Menu
I'm wondering about the standard practice with inner classes (in Java but I suppose it applies to all OO languages).
So I have a JFrame subclass ControllerWindow that contains a JPanel subclass MapPanel which I draw onto (so it needs to overwrite paintComponent method) and which needs to implement a mouse listener. My current solution which works is to have MapPanel in a seperate class implementing MouseListener but when I showed this to the guy who runs my course the other day he seemed to think (we have a bit of a language barrier) this should be in an inner class in ControllerWindow or at least the MouseListener should be an inner class.
So my question is what would be the standard solution here, to put a MouseListener in the inner class, the JPanel in a different inner class or still in its seperate class? The JPanel implementing MouseListener in one inner class? And why?
The most important thing to me is that it works but I'd like to know about and understand the standard practices behind these things if possible.
EDIT: Very simplified version of current code below.
class ControllerWindow extends JFrame{
...
MapPanel drawPanel = new MapPanel();
...
}
and a separate class:
class MapPanel extends JPanel implements MouseListener{
...
public void paintComponent(Graphics g){
...//fillRects etc.
}
//MouseListener methods
public void mouseReleased(MouseEvent e){
requestFocus();
...
repaint()
...
}
public void mousePressed(MouseEvent e){}
public void mouseEntered(MouseEvent e){}
public void mouseExited(MouseEvent e){}
public void mouseClicked(MouseEvent e){}
}
Also could this be a situation where it would be acceptable to put both classes in the same file? I don't envisage using MapPanel for anything other than ControllerWindow.
742
Rules of Local Inner Class: The scope of the local inner class is restricted to the block they are defined in. A local inner class cannot be instantiated from outside the block where it is created in. Till JDK 7, the Local inner class can access only the final local variable of the enclosing block.
Use a non-static nested class (or inner class) if you require access to an enclosing instance's non-public fields and methods. Use a static nested class if you don't require this access.
Inner class should only exist to serve outer class. you do not need an enclosing instance of the outer class to use the nested static class. They often result in readable and maintainable code . ode Optimization: It requires less code to write.
Yes, you can define a class inside an interface. In general, if the methods of the interface use this class and if we are not using it anywhere else we will declare a class within an interface.
It is common to use anonymous inner classes as event listeners because the code is usually quite simple (so a separate class may be overkill) and keeping the handler code "close" to the code that registers the listener can improve readability for people trying to understand your code, since all code related to the event is in one place.
EDIT: This is particularly true for classes that implement only one listener method. Perhaps less true for multi-method interfaces like MouseListener, since a class that implements the full interface will be more verbose.
164
If you love us? You can donate to us via Paypal or buy me a coffee so we can maintain and grow! Thank you!
Donate Us With
