code: public void setContentView(View view) {
          ensureContent();
          if (view == null) {
              throw new IllegalArgumentException("Content view can't be null");
          }
          if (mContentContainer instanceof ViewGroup) {
              ViewGroup contentContainer = (ViewGroup) mContentContainer;
              if (mContentView == null) {
                  contentContainer.addView(view);
              } else {
                  int index = contentContainer.indexOfChild(mContentView);
                  // replace content view
                  contentContainer.removeView(mContentView);
                  contentContainer.addView(view, index);
              }
              mContentView = view;
          } else {
              throw new IllegalStateException("Can't be used with a custom content view");
          }
      }
docs: Set the content view to an explicit view. If the content view was installed earlier,
  the content will be replaced with a new view.
  
  @param view The desired content to display. Value can't be null.
  @see #setContentView(int)
  @see #getContentView()