Question

我正在尝试使用Firebase构建社交应用。所以，基本上我有一个Post类，类似于Firebase docs/guides

中给出的类

public class Post {

        String uid;
        String timeStamp;
        String author;
        String body;
        int starCount = 0;
        Map<String, Boolean> stars = new HashMap<>();

        public Post() {
            // Default constructor required for calls to DataSnapshot.getValue(Post.class)
        }

        public Post(String uid, String author, String body, String timeStamp) {
            this.uid = uid;
            this.author = author;
            this.body = body;
            this.timeStamp = timeStamp;
        }

        @Exclude
        public Map<String, Object> toMap() {
            HashMap<String, Object> result = new HashMap<>();
            result.put("uid", uid);
            result.put("author", author);
            result.put("body", body);
            result.put("starCount", starCount);
            result.put("stars", stars);
            result.put("time", timeStamp);
            return result;
}

}

我使用相同的writeNewPost()方法来保存新帖子，但由于stars hashmap最初为空，因此明星子节点永远不会在“posts”节点中创建为子节点

稍后当我尝试使用postRef.getValue(Post.class)或postRef.setValue(Post.class)时，我收到错误消息，告诉我没有可用的可序列化数据。我尝试了明显的解决方法并试图做到这一点完全正常 -

           //this didn't work
           //Post post = postSnapShot.getValue(Post.class);

           Post post = new Post();

           post.uid = postSnapShot.child("uid").getValue(String.class);
           post.body = postSnapShot.child("body").getValue(String.class);
           post.starCount = postSnapShot.child("starCount").getValue(Integer.class);
           post.timeStamp = postSnapShot.child("time").getValue(String.class);
           post.author = postSnapShot.child("author").getValue(String.class);

但是，当我尝试实现类似/不同的功能时，如Firebase文档中再次提到的那样，就像这样

    public boolean likeOrUnlikePost(String postId, final String uid) {

    DatabaseReference postRef = databaseReference.child(Constants.POSTS).child(postId);

    postRef.runTransaction(new Transaction.Handler() {
        @Override
        public Transaction.Result doTransaction(MutableData mutableData) {
            //Post p = mutableData.getValue(Post.class);
            // above line didn't work again, so used the same workaround
            Post post = new Post();
            post.uid = mutableData.child("uid").getValue(String.class);
            post.body = mutableData.child("body").getValue(String.class);
            post.starCount = mutableData.child("starCount").getValue(Integer.class);
            post.timeStamp = mutableData.child("time").getValue(String.class);
            post.author = mutableData.child("author").getValue(String.class);
            post.stars = mutableData.child("stars").getValue(Map.class);
            if (post == null) {
                return Transaction.success(mutableData);
            }

            if (post.stars.containsKey(uid)) {
                // Unstar the post and remove self from stars
                post.starCount = post.starCount - 1;
                post.stars.remove(uid);
            } else {
                // Star the post and add self to stars
                post.starCount = post.starCount + 1;
                post.stars.put(uid, true);
            }

            // below line didn't work as well
            // mutableData.setValue(post);


            //so I tried this which doesn't work as I assumed it to work.
            mutableData.child("starCount").setValue(post.starCount);
            mutableData.child("stars").setValue(post.stars);

            return Transaction.success(mutableData);
        }

        @Override
        public void onComplete(DatabaseError databaseError, boolean b,
                               DataSnapshot dataSnapshot) {
            // Transaction completed
            Log.d(TAG, "postTransaction:onComplete:" + databaseError);
        }
    });

    return true;
}

所以，我坚持使用mutableData.setValue()无法正常工作。我该如何解决这个问题？

编辑：

行上错误的Stacktraces

    Post p = mutableData.getValue(Post.class);

postTransaction：onComplete：DatabaseError：从Firebase数据库runloop调用的用户代码引发了异常： com.google.firebase.database.DatabaseException：没有在类com.dark.confess.Post上找到要序列化的属性在com.google.android.gms.internal.zzamy $ zza。（未知来源）在com.google.android.gms.internal.zzamy.zzj（未知来源）在com.google.android.gms.internal.zzamy.zze（未知来源）在com.google.android.gms.internal.zzamy.zzb（未知来源）在com.google.android.gms.internal.zzamy.zza（未知来源）在com.google.firebase.database.MutableData.getValue（未知来源）在com.dark.confess.FireBaseHelper $ 5.doTransaction（FireBaseHelper.java:120）在com.google.android.gms.internal.zzajb.zza（未知来源）在com.google.firebase.database.DatabaseReference $ 4.run（未知来源） at java.util.concurrent.Executors $ RunnableAdapter.call（Executors.java:423）在java.util.concurrent.FutureTask.run（FutureTask.java:237） at java.util.concurrent.ScheduledThreadPoolExecutor $ ScheduledFutureTask.run（ScheduledThreadPoolExecutor.java:269）在java.util.concurrent.ThreadPoolExecutor.runWorker（ThreadPoolExecutor.java:1113） at java.util.concurrent.ThreadPoolExecutor $ Worker.run（ThreadPoolExecutor.java:588）在java.lang.Thread.run（Thread.java:818）

Answer 1

No properties to serialize方法中的

DataSnapshot.getValue()表示您错过了Post类字段的getter

public class Post {
    private String uid;
    private String timeStamp;
    private String author;
    private String body;
    private int starCount;
    private Map<String, Boolean> stars;

    public Post() {
    }

    public String getUid() {
        return uid;
    }

    public String getTimeStamp() {
        return timeStamp;
    }

    public String getAuthor() {
        return author;
    }

    public String getBody() {
        return body;
    }

    public int getStarCount() {
        return starCount;
    }

    public Map<String, Boolean> getStars() {
        return stars;
    }
}

喜欢/不同于Firebase中的交易？

1 个答案: