Mobile Application Development-Lecture 13 & 14.pdf
- 1. Mobile Application Development (ITEC-303) Fahim Abid fahim.abid@uettaxila.edu.pk fahim.abid@uoc.edu.pk
- 2. Credits Hours 3(3,0) Recommended Books 1. Professional Android application development, Reto Meier, Wrox Programmer to Programmer, 2015. 2. Android Programming: The Big Nerd Ranch Guides, Phillips, B. & Hardy, B., 2nd Edition, 2014. 3. iOS Programming: The Big Nerd Ranch Guide, Conway, J., Hillegass, A., & Keur, C., 5th Edition, 2014.
- 3. Creating and Saving Preferences To create or modify a Shared Preference, call getSharedPreferences on the application Context, passing in the name of the Shared Preferences to change. Shared Preferences are shared across an application’s components but aren’t available to other applications. Android provides many ways of storing data of an application. One of this way is called Shared Preferences. Shared Preferences allow you to save and retrieve data in the form of key, value pair. Android provides the SharedPreferences object to help you save simple application data. Using the SharedPreferences object, you can save the data you want through the use of key/value pairs, specify a key for the data you want to save, and then both it and its value will be saved automatically to an XML file.
- 4. In order to use shared preferences, you have to call a method getSharedPreferences() that returns a SharedPreference instance pointing to the file that contains the values of preferences. To modify a Shared Preference, use the SharedPreferences.Editor class. Get the Editor object by calling edit on the SharedPreferences object you want to change. To save edits, call commit on the Editor, as shown in the code snippet below. SharedPreferences sharedpreferences = getSharedPreferences(MyPREFERENCES, Context.MODE_PRIVATE);
- 6. Retrieving Shared Preferences Accessing saved Shared Preferences is also done with the getSharedPreferences method. Pass in the name of the Shared Preference you want to access, and use the type-safe get<type> methods to extract saved values. Each getter takes a key and a default value (used when no value is available for that key), as shown in the skeleton code below:
- 8. Persisting Data to Files Persistent data is data which you want to be available even after you fully close and restart your app. The three most common ways to safe this data locally is by using SharedPreferences, a local database or the file system (store data as a file). Android supports the following ways of storing data in the local file system: Files - You can create and update files. Preferences - Android allows you to save and retrieve persistent key-value pairs of primitive data type. SQLite database - instances of SQLite databases are also stored on the local file system.
- 9. Creating and Using Databases SQLite is a open source SQL database that stores data to a text file on a device. Android comes in with built in SQLite database implementation. SQLite supports all the relational database features. Database - Package The main package is android.database.sqlite that contains the classes to manage your own databases. Database - Creation In order to create a database you just need to call this method openOrCreateDatabase with your database name and mode as a parameter. It returns an instance of SQLite database which you have to receive in your own object. Its syntax is given below.
- 10. Database - Insertion we can create table or insert data into table using execSQL method defined in SQLiteDatabase class. Its syntax is given below:
- 11. Database - Fetching We can retrieve anything from database using an object of the Cursor class. We will call a method of this class called rawQuery and it will return a resultset with the cursor pointing to the table. We can move the cursor forward and retrieve the data.
- 12. Database - Helper class For managing all the operations related to the database , an helper class has been given and is called SQLiteOpenHelper. It automatically manages the creation and update of the database. Its syntax is given below: public class DBHelper extends SQLiteOpenHelper { public DBHelper() { super(context,DATABASE_NAME,null,1); } public void onCreate(SQLiteDatabase db) {} public void onUpgrade(SQLiteDatabase database, int oldVersion, int newVersion) {} }