When is Widget OnUnload() is called? - gwt

Question

Can you please tell me when a widget's OnUnload() is called?
I tried to override it however, it is never been accessed. Also what is the best way to unload a composite, I am using RootPanel.get("Dev1").clear();

Answer 1

If you want to stop the timer when you leave the page then use CloseHandler.
This handler is called while page closing and refreshing.
Window.addCloseHandler(new CloseHandler<Window>() {
#Override
public void onClose(CloseEvent<Window> event) {
timer.cancel();
}
});
If you want to stop the timer when clearing a vertical panel then use removeFromParent.
This overridden method is to be called when any widget is removed form its parent.
private Timer timer = null;
/*
* This is the entry point method.
*/
public void onModuleLoad() {
final Label label = new Label("Hello ") {
#Override
public void removeFromParent() {
if (timer != null && this.isAttached()) {
timer.cancel();
System.out.println("timer is stopped");
}
super.removeFromParent();
}
};
timer = new Timer() {
#Override
public void run() {
label.setText("Hello " + (int) (Math.random() * 100));
}
};
timer.scheduleRepeating(500);
final VerticalPanel verticalPanel = new VerticalPanel();
verticalPanel.add(label);
Button button = new Button("Remove Label");
button.addClickHandler(new ClickHandler() {
#Override
public void onClick(ClickEvent event) {
label.removeFromParent();
}
});
verticalPanel.add(button);
RootPanel.get().add(verticalPanel);
}
As per you comments try below code where clear method is overridden for VerticalPanel.
final VerticalPanel verticalPanel = new VerticalPanel(){
#Override
public void clear(){
if(this.isAttached()){
timer.cancel();
}
super.clear();
}
};
verticalPanel.getElement().setId("Div1");