Simple MVVM framework for Java applications
##Configuring annoMVVM for Vaadin
###StateChangeListener
In order for the ViewModelComposer to know how to synchronise a viewmodel's changed State with the bound field in the view, a StateChangeListener has to be provided. There can be different listeners for different types of fields, in the following an example for providing a listener for Vaadin's AbstractField and for a State of this framework:
viewModelComposer.addStateChangeWrapper(AbstractField.class,
new StateChangeWrapper() {
@Override
public StateChangeListener getStateChangeListener(
final Object notified) {
return new StateChangeListener() {
@SuppressWarnings("unchecked")
@Override
public void stateChange(Object value) {
//synchronise the state by invoking AbstractField.setValue
((AbstractField<Object>) notified)
.setValue(value);
}
};
}
});
viewModelComposer.addStateChangeWrapper(State.class,
new StateChangeWrapper() {
@Override
public StateChangeListener getStateChangeListener(
final Object notified) {
return new StateChangeListener() {
@SuppressWarnings("unchecked")
@Override
public void stateChange(Object value) {
//synchronise the state by invoking State.set
((State<Object>) notified).set(value);
}
};
}
});###SourceWrapper
When defining source fields in the @BindAction annotation, a SourceWrapper for the type of a source field has to be provided. It specifies how the data should be extracted from the source field.
viewModelComposer.addSourceWrapper(AbstractField.class,
new SourceWrapper<Object>() {
@SuppressWarnings("unchecked")
@Override
public Object get(Object source) {
return ((AbstractField<Object>) source).getValue();
}
});###ActionHandler
When no source fields are defined in the @BindAction annotation, an ActionHandler has to be provided, which specifies what data should be passed on to the invoked method in the viewmodel.
viewModelComposer.addActionWrapper(ValueChangeNotifier.class,
new ActionWrapper() {
@Override
public void addActionHandler(Object notifier,
final ActionHandler actionHandler) {
((ValueChangeNotifier) notifier)
.addValueChangeListener(new ValueChangeListener() {
private static final long serialVersionUID = -854400079672018869L;
@Override
public void valueChange(
ValueChangeEvent event) {
actionHandler.handle(event.getProperty().getValue());
}
});
}
});
viewModelComposer.addActionWrapper(Button.class, new ActionWrapper() {
@Override
public void addActionHandler(Object notifier,
final ActionHandler actionHandler) {
((Button) notifier).addClickListener(new ClickListener() {
private static final long serialVersionUID = 3154305342571215268L;
@Override
public void buttonClick(ClickEvent event) {
actionHandler.handle(event.getButton().getData());
}
});
}
});##Usage of the annotations Annotations can be used for either passing events in the view to the viewmodel or synchronising a state in the viewmodel with the counterpart in the view.
###@BindAction
For binding an action in a view to a method in a viewmodel, an ActionHandler needs to be declared in the viewmodel:
public interface DoLogout extends ActionHandler {}The declared handler can then be used in a @HandlesAction annotation on a method in the viewmodel:
@HandlesAction(DoLogin.class)
public void doLogin(String username, String password) {
//do something with username and password
}Now the method can be bound in the view:
private TextField user = new TextField("User:");
private PasswordField password = new PasswordField("Password:");
@BindAction(value = DoLogin.class, source = { "user", "password" })
private Button loginButton;Make sure the fields in the view are initialised properly - otherwise you might get a NullPointerException when binding the view to the viewmodel.
###@BindState
For binding a state in a viewmodel to a synchronised field in a view, a State needs to be declared in the viewmodel:
public interface IsLoggedIn extends State<Boolean> {}
public interface UserInformation extends State<String> {}The declared state can then be used in a @ProvidesState annotation on a State field in the viewmodel:
@ProvidesState(IsLoggedIn.class)
public final BasicState<Boolean> isLoggedIn = new BasicState<Boolean>(Boolean.class);
@ProvidesState(UserInformation.class)
public final BasicState<String> userInformation = new BasicState<String>(String.class);Now a field in the view can be synchronised with the State:
@BindState(IsLoggedIn.class)
private BasicState<Boolean> isLoggedIn = new BasicState<Boolean>(Boolean.class);
@BindState(UserInformation.class)
private Label labelUserInformation = new Label();When a State is changed in the viewmodel, it now automatically synchronises with the bound fields in the views:
isLoggedIn.set(false);
userInformation.set("User: abc");Author: David Herrmann, 2013