Foreword

Want to record the two ways of positioning in the Stack layout.

Code

//... omit extraneous code...

child: new Column(
          children: <Widget>[
            new SizedBox(height: 20.0),
            new Stack(
                             Alignment: const FractionalOffset(0.9, 0.1), // Method 1
              children: <Widget>[
                new Image(
                  image: new AssetImage("assets/images/illustration_11.jpg"),
                  width: 300.0,
                  height: 200.0,
                  fit: BoxFit.cover,
                ),
                new Opacity(
                  opacity: 0.8,
                  child: new Image(
                    image: new AssetImage("assets/images/illustration_12.jpg"),
                    width: 200.0,
                    height: 150.0,
                    fit: BoxFit.cover,
                  ),
                ),
                new GestureDetector(
                  onTap: () {
                                         Fluttertoast.showToast (msg: "Share it");
                  },
                  child: new Icon(Icons.share, color: Colors.white),
                ),
              ],
            ),
            new SizedBox(height: 20.0),
            new Stack(
              children: <Widget>[
                new Image(
                  image: new AssetImage("assets/images/illustration_11.jpg"),
                  width: 300.0,
                  height: 200.0,
                  fit: BoxFit.cover,
                ),
                                 New Positioned (/ / method two
                  right: 15.0,
                  top: 15.0,
                  child: new Icon(
                    Icons.share,
                    color: Colors.white,
                  ),
                ),
              ],
            )
          ],
        ),
        
                 //... omit extraneous code...

method one

Use alignment with FractionalOffset: For the parameters of the FractionalOffset, I understand this: the equivalent ratio, the first one represents the horizontal weight, the second represents the vertical weight, the horizontal 0.9 represents the position of nine out of the horizontal, and the vertical 0.1 represents the vertical To one tenth of the position

Method Two

Use the positioning component Positioned, top, right, buttom, left, directly represent the distance from the direction

effect