默认标题居中显示，所有按钮不显示不占位

res/layout/common_title_bar.xml

@@ -37,7 +37,7 @@
             android:contentDescription="@null"
             android:scaleType="center"
             android:src="@drawable/selector_common_back_white_btn"
-            android:visibility="invisible" />
+            android:visibility="gone" />
     </LinearLayout>
 
     <!-- 标题 -->
@@ -46,11 +46,10 @@
         android:id="@+id/tv_title"
         android:layout_width="wrap_content"
         android:layout_height="match_parent"
-        android:layout_marginLeft="6.67dp"
         android:layout_toLeftOf="@+id/ll_right_btns"
         android:layout_toRightOf="@+id/ll_left_btns"
         android:ellipsize="end"
-        android:gravity="left|center_vertical"
+        android:gravity="center"
         android:singleLine="true"
         android:text=""
         android:textColor="@color/white"