动态（清除）删除QLayout布局

QLayoutItem *child;
  while ((child = layout->takeAt(0)) != 0) {
      //删除 child
      layout->removeWidget(child->widget());
      delete child;
}

Removes the widget widget from the layout. After this call, it is the caller's responsibility to give the widget a reasonable geometry or to put the widget back into a layout or to explicitly hide it if necessary.

Note: The ownership of widget remains the same as when it was added.

机器翻译：从布局中删除小部件。在这个调用之后，调用者有责任给小部件一个合理的几何图形，或者将小部件放回布局中，或者在必要时显式地隐藏它。

注意：小部件的所有权与添加时相同。

QLayoutItem *child;
  while ((child = layout->takeAt(0)) != 0) {
      //删除 child
      layout->removeWidget(child->widget());

      //重点 - 敲黑板
      child->widget()->setParent(0);

      delete child;
}