创建一个方法来处理所有类型的Swing组件

Question

In order to save some time when setting the size of Swing Components (JPanel, JLabel, etc.), I am trying to write a method that when called, will set that component's size using 3 of the standard size-defining functions.

I would like to be able to do this:

import CustomComponents;
...
 JPanel xPanel = new JPanel();
 CSize.setDefiniteSize(xPanel, 400, 300);
...

Or (and preferably)

...
 JPanel xPanel = new JPanel();
 xPanel.CSize.setDefiniteSize(400, 300);
...

Here's the code I have so far. The problem is, I want the method to be functional for all types of Swing components, and it seems to only work for the one I specify in the heading.

package CustomComponents;
import javax.swing.JComponent;
import java.awt.Dimension;

public class CSize
{
public static void setDefiniteSize(JComponent c, int h, int w)
{
    Dimension k = new Dimension (h, w);
    c.setMaximumSize(k);
    c.setMinimumSize(k);
    c.setPreferredSize(k);
}
}

As you can see, here I tried using JComponent, but it won't work, as whatever I use it with - say a JPanel - is a JPanel, not a JComponent (even though it's a subclass? I still don't get how this works)

Answer 1

Though what you're trying to do, you may think is crafty, but you may find it later to be discouraging trying to size everything

See this thread Should I avoid the use of set(Preferred|Maximum|Minimum)Size methods in Java Swing?

Instead you should make use of LayoutManagers. and .pack() the frame. Swing was made to be used with LayoutManager. You need to take into account that your program may look good on your development screen, but may look different on others. You will also find out that many LayoutManegers will not even respect your preferred size, so you need to learn which ones do and which ones don't. Here's a simple example

With layout managers, you let the layouts do all the sizing for you. Some layouts will stretch your components, some center them in open spaces. Your program will be a lot more fluid if you use them.

See Laying out Components Within a Container for more details on how you can use them.

Answer 2

You have to use java.awt.Container , because JFrame is not a direct subclass of JComponent !

So it should work with the following code:

package CustomComponents;

import java.awt.Container;
import java.awt.Dimension;

public class CSize {
    public static void setDefiniteSize(Container c, int h, int w) {
        Dimension k = new Dimension (h, w);
        c.setMaximumSize(k);
        c.setMinimumSize(k);
        c.setPreferredSize(k);
    }
}

Look at the hierarchy of the components:

java.awt.Component
  |--java.awt.Container
       |--java.awt.Window
       |    |--java.awt.Frame
       |         |--javax.swing.JFrame
       |--javax.swing.JComponent
            |--javax.swing.JLabel

Even better would be using java.awt.Component , since this class is defining all methods you want to use ( setMinimumSize , setMaximumSize and setPreferredSize ).