Flutter 2 second 在页面加载和 2 秒后成功显示时显示错误

问题描述

你好，这里有一位 Flutter 专家吗？？请帮助我...我想做的是像 Facebook 照片查看器，当用户滑动图像并检查我的代码中是否像我想要的一样... 我制作了我的代码，因为我来自列表页面，当我点击列表时，我可以看到全屏图像......而且我可以滑动（滚动）图像...... BUTTT 当我第一次出现在我编码的屏幕上时，它会在屏幕上显示一些错误 3,4 秒......之后我可以看到图像，请帮助我并显示我的错误

Future<PhotoDetail> pagedetail() async {
sharedPreferences = await SharedPreferences.getInstance();
Map data = {
"Accesstoken": sharedPreferences.getString("Accesstoken"),"CustomerId":  sharedPreferences.getInt("CustomerId"),"ImageId":   indexx == null ? widget.images[widget.currentindex].photoId : indexx
 };
 print(data);
 final http.Response response = await http.post(
 Constants.CUSTOMER_WEBSERVICE_URL + "/photo/detail",headers: <String,String>{
  'Content-Type': 'application/json; charset=UTF-8',},body: jsonEncode(data),);
   var jsonResponse = json.decode(response.body);
   if (response.statusCode == 200) {

    print("Response status : ${response.statusCode}");
    print("Response status : ${response.body}");

    isLike = jsonResponse["IsLike"]; //here i saving value when api is run
    print("iSLiked Value:" +isLike.toString());  // value is printing here
    return PhotoDetail.fromJson(json.decode(response.body));

    } else {

    throw Exception('Failed to load data');
     }
    }

  Future<PhotoDetail> _photoDetail;


 @override
 void initState() {
_photoDetail = pagedetail();
 setState(() {
pagedetail(); //here is my api run when page is load
 });
 super.initState();

 }


 void pageChange(int index){  //this method is when i scroll page 
 setState(() {
  pagedetail();  // api is call again and again
   
  });
  }


@override
Widget build(BuildContext context) {
return Scaffold(
extendBodyBehindAppBar: true,body: Stack(
  children: <Widget>[
    Container(
        child:
        Center(
            child: PhotoViewgallery.builder(
              itemCount: widget.images.length,builder: (BuildContext context,int index) {
                return PhotoViewgalleryPageOptions(
                  imageProvider:
                  NetworkImage(widget.images[index].photoPreviewImagePath),maxScale: PhotoViewComputedScale.covered * 1.8,minScale: PhotoViewComputedScale.contained * 1.0,);
              },pageController:  _pageController,enableRotation: false,scrollDirection: Axis.horizontal,onPageChanged: pageChange,loadingBuilder: (BuildContext context,ImageChunkEvent event){
                return Center(child: CircularProgressIndicator(),)
        )
    ),Positioned(
        bottom: 10,left: 30,right: 30,child: (_photoDetail == null) ? Text("error")
        : FutureBuilder<PhotoDetail>(
          future: _photoDetail,// ignore: missing_return
          builder: (context,snapshot){
            int like = snapshot.data.isLike;
            int Slection = snapshot.data.selectedCount;
            print("like ?????:" +like.toString());
            print("Selection ????? :" + Slection.toString());
            if (snapshot.hasData){
              return Row(
                  mainAxisAlignment: MainAxisAlignment.spaceBetween,children: <Widget>[
                    InkWell(
                      child: InkWell(
                          Likes();
                          Fluttertoast.showToast(
                              msg: "Liked",toastLength: Toast.LENGTH_SHORT,gravity: ToastGravity.BottOM,timeInSecForIosWeb: 1,backgroundColor: Color(0xfff58634),textColor: Colors.white,fontSize: 16.0
                          );
                        },child:  Icon(Icons.thumb_up,size: 20,color: like == 1 ? Color(0xfff58634) : Colors.white),),InkWell(

                      child:  Icon(Icons.comment,color: Colors.white),InkWell(
                      onTap: (){
                        _onShare();
                      },child: Icon(Icons.share,color: Colors.white,InkWell(
                      onTap: (){},child:  Icon(Icons.photo_album,color: Slection == 0 ? Colors.white : Color(0xfff58634)),InkWell(
                      onTap: (){
                        setState(() {
                          viewwholike();
                        });
                      },child:  Icon(Icons.card_giftcard,color: 
         Colors.white,]
              );
            }
            else {
              Text("error");
            }
          },],);
}
   ERROR::════════ Exception caught by widgets library 
  ═══════════════════════════════════════════════════════
   The following NoSuchMethodError was thrown building 
   FutureBuilder<PhotoDetail>(dirty,state: 
  _FutureBuilderState<PhotoDetail>#ef81b):
  The getter 'isLike' was called on null.
  Receiver: null
  Tried calling: isLike

  The relevant error-causing widget was: 
   FutureBuilder<PhotoDetail>  
  file:///C:/Users/Hello%20Devloper/AndroidStudioProjects/
   September/PhotoGranth- 
    App/lib/CampaignSinglePhotos.dart:400:15
   When the exception was thrown,this was the stack: 
    #0      Object.noSuchMethod (dart:core-patch/object_patch.dart:53:5)
     #1      _CampaignSinglePhotosstate.build.<anonymous closure> 
     (package:photogranth2020/CampaignSinglePhotos.dart:404:42)
     #2      _FutureBuilderState.build 
     (package:Flutter/src/widgets/async.dart:732:55)
     #3      StatefulElement.build 
    (package:Flutter/src/widgets/framework.dart:4619:28)
    #4      ComponentElement.performRebuild 
      (package:Flutter/src/widgets/framework.dart:4502:15)

解决方法

Flutter 会在您测试 snapshot.data.isLike 时告诉您数据尚未准备好。 如果snapshot.hasData，您应该始终在开始时进行测试，只有在此之后您才能制作所需的一切。 否则，如果 snapshot.hasData 为 false，只需返回 CircularProgressIndicator() 。