Tooltip

const Tooltip({     super.key,     this.message,     this.richMessage,     this.height,     this.padding,     this.margin,     this.verticalOffset,     this.preferBelow,     this.excludeFromSemantics,     this.decoration,     this.textStyle,     this.textAlign,     this.waitDuration,     this.showDuration,     this.triggerMode,     this.enableFeedback,     this.onTriggered,     this.child,   })   注意：是在所child控件上长按才显示message  

Tooltip(
              message: '点击进行用户名和密码认证，完成系统登录',
              child: ElevatedButton(
                onPressed: () {
                  _login();
                },
                child: const Text('Login'),
              ),
            ),