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- ---
- title: Composite Fields with CustomField
- order: 34
- layout: page
- ---
-
- [[components.customfield]]
- = Composite Fields with CustomField
-
- The [classname]#CustomField# is a way to create composite components as with [classname]#CustomComponent#, except that it implements the [interfacename]#Field# interface and inherits [classname]#AbstractField#, described in <<components-fields#components.fields,"Field Components">>.
- A field allows editing a property value in the data model, and can be bound to data with [classname]#Binder#, as described in <<../datamodel/datamodel-forms#datamodel.forms, "Binding Data to Forms">>.
-
- A composite field class must implement [methodname]#initContent()# method.
- It should return the content composite of the field.
-
- Methods overriding
- [methodname]#setInternalValue()# should call the superclass method.
-
- [[components.customfield.basic]]
- == Basic Use
-
- Let us consider a simple custom switch button component that allows you to click a button to switch it "on" and "off", as illustrated in <<figure.components.customfield.basic>>.
-
- [[figure.components.customfield.basic]]
- .A custom switch button field
- image::img/customfield-basic.png[width=25%, scaledwidth=40%]
-
- The field has [classname]#Boolean# value type, which the [methodname]#getType()# returns.
- In [methodname]#initContent()#, we initialize the button and the layout.
- Notice how we handle user interaction with the button to change the field value.
- We customize the [methodname]#setValue()# method to reflect the state back to the user.
-
- [source, Java]
- ----
- public class BooleanField extends CustomField<Boolean> {
- private final Button button = new Button("Off");
- private boolean value;
-
- @Override
- protected Component initContent() {
- button.addClickListener(event -> {
- setValue(!getValue());
- button.setCaption(getValue() ? "On" : "Off");
- });
-
- VerticalLayout layout = new VerticalLayout();
- layout.addComponent(new Label("Click the button"));
- layout.addComponent(button);
- return layout;
- }
-
- @Override
- public Boolean getValue() {
- return value;
- }
-
- @Override
- protected void doSetValue(Boolean value) {
- this.value = value;
- button.setCaption(value ? "On" : "Off");
- }
- }
- ----
-
- We can now use the field in all the normal ways for a field:
-
- [source, Java]
- ----
- // Create it
- BooleanField field = new BooleanField();
-
- // It's a field so we can set its value
- field.setValue(new Boolean(true));
-
- // ...and read the value
- Label value = new Label(field.getValue()?
- "Initially on" : "Initially off");
-
- // ...and handle value changes
- field.addValueChangeListener(event ->
- value.setValue(field.getValue()?
- "It's now on" : "It's now off"));
- ----
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