Lecture 8 Database in Android

8/13/2019 Lecture 8 Database in Android

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Lecture 8DATABASE IN ANDROID


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Data Storage Options in Android

Shared PreferencesStore private primitive data in key-value pairs.

Internal Storage

Store private data on the device memory.

External Storage

Store public data on the shared external storage.

SQLite Databases

Store structured data in a private(to application) database.


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Shared PreferencesProvides a general framework that allows you to save and retrieve persistent key-vprimitive data types.

To get a shared preferences object, use one of those methods


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Shared Preferencespublic abstract SharedPreferences getSharedPreferences (String name, int mode)

Retrieve and hold the contents of the preferences file 'name', returning a SharedPthrough which you can retrieve and modify its values.

mode represent permissions and could be : MODE_PRIVATE, MODE_WORLD_REAMODE_WORLD_WRITEABLE


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Saving To Shared PreferencesSharedPreferences settings = getSharedPreferences(PREF_NAME, 0);

SharedPreferences.Editor editor = settings.edit();

editor.putBoolean(MyData", false);

editor.commit(); // Commit the edits

PREF_NAME is the name of the shared pref file. String


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Retrieve Shared preferences datSharedPreferences myPref = getSharedPreferences(PREF_NAME, 0);myPref.getTYPE(Name,RETURN_IF_NOT_EXSITS);

PREF_NAME is the name of the shared pref file. String


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Clearing PreferencesFrom Code

preferencesEditor.clear(); preferencesEditor.commit();

By Users From Device

On your device, if you go to Settings> Applications> Manage Applications> Yosee a button to Clear Data. Clicking this clears any data your app has saved, includSharedPreferences: preferencesEditor.clear(); preferencesEditor.commit();


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Using Internal StorageSaved on the device's internal storage

When the user uninstalls your application, these files are removed.

Files are stored in the file folder under you package directory

in the device. /data/data/yourAPP/files


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Writing to SD CardFrom previous session we used:

OutputStream output = new FileOutputStream("/mnt/sdcard/image2.jpg");

Use getExternalFilesDir() to open a File that represents the external storage directyou should save your files. (API Level 8 or greater)

Parameter can be predefined path or null to get the root folder

Predefined paths examples are :

DIRECTORY_MUSIC | DIRECTORY_RINGTONES


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Writing to SDCard

Helper Methods :


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Checking Media Availability


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Google Documentation Referenchttp://developer.android.com/guide/topics/data/data-storage.html
http://developer.android.com/guide/topics/data/data-storage.htmlhttp://developer.android.com/guide/topics/data/data-storage.htmlhttp://developer.android.com/guide/topics/data/data-storage.htmlhttp://developer.android.com/guide/topics/data/data-storage.htmlhttp://developer.android.com/guide/topics/data/data-storage.html


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SQLite


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SQLiteSQLite is a lightweight transactional database engine that occupies a small amoun

storage and memory.

It is a software library that implements a self-contained, serverless, zero-configuratransactional SQL database engine. http://www.sqlite.org/

You use SQLite to manipulate databases, create, update, delete and insert data in tables


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Using SQLiteStandard SQL

Support for Triggers

Does not implement referential integrity constraints. Use Triggers to handle this

Null, Integer, Real and Text data types allowed

Its possible to insert different types in the same column. You can insert, for examptext and vice versa

Refer to SQLite limits in the official documentation here : http://www.sqlite.org/li


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SQLite and AndroidAndroid provides full support for SQLite databases.

Database created are private to your application.


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Contacts Example


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Table Structure


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SQlite Open Helper


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Inserting new Record


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Reading Row(s) with Conditions


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Reading Row(s)


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Rows Count


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Updating Record


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Deleting Record


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Using the database in an activity

Lecture 8 Database in Android

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