Paint, repaint , paintComponent

Question

excuse me i search a lot to find how those 3 functions (paint, repaint, paintComponent) interact between them but i have no idea. Can you explain me exactly when they are called ( because sometimes java call it without me asking him) what they do exactly and what is the difference between them. Thank you

Answer 1

I am not sure about "paint", but I can explain the relationship between repaint() and paintComponent().

In my limited experience with java, the paintComponent() method is a method in the JPanel class and is a member of "swing".

The paintComponent() method handles all of the "painting". Essentially, it draws whatever you want into the JPanel usings a Graphic object.

repaint() is an inherited instance method for all JPanel objects. Calling [your_JPanel_object].repaint() calls the paintComponent() method.

Every time you wish to change the appearance of your JPanel, you must call repaint().

Certain actions automatically call the repaint() method:

• Re-sizing your window
• Minimizing and maximizing your window

to name a few.

IN SHORT paintComponent() is a method defined in JPanel or your own custom class that extends JPanel. repaint() is a method called in another class (such as JFrame) that eventually calls paintComponent().

here is an example:

    public class MyPanel extends JPanel{

    public void paintComponent(Graphics g){
        super.paintComponent(g);

        g.draw([whatever you want]);

        ...
        ...

    }
}
public class MyFrame extends JFrame{

    public MyFrame(){

    MyPanel myPanel = new MyPanel();

    myPanel.repaint();

    }

}