如何在底部放置一个 child(带有文本的容器)并使其宽度与他的 sybilings 相同并将文本保持在中心

how to position a child (the container with the text) in the bottom and make it's width the same as his sybilings and keep the text in the center

我正在尝试将第二个容器(带有文本的那个)放在底部,我想使黑色不透明度与第一个容器(图像)的宽度相同,并将文本保留在中心

child: Stack(

             children: <Widget>
                [
           Container
           (
             padding: EdgeInsets.fromLTRB(0,0,0,0),

             child: new Image
                (
                  image: new AssetImage('images/99.jpg'), 
                  fit: BoxFit.cover
                )
                ),

            new Positioned(

               bottom: 0,

               child: Container
              (
                padding: EdgeInsets.all(7.0),

                color: Colors.black.withOpacity(0.3),


                child: Text("The text", style: TextStyle(color: Colors.white, fontSize: 25.0), textAlign: TextAlign.center,), 


                ),


                  ),

enter image description here

我想,你正在搜索它--

这是这个容器的代码 --

 child: Stack(
            children: <Widget>[
              Container(
                color: Colors.green,
                width: MediaQuery.of(context).size.width,
                height: MediaQuery.of(context).size.height / 2,
              ),
              Container(
                width: MediaQuery.of(context).size.width,
                height: MediaQuery.of(context).size.height / 2,
                child: Align(
                    alignment: Alignment.bottomCenter,
                    child: Container(
                      color: Colors.black12,
                      height: 50.0,
                      width: MediaQuery.of(context).size.width,
                      child: Center(child: Text("abirahsan122@gmail.com")),
                    )),
              )
            ],
          ),