Question

我如何获得

“在黑暗中跳舞”

如果快照不存在，则从此快照

：？我想它必须保存在某处的快照中。请阅读内联代码注释..

  private void addListenerForSingleValueEvent(String streetAddress, StringBuilder targetAddress){

        DatabaseReference firebase = FirebaseDatabase.getInstance().getReference();
        firebase.child("catalog/trax").orderByChild("namn").equalTo("Dancing in the dark")
                .addListenerForSingleValueEvent(new ValueEventListener() {
            @Override
            public void onDataChange(DataSnapshot snapshot) {
                if (snapshot.exists()) {
                 // do sowm work on existing data
                } else {
                 // How can I get the "Dancing in the dark" from the snapshot?
                }
            }

            @Override
            public void onCancelled(DatabaseError databaseError) {
                Toast.makeText(Application.getInstance(), databaseError.getMessage(), Toast.LENGTH_LONG).show();
            }
        });

}

Answer 1

对Firebase数据库执行查询时，可能会有多个结果。因此快照包含这些结果的列表。即使只有一个结果，快照也会包含一个结果的列表。通过监听value事件，您可以在一个快照中获得所有匹配的结果，因此您必须遍历这些子项。

    DatabaseReference firebase = FirebaseDatabase.getInstance().getReference();
    firebase.child("catalog/trax").orderByChild("namn").equalTo("Dancing in the dark")
            .addListenerForSingleValueEvent(new ValueEventListener() {
        @Override
        public void onDataChange(DataSnapshot snapshot) {
            for (DataSnapshot item: snapshot.getChildren()) {
                // In this loop item is the snapshot of a single item.
                // This means we can get the namm of the item
                System.out.println(item.child("namm").getValue(String.class));
            }
        }

        @Override
        public void onCancelled(DatabaseError databaseError) {
            Toast.makeText(Application.getInstance(), databaseError.getMessage(), Toast.LENGTH_LONG).show();
        }
    });

如何从此FireBase DataSnapshot中获取搜索值

1 个答案: