您设置tools:background="#ab5442"(仅用于预览)，用于在运行时设置android:background="#ab5442"中设置背景 工具命名空间只是为了在开发时提供便利，并且不影响运行时

You set tools:background="#ab5442"(It setting just for preview), for setting backgroun in runtime set android:background="#ab5442" tools namespace just for convinience when developing and not affecting runtime