我将应用程序发布的想法存储在 Firestore 中。数据像这样存储在 Firestore 中 Ideas/{documentID}/IdeaObject。问题是当我检索数据时，它没有按发布时间排序。检索到的想法是根据 Firestore 自动创建的 documentID 的 id。我在我的模型类中使用了 ServerTimestamp 并且当我检索它时，我将 orderBy 方法与我的 Firestore 引用一起使用，但仍然没有。

想法.java

public class Idea {
    @ServerTimestamp
    private Date date;
    private String title, idea, timeCommitment, ideaStage, postedBy, website, videoPitch;
    private int views, favorites;
    private ArrayList<String> lookingFor = new ArrayList<>();
    private ArrayList<String> tags = new ArrayList<>();
    private String userID;
    private String timeStamp;

    public Idea() {
    }

    public Idea(String title, String idea, String timeCommitment, String ideaStage, String postedBy, String website, String videoPitch, int views, int favorites, ArrayList<String> lookingFor, ArrayList<String> tags, String userID, String timeStamp) {
        this.title = title;
        this.idea = idea;
        this.timeCommitment = timeCommitment;
        this.ideaStage = ideaStage;
        this.postedBy = postedBy;
        this.website = website;
        this.videoPitch = videoPitch;
        this.views = views;
        this.favorites = favorites;
        this.lookingFor = lookingFor;
        this.tags = tags;
        this.userID = userID;
        this.timeStamp = timeStamp;
    }

想法发布方法

  private void postIdea() {

        final String ideaID = UUID.randomUUID().toString();
        final SimpleDateFormat sdf = new SimpleDateFormat("yyyy.MM.dd.HH.mm.ss");
        Timestamp timestamp = new Timestamp(System.currentTimeMillis());


        Idea ideas = new Idea(title, idea, timeCommitment, ideaStage, AppValues.fullName, website, videoPitch, 0, 0, lookingFor, tags, AppValues.userId, "" + timestamp.getTime());

        firestoreDb.collection("ideas")
                .document(ideaID)
                .set(ideas)
                .addOnSuccessListener(new OnSuccessListener<Void>() {
                    @Override
                    public void onSuccess(Void aVoid) {
                        postIdeaUser(ideaID);
                    }
                })
                .addOnFailureListener(new OnFailureListener() {
                    @Override
                    public void onFailure(@NonNull Exception e) {
                        hideLoadingDialog();
                        showToast(e.getMessage());
                    }
                });
    }

按时间检索所有想法

   firestoreDb.collection("ideas")
                .orderBy("timeStamp", Query.Direction.ASCENDING)
                .get()
                .addOnCompleteListener(new OnCompleteListener<QuerySnapshot>() {
                    @Override
                    public void onComplete(@NonNull Task<QuerySnapshot> task) {
                        if (task.isSuccessful()) {

                            ideaArrayList = new ArrayList<>();
                            ideaArrayList.clear();

                            for (DocumentSnapshot documentSnapshot : task.getResult()) {
                                Idea idea = documentSnapshot.toObject(Idea.class);
                                if (!idea.getUserID().equals(AppValues.userId)) {
                                    ideaArrayList.add(idea);
                                }
                            }

                            callAdapter();

                        } else {
                            Log.d(TAG, "Error getting documents: ", task.getException());
                            progressBar.setVisibility(View.GONE);
                            swipeRefresh.setEnabled(true);
                            errorText.setVisibility(View.VISIBLE);
                        }
                    }
                }); 

我想要实现的是检索所有想法并让它们按 TimeStamp 值升序排列。

最佳答案

在查询数据库时，您不能使用字符串 (timeStamp) 而不是日期 (date) 并期望其行为与日期相同。所以要解决这个问题，请更改以下代码行:

firestoreDb.collection("ideas")
            .orderBy("timeStamp", Query.Direction.ASCENDING)

到

firestoreDb.collection("ideas")
            .orderBy("date", Query.Direction.ASCENDING)

要使其工作，这种查询需要一个索引。要创建一个，请查看我在以下帖子中的回答:

• Firestore whereEqualTo, orderBy and limit(1) not working

关于java - 按时间戳按升序排列 Firestore 数据，我们在Stack Overflow上找到一个类似的问题： https://stackoverflow.com/questions/50224638/