android - 获取 Firebase Android 评分的平均值

Question

我正在关注 this post关于如何获得评分的平均值，但我收到一条错误消息:

E/AndroidRuntime: FATAL EXCEPTION: main
Process: com.fixitph.client, PID: 25744
com.google.firebase.database.DatabaseException: Failed to convert a value of type java.util.HashMap to double
at com.google.android.gms.internal.zzelw.zzbz(Unknown Source)
at com.google.android.gms.internal.zzelw.zzb(Unknown Source)
at com.google.android.gms.internal.zzelw.zza(Unknown Source)
at com.google.firebase.database.DataSnapshot.getValue(Unknown Source)
at com.fixitph.client.ReceiptActivity$2.onDataChange(ReceiptActivity.java:85)

这是我的代码:

ratingBar.setOnRatingChangeListener(new MaterialRatingBar.OnRatingChangeListener() {
    @Override
    public void onRatingChanged(MaterialRatingBar ratingBar, float rating) {
        final DatabaseReference dbRef = FirebaseDatabase.getInstance().getReference(Common.worker_rating_table)
                .child(Common.workerId).child(uid).child("Rating");

        double dbRating = rating;
        dbRef.setValue(dbRating);
    }
});

public void submitRating(View view) {
    final DatabaseReference dbRef = FirebaseDatabase.getInstance().getReference(Common.worker_rating_table)
            .child(Common.workerId);

    dbRef.addValueEventListener(new ValueEventListener() {
        @Override
        public void onDataChange(DataSnapshot dataSnapshot) {
            double total = 0.0;
            double count = 0.0;
            double average = 0.0;
            for(DataSnapshot ds: dataSnapshot.getChildren()) {
                double rating = dataSnapshot.getValue(Double.class);
                total = total + rating;
                count = count + 1;
                average = total / count;
            }

            final DatabaseReference newRef = dbRef.child(uid);
            newRef.child("averageRating").setValue(average);
        }

        @Override
        public void onCancelled(DatabaseError databaseError) {
            throw databaseError.toException();
        }
    });
}

我的数据库如下所示。

这是引用 ReceiptActivity.java:85

的行

double rating = dataSnapshot.getValue(Double.class);

我想知道这是否是因为我试图找到一个 Double 但评级中有一个 Int，如果是这种情况，我如何调整它以获得评级的平均值？请帮忙。谢谢你! :)

Answer 1

for(DataSnapshot ds: dataSnapshot.getChildren()) {
    double rating = Double.parseDouble(ds.child("Rating").getValue());
    total = total + rating;
    count = count + 1;
    average = total / count;
}

您需要从 Rating 子级获取值并将其解析为 double。