I have been asked to create a tiny android app.
In everyday work i code for .NET and I have no experience connected with Android, but as it is a really small app I guess it's going to be a good experience rather than something hard.
The core of the app would be a small database (probably XML, unless somebody suggest better solution) that would contain categories, names of the institutions assigned with each category and logo (not very high resolution I guess a single file would be <100kB) of the institution.
The database also would not be very big - I expect not more than 1000 records in total. The DB has to be totally offline and local, it cannot require Internet access when operating.
The model I assume would be to ship new version of the application when the database changes (which is not going to be very frequent).
What is the best way to deal with these requirements?
My first idea was to create an XML file that would contain the records and link to the image. The XML and all the images linked to it would be stored in single file (preferably zip) that would be stored in app resources. This is very good as it is going to be very easy to update the database.
The second idea that somebody suggested me would be to use SQLite and store images in BLOB. In general I have read that it isn't a good idea to store images in database directly, and I am afraid if it's going to be possible to meet all requirements mentioned above.
Mostly I have no idea how to update the database easily and attach it to new version of application.
Any suggestions?
I would be grateful for any response.
I wouldn't go about using XML to save your data and by no means zip anything.
I think your way of thinking is ok, but you're making things really complicated for yourself.
Seeing as you're used to .NET I suppose you're also pretty confident with SQL, so I'd suggest you have a look at how to use the built-in SQLite database in Android.
If you would go the XML route you'd have to serialize and de-serialize the XML file over and over again and then parse the XML. Ok you don't have a lot of data, but searching inside an XML file with at least 1000 nodes would be slow in comparison to the performance of a database.
Also upgrading an existing SQLite database is not that hard - Android has methods for that (onUpgrade coming from the SQLiteOpenHelper).
As to saving images I'm assuming that you won't fetch new pictures from the Internet, so it would be best just to store them in the drawable folder of your app (be mindful of different screensizes) and then reading them into an ImageView when needed. To figure out what image should go for what institution I would store either the image name of each image in the SQLite database or store the resource id for each image in the database - for instance R.drawable.myawesomepictureformyinstitution.
I know my answer is somewhat "superficial", but your question is also somewhat "broad" and hard to answer without me actually writing most of the code, and that's not my intention ;-)
Hope this helps - let me know if anything is unclear.
Related
I saw a similar question but it was a decade old:
My objective is to create an app (Android/Kotlin) where the users can search/reference/lookup an individual item from a reference 'book'. Something along the lines of a dictionary or book of recipes.
The intent is for the app to be able to work offline, when the user may be anywhere.
As there could be thousands of items/records to reference it would seem to be too much for an array.
Is a Room database a good option and, if so, can a pre-loaded database be included in the package that is uploaded to Google Play?
What is best in 2022?
Yes, Room will do exactly what you want, but pre-loading it with data will be tricky (but doable).
You can't technically "pre-load" the database, but what you can do is save all the database objects to a file, using either XML, JSON, or any other format. You will then need to save that file in your project as either an Asset or Raw, and on first app launch, you'll need to read that Asset or Raw resource, parse each record, and save it to the database.
Needless to say, that initial process may take some time, so I'm not sure how good that will be from the user's perspective. But it's definitely pretty straight-forward to implement
Creating the Assets folder
Reading files from Assets
I am developing a notepad app which can store simple text files and checklists. Currently I maintain a separate file (say info.txt) that maintains information about whether a given file is a simple text file or a checklist and based on that I render my UI (for either listing all files or opening a file) to show that file in my app. However I am not very happy with this approach because is slow and does not appear to scale well.
Is there a better way to add "metadata" (e.g. if it is a simple text or cheklist, tags, etc) about a file in android?
Any help will be greatly appreciated
There are several ways of storing persistent data in Android.
The way you are currently doing it is through the device storage, and you are quite right it would probably not scale well in addition to being directly accessible to the user meaning they could edit or delete your metadata.
Using SharedPreferences would be one way of storing the metadata which has the advantage of being completely hidden from the user, as well as being relatively easy to set up. The main disadvantages I can see are that it may not scale well if a user has a large number of files, and it is much more difficult to retrieve files with certain criteria, a certain tag for instance, as you mention in the comments.
The best way to store data that will scale well, be persistent, and let you run queries on the data would be an on device SQLite database. SQLite will usually have more overhead in terms of setup time, but is far more robust and featured than any of the other options besides perhaps network based storage, which based on the information you have given is probably not something you are interested in. Based on your problem the SQLite database is probably the way to go and has the bonus of being expandable in case you ever decide to add more information, or even store the files in the SQLite database.
I have some really huge data that is required for my android app. I've put it into a sqlite db now. Roughly it is 39k rows and 5 columns. I want this data to be available for my app.
I'm kind of confused as to how I ship my app with it. i can ship the db file with it like discussed in this thread. or I can somehow create XML out of that data and ship it along. But the XML would be really huge. So what is the right way of doing it?
I do not want to download it after user installs the app. That'd be my last option if there are no better clean ways of doing it.
This should help you.
http://www.reigndesign.com/blog/using-your-own-sqlite-database-in-android-applications/
Basically just ship the database with your apk file.
I think shipping your DB could make some problems with compatibility.
Maybe it will be better to use GZIP'ed SQL code bundled to your .APK?
Or instead of XML for intermediate representation you can use google protobuf, which is most effective data representation format(Also, if you have a lot of strings, you can use it in combination with GZIP).
Check the example here to achieve this functionality.
I apologize in advance if this question is too broad or too "it-depends."
Basically, I need to make a decision about how to store and access data in my app. The app works very much like flashcards; the "front" of the card presents the topic and the "back" presents the details/explanation. At first it seemed like a SQLite database would work best for this type of structure (and maybe it really is, I just don't know) because the data is static and this model works well with the rows and columns structure of a db. (btw, as of now, I'm using openCSV to parse the csv files containing my cards. Thought it was easier than SQLite...)
My issue (finally) is that I want to be able to display images for some of the data items. Some cards, for example, should display a corresponding image. Is this something that I can do with a SQLite db? Like, have one column store the path to an image....? Maybe what I'm asking is really basic, but I just haven't seen too many examples to really have a good sense of the design options out there.
I might also be confused about how I would dynamically change my views based on whether there is an image available. Maybe that's just an issue of dynamically creating an imageview whose source is the file that the db points to...
In summary, I'd really appreciate some guidance on how I can fetch and display text data along with images when they're available, whether it be in SQLite or some other way.
Thanks!
If all this data is being shipped with the app, I'd suggest just keeping everything stored as resources. You can have string arrays for the topics and details, and you can store images either as drawable resources or as assets. In the latter case, you could store the asset names as another string array resource. (In the former case, you'd have to build a map from each card to the resource identifier. This is, unfortunately, one area in which the Android resources architecture doesn't shine.)
If you want to use SQLite, it has BLOB fields in which you could store the images themselves, or int fields in which you could store image resource identifiers. Take a look at the searchable dictionary sample project for how to build an SQLite data base from resource data.
Sorry but this really is a 'it depends' kind of topic.
Unless you're storing a large number of rows of data (around the order of 10 000) then an XML file would be your best bet. In a Train Timetable app I recently wrote we went with a XML SAX parser loading a 14 000 record database to memory and it took no more than 2 seconds on an HTC Hero, so even for large databases its pretty fast.
The SQLite option is preferable only if you want to make use of relationships that come with a database structure. It is better at handling large numbers of rows but terrible at handling images.
Since you're flash cards are not relational I would recommend an xml file, using the xmlSax parser, and a folder of images within your assets folder. You could even run the images through pngCrunch to save some space.
XML is very flexible, below is an example of what your xml file could look like. Check out http://www.w3schools.com/schema/ for more information on writing an xml schema.
<?xml version="1.0" encoding="UTF-8"?>
<cards>
<card title="card 1" topic="atopic" image="image file name">
<front>Lots of text</front>
<back>Lots of text</back>
</card>
<card ..>
..
</card>
</cards>
I would like to build some simple application - for example Todo list - and I am thinking about the problem and its solving - how can I to store data in my own application on Android platform?
I should to use some text file, xml file or some database? What will be better for beginner on this field?
You'll have a VERY hard time getting anywhere with Android if you don't read through their website/dev resources. I would highly recommend visiting their site.
As far as data storage is concerned, that varies based on your need. Explained here
My suggestion is to use SQLite that comes with Android. http://developer.android.com/reference/android/database/sqlite/SQLiteDatabase.html
In my opinion, a SQLite database seems most appropriate for this kind of application. There is lots of support for using the SQLite database in conjuction with ListViews (which I imagine you'd want to use in your to-do list app).
In case you haven't already checked it out, see the page on the developer site:
http://developer.android.com/guide/topics/data/data-storage.html#db
Theres a few ways you can store data. I've created a few applications thats store data using shared preferences
They're quite handy for storing strings, ints, bool values etc. However if you have a large scaled application, that requires better database management, I would look into sqlLite.
Android has supported classes and functions to help access/store the information.
Theres a good tutorial on the android site called notepad that takes you through how to use sqlite.
That should get you started :)
Look at this Thread klick
Edit: its cool for less data, if you want to store and browse lots of data, you should use as SQLite Database
Using a file, database or xml based depends entirely on what kind of application you are building. For eg: If you parse an XML feed and store the results back in an XML file - it totally defeats the storage purpose!
Databases are used to store structured and related content like - news feed results, email client data, etc.
Files are more used for storing raw / binary content like storing images, attachments, etc.
BTW, if you are a beginner - you should try all of them! :)
Hope this helps!