Chapter 1 About this Tutorial Book

To program my health app GeDaMa in Kotlin and Android Studio, I got hold of two books: Head First Android Programming [1] and Head First Kotlin [2]. They formed a good basis for programming a CRUD app (Create Read Update Delete).

What quickly became apparent while programming the GeDaMa app, however, was the fact that while the Head First Android book covers many useful topics, the programming examples used are always based on very simple problems. For example, the book suggests using Room to store data in a SQLite database, but demonstrates this with a very simple data model that does not use foreign keys at all (which is unlikely to be the case in practice).

A lot of time spent while programming the GeDaMa app was therefore used for finding solutions to much more complex problems online on websites like stackoverflow.com or in the Android Developer Guides.

And even more time was spent on adapting the code fragments found at these sites to my purposes. It was not uncommon for Android Studio to complain that the adopted code used deprecated methods or an approach that was no longer recommended.

For programmers facing similar challenges, I would like to provide this online tutorial book to help them solve the problems they encounter more easily and quickly, especially with regard to the development of a (more complex) CRUD app and the associated user interface. The following points are covered in the tutorial:

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  1:n relations

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  m:n relations

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  Drop-down menus with database values

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  Interception of SQL constraint violations

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  Raw queries

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  Pre-filling the database with language-specific values

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  Searching database values

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  Filtering database values

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  Reusable XML blocks for insertions and updates

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  Speech input

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  Saving images and PDF files

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  Open PDF for reading in PDF app

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  Enlarge image

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  Basic fragment class with useful methods for all further fragments

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  Basic viewmodel class with useful methods for all other view models

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  Notifications and AlarmManager

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  Resumption of notifications after a device restart

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  Access and authorisation to external file system

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  Google Ads Banner, Native Ads in Recycler View, Interstitial Ads, Rewarded Ads, Fallback Ads and DSGVO form for user consent

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  Control of the frequency for advertising insertions

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  Form validations in the user interface

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  Database converters

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  Generic date-time picker for date values

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  Global app class that can be accessed from anywhere in the code

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  Show/hide menu items

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  Dark mode

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  Defining attributes in our themes

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  Styles to unify the user interface

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  Version allocation in build.gradle

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  AdMob and Google Ads-IDs for test and production

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  Multilingualism

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  Export of a Recycler View list to CSV

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  Deactivate/delete records

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  Backing up and restoring the database

Whether the presented code is the best possible solution at all remains to be seen: In any case, my code serves its purpose and does what I wanted to implement in my GeDaMa app. Many code lines were taken practically 1:1 from the Head First Android Programming book. And much more code was taken from program snippets of passionate programmers who uploaded their solutions on stackoverflow.com or elsewhere on the internet. Whenever I have reused something from some other programmer, I have (hopefully) indicated this in the comments.

In the Head First Android Programming book, it is pointed out at several places that you don’t need to understand the code (e.g. RecyclerView.ViewHolder or DiffUtil.ItemCallback) and that it is sufficient to simply use the code in concrete situations exactly as it is. This is not entirely satisfying, but I’ve come to terms with it, and I’ve often felt the same way about other programmers’ code when it comes to understanding it. But the code does what it’s supposed to do, and that’s what matters, at least to me!

All the problems mentioned in the list above are dealt with and solved in the tutorial app. With the tutorial code, it should be easy for programmers to realise a much more extensive CRUD app such as GeDaMa.