Android Firebase MVVM Jetpack - Many Offline-First CRUD Apps

In this lesson we examine our gradle scripts. We are interested in two files specifically:

1. build.gradle - Project Level

2. build.gradle - App Level

We examine their roles with regards to our project.

In this lesson we just want to add custom fonts to our assets folder. We show where to create an assets folder then how to add any font right there. You can search for any font you like online and download then add it. Later on we will see how to load it programmatically using Calligraphy.

MAIN ROLES

1. Addition of Custom Fonts to our Assets folder.

In this class we:

1. Add/Define XML animations in an anim folder under our resources.

2. These animations will either be applied to our widgets in the splas screen or in our activities when transitioning from one activity to the other.

In this section we look at:

1. Drawables - Images we use throughout project.

2. Menus - Toolbar menus we will be inflating in our activities.

3. Colors - Basically colors we will be using throughout our project.

4. Strings - Strings we use in our project like app_name.

5. Styles - Themes for our activities.

We look at each of them in this section.

This is our Second model class.

MAIN ROLES

1. Represent a network request/firebase operation. That operation will have properties like state,message and an optional list of downloaded data.

This is our Application class. android.app.Application, take note, is one of android's main components.

MAIN ROLES:

1. Initialize our LRU Hard Disk Cache library.

2. Initialize Calligraphy our font loading library.

This is our Application Constants Class.

MAIN ROLES:

1. Define and hold for us all our application constants.

2. We will also hold Firebase Database reference here.

In this lesson we look at our CacheManager class.  NB/= Normally Firebase provides default caching mechanism where data is cached for the application lifetime but needs to be reloaded everytime the app is restarted. We want to override this functionality with our caching mechanism where data is cached permanently on the device. Even if the app is restarted we will still have our data without connecting to Firebase. In other words we are creating an OFFLINE - FIRST APP.

MAIN ROLES

1. Cache our Firebase data in the hard disk permanently asynchronously

2. Retrieve data From our Cache asynchronously.

This is our repository class. Remember we are using the Model View ViewModel design pattern. This class will be categorized under our model though it isn't strictly a model or data object class. It is here where we will be writing our CRUD operations logic. That is the code that allows us to post/insert, edit/update, read/select as well as delete data to and from Firebase Realtime Database. This will be a fairly long class.

Our methods will be returning MutableLiveData objects. These LiveData objects will be observed by subscribers thus notifying those subscribers of updates in the data.

YOU CAN RE-USE THE METHODS HERE in any app if you just want a pluggable class to perform CRUD operations including search and filter.

MAIN ROLES

1. Post Data to Firebase realtime database.

2. Update existing data in Firebase.

3. Read and return data in Firebase realtime database.

4. Delete data from  firebase.

5. Search existing data in Firebase.

This is our FragmentsAdapter class. This class will allow us easily create swipeable tabs whenever we want.

MAIN ROLES

1. Maintain for us an array to hold fragments through which users will be able to swipe with the help of the ViewPager class.

2. Return the Fragment title as a CharSequence.

3. Receive a param of Fragments for which tabs will be created.

4. Connect our tabs with our fragments as well as viewpager.

This is our base activity class. We want to take advantage of inheritance, one of Object oriented programming pillars so we create a class that will contain functionalities/methods that are common or usable to different activities. Then those methods can simply be inherited by child activities.

MAIN DEFINITIONS

1. Method for Showing a toast message.

2. Method for creating a single-choice material dialog that can be used to select an item from an array then render the returned item in an edittext.

3. method for creating and showing a progress card. That can show us the progress of a firebase operation, its completion as well as failure. It will be capable of showing a title, message and progress dialog.

This method has the same functionality for the BaseActivity had only that it is used for Fragments as opposed to activities. It basically defines functionalities that are common across several fragments.

This is our splash activity, an optional part of any application. You can use a splash screen to portray your brand.

WHAT THIS ACTIVITY DOES

1. Show logo, title and subtitle when application starts.

2. Load animations and apply them to those widgets.

3. Delay/Suspend a thread for a fraction of a second before opening dashboard activity.

APIS/CLASSES USED

1. TextViews - To show title and subtitle.

2. ImageView - To show company logo.

3. AnimationUtils class - To load our animations from an XML resource.

4. Animation class - To hold the loaded animation so that it can be applied to our widgets.

5. Thread - To be delayed for a fraction of a second.

WHAT YOU WILL LEARN FROM THIS LESSON

1. How to load animations from an XML resource into an Animation object, then apply that animation to any android view.

2. How to delay a thread before opening a new activity.

   
   

In this class we will add transition animations in our anim folder under the resources. These animations will be applied in our activities as we transition from one activity to another.

You can download the full source code below. NB/= VIDEO LESSONS ARE COMING SOON.