Hands-On Android UI Development: Design and develop attractive user interfaces for Android applications by Jason Morris

Author:Jason Morris [Morris, Jason]
Language: eng
Format: epub, pdf
Tags: COM051280 - COMPUTERS / Programming Languages / Java, COM051460 - COMPUTERS / Programming / Mobile Devices, COM070000 - COMPUTERS / User Interfaces
Publisher: Packt Publishing
Published: 2017-11-21T00:00:00+00:00

At the bottom of the file, you'll find a dependencies block; at the bottom of the block, add the following two lines of code:

implementation 'android.arch.lifecycle:runtime:+'

implementation 'android.arch.lifecycle:extensions:+'

annotationProcessor 'android.arch.lifecycle:compiler:+'

Use the Sync Now link at the top of the editor to synchronize your project with it's Gradle file, and download the new dependencies.

Implementing Data Access Objects in Room

You'll need to implement two different Data Access Object classes for the Claim application, one for each Entity object. Technically speaking, Room doesn't enforce one DAO per entity, and you can have a single DAO interface for your entire application or have one per screen. However, the most common pattern is to have one DAO class per entity type, even when some of its query methods return statistics or other views on the data. When working with more complex datasets, it's worth considering introducing additional DAO interfaces to cover queries that are either screen-specific or where the data overlaps several entities.

Here's how to implement the Data Access Object interfaces for the Claim example application, step by step:

Right-click on the model package in Android Studio and select New | Java Class.

Name the new class db.ClaimItemDao.

Change the Kind field to Interface. Room DAO types are normally interfaces, although this isn't a strict requirement, and they can also be abstract classes.

Click OK to create the new package and class.

Annotate the interface with @Dao to mark it as a data-access-object:

Download

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