I have a large data that I have to use in my first android application, could any one guide me the best way to achieve this?
Is there something like embedded database in android framework?
Can i keep my database on my custom server and provide web service to my application?
Which one of the above is better, since I can offer the user to purchase the application and keep the data locally on his device in compressed format.
Thanks
You can ship an android application with the database file in the res/raw folder, and then programmatically copy the file onto SD Card. I personally compress my database file into a zip and uncompress it on first run.
Android has support for SQLite databases which is a very efficient, embedded, crossplatform database. Would recommend this.
Using a remote server might not be a good idea, since signal on wireless networks is often slow and unreliable.
See this answer for me details.
Ship an application with a database
But if the file size of the compressed database is >1MB then you'll need to download it from a webserver and store it locally (Android has a 1MB file size limit on internal files/resources)
Here are some brief thoughts.
Android has SQLite, you could use that for storing and accessing data.
But there are restrictions on such file sizes of 1mb.
I'd recommend setting up a simple web server that can accept GET requests.
Related
I'm working on a project using android studio and moodle.
One of the objectives of the mission is to get data from moodle into an archive and get that archive into an SD card to access the data into the mobile without internet connexion.
The client wants the data on the SD card, not te be read by anyone.
So I thought of multiple solutions:
Creating a key on the RAR archive
Encrypting the archive
Encrypting each file within the archive (and the archive ?)
But I still don't know how to pass the data to the android safely. And if those solutions which I thought are good because you need to decrypt it with android later. The best would be that it could be done without internet.
I'm not familiar with moodle, but I assume it is a web app? If so, the easiest way to handle the data securely would be:
Download the file from the web app over HTTPS
Use the Android Jetpack security libraries to store the file on the SD card
Here is an article (from the Google Android Security team) that shows how to generate keys and store encrypted files using Jetpack: https://medium.com/androiddevelopers/data-encryption-on-android-with-jetpack-security-e4cb0b2d2a9
It abstracts away a lot of the crypto work for you.
i have developed a android app for farmers. it is a informative app for indian farmer.The users will be sending me the images and video files to me through my app. here i used (integrated) dropbox to receive those files directly to my dropbox space. whatever the image or video taken by the user, it will be stored on a folder in my mobile storage. Here what i want is, i want the folder in my mobile storage to be in sync with the folder in my dropbox.
How can i do this?
there is a app in market called Foldersync which exactly fulfil my requirement. how they are doing it? How can i keep a folder in my mobile storage and a folder in my dropbox to be in Sync?
Note :
i have gone through drop-box api and created a simple app to send files directly to my dropbox space and i know how to download a entire folder from dropbox.
But here my question is unique from that... pls don't answer the above points which i already know..
Please help!
Thank You
You can use the Dropbox API to keep a local client in sync with Dropbox. There are two main pieces to this:
1) Metadata:
Assuming you're using the Core API, the best way to get information about all of the file and folders in an account (or optionally under a specific path) is to use /delta:
https://www.dropbox.com/developers/core/docs#delta
With this, you can get information about everything your app can see, and then easily stay up to date with changes. There are some useful blog posts on using /delta here:
https://blogs.dropbox.com/developers/2013/12/efficiently-enumerating-dropbox-with-delta/
https://blogs.dropbox.com/developers/2013/12/filtering-dropbox-delta-results-by-path/
2) File content:
Using the metadata retrieved from #1, you can download any files you need access to locally using /files (GET):
https://www.dropbox.com/developers/core/docs#files-GET
You can upload locally changed files using /files_put:
https://www.dropbox.com/developers/core/docs#files_put
Or, for larger files, use chunked uploading:
https://www.dropbox.com/developers/core/docs#chunked-upload
https://www.dropbox.com/developers/core/docs#commit-chunked-upload
The main work here will involve programming the logic in your app to correctly receive changes from the server as well as upload local changes, in order to keep everything in sync.
Also, be aware that on mobile devices, bandwidth can be limited and/or expensive, so be careful to not accidentally automatically download a lot of data the user doesn't want or need.
We had initially planned on developing a native app for Android but PhoneGap is looking like a better option.
One thing we need to have is when the user installs the app, they need to have local access to a sample of the data in our back end database but have it stored locally. On the native app we had planned that when the user installed the app, the installation process would also trigger a retrieval of a chunk of the data in the back end database so that they could make basic usage of the app without relying on an internet connection all the time.
This data will include JPG files and perhaps some audio files. Will HTML5's local storage address this requirement?
short answer: YES
That's what makes phonegap awesome, you may create a database in to store the persisting data details (name & path)
When you run your application, you will test the connection, if there is no connection you can refer to the local files through your database else if there is connection you may download the new data, save them to the local database and then delete them from the local storage (Sdcard & database).
to find more check the phonegap's file docs
Just to add to what T.Baba has said, yes it is very possible, and I have recently built a webapp with PhoneGap and jQuery Mobile that does just that.
I used localStorage to contain all the data, and in particular localstoragedb. I haven't stored any images and/or audio files in localStorage and wouldn't recommend it anyway as most devices will limit the space to 5MB, but PhoneGap does give you access to APIs which will allow you to save files on the user's device. You can also of course bundle the files with the app and access them accordingly.
Indeed it is. Phonegap is best option for that.
I am downloading files from a remote server to be saved for use on an android device. These files are mostly images and audio but I would like it so that a user cannot access this data using methods other than the app.
The issue is that these files could be large and that's why I use external storage. The problem here is that users can access the data stored on external storage by hooking the phone up to a computer.
Apart from using internal storage, do I have any options to secure the files written to disk?
If I do have to use internal storage, are there any other disadvantages other than the fact that some users might have a small amount of internal storage?
Thanks for your time! Any help will be much appreciated! :)
EDIT 1 :
The data being downloaded is paid content (via In App Billing). This is why I'm concerned about restricting access.
EDIT 2 :
I am already adding a "." before the folder I'm saving my data to. I'm more concerned about 'power' users who would know to look in hidden folders.
Seems like you are populating app's cache from web. It is always recommended to use external storage for such purposes because some users may not have enough internal memory to accommodate this.
Since you downloading includes images and audios, i wouldn't suggest you to use encryption/decryption as it will slow down the app's processing. So there's nothing much you can do to secure your data if you want to put on external memory and skip its encryption.
I personally don't think any harm/disadvantage to leave such data as it is (not encrypted). But if you have some of the files important, perhaps you may perform encryption on those particular files only.
I have to store a lot of images that have to be downloaded from the web server. The size of the images might be 80Mb. So I want a guidance where to store them, whether in internal or external storage. Both create some problems for me. Internal storage is as every one knows is very limited but the problem with external storage is that images can be accessed by user. I don't wanna my application images to be exposed to user and changed or deleted. So is there any alternative or is there any technique to safely put data into external storage?
Unfortunately no, external storage has FAT file system, which does not support access restriction. And you simply must not store such large chunks of data in internal memory (or otherwise users will not like you, to put it mildly).
So the only way to go, is to use external storage. If you need some protection, then you may either encrypt/decrypt data. Or just obfuscate data, like changing file extensions, or adding 10 bytes at the beginning of each file. Obfuscation is more efficient resource-wise, but much less protected. Though encryption key can still be extracted from your application, so both of this approaches have their flows.
I would advice to store them in the external storage. If you don't want the user to be able to read it, protect it with an encryption. I think it's a bad idea to impose large data to the user. If the user wants to remove it, you shouldn't want to prevent it. Perhaps consider the possibility of re-download the pictures from the web if it has been deleted.
Use encryption for file content:
i found nice and lightweight sample code on http://www.androidsnippets.com/encryptdecrypt-strings
I recommend saving to external. Preventing the user from deleting his data is not recommended. Also user can format the sdcard to delete it. so you cannot stop the user. You can hide it from him. Just prefix a dot to the folder name to make it hidden.
If you are using Android 2.3, OBB is your choice.
http://developer.android.com/reference/android/os/storage/StorageManager.html
OBBs contain a filesystem that maybe be encrypted on disk and mounted on-demand from an application. OBBs are a good way of providing large amounts of binary assets without packaging them into APKs as they may be multiple gigabytes in size. However, due to their size, they're most likely stored in a shared storage pool accessible from all programs. The system does not guarantee the security of the OBB file itself: if any program modifies the OBB, there is no guarantee that a read from that OBB will produce the expected output.
Related
What is OBB(Opaque Binary Blob) in Android develop site?