如何解决这个Android Studio Firebase问题? [英] How can I solve this Android Studio Firebase problem?

问题描述

我正在尝试将数据从Firebase获取到bilgiler变量.但是我一直都出错.我该如何解决?

I am trying to get data from Firebase to bilgiler variable. But I get error all the time. How can I solve this?

Map<String, String> bilgiler = new HashMap<>();

db.collection("tarihBilgi")
                .get()
                .addOnCompleteListener(new OnCompleteListener<QuerySnapshot>() {
                    @Override
                    public void onComplete(@NonNull Task<QuerySnapshot> task) {
                        if (task.isSuccessful()) {
                            for (QueryDocumentSnapshot document : Objects.requireNonNull(task.getResult())) {
                                //Log.d("TAG", document.getId() + " => " + document.getData());
                                bilgiler.put("asdf", document.getData().toString());
                            }
                        } else {
                            Log.w("TAG", "Error getting documents.", task.getException());
                        }
                    }
                });
        Log.i("asdfads",(bilgiler.get("asdf")));

推荐答案

数据是从Firebase异步加载的.现在，您的 Log.i("asdfads"，(bilgiler.get("asdf"))); 在 bilgiler.put("asdf"，document.getData()之前运行.toString())运行，这说明了为什么看不到数据库中的值.

Data is loaded from Firebase asynchronously. Right now your Log.i("asdfads",(bilgiler.get("asdf"))); is run before bilgiler.put("asdf", document.getData().toString()) runs, which explains why you don't see the value from the database.

任何需要数据库中数据的代码，都必须在 onComplete 方法内部，或者从那里调用.所以:

Any code that needs data from the database, needs to be inside the onComplete method, or be called from there. So:

db.collection("tarihBilgi")
    .get()
    .addOnCompleteListener(new OnCompleteListener<QuerySnapshot>() {
        @Override
        public void onComplete(@NonNull Task<QuerySnapshot> task) {
            if (task.isSuccessful()) {
                for (QueryDocumentSnapshot document : Objects.requireNonNull(task.getResult())) {
                    bilgiler.put("asdf", document.getData().toString());
                    Log.i("asdfads",(bilgiler.get("asdf")));
                }
            } else {
                Log.w("TAG", "Error getting documents.", task.getException());
            }
        }
    });

另请参阅:

• 如何检查Firestore中是否已经存在某些数据
• 用户在Firebase中登录
• 如何退货是由于方法而导致的DocumentSnapShot?
• 请等到Firestore数据检索以启动活动
• 执行线程的Firestore连接问题

这篇关于如何解决这个Android Studio Firebase问题?的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！