增加修改昵称字数限制

student/src/main/res/layout/activity_modify_nickname.xml

@@ -23,6 +23,7 @@
             android:background="@null"
             android:gravity="left|center_vertical"
             android:hint="请输入昵称"
+            android:maxLength="7"
             android:paddingLeft="14dp"
             android:paddingRight="30dp"
             android:textColor="@color/color_1a1a1a"

teacher/src/main/res/layout/activity_modify_nickname.xml

@@ -25,6 +25,7 @@
             android:hint="请输入昵称"
             android:paddingLeft="14dp"
             android:paddingRight="30dp"
+            android:maxLength="7"
             android:textColor="@color/color_1a1a1a"
             android:textColorHint="@color/color_999999"
             android:textSize="@dimen/sp_16" />