package org.litesoft.sandbox.infrastructure.client;

import com.google.gwt.user.client.ui.*;

public interface Activity {
    /**
     * Called when the user is trying to navigate away from this activity.
     *
     * @return A message to display to the user, e.g. to warn of unsaved work, or
     * null to say nothing
     */
    String mayStop();

    /**
     * Called when {@link #start} has not yet replied to its callback, but the
     * user has lost interest.
     */
    void onCancel();

    /**
     * Called when the Activity's widget has been removed from view.
     */
    void onStop();

    /**
     * Called when the Activity should ready its widget for the user. When the
     * widget is ready (typically after an RPC response has been received),
     * receiver should present it by calling
     * {@link AcceptsOneWidget#setWidget} on the given panel.
     *
     * @param panel the panel to display this activity's widget when it is ready
     */
    void start( AcceptsOneWidget panel );
}