從 flutter 和 dart 中的另一個 class 調用一個 class 中的方法

Question

所以我正在嘗試使用 flutter 構建一個像 insta 這樣的網絡應用程序。 因此，當我嘗試從我的時間線中刪除帖子時，它確實會被刪除，但因為數據已經在客戶端，所以我遇到了 docsnapshot 錯誤。 但是要重建我的屏幕，我的 buildTimeLine function 位於時間線頁面中，而帖子位於小部件中，我無法從那里調用 buildtimeline。 請提供任何幫助。 在過去的 3 天里一直堅持這一點。

我的時間軸頁面：

class Timeline extends StatefulWidget {
  final User currentUser;

  Timeline({this.currentUser});

  @override
  _TimelineState createState() => _TimelineState();
}

class _TimelineState extends State<Timeline> {
  List<Post> posts;
  List<String> followingList = [];

  @override
  void initState() {
    super.initState();
    getTimeline();
    getFollowing();
  }

  getTimeline() async {
    QuerySnapshot snapshot = await timelineRef
        .doc(widget.currentUser.id)
        .collection('timelinePosts')
        .orderBy('timestamp', descending: true)
        .get();
        
    List<Post> posts =
        snapshot.docs.map((doc) => Post.fromDocument(doc)).toList();
    setState(() {
      this.posts = posts;
    });
  }

  buildTimeline() {
    if (posts == null) {
      return MyIconSpinner();
    } else if (posts.isEmpty) {
      return buildUsersToFollow();
    } else {
      return ListView(children: posts);
    }
  }

  getFollowing() async {
    QuerySnapshot snapshot = await followingRef
        .doc(currentUser.id)
        .collection('userFollowing')
        .get();
    setState(() {
      followingList = snapshot.docs.map((doc) => doc.id).toList();
    });
  }

  buildUsersToFollow() {
    return StreamBuilder(
      stream:
          usersRef.orderBy('timestamp', descending: true).limit(30).snapshots(),
      builder: (context, snapshot) {
        if (!snapshot.hasData) {
          return MyIconSpinner();
        }
        List<UserResult> userResults = [];
        snapshot.data.documents.forEach((doc) {
          User user = User.fromDocument(doc);
          final bool isAuthUser = currentUser.id == user.id;
          final bool isFollowingUser = followingList.contains(user.id);
          // remove auth user from recommended list
          if (isAuthUser) {
            return;
          } else if (isFollowingUser) {
            return;
          } else {
            UserResult userResult = UserResult(user);
            userResults.add(userResult);
          }
        });
        return Container(
          color: Theme.of(context).accentColor.withOpacity(0.2),
          child: Column(
            children: <Widget>[
              Container(
                padding: EdgeInsets.all(12.0),
                child: Row(
                  mainAxisAlignment: MainAxisAlignment.center,
                  children: <Widget>[
                    Icon(
                      Icons.person_add,
                      color: Theme.of(context).primaryColor,
                      size: 30.0,
                    ),
                    SizedBox(
                      width: 8.0,
                    ),
                    Text(
                      "Users to Follow",
                      style: TextStyle(
                        color: Theme.of(context).primaryColor,
                        fontSize: 30.0,
                      ),
                    ),
                  ],
                ),
              ),
              Column(children: userResults),
            ],
          ),
        );
      },
    );
  }

  talkToAExpert() {
    return Container(
      padding: EdgeInsets.only(top: 20, bottom: 5),
      child: FlatButton(
        onPressed: () {
          Navigator.push(
              context,
              MaterialPageRoute(
                  builder: (context) =>
                      Experts(currentUser: widget.currentUser)));
        },
        child: Container(
          width: 250.0,
          height: 50.0,
          child: Text(
            'Talk to a Expert',
            style: TextStyle(
              color: Colors.white,
              fontWeight: FontWeight.normal,
              fontSize: 20,
            ),
          ),
          alignment: Alignment.center,
          decoration: BoxDecoration(
            color: Colors.blue,
            // border: Border.all(
            //   color: Colors.grey,
            // ),
            borderRadius: BorderRadius.circular(50.0),
          ),
        ),
      ),
    );
  }

  @override
  Widget build(context) {
    return Scaffold(
      appBar: header(context, isAppTitle: true),
      //floatingActionButtonLocation: FloatingActionButtonLocation.endFloat,
      body: 
      ListView(
        children: [
           talkToAExpert(),
          Divider(
            height: 1.0,
          ),
          Container(
            height: MediaQuery.of(context).size.height * 0.7,
            child: RefreshIndicator(
                onRefresh: () => getTimeline(), child: buildTimeline()),
          ),
        ],
      ),
      floatingActionButton: FloatingActionButton(
        child: Icon(Icons.add),
        onPressed: () {
          Navigator.push(
              context,
              MaterialPageRoute(
                  builder: (context) =>
                      Upload(currentUser: widget.currentUser)));
        },
      ),
    );
  }
}

我的帖子頁面：

import 'dart:async';
import 'package:animator/animator.dart';
import 'package:cached_network_image/cached_network_image.dart';
import 'package:cloud_firestore/cloud_firestore.dart';
import 'package:flutter/material.dart';
import 'package:momma_app/pages/social/activity_feed.dart';
import '../../models/user.dart';
import '../social/progress.dart';
import '../../pages/social/comments.dart';
import '../../pages/home.dart';
import '../../pages/social/timeline.dart';

class Post extends StatefulWidget {
  final String postId;
  final String ownerId;
  final String username;
  final String location;
  final String description;
  final String mediaUrl;
  final dynamic likes;
  final Function buildTimeline;

  Post({
    this.postId,
    this.ownerId,
    this.username,
    this.location,
    this.description,
    this.mediaUrl,
    this.likes,
    this.buildTimeline,
  });

  factory Post.fromDocument(DocumentSnapshot doc) {
    return Post(
      postId: doc['postId'],
      ownerId: doc['ownerId'],
      username: doc['username'],
      location: doc['location'],
      description: doc['description'],
      mediaUrl: doc['mediaUrl'],
      likes: doc['likes'],
    );
  }

  int getLikeCount(likes) {
    // if no likes, return 0
    if (likes == null) {
      return 0;
    }
    int count = 0;
    // if the key is explicitly set to true, add a like
    likes.values.forEach((val) {
      if (val == true) {
        count += 1;
      }
    });
    return count;
  }

  @override
  _PostState createState() => _PostState(
        postId: this.postId,
        ownerId: this.ownerId,
        username: this.username,
        location: this.location,
        description: this.description,
        mediaUrl: this.mediaUrl,
        likes: this.likes,
        likeCount: getLikeCount(this.likes),
      );
}

class _PostState extends State<Post> {
  final String currentUserId = currentUser?.id;
  final String postId;
  final String ownerId;
  final String username;
  final String location;
  final String description;
  final String mediaUrl;
  bool showHeart = false;
  bool isLiked;
  int likeCount;
  Map likes;

  _PostState({
    this.postId,
    this.ownerId,
    this.username,
    this.location,
    this.description,
    this.mediaUrl,
    this.likes,
    this.likeCount,
  });

  buildPostHeader() {
    return FutureBuilder(
      future: userRef.doc(ownerId).get(),
      builder: (context, snapshot) {
        if (!snapshot.hasData) {
          return circularProgress();
        }
        User user = User.fromDocument(snapshot.data);
        bool isPostOwner = currentUserId == ownerId;
        return ListTile(
          leading: CircleAvatar(
            backgroundImage: user.userPhotoUrl == ''
                ? CachedNetworkImageProvider(user.photoUrl)
                : CachedNetworkImageProvider(user.userPhotoUrl),
            backgroundColor: Colors.grey,
          ),
          title: GestureDetector(
            onTap: () => showProfile(context, profileId: user.id),
            child: Text(
              user.username,
              style: TextStyle(
                color: Colors.black,
                fontWeight: FontWeight.bold,
              ),
            ),
          ),
          subtitle: Text(location),
          trailing: isPostOwner
              ? IconButton(
                  onPressed: () => handleDeletePost(context),
                  icon: Icon(Icons.more_vert),
                )
              : Text(''),
        );
      },
    );
  }

  handleDeletePost(BuildContext parentContext) {
    return showDialog(
        context: parentContext,
        builder: (context) {
          return SimpleDialog(
            title: Text("Remove this post?"),
            children: <Widget>[
              SimpleDialogOption(
                  onPressed: () {
                    Navigator.pop(context);
                    deletePost();
                  },
                  child: Text(
                    'Delete',
                    style: TextStyle(color: Colors.red),
                  )),
              SimpleDialogOption(
                  onPressed: () => Navigator.pop(context),
                  child: Text('Cancel')),
            ],
          );
        });
  }

  // Note: To delete post, ownerId and currentUserId must be equal, so they can be used interchangeably
  deletePost() async {
    print('deletePost begining');
    // delete post itself
    postsRef.doc(ownerId).collection('userPosts').doc(postId).get().then((doc) {
      if (doc.exists) {
        doc.reference.delete();
      }
    });
    // delete uploaded image for thep ost
    storageRef.child("post_$postId.jpg").delete();
    // then delete all activity feed notifications
    QuerySnapshot activityFeedSnapshot = await activityFeedRef
        .doc(ownerId)
        .collection("feedItems")
        .where('postId', isEqualTo: postId)
        .get();
    activityFeedSnapshot.docs.forEach((doc) {
      if (doc.exists) {
        doc.reference.delete();
      }
    });
    // then delete all comments
    QuerySnapshot commentsSnapshot =
        await commentsRef.doc(postId).collection('comments').get();
    commentsSnapshot.docs.forEach(
      (doc) {
        if (doc.exists) {
          doc.reference.delete();
        }
      },
    );
    print('deletePost ending');
    
  }

  handleLikePost() {
    bool _isLiked = likes[currentUserId] == true;

    if (_isLiked) {
      postsRef
          .doc(ownerId)
          .collection('userPosts')
          .doc(postId)
          .update({'likes.$currentUserId': false});
      removeLikeFromActivityFeed();
      setState(() {
        likeCount -= 1;
        isLiked = false;
        likes[currentUserId] = false;
      });
    } else if (!_isLiked) {
      postsRef
          .doc(ownerId)
          .collection('userPosts')
          .doc(postId)
          .update({'likes.$currentUserId': true});
      addLikeToActivityFeed();
      setState(() {
        likeCount += 1;
        isLiked = true;
        likes[currentUserId] = true;
        showHeart = true;
      });
      Timer(Duration(milliseconds: 500), () {
        setState(() {
          showHeart = false;
        });
      });
    }
  }

  addLikeToActivityFeed() {
    // add a notification to the postOwner's activity feed only if comment made by OTHER user (to avoid getting notification for our own like)
    bool isNotPostOwner = currentUserId != ownerId;
    if (isNotPostOwner) {
      activityFeedRef.doc(ownerId).collection("feedItems").doc(postId).set({
        "type": "like",
        "commentData": '',
        "username": currentUser.username,
        "userId": currentUser.id,
        "userProfileImg": currentUser.photoUrl,
        "postId": postId,
        "mediaUrl": mediaUrl,
        "timestamp": timestamp,
      });
    }
  }

  removeLikeFromActivityFeed() {
    bool isNotPostOwner = currentUserId != ownerId;
    if (isNotPostOwner) {
      activityFeedRef
          .doc(ownerId)
          .collection("feedItems")
          .doc(postId)
          .get()
          .then((doc) {
        if (doc.exists) {
          doc.reference.delete();
        }
      });
    }
  }

  buildPostImage() {
    return GestureDetector(
      onDoubleTap: handleLikePost,
      child: Stack(
        alignment: Alignment.center,
        children: <Widget>[
          Container(
            width: double.infinity,
            height: MediaQuery.of(context).size.height * 0.3,
            decoration: BoxDecoration(
              image: DecorationImage(
                fit: BoxFit.cover,
                image: CachedNetworkImageProvider(mediaUrl),
              ),
            ),
          ),
          // cachedNetworkImage(mediaUrl),
          showHeart
              ? Animator(
                  duration: Duration(milliseconds: 300),
                  tween: Tween(begin: 0.8, end: 1.4),
                  curve: Curves.elasticOut,
                  cycles: 0,
                  builder: (context, animatorState, child) => Transform.scale(
                    scale: animatorState.value,
                    child: Icon(
                      Icons.favorite,
                      size: 80.0,
                      color: Colors.red,
                    ),
                  ),
                )
              : Text(""),
        ],
      ),
    );
  }

  buildPostFooter() {
    return StreamBuilder(
        stream: commentsRef
            .doc(postId)
            .collection('comments')
            .doc('counter')
            .snapshots(),
        builder: (context, snapshot) {
          if (!snapshot.hasData) {
            return circularProgress();
          }
          {
            int counterValue = snapshot.data['counter'] - 1;

            return Column(
              children: <Widget>[
                if (mediaUrl != 'No mediaUrl')
                  SizedBox(
                    height: 10,
                  ),
                Row(
                  crossAxisAlignment: CrossAxisAlignment.start,
                  children: <Widget>[
                    Container(
                      margin: EdgeInsets.only(left: 20.0),
                      child: Text(
                        "$username ",
                        style: TextStyle(
                          color: Colors.black,
                          fontWeight: FontWeight.bold,
                        ),
                      ),
                    ),
                    Expanded(child: Text(description))
                  ],
                ),
                Row(
                  mainAxisAlignment: MainAxisAlignment.start,
                  children: <Widget>[
                    Padding(padding: EdgeInsets.only(top: 40.0, left: 20.0)),
                    GestureDetector(
                      onTap: handleLikePost,
                      child: Icon(
                        isLiked ? Icons.favorite : Icons.favorite_border,
                        size: 25.0,
                        color: Colors.pink,
                      ),
                    ),
                    Padding(padding: EdgeInsets.only(right: 25.0)),
                    GestureDetector(
                      onTap: () => showComments(
                        context,
                        postId: postId,
                        ownerId: ownerId,
                        mediaUrl: mediaUrl,
                      ),
                      child: Icon(
                        Icons.chat,
                        size: 25.0,
                        color: Colors.blue[900],
                      ),
                    ),
                  ],
                ),
                Row(
                  children: <Widget>[
                    Container(
                      margin: EdgeInsets.only(left: 20.0),
                      child: Text(
                        "$likeCount likes",
                        style: TextStyle(
                          color: Colors.black,
                          fontWeight: FontWeight.bold,
                        ),
                      ),
                    ),
                    Container(
                      margin: EdgeInsets.only(left: 10.0),
                      child: Text(
                        "$counterValue comment",
                        style: TextStyle(
                          color: Colors.black,
                          fontWeight: FontWeight.bold,
                        ),
                      ),
                    ),
                  ],
                ),
              ],
            );
          }
        });
  }

  @override
  Widget build(BuildContext context) {
    isLiked = (likes[currentUserId] == true);
    return Column(
      mainAxisSize: MainAxisSize.min,
      children: <Widget>[
        buildPostHeader(),
        if (mediaUrl != 'No mediaUrl') buildPostImage(),
        buildPostFooter()
      ],
    );
  }
}

showComments(BuildContext context,
    {String postId, String ownerId, String mediaUrl}) {
  Navigator.push(context, MaterialPageRoute(builder: (context) {
    return Comments(
      postId: postId,
      postOwnerId: ownerId,
      postMediaUrl: mediaUrl,
    );
  }));
}

請查看帖子頁面中的 deletePost 方法以及時間線頁面中的 getTimeline() 和 buildTimeline()。

Answer 1

您可以提取您的buildTimeline()方法以將其投入使用，因此snapshot 、 posts和followingList將是全局變量