Develop Reference

ObjectBox lazyList behaviour

I'm not sure I understand from the documentation how should I use the Lazy List.
What the different between findLazy() and findLazyCached() the function description is exactly the same.
Should I make a find() query first time and just then use findLazy()?
Example of using:
Box<FastCacheData> box = box.boxFor(FastCacheData.class);
LazyList<FastCacheData> build = box.query().build().findLazy();

What the different between findLazy() and findLazyCached() the function description is exactly the same.
They both return a LazyList, which will only load the member objects as they're each accessed. The difference between the two is that the cached version will cache the object so that further accesses won't result in extra loads - the non-cached version will load a fresh object every time.
Should I make a find() query first time and just then use findLazy()
It's a question of when you want the loading to happen. If you want the whole thing loaded when the find() call is made, use the find() call. Else if you want to defer the loading to when you access the data, use the findLazy() call.

getReference() vs. getChild()

I was wondering what the difference between database.getReference("foo/bar/123") and database.getReference("foo").child("bar").child("123") is?
I'm assuming that the later one will load the complete "foo" object whereas database.getReference("foo/bar/123") just loads the "123" object?
Is my assumption correct or what is the correct / most efficient way to only load data of "123"?

The two are equivalent. You can inspect this manually this by printing the toString() format for both References.
References are cheap - there's nothing inefficient about either solution. Neither one has yet loaded any data. A Reference is just a pointer to a location in the database.

It should not make a difference, a reference is not actually accessed when instantiated. This is the most relevant document I can find,
https://firebase.google.com/docs/reference/node/firebase.database.Reference
The docs don't say it explicitly, but requests are only performed when using the .set() or .on() methods

How to get programmatically the data usage limit set by user on Android OS configuration?

User can define at Data Usage screen a limite and/or a warning limit for mobile data usage. So how can I get this information by code?
Screen of Data Usage configuration of native OS.
I wanna the limit value and warning value.
I've already tried this but not work and always return NULL to both:
final Long recommendedBytes = DownloadManager.getRecommendedMaxBytesOverMobile( this.context );
final Long maximumBytes = DownloadManager.getMaxBytesOverMobile( this.context );
// recommendedBytes and maximumBytes are NULL
And TrafficStats class just have a data transferred not the limits.

After days searching and research about this problem I couldn't find a answer for that. Bellow I will lift every attempt that I did.
1. Download Manager
With this class you can start download over any network or device
state and it will handle all states e.g. network loss, device reboot,
etc...
There are two methods called getMaxBytesOverMobile and
getRecommendedMaxBytesOverMobile, they was a pretty candidate
to solve this problem at first time. But after code tests and
Download Manager implementantion research I'd found that there is
no way to get thoose values by DownloadManager.
Reason
Thoose methods call Settings.Secure.getLong with they
respective labels
Settings.Secure.DOWNLOAD_MAX_BYTES_OVER_MOBILE and
Settings.Secure.DOWNLOAD_RECOMMENDED_MAX_BYTES_OVER_MOBILE in
the turn makes a call to a lazy String map inside inside a
inner class called NameValueCache.
Ok so far but none of inner classes or Settings implementation it
self use DOWNLOAD_MAX_BYTES_OVER_MOBILE or
DOWNLOAD_RECOMMENDED_MAX_BYTES_OVER_MOBILE inside.
I considered the lazy map was populate by a third entity, what
actually happens, so I found the NameValueTable Settings
inner class that handle the new values to lazy map. The
putString is a protected method call by Settings.Secure
and Settings.System inner classes (calls of Secure and
System).
So I could conclude that if the OS implementantion do not put thoose String values I can't get them.
2. TrafficStats
Just a quick look on official reference I could notice that it will
not help me because this class just provide the amount of bytes and
packages that was trafficked since last device boot.
http://developer.android.com/reference/android/net/TrafficStats.html
3. NetworkPolicyManager and NetworkPolicy
As #bina posted here the both classes are hidden and could not
be use by normal apps e.g. that will be published in Google Play.
https://stackoverflow.com/a/24445424/575643
4. ConnectivityManager
In short, you just can get the NetworkInfo that not provide
much information about user preferences (really none!). Just provide
informations about network and e.g. mobile network provider.
http://developer.android.com/reference/android/net/ConnectivityManager.html
After all I assume that no way to get this information nowadays. Please if you read it and found a way post here!
Thanks for all.
PS.: Sorry by english mistakes.

Do you want to get limit value(5GB) and warnning value(2GB) in this example?
If so, you can get limitBytes and warningBytes by the following code, if you can use android.permission.MANAGE_NETWORK_POLICY and android.permission.READ_PHONE_STATE.
However, android.permission.MANAGE_NETWORK_POLICY protectionLevel is signature.
NetworkPolicyManager manager = (NetworkPolicyManager) getSystemService("netpolicy");
NetworkPolicy[] networkPolicies = manager.getNetworkPolicies();
Log.d("NetworkPolicy", "limitBytes is " + networkPolicies[0].limitBytes);
Log.d("NetworkPolicy", "warningBytes is " + networkPolicies[0].warningBytes);
(NetworkPolicyManager and NetworkPolicy classes are hidden)

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.

What is the best way to use threading on a sorting algorithm, that when completed, creates a new activity and gives its data to the new activity?

I will start this by saying that on iOS this algorithm takes, on average, <2 seconds to complete and given a simpler, more specific input that is the same between how I test it on iOS vs. Android it takes 0.09 seconds and 2.5 seconds respectively, and the Android version simply quits on me, no idea if that would be significantly longer. (The test data gives the sorting algorithm a relatively simple task)
More specifically, I have a HashMap (Using an NSMutableDictionary on iOS) that maps a unique key(Its a string of only integers called its course. For example: "12345") used to get specific sections under a course title. The hash map knows what course a specific section falls under because each section has a value "Course". Once they are retrieved these section objects are compared, to see if they can fit into a schedule together based on user input and their "timeBegin", "timeEnd", and "days" values.
For Example: If I asked for schedules with only the Course ABC1234(There are 50 different time slots or "sections" under that course title) and DEF5678(50 sections) it will iterate through the Hashmap to find every section that falls under those two courses. Then it will sort them into schedules of two classes each(one ABC1234 and one DEF5678) If no two courses have a conflict then a total of 2500(50*50) schedules are possible.
These "schedules" (Stored in ArrayLists since the number of user inputs varies from 1-8 and possible number of results varies from 1-100,000. The group of all schedules is a double ArrayList that looks like this ArrayList>. On iOS I use NSMutableArray) are then fed into the intent that is the next Activity. This Activity (Fragment techincally?) will be a pager that allows the user to scroll through the different combinations.
I copied the method of search and sort exactly as it is in iOS(This may not be the right thing to do since the languages and data structures may be fundamentally different) and it works correctly with small output but when it gets too large it can't handle it.
So is multithreading the answer? Should I use something other than a HashMap? Something other than ArrayLists? I only assume multithreading because the errors indicate that too much is being done on the main thread. I've also read that there is a limit to the size of data passed using Intents but I have no idea.
If I was unclear on anything feel free to ask for clarification. Also, I've been doing Android for ~2 weeks so I may completely off track but hopefully not, this is a fully functional and complete app in the iTunes Store already so I don't think I'm that far off. Thanks!

1) I think you should go with AsynTask of Android .The way it handle the View into `UI
threadandBackground threadfor operations (Like Sorting` ) is sufficient enough to help
you to get the Data Processed into Background thread And on Processing you can get the
Content on UI Thread.
Follow This ShorHand Example for This:
Example to Use Asyntask
2) Example(How to Proceed):
a) define your view into onPreExecute()
b) Do your Background Operation into doInBackground()
c) Get the Result into onPostExceute() and call the content for New Activty
Hope this could help...

I think it's better for you to use TreeMap instead of HashMap, which sorts data automatically everytime you mutate it. Therefore you won't have to sort your data before start another activity, you just pass it and that's all.
Also for using it you have to implement Comparable interface in your class which represents value of Map.
You can also read about TreeMap class there:
http://docs.oracle.com/javase/7/docs/api/java/util/TreeMap.html