Supercharge Your Android Apps with LiveData: A Practical Guide

Want to simplify data handling in your Android apps? This article explains how to use Android LiveData, a powerful architecture component, to create reactive and lifecycle-aware applications. We'll guide you through practical examples and code snippets, ensuring you grasp how to effectively integrate LiveData into your projects.

What is Android LiveData?

Android LiveData is a data holder class that's lifecycle-aware, meaning it respects the lifecycle of your app components like Activities and Fragments. LiveData holds data and automatically notifies observers (like your UI) when the data changes. This simplifies updating the UI and ensures updates only happen when the UI is visible. Think of it as a smart data container for Android.

• Data Holder: Stores your app's data.
• Lifecycle-Aware: Only updates active UI components.
• Observer Pattern: Notifies the UI automatically when data changes.

LiveData vs. RxJava: What's the Difference?

While both LiveData and RxJava handle asynchronous data streams, LiveData is tailor-made for Android's lifecycle. LiveData prevents updates when your UI is in the background, avoiding common errors like IllegalStateException. RxJava, on the other hand, offers more versatility for complex data transformations but requires careful management of subscriptions to avoid memory leaks. If you're looking for lifecycle-aware data handling, LiveData is the easier choice.

• LiveData: Simpler, lifecycle-aware, less prone to memory leaks.
• RxJava: More powerful, complex, requires careful subscription management.

MutableLiveData: Making LiveData Flexible

MutableLiveData is a subclass of LiveData that lets you modify the data it holds. It provides postValue() and setValue() methods to update the LiveData's value. setValue() updates the value on the main thread (UI thread), while postValue() posts a task to a background thread to update the value.

• setValue(): Update LiveData on the main thread.
• postValue(): Update LiveData from a background thread.

Building an Android LiveData Example Project

Let’s dive into a practical example: updating a RecyclerView with data from an SQLite database using MutableLiveData. We'll use DiffUtil for efficient RecyclerView updates, changing only the necessary rows.

Project Setup

1. Add Dependencies: Include the following dependencies in your build.gradle file.

   implementation 'com.android.support:design:27.1.1'
   implementation 'com.android.support:cardview-v7:27.1.1'
   implementation 'android.arch.lifecycle:extensions:1.1.1'
   

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2. Sync Gradle: Sync Gradle files to apply these changes in the Project.

Key Classes Explained

• Favourites.java (Model): Represents the data structure for your items (e.g., a favorite URL and date).

• FavouritesViewModel.java (ViewModel): Fetches data from the SQLite database and exposes it as MutableLiveData. It also handles adding and removing data.

  public class Favourites {
      public long mId;
      public String mUrl;
      public long mDate;
  
      public Favourites(long id, String name, long date) {
          mId = id;
          mUrl = name;
          mDate = date;
      }
  }
  

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• MainActivity.java (View): Observes the MutableLiveData from the FavouritesViewModel and updates the RecyclerView when the data changes.

MainActivity: Observing LiveData and Updating UI

In MainActivity, we observe the LiveData exposed by the FavouritesViewModel. The onChanged() method in our Observer is triggered whenever the LiveData's data changes. This is where we update the RecyclerView's adapter with the new data.

mFavViewModel.getFavs().observe(this, favsObserver);

Add function on the ViewModel

 public void addFav(String url, long date) {

        SQLiteDatabase db = mFavHelper.getWritableDatabase();
        ContentValues values = new ContentValues();
        values.put(DbSettings.DBEntry.COL_FAV_URL, url);
        values.put(DbSettings.DBEntry.COL_FAV_DATE, date);
        long id = db.insertWithOnConflict(DbSettings.DBEntry.TABLE,
                null,
                values,
                SQLiteDatabase.CONFLICT_REPLACE);
        db.close();

        List favourites = mFavs.getValue();

        ArrayList clonedFavs;
        if (favourites == null) {
            clonedFavs = new ArrayList<>();
        } else {
            clonedFavs = new ArrayList<>(favourites.size());
            for (int i = 0; i < favourites.size(); i++) {
                clonedFavs.add(new Favourites(favourites.get(i)));
            }
        }

        Favourites fav = new Favourites(id, url, date);
        clonedFavs.add(fav);
        mFavs.setValue(clonedFavs);
    }

Benefits of Using Android LiveData

• Simplified UI Updates: Automatically updates the UI when data changes.
• Memory Leak Prevention: Avoids updating inactive UIs, preventing memory leaks and crashes.
• Lifecycle Awareness: Respects the lifecycle of Android components.
• Thread Safety: Offers postValue() for safe background thread updates.

Level up your Android development skills

Android LiveData simplifies data management and UI updates in your applications. By understanding its lifecycle awareness and using MutableLiveData effectively, you can build robust and responsive Android applications.