Develop Reference

Android Firebase Database Add Object To List

I have a list of comment objects inside of an object. If I want to add a comment without touching the other comments how would I do that? I have used transactions in the past for editing an integer efficiently but I don't know if I can do that with a list. The end goal is for multiple users to be a ble to add comments at the same time without cutting eachother off (overriding their edits).
Here is an example of my database:

Solved it! Super simple. Just had to add push() to the end of my DatabaseRefercence like so. It gives every comment a key.
commentRef = pollRef.child("comments").push();
commentRef.setValue(comment);

Checking if Realm is empty?

I'm trying to use Realm to store a local database of objects. The app checks if the current session is first load and if so populates the local database with an api call. But, if the database is not empty, I would like to use the data already available. To do this, I need to know whether the database is empty or not.
I found this issue on github, but they dont provide a workaround:
https://github.com/realm/realm-java/issues/766
So how should this be done?

If you scroll down that issue page, you can see Realm.isEmpty() is added. :)

Add a realm.isEmpty() method that returns true if there is no objects
in the Realm. It is just a utility method, but fits nicely with the
Realm object store abstraction.
use realm.isEmpty()

I used
if(realmResults.isEmpty()) {action...}
or
if(realmResults.isNullOrEmpty()) {action...]
there's false but action..
What's wrong!? ...T0T

android greendao update only specific fields in entity

i have been searching for a while for a solution to my problem without success.
I have an application in which I receive information for a particular entity in my database from different services, so I am using greenDAOs insertOrReplace methods so whenever the entity already exists in my DB it gets updated instead of recreated.
So far so good.
The problem is.. let's say for example sake my entity is called User, with fields id, title, and displayName.
So in the first call I get a JSON object containing a user with only its id and title fields, so I insert it into the DB and naturally the displayName gets inserted as NULL.
Afterwards from another service I get another JSON containing the same user (same id field), but it comes with the displayName as well, but doesn't include the title info at all.
So whenever I run the insertOrReplace on the DAO object automatically generated by greenDAO, the user gets updated but as the title info was not present, when it gets updated the title field gets reset to NULL, so I end up losing data.
Unfortunately I am unable to change the data being returned from the services, and haven't been able to fix this issue. I find it hard to believe there is no easy way to tell the DAO object to update only certain fields and no all of them.
I was looking at the code generated by greenDAO and in the dao objects generated there is a bindValues method which gets called before the query gets executed, and apparently it filters out the NULL properties from the object, but either way it gets updated with the NULL value.
I was able to come up with some sort of fix by modifying the final dao object being generated by adding some methods from the parent class, but I don't think this is a good solution because I would have to do this for all the dao objects. (I know it's possible to define a custom superclass but this only applies for the entity object and not the DAO one).
I would really appreciate if someone has any idea on how I could resolve this, and sorry for the long explanation, I just wanted to be clear on my issue.
Thanks.

First of all: I wouldn't tamper with the generated code unless you really know what you are doing. Modifications may have effects on caches and data-integrity.
Generally you are following this (insert-or)-update-approach if you are using a ORM-Framework (like greendao):
Try to get the entity, that you want to modify from the db (maybe it is already in cache, so this may not be a real database operation)
If you don't have such an entity: create it
Modify the entity according to your needs
Insert or Update it in database (in greendao you would use insertOrReplace)

SimpleDB - how long after insert until item is available to be read?

I have a Fragment, and once the user presses OK, an Item is added to my database and its ID is added to the ArrayAdapter. Immediately after, the adapter tries to draw the view, but the first time it tries to get its attributes, it returns a null HashMap (it gets drawn properly the following times).
Is there a way to make sure the item is in the table before trying to get its attributes?
Even putting the attribute retrieval into a while loop until it returns a not-null HashMap doesn't work so it doesn't look to be an issue of time.

You need to do Select or GetAttributes with ConsistentRead=true as Amazon SimpleDB supports two read consistency options: eventually consistent read and consistent read. Eventually consistent read is default. For more detail please refer doc. link

Try using AsynTask.
Add item to database in doInBackground.
Read it in postExecute.
You are done.

Corona Labs - How to remove ALL objects?

I have problem, as you can see I want to delete all objects in corona. I'm looking for one function that will remove all of them.
I can't find it, I'm not sure if it's even possible.
I'd like it to work like this:
Display all objects
Wait for event
When you touch, then remove all objects from 1 and go back to it.
Possible or not?

I'm not aware of one function that does that. But what you can do is every time you create an object you put it in a table. Then when you want to remove them all you iterate over the table and call removeSelf on each. After the loop, you reset the table. See my answer to remove all spawned coins.