Clear chatBox on Navigation up

Author: kunall17

app/src/main/java/com/zulip/android/activities/MessageListFragment.java

@@ -68,6 +68,7 @@ void openCompose(final MessageType type, String stream, String topic,
                          String pmRecipients);
         void addToList(Message message);
         void muteTopic(Message message);
+        void clearChatBox();
     }
 
     private static final String PARAM_FILTER = "filter";
@@ -260,6 +261,7 @@ public void onAttach(Activity activity) {
     @Override
     public void onDetach() {
         super.onDetach();
+        mListener.clearChatBox();
         mListener = null;
     }
 

app/src/main/java/com/zulip/android/activities/ZulipActivity.java

@@ -722,6 +722,15 @@ public void switchView() {
     }
     String tempStreamSave = null;
 
+    @Override
+    public void clearChatBox() {
+        if (messageEt != null) {
+            if (TextUtils.isEmpty(messageEt.getText())) {
+                topicActv.setText("");
+                streamActv.setText("");
+            }
+        }
+    }
     public void onBackPressed() {
         if (narrowedList != null) {
             narrowedList = null;