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Should we interact with a db storage often in android?

Is performance in android degrading when interacting with a database storage often?
Is it better to load objects from DB and pass them around or access database frequently to get the objects?
I was thinking if the accessing the DB had more overhead due to instantiating objects from the result set each time.

I was thinking if the accessing the DB had more overhead due to instantiating objects from the result set each time.
Yes, it does, which is why if you are worried about performance, you should not use ORM tools to instantiate objects.
Is performance in android degrading when interacting with a database storage often?
Probably... you are reading from disk, which is slower than in-memory storage (which, hint, SQLite can do)
Is it better to load objects from DB and pass them around or access database frequently to get the objects?
Depends in what context you need actual class objects. If you store data in a database, then you should only query for that data when you need it, load it into an object, then do whatever calculation logic and save it. At least, that is my opinion on the matter. You shouldn't need to be serializing any objects between Activities primarily because you could lose state if you update an object in one Activity, pass it to another, then don't / forget to save it back to the database.

As google writes:
Note: Because they can be long-running, be sure that you call getWritableDatabase() or getReadableDatabase() in a background thread, such as with AsyncTask or IntentService.
which makes interacting with database out of main thread. So it can be not immadiate, so user will see some delay in app or fast appearing progress bar, or something. Especially when there will be big queries with 'union' and 'join'. But in most cases it is fast enough.
About your thinkig to access object due memory cache. It makes sense. Exact the same working with images provided by google here. So in your case db is disc cache other is same. You will need to provide some memory cache for your objects, but beware. If you working with huge number of them or each will be so heavy, you will need to provide not just simple wrapper to Map, that stores your objects, but something like LruCache.
So gathering all, you will recieve data from db, then store it in memory until app will need more memory.

Android Parcelable vs SQLite

Is it cheaper to send data across Activity using Parcelable or using SQLite? I am using SQLite (through Content Provider) to persist my data. So really I always have access to my data through SQLite. But I am not sure whether I should send data across Activity using Parcelable or should I just grab them each time.
The details. say I have a Village object. So naturally Village is relatively big: it contains Lists of People for instance, which in turn may contain List of Clothes. In onPause of each activity I persist Village to my Content Provider. But sometimes I want to send a Village object from one Activity to another. I have two choices: I can send the dbId to the next activity and then query the URI (and then convert the cursor to a POJO), or I can send a Parcelable of Village. Which is more expensive?
Say Parcelable is cheaper (I don’t know yet). Right now I am struggling to get the Parcelable to work. Is it worth the effort to get Parcelable to work?

If your object can be large, then accessing via the ContentProvider is the way to go. Not only will you avoid the marshalling/unmarshalling time & code, but Parcelables are limited to 1MB.
The Binder transaction buffer has a limited fixed size, currently 1Mb, which is shared by all transactions in progress for the process.

Best practice to client-server communication on Android, when and how

I am implementing the client-server communication for an app on android. I have some high-level questions before I start to code. Apologize if the question turns out vague or confusing. I am really new to this (2 days of Google-ing is all I have), and I haven't coded anything because this design issue I am asking.
Background: Our android app records users activities. These activities are, for example, the user bookmarks an article. Eventually we want to synchronize these activities with server's database. However this sync is not time-critical, meaning it is not necessary that we send the activity to the server every time there is a new activity.
Current Design: Every time there is an activity, we get the activities and put it in a Java object, mark as "notSync", then make an update call to the database (SQLite) on the mobile. Every 5 minutes or so we make a call into the database, pull the nonSync items into an array of objects, convert it to JSON, and send it to the server.
Question 1: It seems rather inefficient to put an object into database, then every a few minutes pull it out from database as an array of objects, then convert to JSON. Would that be a better design, if we just append all the activities to an array of objects, then convert to JSON directly from that array and clear that array? My dilemma is that, If we implement the latter, there might potentially be a huge array floating around in phone's memory. How do we choose what is the best to implement?
Question 2 When sync mobile SQLite with server MySQL, is our design (using java to pull the rows out as an array of objects, then converting it to JSON) a reasonable practice?
Thanks in advance!

The first thing to keep in mind is where the bottlenecks really are. In my experience communicating with a MySQL server, the connection takes by far the longest, followed by uploading/downloading data, followed by anything I did on the phone. So even without knowing exactly what you're going to be recording, I think it's a safe bet that using SQLite and creating objects will not have a big time impact compared to your network activity.
I would run some basic tests to measure how long various operations take, but to answer your questions:
If you clear the array properly, you won't have to worry about it growing too big and, if your array ever did get that big, you probably have other things to worry about (uploading many MBs of data). However, if your user does something for 4 minutes, then quits the app or something, they'll lose their data. Storing it in the DB is safer.
JSON seems to be the best way to send your data, it's quite efficient for that, and as I said above, I don't thing the SQLite/object creation time will be too great.

Why to use sqlite Database in Android?

Why do we use the sqlite data base in android.I am developing an android application where the data is to be fetched from the server and do some data calculation and show it on the UI.
Is it good for me to fetch the data into the sqlite DB and update the UI on regular interval from the sqlite in evry 20 minutes or will it be good to sent the Http get request to the server and update the data from teh response on the UI.
I wanted to know which one will be better and why?Why to involve sqlite DB?
The data corresponds to some 40X40 table data on which some heavy mathematical processing is to be done and then displayed on the UI(similar to Stock market application) and data needs to be cleared after every 12 hours.
plz advice
Rgds,
Raul

It is good to use database in your case.
Pros:
If your application gets closed the in memory data will be lost, but after that you will be able to restore the state from the database if you have one
Especially for the case of complex calculations it is good to store the result once in the database and not recalculate it multiple times on demand
The database will untie your UI from the internet connection and thus you will be able to display results even if there is not internet connection
Using database you will be able to fetch the updated data from a background service, without impacting your UI
Organizing your data in database usually makes it a lot easier to manage all the application data.
Cons:
Adding database will require a bit of additional effort on your side
As you can see my list proves you SHOULD use database in your case. Maybe I am biased, but at least I provide you with things to consider.

It's really a design decision, SQLite offers a very robust way to organize and persist your data, you're only other options are to write to a file, or to save in SharedPrefs, both methods become a lot harder to manage once the size of your data begins to grow, as you must manually keep a list of objects and manage their names etc etc. 40 x 40 table data is large enough to justify using SQLite, even if you are dropping and recreating the table every 12 hours.
You might want to consider using an ORM library to make fetching and saving data from the DB simpler, ORMLite is good and compatible with Android
http://ormlite.com/

If your application relies heavily on an internet connection you don't need to buffer information in the database. However if you want to use the app where you have bad or no signal you might want to used cached values from the sqlite database.
With slow internet connection your application may be unresponsive so caching may be a good idea - but it doesn't necessarily be in the sqlite database. You should use the sqlite database for data that is required by the device frequently and that is irrelevant to your server component.
If the data is updated frequently but only while the application runs you might want to cache in the devices memory. I assume your app is not running all the time within the 12 hours but is called regularly instead to check something.

12hrs is a long time, so rather than leaving your data wander in RAM, i would suggest you to use database. Because you never know when you may need to read it again.
Otherwise, if your purpose is only to downloaded data, process it and display in activity, then you dont need to involve database because if your app is closed (due to user or low memory), in anyway your app will be downloading fresh data from server... am i right?

> update the UI on regular interval from the sqlite in evry 20 minutes
Dont expect your app to be open for such a long duration.
To precisely suggest to your case
Avoid DB
Fetch Data at app start or at appropriate time when app is opened
and save it in plain java objects.
Define Methods within it that perform operation in it.
Make map or list to save those POJO
Define Seprate Controller Classes within your project to update map of pojo at any
specific change to make fresh data available to UI.

efficiency of application variable?

I have a database from where i need to extract quite a lot of data.
Now i get that data when required, i.e. I have made a class that handles database interactions and whenever an activity requires data it will call that class for the data. So at a time an Activity only has the bare minimum amount of data in memory (i.e. the data that it is using). But everytime i change an activity i have to perform database access to fetch data for the new activity.
Method 2
As opposed to this i have this other alternative, in which i make an application object and then perform database access in the beginning and then store all the data that i would require (in all the activities) in the application object. Whenever i need the data, i refer to the application object. The downside of this that i will be holding too much extra data that i am not using at a given instant.
Which of the above 2 approaches is better?
Thank you in advance.

It depends on your requirements and their priorities. If the time required for solution 2 is too long for you to accept then optimize (e.g. by using method 2, but in general I would advise against storing potentially all of your database in memory ... assuming the amount of memory will suffice).
Did you try solution 1. If the problem is only to read the data from database, it should not take too long to load the data for one activity. If complex calculations are involved you might be pressed to optimize. But don't optimize just in case!

I prefer the first approach because making a call to database is not costly until and unless it is being accessed by multiple applications.