ColorPicker
ColorPicker is the colour picker itself, standing open on the page: a colour
field, a hue bar and the hex, RGB and HSB values.
ColorPicker picker = new ColorPicker();
picker.setValue("c05a2a");
cp.add(picker);
//-- somewhere later
String colour = picker.getValue(); // "c05a2a"
The value
The value is a String of six hexadecimal digits without a leading #. A
# handed to setValue() is stripped, and null becomes 000000 - the
control has no empty state.
| Method | What it does |
|---|---|
setValue(String) |
set the colour; also updates the open picker |
getValue() |
the six hex digits currently picked |
setOnValueChanged(IExecute) |
stored, but see below |
How the value gets back
Every move in the picker writes the new colour straight into a hidden input, in the browser. That input travels with the next request like any other, so by the time a click handler runs the control already holds what the user picked - without a round trip per movement.
The consequence is that a change handler on this control does not fire when
the colour changes: nothing tells the server it happened.
ColorPickerButton and
ColorPickerInput do report a change, and are
the ones to use when something on the screen has to follow the colour.
What it is not
ColorPicker implements IHasChangeListener, not IControl<String>: it has no
mandatory, read-only or disabled state, and it cannot be bound or handed to a
form builder. It is a picker on a page, not a form field. For a form field use
one of the other two.
The picker takes about 356 by 176 pixels and is always open, so it belongs on a screen with room for it - a settings page, a panel of its own.