Updating and deleting data in Firebase

Question

This is my database:

{ "UID1" : { "KEY" : { "Name" : "name1", "Email" : " [e-mail] ", "userid" : "UID1" } }, "UID2" : { "KEY2" : { "Name" : "name1", "Email" : " [e-mail] ", "userid" : "UID2" }, "KEY3" : { "Name" : "name2", "Email" : " [e-mail] ", "userid" : "UID2" }, "KEY4" : { "Name" : "name3", "Email" : " [e-mail] ", "userid" : "UID2" } } 

I would like to update and delete the data, which, for example, will be in the position "KEY2".

How can i achieve this? I have not tried the code in Android yet.

Answer 1

To write single data, you can use the setValue() method on your DatabaseReference with your child identifiers:

 private void writeNewData(String userId, String name, String email) { User user = new User(name, email); mDatabase.child("users").child(userId).setValue(user); } 

In your case, you can do something like: mDatabase.child("UID2").child("KEY2").setValue(yourNewValueOrObject);

If you want to update a specific value, you should be more concise: mDatabase.child("UID2").child("KEY2").child("email").setValue(newEmail);

In any case, I recommend that you use custom classes like POJO (plain old Java object) with the values ​​of each of your items in the database. For instance:

 public class User { public String username; public String email; public User() { // Default constructor required for calls to DataSnapshot.getValue(User.class) } public User(String username, String email) { this.username = username; this.email = email; } } 

Finally, to remove data, you must use the removeValue() method in the same way.

  private void deleteUserData(String userId) { mDatabase.child("users").child(userId).removeValue(); } 

This method will remove the entire link from your database, so be careful with it. In case you want to delete a specific field, you must add another .child() call to the tree. For example, say we want to remove the email value from the "KEY2" node: mDatabase.child("users").child(userId).child("email").removeValue();

Finally, there is a case that, perhaps, we want to update several fields in different database nodes. In this case, we should use the updateChildren() method with a map of links and values.

 private void writeNewPost(String userId, String username, String title, String body) { // Create new post at /user-posts/$userid/$postid and at // /posts/$postid simultaneously String key = mDatabase.child("posts").push().getKey(); Post post = new Post(userId, username, title, body); Map<String, Object> postValues = post.toMap(); Map<String, Object> childUpdates = new HashMap<>(); childUpdates.put("/posts/" + key, postValues); childUpdates.put("/user-posts/" + userId + "/" + key, postValues); mDatabase.updateChildren(childUpdates); } 

What does the updateChildren method do. Is setValue () call to each line in the specified Map<String, Object> , which is the key to the full reference to the node and Object value.

You can read more updates and delete data in the official Firebase documentation.