add a clear-history menu to chat

xwords4/android/XWords4/res/menu/chat_menu.xml

@@ -0,0 +1,7 @@
+<?xml version="1.0" encoding="utf-8"?>
+
+<menu xmlns:android="http://schemas.android.com/apk/res/android">
+    <item android:id="@+id/chat_menu_clear"
+          android:title="@string/chat_menu_clear"
+          />
+</menu>

xwords4/android/XWords4/res/values/strings.xml

@@ -402,6 +402,7 @@
     <string name="chat_local_id">Me: </string>
     <string name="chat_other_id">Not me: </string>
     <string name="chat_send">Send</string>
+    <string name="chat_menu_clear">Clear history</string>
 
     <string name="notify_title">Moves made</string>
     <string name="notify_body">New game moves have arrived</string>

xwords4/android/XWords4/src/org/eehouse/android/xw4/ChatActivity.java

@@ -28,6 +28,9 @@ import android.widget.EditText;
 import android.widget.TextView;
 import android.view.LayoutInflater;
 import android.view.View;
+import android.view.Menu;
+import android.view.MenuItem;
+import android.view.MenuInflater;
 import android.widget.LinearLayout;
 
 public class ChatActivity extends XWActivity implements View.OnClickListener {
@@ -64,6 +67,29 @@ public class ChatActivity extends XWActivity implements View.OnClickListener {
         ((Button)findViewById( R.id.send_button )).setOnClickListener( this );
     }
 
+    @Override
+    public boolean onCreateOptionsMenu( Menu menu )
+    {
+        MenuInflater inflater = getMenuInflater();
+        inflater.inflate( R.menu.chat_menu, menu );
+        return true;
+    }
+
+    @Override
+    public boolean onOptionsItemSelected( MenuItem item ) 
+    {
+        boolean handled = R.id.chat_menu_clear == item.getItemId();
+        if ( handled ) {
+            DBUtils.clearChatHistory( this, m_path );
+            LinearLayout layout = 
+                (LinearLayout)findViewById( R.id.chat_history );
+            layout.removeAllViews();
+        } else {
+            handled = super.onOptionsItemSelected( item );
+        }
+        return handled;
+    }
+
     @Override
     public void onClick( View view ) 
     {

xwords4/android/XWords4/src/org/eehouse/android/xw4/DBUtils.java

@@ -533,13 +533,28 @@ public class DBUtils {
             msg = cur + "\n" + msg;
         }
 
+        saveChatHistory( context, path, msg );
+    } // appendChatHistory
+
+    public static void clearChatHistory( Context context, String path )
+    {
+        saveChatHistory( context, path, null );
+    }
+
+    private static void saveChatHistory( Context context, String path,
+                                         String history )
+    {
         initDB( context );
         synchronized( s_dbHelper ) {
             SQLiteDatabase db = s_dbHelper.getWritableDatabase();
 
             String selection = DBHelper.FILE_NAME + "=\"" + path + "\"";
             ContentValues values = new ContentValues();
-            values.put( DBHelper.CHAT_HISTORY, msg );
+            if ( null != history ) {
+                values.put( DBHelper.CHAT_HISTORY, history );
+            } else {
+                values.putNull( DBHelper.CHAT_HISTORY );
+            }
 
             long timestamp = new Date().getTime();
             values.put( DBHelper.LASTPLAY_TIME, timestamp );
@@ -548,7 +563,7 @@ public class DBUtils {
                                     values, selection, null );
             db.close();
         }
-    } // appendChatHistory
+    }
 
     private static String[] parsePlayers( final String players, int nPlayers ){
         String[] result = null;