在我的flutter应用程序中有帖子列表。帖子可能有多个图像。我使用按钮导航到下一个和上一个。每次单击按钮导航到下一个/上一个图像时，加载都需要一些时间。我想一次加载所有图像，以便当我单击按钮导航到下一个/上一个图像时，它应该可用而没有任何延迟。 正如我观察到的那样，在Instagram应用中，当帖子中有多个图像时，我们可以立即导航到下一个/上一个图像。
class SuggestPostListItem extends StatefulWidget {
final SuggestPostBeen item;
final int index;
String userName;
String userImage;
SuggestPostListItem({
@required this.index,
@required this.item,
@required this.userName,
@required this.userImage,
});
@override
SuggestPostListItemState createState() => new SuggestPostListItemState();
}
class SuggestPostListItemState extends State<SuggestPostListItem> {
var _imageCount;
@override
void initState() {
_imageCount = widget.item.media_list.length;
// TODO: implement initState
setStatus();
super.initState();
}
int traker = 0;
int _imageIndex = 0;
Widget showLeftButton() {
return _imageCount > 1 && traker > 0
? IconButton(
icon: Icon(Icons.arrow_back_ios),
onPressed: () {
setState(() {
print("left clicked $traker");
traker = traker - 1;
_imageIndex = traker;
});
},
color: Colors.white,
)
: Container();
}
Widget showRightButton() {
return _imageCount > 1 && traker < _imageCount - 1
? IconButton(
icon: Icon(Icons.arrow_forward_ios),
onPressed: () {
setState(() {
print("right clicked $traker");
traker = traker + 1;
_imageIndex = traker < _imageCount ? traker : traker - 1;
});
},
color: Colors.white,
)
: Container();
}
Widget _loadImage(int index) {
return FadeInImage.assetNetwork(
fit: BoxFit.fitHeight,
image: _imageCount > 0 ? widget.item.media_list[index]["imageUrl"] : "",
placeholder: 'images/dummi_rect.png');
}
@override
Widget build(BuildContext context) {
return _buildTextContainer();
}
Widget _buildTextContainer() {
Widget upperSectionWidget = new Container(
child: new Row(
mainAxisAlignment: MainAxisAlignment.start,
children: <Widget>[
new Expanded(
child: new ListTile(
contentPadding: const EdgeInsets.only(left: 10.0),
leading: new Container(
width: 30.0,
height: 30.0,
child: new CircularLabelImage(
radious: 30.0,
textValue: widget.userName,
imageUrl: widget.userImage,
),
),
title: new Text(widget.userName,
style: TextStyle(color: Colors.black, fontSize: 20.0)),
subtitle: new Text(DateUtil.getDate(widget.item.created_at),
style: TextStyle(fontSize: 14.0)),
),
),
],
),
);
// var postImage = FadeInImage.assetNetwork(
// fit: BoxFit.fitHeight,
// image:widget.item.image_url,
// placeholder: 'images/dummi_rect.png');
//enhancement to show horizontal list
// var postImage=FadeInImage.assetNetwork(
//
// fit: BoxFit.fitHeight,
// image:_imageCount>0?widget.item.media_list[_imageIndex]["imageUrl"]:"",
// placeholder: 'images/dummi_rect.png');
var imageOverlayGradient = DecoratedBox(
decoration: BoxDecoration(
gradient: LinearGradient(
begin: FractionalOffset.topCenter,
end: FractionalOffset.bottomCenter,
colors: [
const Color(0x80000000),
const Color(0x20000000),
],
),
),
);
Widget listItem = new Container(
child: new Column(
crossAxisAlignment: CrossAxisAlignment.start,
children: [
upperSectionWidget,
new Container(
height: 200.0,
width: double.infinity,
child: new Material(
type: MaterialType.card,
// elevation: 8.0,
// borderRadius: new BorderRadius.only(topLeft: const Radius.circular(8.0), topRight: const Radius.circular(8.0)),
child: new Stack(
//if fit not specified then, it aligns to top left....
fit: StackFit.expand,
children: <Widget>[
Positioned.fill(
top: 0.0,
child: new Parallax.inside(
child: _loadImage(
_imageIndex), //new Image.network('https://flutter.io/images/homepage/header-illustration.png'),
mainAxisExtent: 150.0,
) //new ParalllexImageWidget(imageUrl: result.imageUrl,controller: controller,)
),
imageOverlayGradient,
Positioned(
top: 10.0,
bottom: 10.0,
left: 10.0,
right: 10.0,
child: new Text(
widget.item.title,
style: TextStyle(color: Colors.white, fontSize: 20.0),
overflow: TextOverflow.ellipsis,
),
),
new Positioned(
bottom: 10.0,
right: 10.0,
child: new Chip(
label: new Text(status,
style: new TextStyle(
fontSize: 14.0,
color: Colors.white,
)),
backgroundColor: statusColor,
),
),
Positioned(
left: 0,
height: 200,
child: showLeftButton(),
),
Positioned(right: 0, height: 200, child: showRightButton()),
],
),
),
),
new Container(
padding: const EdgeInsets.all(10.0),
child: new Text(widget.item.description,
style: TextStyle(fontSize: 16.0)),
),
isPointsVisible ? getActionsList() : new Container(),
],
),
);
return new Container(
child: new Container(
padding: EdgeInsets.only(top: 10.0),
child: new Material(
type: MaterialType.card,
elevation: 2.0,
borderRadius: new BorderRadius.circular(8.0),
child: listItem,
)));
}
Widget getActionsList() {
return new Container(
height: 77.0,
color: Colors.white,
child: new Row(
crossAxisAlignment: CrossAxisAlignment.center,
mainAxisAlignment: MainAxisAlignment.spaceEvenly,
children: [
buildButtonColumn(
context, 'images/share.png', 'Shares', widget.item.post_share),
buildButtonColumn(
context, 'images/clicks.png', 'Clicks', widget.item.post_click),
buildButtonColumn(context, 'images/reaction.png', 'Recations',
widget.item.post_reactions),
buildButtonColumn(
context, 'images/view.png', 'View', widget.item.post_view),
],
),
);
}
Column buildButtonColumn(
BuildContext context, String iconPath, String label, int points) {
return new Column(
mainAxisSize: MainAxisSize.min,
mainAxisAlignment: MainAxisAlignment.center,
children: [
new IconButton(
icon: Image(
image: new AssetImage(iconPath),
width: 20.0,
height: 20.0,
),
iconSize: 20.0,
),
/*new Container(
child: new Text(
label,
style: new TextStyle(
fontSize: 16.0,
fontWeight: FontWeight.w400,
color: Colors.black54,
),
),
),*/
new Text(
points.toString(),
style: new TextStyle(
fontSize: 16.0,
fontWeight: FontWeight.w400,
color: Colors.black54,
),
),
new Container(
height: 10.0,
),
],
);
}
var statusColor;
String status;
bool isPointsVisible = false;
setStatus() {
switch (widget.item.status) {
case 24:
statusColor = Colors.orange;
status = 'Pending';
break;
case 25:
statusColor = Colors.red;
status = 'Excluded';
break;
case 26:
statusColor = Colors.blue;
status = 'Schedule';
break;
case 27:
statusColor = Colors.green;
status = 'Published';
isPointsVisible = true;
break;
}
}
}