How to Cache or Save Custom Class Objects in Android Applications?

What are the best methods to cache or save custom class objects in Android?

// Sample of a custom class
class User {
    String name;
    int age;
    
    User(String name, int age) {
        this.name = name;
        this.age = age;
    }
}

Caching or saving custom class objects in Android can be accomplished using several methods, including SharedPreferences, local files, and SQLite databases. The choice of method depends on the size of the data and the usage context. Using serialization techniques allows us to easily store and retrieve complex objects.

// Using SharedPreferences to save a custom object
User user = new User('John', 30);
String json = new Gson().toJson(user);
SharedPreferences sharedPreferences = getSharedPreferences('app_prefs', MODE_PRIVATE);
SharedPreferences.Editor editor = sharedPreferences.edit();
editor.putString('user', json);
editor.apply(); // Save the data

// To retrieve the object
String json = sharedPreferences.getString('user', '');
User retrievedUser = new Gson().fromJson(json, User.class);

Causes

• Need to persist data across app sessions
• Reducing the need to re-fetch data from the network
• Improving app performance by caching frequently accessed data.

Solutions

• **SharedPreferences**: Best for storing small amounts of primitive data. Custom objects can be converted to JSON strings for storage.
• **File Storage**: Use this method when saving larger objects. You can serialize your objects to files using `ObjectOutputStream` and read them back using `ObjectInputStream`.
• **SQLite Database**: This method is ideal for storing structured data. You can create a database schema to store class object attributes and retrieve them when needed.

Mistake: Using SharedPreferences for large objects

Solution: SharedPreferences is designed for primitive types and small datasets. Use file storage or SQLite for larger datasets.

Mistake: Forgetting to handle exceptions during file I/O operations

Solution: Always use try-catch blocks to handle I/O exceptions when reading or writing files.

Mistake: Not considering data format while saving and retrieving

Solution: Ensure you maintain consistency in the format (e.g., JSON) across save and retrieval processes.