graphics g) {
super.paintComponent(g);
Graphics2D g2 = (Graphics2D) g;
for (int i = 0; i < boxes.size(); i++){
g2.draw(boxes.get(i));
}
g2.setColor(Color.BLUE);
for (int i = 0; i < boxes.size(); i++){
g2.fill(boxes.get(i));
}
}
@Override
public Dimension getPreferredSize() {
return new Dimension(boxes.size()*(width+startX)+startX, height+startY*2);
}
}