android通过泛型获取控件或视图

     @SuppressWarnings("unchecked")
     public <T extends Fragment> T getFragment(int id) {
         T result = (T)getFragmentManager().findFragmentById(id);
         if (result == null) {
             throw new IllegalArgumentException("fragment 0x" + Integer.toHexString(id)
                     + " doesn't exist");
         }
         return result;
     }

     /**
      * Convenient version of {@link #findViewById(int)}, which throws
      * an exception if the view doesn't exist.
      */
     @SuppressWarnings("unchecked")
     public <T extends View> T getView(int id) {
         T result = (T)findViewById(id);
         if (result == null) {
             throw new IllegalArgumentException("view 0x" + Integer.toHexString(id)
                     + " doesn't exist");
         }
         return result;
     }