Swing - Custom Buttons w/Synth

Question

I am working on a project using Synth for the UI and want to implement some custom buttons. The buttons need to make use of style settings from a synth XML settings file - e.g. font colors which are different for different states (MOUSE_OVER, PRESSED, etc).

The problem I'm stuck on is that some of the buttons need to have extra sub-components - e.g. some need more than one label. I want the sub-components to pick up the same style settings as the standard button sub-components.

I feel like I ought to be able to just extend JButton and override/extend paintComponent to call the draw methods of some child components. I'm a bit unsure about a few aspects of that approach though: e.g. what parameters to pass to paintComponent; and how to ensure the sub-components get the correct Synth style settings (particularly wrt. the states).

An aside: I have tried extending JPanel but have run into some difficulties with that approach (see here: JPanel states for Synth).

EDIT: So, I've discovered that it is possible to add sub-components to buttons and have them render correctly. It seems that even though JButton.getLayout() returns null, the button will use an OverlayLayout unless you call JButton.setLayout(). Calling JButton.setLayout(null) does prevent the OverlayLayout being used, so that's how I'm handling the layout.

I'm looking into a couple of different approaches to updating the styles for the child controls, will report back on those later.

Answer 1

So, in case it's of use to anyone else here's the approach I took in the end:

class CustomButton extends JButton {
    CustomButton() {
        // ... normal button init

        // Enable absolute positioning of sub-components.
        setLayout(null);

        updateStyles();

        getModel().addChangeListener(new ChangeListener() {
            @Override
            public void stateChanged(ChangeEvent e) {
                updateStyles();
            }
        });
    }

    private void updateStyles() {
        // See below for implementation.
    }

    private int getSynthComponentState() {
        // This is basically a copy of SynthButtonUI.getComponentState(JComponent)
        int state = SynthConstants.ENABLED;
        if (!isEnabled()) {
            state = SynthConstants.DISABLED;
        }

        if (model.isPressed()) {
            if (model.isArmed()) {
                state = SynthConstants.PRESSED;
            } else {
                state = SynthConstants.MOUSE_OVER;
            }
        }
        if (model.isRollover()) {
            state |= SynthConstants.MOUSE_OVER;
        }
        if (model.isSelected()) {
            state |= SynthConstants.SELECTED;
        }
        if (isFocusOwner() && isFocusPainted()) {
            state |= SynthConstants.FOCUSED;
        }
        if (isDefaultButton()) {
            state |= SynthConstants.DEFAULT;
        }
        return state;
    }
}

I found 2 approaches to how to implement the updateStyles() method: (A) change the name of the component to use a different named style, or (B) copy the style settings from the button to the sub-components. Approach (A) is pretty straightforward, approach (B) works as follows:

private void updateStyles() {
    SynthStyle ss = SynthLookAndFeel.getStyle(this, Region.BUTTON);
    SynthContext sc = new SynthContext(this, Region.BUTTON, ss, getSynthComponentState());

    for (Component c : getComponents()) {
        c.setFont(ss.getFont(sc));
        c.setBackground(ss.getColor(sc, ColorType.BACKGROUND));
        c.setForeground(ss.getColor(sc, ColorType.FOREGROUND));
        // ... and so on if you have other style elements to be changed.
    }
}

Approach (A) is probably better if you're changing more than a couple of style settings with each different state, although it could get unwieldy if you have different styles for a lot of different states. If you're only changing a couple of style settings (e.g. in my case I only care about colours, at least for now) then approach (B) seems best.

There's also the approach suggested by trashgod of implementing a custom UI delegate (extending BasicButtonUI) but if you take that route I think you'll have to re-implement much of SynthButtonUI.