Java – How to set a JPanel maximum or preferred size that uses gridLayout

grid layoutjavajpanellayoutlayout-manager

I had problem using a very simple frame containing two JPanel.
The problem is on the layout of the Center JPanel that contains four JButton.
How can I set a better size for buttons or directly for JPanel that uses the GridLayout. On the picture the problem:

alt http://img42.imageshack.us/img42/4601/horrible.jpg
!

Here the code: ` JFrame window = new JFrame("Horrible! LOL");

    JTextField textField = new JTextField("");
    textField.setPreferredSize(new Dimension(200,20));
    JPanel textPanel = new JPanel(new FlowLayout(FlowLayout.CENTER));
    textPanel.add(textField);
    window.add(textPanel, BorderLayout.NORTH);

    JButton plus = new JButton("+");
    //plus.setPreferredSize(new Dimension(50,50)); nothing would change
    JButton minus = new JButton("-");
    JButton per = new JButton("x");
    JButton divide = new JButton("/");
    JPanel prova = new JPanel(new GridLayout(2,2,10,10));
    Dimension d = new Dimension(20,20);
    prova.setMaximumSize(d); // nothing changed!

    prova.add(plus);
    prova.add(minus);
    prova.add(per);
    prova.add(divide);
    window.add(prova, BorderLayout.CENTER);

    window.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
    window.setSize(250,300);
    window.setResizable(false);
    window.setVisible(true);`

Which is a good solution?

Kind regards

Best Answer

Unfortunately gridlayout doesent respect preferred sizes. But still if you want to stick to grid layout then you can try something like this:

    public static JComponent wrap(JComponent comp)
    {
        JPanel panel = new JPanel();
        panel.add(comp);
        return panel;
    }

And then instead of direclty adding in to prova add like this:

            prova.add(wrap(plus)); 
            prova.add(wrap(minus)); 
            prova.add(wrap(per)); 
            prova.add(wrap(divide));

Tested, Works perfect!! There are other better ways though

SI (1 k = 1,000)

public static String humanReadableByteCountSI(long bytes) {
    if (-1000 < bytes && bytes < 1000) {
        return bytes + " B";
    }
    CharacterIterator ci = new StringCharacterIterator("kMGTPE");
    while (bytes <= -999_950 || bytes >= 999_950) {
        bytes /= 1000;
        ci.next();
    }
    return String.format("%.1f %cB", bytes / 1000.0, ci.current());
}

Binary (1 Ki = 1,024)

public static String humanReadableByteCountBin(long bytes) {
    long absB = bytes == Long.MIN_VALUE ? Long.MAX_VALUE : Math.abs(bytes);
    if (absB < 1024) {
        return bytes + " B";
    }
    long value = absB;
    CharacterIterator ci = new StringCharacterIterator("KMGTPE");
    for (int i = 40; i >= 0 && absB > 0xfffccccccccccccL >> i; i -= 10) {
        value >>= 10;
        ci.next();
    }
    value *= Long.signum(bytes);
    return String.format("%.1f %ciB", value / 1024.0, ci.current());
}

Example output:

                              SI     BINARY

                   0:        0 B        0 B
                  27:       27 B       27 B
                 999:      999 B      999 B
                1000:     1.0 kB     1000 B
                1023:     1.0 kB     1023 B
                1024:     1.0 kB    1.0 KiB
                1728:     1.7 kB    1.7 KiB
              110592:   110.6 kB  108.0 KiB
             7077888:     7.1 MB    6.8 MiB
           452984832:   453.0 MB  432.0 MiB
         28991029248:    29.0 GB   27.0 GiB
       1855425871872:     1.9 TB    1.7 TiB
 9223372036854775807:     9.2 EB    8.0 EiB   (Long.MAX_VALUE)

Java – Should I avoid the use of set(Preferred|Maximum|Minimum)Size methods in Java Swing

Should I completely avoid the use of those methods?

Yes for application code.
The methods have been defined for a reason. So when should I use them? In which context? For what purposes?

I don't know, personally I think of it as an API design accident. Slightly forced by compound components having special ideas about child sizes. "Slightly", because they should have implemented their needs with a custom LayoutManager.
What exactly are the negative consequences of using those methods? (I can only think adding portability between systems with different screen resolution.)

Some (incomplete, and unfortunately the links are broken due to migration of SwingLabs to java.net) technical reasons are for instance mentioned in the Rules (hehe) or in the link @bendicott found in his/her comment to my answer. Socially, posing tons of work onto your unfortunate fellow who has to maintain the code and has to track down a broken layout.
I don't think any LayoutManager can exactly satisfy all desired layout needs. Do I really need to implement a new LayoutManager for every little variation on my layout?

Yes, there are LayoutManagers powerful enough to satisfy a very good approximation to "all layout needs". The big three are JGoodies FormLayout, MigLayout, DesignGridLayout. So no, in practice, you rarely write LayoutManagers except for simple highly specialized environments.
If the answer to 4 is "yes", won't this lead to a proliferation of LayoutManager classes which will become difficult to maintain?

(The answer to 4 is "no".)
In a situation where I need to define proportions between children of a Component (for example, child 1 should use 10% of space, child 2 40%, child 3 50%), is it possible to achieve that without implementing a custom LayoutManager?

Any of the Big-Three can, can't even GridBag (never bothered to really master, too much trouble for too little power).

Best Answer

Related Solutions

Java – How to convert byte size into a human-readable format in Java

SI (1 k = 1,000)

Binary (1 Ki = 1,024)

Example output:

Java – Should I avoid the use of set(Preferred|Maximum|Minimum)Size methods in Java Swing

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