Removed coupling with UI. Used event driven model to trigger UI changes.

src/main/java/seedu/savvytasker/MainApp.java

@@ -69,14 +69,6 @@ public void init() throws Exception {
 
         initEventsCenter();
     }
-
-    public static Ui getUiManager() {
-        if (instance != null) {
-            return instance.ui;
-        } else {
-            return null;
-        }
-    }
 
     private String getApplicationParameter(String parameterName){
         Map<String, String> applicationParameters = getParameters().getNamed();

src/main/java/seedu/savvytasker/commons/core/Messages.java

@@ -9,6 +9,7 @@ public class Messages {
     public static final String MESSAGE_INVALID_COMMAND_FORMAT = "Invalid command format! \n%1$s";
     public static final String MESSAGE_INVALID_TASK_DISPLAYED_INDEX = "The task index provided is invalid";
     public static final String MESSAGE_TASKS_LISTED_OVERVIEW = "%1$d tasks listed!";
+    public static final String MESSAGE_ALIASES_LISTED_OVERVIEW = "%1$d aliases listed!";
     public static final String MESSAGE_INVALID_START_END = "The end time cannot be earlier than the start time";
 
 }

src/main/java/seedu/savvytasker/commons/events/ui/ChangeListRequestEvent.java

@@ -0,0 +1,26 @@
+package seedu.savvytasker.commons.events.ui;
+
+import seedu.savvytasker.commons.events.BaseEvent;
+
+/**
+ * Indicates a request to jump to the list of tasks
+ */
+public class ChangeListRequestEvent extends BaseEvent {
+
+    public enum DisplayedList {
+        Task,
+        Alias
+    }
+
+    public final DisplayedList displayedList;
+
+    public ChangeListRequestEvent(DisplayedList displayedList) {
+        this.displayedList = displayedList;
+    }
+
+    @Override
+    public String toString() {
+        return this.getClass().getSimpleName();
+    }
+
+}

src/main/java/seedu/savvytasker/logic/LogicManager.java

@@ -9,8 +9,11 @@
 import javafx.collections.ObservableList;
 import seedu.savvytasker.MainApp;
 import seedu.savvytasker.commons.core.ComponentManager;
+import seedu.savvytasker.commons.core.EventsCenter;
 import seedu.savvytasker.commons.core.LogsCenter;
 import seedu.savvytasker.commons.events.model.AliasSymbolChangedEvent;
+import seedu.savvytasker.commons.events.ui.ChangeListRequestEvent;
+import seedu.savvytasker.commons.events.ui.ChangeListRequestEvent.DisplayedList;
 import seedu.savvytasker.logic.commands.Command;
 import seedu.savvytasker.logic.commands.CommandResult;
 import seedu.savvytasker.logic.commands.ListCommand;
@@ -67,10 +70,7 @@ public CommandResult execute(String commandText) {
 
         if (!(command instanceof ListCommand)) {
             // forcefully show the task list instead
-            Ui uiManager = MainApp.getUiManager();
-            if (uiManager != null) {
-                uiManager.showTaskList(true);
-            }
+            EventsCenter.getInstance().post(new ChangeListRequestEvent(DisplayedList.Task));
         }
 
         //@@author A0097627N

src/main/java/seedu/savvytasker/logic/commands/Command.java

@@ -19,6 +19,15 @@ public abstract class Command {
     public static String getMessageForTaskListShownSummary(int displaySize) {
         return String.format(Messages.MESSAGE_TASKS_LISTED_OVERVIEW, displaySize);
     }
+    /**
+     * Constructs a feedback message to summarise an operation that displayed a listing of aliases.
+     *
+     * @param displaySize used to generate summary
+     * @return summary message for tasks displayed
+     */
+    public static String getMessageForAliasListShownSummary(int displaySize) {
+        return String.format(Messages.MESSAGE_ALIASES_LISTED_OVERVIEW, displaySize);
+    }
 
     /**
      * Executes the command and returns the result message.

src/main/java/seedu/savvytasker/logic/commands/ListCommand.java

@@ -1,6 +1,8 @@
 package seedu.savvytasker.logic.commands;
 
-import seedu.savvytasker.MainApp;
+import seedu.savvytasker.commons.core.EventsCenter;
+import seedu.savvytasker.commons.events.ui.ChangeListRequestEvent;
+import seedu.savvytasker.commons.events.ui.ChangeListRequestEvent.DisplayedList;
 import seedu.savvytasker.model.ListType;
 
 /**
@@ -39,7 +41,6 @@ public CommandResult execute() {
 
         // shows the task list by default, unless user
         // specifies to show the alias
-        MainApp.getUiManager().showTaskList(true);
         switch (_listType)
         {
         case DueDate:
@@ -52,13 +53,18 @@ public CommandResult execute() {
             model.updateFilteredListToShowArchived();
             break;
         case Alias:
-            MainApp.getUiManager().showTaskList(false);
+            EventsCenter.getInstance().post(new ChangeListRequestEvent(DisplayedList.Alias));
             break;
         default:
             // nothing to do
             break;
         }
-        return new CommandResult(getMessageForTaskListShownSummary(model.getFilteredTaskList().size()));
+        if (_listType != ListType.Alias) {
+            EventsCenter.getInstance().post(new ChangeListRequestEvent(DisplayedList.Task));
+            return new CommandResult(getMessageForTaskListShownSummary(model.getFilteredTaskList().size()));
+        } else {
+            return new CommandResult(getMessageForAliasListShownSummary(model.getAliasSymbolCount()));
+        }
     }
     //@@author
 

src/main/java/seedu/savvytasker/model/Model.java

@@ -77,4 +77,7 @@ public interface Model {
 
     /** Removes an the given AliasSymbol. */
     void removeAliasSymbol(AliasSymbol symbol) throws SymbolKeywordNotFoundException;
+
+    /** Gets the number of aliases */
+    int getAliasSymbolCount();
 }

src/main/java/seedu/savvytasker/model/ModelManager.java

@@ -139,6 +139,11 @@ public synchronized void removeAliasSymbol(AliasSymbol symbol) throws SymbolKeyw
         indicateSavvyTaskerChanged();
         indicateAliasSymbolRemoved(symbol);
     }
+
+    @Override
+    public int getAliasSymbolCount() {
+        return savvyTasker.getAliasSymbolCount();
+    }
     //@@author
 
     //=========== Filtered/Sorted Task List Accessors ===============================================================

src/main/java/seedu/savvytasker/model/SavvyTasker.java

@@ -252,6 +252,10 @@ public void removeAliasSymbol(AliasSymbol symbol) throws SymbolKeywordNotFoundEx
     }
     //@@author
 
+    public int getAliasSymbolCount() {
+        return symbols.size();
+    }
+
 //// util methods
 
     @Override

src/main/java/seedu/savvytasker/ui/Ui.java

@@ -12,8 +12,5 @@ public interface Ui {
 
     /** Stops the UI. */
     void stop();
-
-    /** Shows/Hides the task list */
-    void showTaskList(boolean isShown);
 
 }

src/main/java/seedu/savvytasker/ui/UiManager.java

@@ -14,6 +14,8 @@
 import seedu.savvytasker.commons.core.Config;
 import seedu.savvytasker.commons.core.LogsCenter;
 import seedu.savvytasker.commons.events.storage.DataSavingExceptionEvent;
+import seedu.savvytasker.commons.events.ui.ChangeListRequestEvent;
+import seedu.savvytasker.commons.events.ui.ChangeListRequestEvent.DisplayedList;
 import seedu.savvytasker.commons.events.ui.JumpToListRequestEvent;
 import seedu.savvytasker.commons.events.ui.ShowHelpRequestEvent;
 import seedu.savvytasker.commons.events.ui.TaskPanelSelectionChangedEvent;
@@ -65,11 +67,6 @@ public void stop() {
         mainWindow.hide();
         mainWindow.releaseResources();
     }
-
-    @Override
-    public void showTaskList(boolean isShown) {
-        mainWindow.showTaskList(isShown);
-    }
 
     private void showFileOperationAlertAndWait(String description, String details, Throwable cause) {
         final String content = details + ":\n" + cause.toString();
@@ -117,6 +114,16 @@ private void handleShowHelpEvent(ShowHelpRequestEvent event) {
         mainWindow.handleHelp();
     }
 
+    @Subscribe
+    private void handleChangeListRequestEvent(ChangeListRequestEvent event) {
+        logger.info(LogsCenter.getEventHandlingLogMessage(event));
+        if (event.displayedList == DisplayedList.Task) {
+            mainWindow.showTaskList(true);
+        } else {
+            mainWindow.showTaskList(false);
+        }
+    }
+
     @Subscribe
     private void handleJumpToListRequestEvent(JumpToListRequestEvent event) {
         logger.info(LogsCenter.getEventHandlingLogMessage(event));