如何在Firebase Android中检索父键 [英] How to retrieve parent key in firebase android

问题描述

我要获取 houfxWvbwyVmbHX60IGjpNkZR9w2 密钥，怎么办?

I want to retrieve houfxWvbwyVmbHX60IGjpNkZR9w2 key , How to do?

这是相同的代码

mQuery = mfollowing.orderByChild("following").equalTo(user_id);
mQuery.addListenerForSingleValueEvent(new ValueEventListener() {
    @Override
    public void onDataChange(DataSnapshot dataSnapshot) {


        final String key = dataSnapshot.getKey();

        mdatabaseUsers.child(user_id).addValueEventListener(new ValueEventListener() {
            @Override
            public void onDataChange(DataSnapshot dataSnapshot) {

                DatabaseReference newfollscreen = mdatabaseFollwer.child(key).child(newPost.getKey());

                newfollscreen.child("screen").setValue(downloadUrl.toString());
                newfollscreen.child("engagement").setValue("NA");
                newfollscreen.child("url").setValue("NA");
                newfollscreen.child("uid").setValue(user_id);
                newfollscreen.child("name").setValue(dataSnapshot.child("name").getValue());
                newfollscreen.child("image").setValue(dataSnapshot.child("image").getValue()).addOnCompleteListener(new OnCompleteListener<Void>() {
                    @Override
                    public void onComplete(@NonNull Task<Void> task) {

                        if (task.isSuccessful()){

                            Toast.makeText(AddimageActivity.this, "Posted among your followers", Toast.LENGTH_SHORT).show();
                        }else {

                            Toast.makeText(AddimageActivity.this, "Error", Toast.LENGTH_SHORT).show();
                        }
                    }
                });
            }

            @Override
            public void onCancelled(DatabaseError databaseError) {

            }
        });


    }

    @Override
    public void onCancelled (DatabaseError
       databaseError){

    }

});

这是Firebase数据库

Here is the Firebase database

第二张图片

在此处输入图片描述

我尝试使用子数据快照方法，但是没有用.任何帮助，将不胜感激.

I tried using child data snapshot method but did not worked. Any help for this will be much appreciated.

推荐答案

假设您有一个指向子代 rhZ4 ... wt2 的 DataSnapshot ，则可以调用 snapsthot.getRef().toString()，它将返回类似 https://xxx.firebaseio.com/.../houfxWvbwyVmbHX60IGjpNkZR9w2/rhZ4...wt2 的内容.从那里可以提取父密钥.

Assuming you have a DataSnapshot that points to the children rhZ4...wt2, you can call snapsthot.getRef().toString() which will return you something like https://xxx.firebaseio.com/.../houfxWvbwyVmbHX60IGjpNkZR9w2/rhZ4...wt2. From there you can extract the parent key.

在您的示例中，使用 mQuery 查询数据库之后，在 onDataChange 内部，您具有 DataSnapshot .

From your example, after you query the database using mQuery, inside onDataChange you have a DataSnapshot.

因此，调用 dataSnapshot.getRef().toString()将为您提供 https://xxx.firebaseio.com/.../houfxWvbwyVmbHX60IGjpNkZR9w2/rhZ4...wt2/以下.

So calling dataSnapshot.getRef().toString() will give you https://xxx.firebaseio.com/.../houfxWvbwyVmbHX60IGjpNkZR9w2/rhZ4...wt2/following.

提取父键的代码(将其放入您的第一个 onDataChange 中):

Code to extract the parent key (put it inside your 1st onDataChange):

String reference = dataSnapshot.getRef().toString();
String[] tokens = reference.split("/");
String parentKey = tokens[tokens.length - 3];

此 parentKey 应该是您的 houfxWvbwyVmbHX60IGjpNkZR9w2 .

这篇关于如何在Firebase Android中检索父键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！