Qt desiner ui问题? 400 报错

Qt desiner ui问题? 400 报错

ui以代码形式打开了而不是界面怎么办？
<UI version="4.0" >
<class>MyClassClass</class>
<widget class="QMainWindow" name="MyClassClass" >
<property name="objectName" >
<string notr="true">MyClassClass</string>
</property>
<property name="geometry" >
<rect>
<x>0</x>
<y>0</y>
<width>600</width>
<height>400</height>
</rect>
</property>
<property name="windowTitle" >
<string>MyClass</string>
</property>
<widget class="QMenuBar" name="menuBar" />
<widget class="QToolBar" name="mainToolBar" />
<widget class="QWidget" name="centralWidget" />
<widget class="QStatusBar" name="statusBar" />
</widget>
<layoutDefault spacing="6" margin="11" />
<pixmapfunction></pixmapfunction>
<resources>
<include location="myclass.qrc"/>
</resources>
<connections/>
</UI>