--- a/flys-client/src/main/java/de/intevation/flys/client/client/ui/ParameterList.java	Mon Jul 04 07:15:44 2011 +0000
+++ b/flys-client/src/main/java/de/intevation/flys/client/client/ui/ParameterList.java	Tue Jul 05 16:12:34 2011 +0000
@@ -30,6 +30,7 @@
 import de.intevation.flys.client.client.Config;
 import de.intevation.flys.client.client.FLYS;
 import de.intevation.flys.client.client.FLYSConstants;
+import de.intevation.flys.client.client.event.AdvanceHandler;
 import de.intevation.flys.client.client.event.CollectionChangeEvent;
 import de.intevation.flys.client.client.event.CollectionChangeHandler;
 import de.intevation.flys.client.client.event.HasParameterChangeHandler;
@@ -57,7 +58,7 @@
 extends      Tab
 implements   StepBackHandler, StepForwardHandler, ParameterChangeHandler,
              HasParameterChangeHandler, CollectionChangeHandler,
-             OutputModesChangeHandler
+             OutputModesChangeHandler, AdvanceHandler
 {
     /** The message class that provides i18n strings.*/
     protected FLYSConstants MSG = GWT.create(FLYSConstants.class);
@@ -329,6 +330,10 @@
     public void addOldDatas(DataList[] old) {
         if (old != null && old.length > 0) {
             for (DataList o: old) {
+                if (o == null) {
+                    continue;
+                }
+
                 if (!exists(o)) {
                     GWT.log("Data '" + o.getLabel() + "' is new.");
                     addOldData(o);
@@ -343,6 +348,10 @@
 
 
     public boolean exists(DataList data) {
+        if (data == null) {
+            return false;
+        }
+
         String stateName = data.getState();
 
         for (DataList o: old) {
@@ -399,6 +408,10 @@
 
         if (current != null && uiProvider != null) {
             Canvas c = uiProvider.create(current);
+            currentItems.addMember(c);
+        }
+        else if (uiProvider != null) {
+            Canvas c = uiProvider.create(null);
             c.setLayoutAlign(VerticalAlignment.TOP);
 
             currentItems.addMember(c);
@@ -470,6 +483,31 @@
     }
 
 
+    public void onAdvance(final String target) {
+        Config config          = Config.getInstance();
+        final String serverUrl = config.getServerUrl();
+        final String locale    = config.getLocale();
+
+        advanceService.advance(serverUrl, locale, artifact, target,
+            new AsyncCallback<Artifact>() {
+                public void onFailure(Throwable caught) {
+                    GWT.log("Could not go to '" + target + "'");
+                    SC.warn(MSG.getString(caught.getMessage()));
+                }
+
+                public void onSuccess(Artifact artifact) {
+                    GWT.log("Successfully advanced to '" + target + "'");
+
+                    old.clear();
+                    oldItems.removeMembers(oldItems.getMembers());
+
+                    setArtifact(artifact);
+                }
+            }
+        );
+    }
+
+
     /**
      * Implements the onCollectionChange() method to do update the GUI after the
      * parameterization has changed.
@@ -501,8 +539,22 @@
             setCurrentData(currentData, provider);
         }
         else {
-            // we have reached a final state with no more user input
-            setCurrentData(null, null);
+            String[] reachable = desc.getReachableStates();
+            if (reachable != null && reachable.length > 0) {
+                // We have reached a final state with the option to step to
+                // further to a next state. But in the current state, no user
+                // data is required.
+                UIProvider ui = UIProviderFactory.getProvider("continue");
+                ui.setArtifact(art);
+
+                ((ContinuePanel) ui).addAdvanceHandler(this);
+
+                setCurrentData(null, ui);
+            }
+            else {
+                // we have reached a final state with no more user input
+                setCurrentData(null, null);
+            }
         }
 
         addOldDatas(desc.getOldData());