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Signal Binding

Connect widget properties to reusable typed signals with bidirectional updates.

Binding model

Call widget.bind(key, signal) to connect a supported widget property to a signal. Binding is bidirectional: the signal's current value is applied immediately, later signal changes update the widget, and user edits update the signal. Built-in keys are BindingKeys.TEXT for TextInput and its subclasses, and BindingKeys.CHECKED for ToggleButton and its subclasses.

A key is matched by object identity, so declare a custom key once and reuse it: static final BindingData<BooleanSignal> MY_CHECKBOX_VALUE = new BindingData<>(BooleanSignal.class);. A custom WidgetBase subclass handles its keys in createBinding(...) and returns null for unknown keys. Unsupported keys are ignored; passing a source of the wrong type is an error. Rebinding the same key replaces the previous connection, and WidgetBase.dispose() closes active bindings.

Signal callbacks run synchronously on the thread that calls set(). Change UI-bound signals on the UI thread.

Share model state between controls

StringSignal name = new StringSignal("Ada");
TextField editor = new TextField();
TextField mirror = new TextField();
editor.bind(BindingKeys.TEXT, name);
mirror.bind(BindingKeys.TEXT, name);

BooleanSignal enabled = new BooleanSignal(true);
Checkbox checkbox = new Checkbox("Enabled");
ToggleButton toggle = new ToggleButton("Enabled");
checkbox.bind(BindingKeys.CHECKED, enabled);
toggle.bind(BindingKeys.CHECKED, enabled);