在颤动列表视图中检测焦点小部件

Question

I have an horizontal listview.builder widget, each child in the list is about 90℅ of the total width, how can I detect which widget is in focus.

This is my the widget.

new ListView.builder(
                              scrollDirection: Axis.horizontal,
                              itemCount: categories.length,
                              itemBuilder: (context, index) {
                                return new InkWell(
                                  onTap: () {
                                    Navigator
                                        .of(context)
                                        .push(new MaterialPageRoute(
                                          builder: (_) => new StakePage(),
                                        ));
                                  },
                                  child: new Card(
                                    child: new Container(
                                      decoration: new BoxDecoration(
                                        image: new DecorationImage(
                                          fit: BoxFit.cover,
                                          image: categories[index].cover,
                                          colorFilter: new ColorFilter.mode(
                                              Colors.black12,
                                              BlendMode.screen),
                                        ),
                                      ),
                                      constraints: new BoxConstraints(
                                          maxWidth: 400.0,
                                          maxHeight: 600.0),
                                      height: size.height / 2,
                                      width: size.width * 0.85,
                                    ),
                                  ),
                                );
                              }),

Answer 1

你可以用与你的widget visibility_detector小部件，它会触发一个回调，只要你的控件在屏幕上。