This here code should create a window and then draw a polygon on it.
import java.awt.*;
import javax.swing.*;
public class gui extends JComponent {
gui(String title){
JPanel pane = new JPanel();
JFrame frame = new JFrame(title);
Container con = frame.getContentPane();
con.add(pane);
frame.setBounds(100,100,500,500);
frame.setVisible(true);
}
public static void main(String[] args){
gui myGUI = new gui("test");
new Drawer();
repaint();
}
}
class Drawer extends JComponent {
public Drawer() {
System.out.println("drawer");
repaint();
}
public void paintComponent(Graphics g) {
super.paintComponent(g);
System.out.println("drawerpC");
Point p1 = new Point(400, 100);
Point p2 = new Point(100, 300);
Point p3 = new Point(200, 400);
int[] xs = { p1.x, p2.x, p3.x };
int[] ys = { p1.y, p2.y, p3.y };
Polygon triangle = new Polygon(xs, ys, xs.length);
g.setColor(new Color(255,255,255));
g.fillPolygon(triangle);
}
}
The window is created, but paintComponent()
is not called.
repaint()
in public Drawer()
seems to do nothing.
How do I call paintComponent()
?
You need to add the Drawer
component to your JFrame
:
Drawer drawer = new Drawer();
con.add(drawer);
No need to explicitly call paintComponent
. Also, calling repaint()
in the Drawer
component is unnecessary.
The above displaces your pane
JPanel
so you may want to re-think the layout of your frame.
You created a new JComponent
called Drawer
, which does the drawing on itself . So, you have to add an instance of it to your Frame.
Drawer drawer = new Drawer();
con.add(drawer);
Manually calling repaint()
shouldn't be necessary if you don't change what is painted on the component. The Swing framework will call it for you, for example when the window-size changes.
Also, class-names should start upper-case.
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