android - 云 Firestore : retrieving cached data via direct get?

Question

从服务器检索数据可能需要几秒钟。有没有办法同时使用直接获取来检索缓存数据？

onComplete 似乎仅在从服务器检索数据时被调用:

db.collection("cities").whereEqualTo("state", "CA").get()
        .addOnCompleteListener(new OnCompleteListener<DocumentSnapshot>() {
            @Override
            public void onComplete(@NonNull Task<DocumentSnapshot> task) {
                if (task.isSuccessful()) {
                ...
                }
            }
        });

缓存数据是否有回调？

Answer 1

现在可以只从缓存版本加载数据。来自 docs

You can specify the source option in a get() call to change the default behavior.....you can fetch from only the offline cache.

如果失败，您可以重新尝试在线版本。

例子:

DocumentReference docRef = db.collection("cities").document("SF");

// Source can be CACHE, SERVER, or DEFAULT.
Source source = Source.CACHE;

// Get the document, forcing the SDK to use the offline cache
docRef.get(source).addOnCompleteListener(new OnCompleteListener<DocumentSnapshot>() {
    @Override
    public void onComplete(@NonNull Task<DocumentSnapshot> task) {
        if (task.isSuccessful()) {
            // Document found in the offline cache
            DocumentSnapshot document = task.getResult();
            Log.d(TAG, "Cached document data: " + document.getData());
        } else {
            Log.d(TAG, "Cached get failed: ", task.getException());
            //try again with online version
        }
    }
});