切换super.onCreate第一，然后的setContentView。

Switch super.onCreate first, then setContentView.

这是因为super.onCreate调用框架的Activity.onCreate分配膨胀任何布局所需要的资源。因此，必须充气任何布局，XML /编程之前被调用。

This is because super.onCreate calls the framework's Activity.onCreate to allocate the resources needed to inflate any layouts. Hence , must be called before inflating any layouts, xml/programmatic.