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Questions and Answers
Which method is used to fetch data from a specific table in a content provider?
Which method is used to fetch data from a specific table in a content provider?
What is the purpose of the insert() method in a content provider?
What is the purpose of the insert() method in a content provider?
What is the role of create a class that extends the ContentProvider base class when creating a content provider?
What is the role of create a class that extends the ContentProvider base class when creating a content provider?
What does the update() method do in a content provider?
What does the update() method do in a content provider?
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Why is it important to register the content provider in AndroidManifest.xml file?
Why is it important to register the content provider in AndroidManifest.xml file?
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When is the onCreate() method called in relation to a content provider's creation?
When is the onCreate() method called in relation to a content provider's creation?
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What does the getType() method return in a content provider?
What does the getType() method return in a content provider?
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Why does a class that creates a content provider need to define a content provider URI address?
Why does a class that creates a content provider need to define a content provider URI address?
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What information does the delete() method return when executed in a content provider?
What information does the delete() method return when executed in a content provider?
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What is one of the purposes of implementing abstract methods when creating a content provider?
What is one of the purposes of implementing abstract methods when creating a content provider?
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Study Notes
Storing and Retrieving Data in Android
- SQLite is a relational database technology used in Android apps, included with the Android system.
- To create a database in Android, a subclass of SQLiteOpenHelper is created, which provides functionality to create a database and calls a function that can be overridden by the derived class.
Creating a Database in Android
- SQLiteOpenHelper constructor accepts four arguments: Context, Name, Factory, and Version.
- The Version number is used to identify if there is an upgrade or downgrade of the database.
- onCreate() method is called when creating the database, and it is passed the SQLiteDatabase reference.
- onUpgrade() method is called when the database is upgraded, and it is passed the SQLiteDatabase, oldVersion, and newVersion.
Writing and Reading Data
- To write data to the database, use getWritableDatabase().
- To read data from the database, use getReadableDatabase().
- The insert function on the SQLiteDatabase class is used to add values to the database, taking three arguments: table name, column name, and ContentValues.
- Running a raw SQL query returns a cursor that points to all the rows found by the query.
Working with Content Providers
- Content Providers are central repositories that store and share application data in Android.
- Content Providers store data in several ways/formats and facilitate secure access and modification by other applications.
- Content Providers have permissions to grant or restrict access to data.
Content URI
- Content URI is a key concept in Content Providers, used to access data from a Content Provider.
- The Content URI consists of: content://, authority, optionalPath, and optionalID.
- The authority signifies the name of the Content Provider, and the optionalPath specifies the type of data provided.
Operations in Content Provider
- Four fundamental operations are possible in Content Provider: Create, Read, Update, and Delete (CRUD operations).
- These operations are used to create, fetch, modify, and delete data from the Content Provider.
Creating a Content Provider
- To create a Content Provider, follow these steps:
- Create a class that extends the ContentProvider base class.
- Define a content provider URI address.
- Create a database to store the application data.
- Implement the six abstract methods of ContentProvider class.
- Register the Content Provider in AndroidManifest.xml file using the provider tag.
Six Abstract Methods of ContentProvider Class
- query(): fetches data from the desired table and returns a cursor object.
- insert(): inserts a new row in the database and returns the content URI of the inserted row.
- update(): updates the fields of an existing row and returns the number of rows updated.
- delete(): deletes existing rows and returns the number of rows deleted.
- getType(): returns the MIME type of data to the given Content URI.
- onCreate(): initializes the Content Provider when it is created.
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Description
Test your knowledge on storing and retrieving data in an Android application using SQLite. Learn about creating a database, using SQLiteOpenHelper class, and working with relational database technology on Android systems.
