在按钮按下颤动时开始滑入动画

Question

如何重构此滑入式动画代码以在我的按钮上使用 onLongPress：

@override void initState() {
super.initState();
_controller = AnimationController(
  duration: const Duration(seconds: 2),
  vsync: this,
)..repeat(reverse: true);
_offsetAnimation = Tween<Offset>(
  begin: Offset.zero,
  end: const Offset(1.5, 0.0),
).animate(CurvedAnimation(
  parent: _controller,
  curve: Curves.elasticIn,
));

}

现在动画会自动重复播放。我希望列表仅在按下按钮 3 秒后滑入。这是我的按钮代码。

  child: RaisedButton(
                  onPressed: (null),
                  autofocus: false,
                  clipBehavior: Clip.none,
                  color: Colors.red,
                  onLongPress: () => {
                    setState(() {
                      isEmerg = !isEmerg;
                    }),
                    // Navigator.pushReplacement(
                    //     context,
                    //     MaterialPageRoute(
                    //         builder: (context) => AnimationTest()))
                  },
                  child: Text(
                    'Hold for 3 Secs',
                    style: TextStyle(
                        fontWeight: FontWeight.w400,
                        color: Colors.white,
                        fontSize: 24.0,
                        fontFamily: 'Circular'),
                  ),
                  shape: CircleBorder(),
                  padding: EdgeInsets.all(70),
                ),

这是我在LongPress上显示的列表：

  SlideTransition(
          position: _offsetAnimation,
          child: Container(
              child: ListView.builder(
                  itemCount: messages.length,
                  itemBuilder: (context, index) {
                    return Card(
                      child: ListTile(
                        onTap: () {},
                        title: Text(messages[index].emergencyType),
                        subtitle: Text(messages[index].description),
                        leading: Icon(Icons.message_outlined),
                        trailing: Text('Send'),
                        tileColor: Colors.white,
                      ),
                    );
                  })),
        ),

Answer 1

在初始化时改变

_controller = AnimationController(
  duration: const Duration(seconds: 2),
  vsync: this,
)..repeat(reverse: true);

到

 _controller = AnimationController(
  duration: const Duration(seconds: 2),
  vsync: this,
); 

和 onLongPress 添加

_controller.forward();