Passing Data Between Activities in Android

In Android application development, it is common to need to pass data between different activities. This can be achieved through various methods, including using intents, extending the Application class, and utilizing static variables. In this tutorial, we will focus on the most recommended approach: using intents.

Introduction to Intents

An intent is a messaging object that allows you to request an action from an app component. When you want to pass data between activities, you can use intents to carry the data as "extras." These extras are key-value pairs that can be of various data types such as strings, integers, and more.

Passing Data Using Intents

To pass data from one activity to another using intents, follow these steps:

1. Create an Intent: In your source activity, create a new intent specifying the target activity you want to start.
2. Add Extras to the Intent: Use methods like putExtra() to add the data you want to pass as extras to the intent.
3. Start the Target Activity: Call startActivity() with the intent containing the extras.

Here’s an example of how to do this:

// Source activity
String value = "Hello, World!";
Intent i = new Intent(CurrentActivity.this, NewActivity.class);
i.putExtra("key", value);
startActivity(i);

// Target activity (in onCreate method)
Bundle extras = getIntent().getExtras();
if (extras != null) {
    String value = extras.getString("key");
    // Use the received value
}

Accessing Extras in the Target Activity

In the target activity, you can access the extras passed through the intent using getIntent().getExtras(). Then, use methods like getString(), getInt(), or getBoolean() to retrieve the specific data type you are expecting.

// Retrieving a string extra
String sessionId = getIntent().getStringExtra("EXTRA_SESSION_ID");

// Retrieving other types of extras (e.g., long, boolean)
long value = getIntent().getLongExtra("Variable name", defaultValue);
boolean flag = getIntent().getBooleanExtra("Flag key", false);

Alternative Approach: Extending the Application Class

For scenarios where you need to share data across multiple activities or when dealing with more complex objects, extending the Application class can be a viable alternative. This approach involves creating a custom application class that holds your shared data and accessing it from any activity through getApplication().

// Custom application class
public class MyApp extends Application {
    private String sessionId;

    public void setSessionId(String id) {
        this.sessionId = id;
    }

    public String getSessionId() {
        return sessionId;
    }
}

// Accessing the shared data in an activity
MyApp app = (MyApp) getApplication();
String sessionId = app.getSessionId();

Best Practices and Considerations

• Avoid Using Static Variables: While static variables can seem like a simple way to share data, they can lead to memory leaks. Prefer using intents or the Application class instead.
• Choose the Right Approach: Intents are suitable for passing data between activities, but if you’re dealing with complex state management across your app, consider extending the Application class.

By following these guidelines and examples, you can effectively pass data between activities in Android, ensuring a robust and maintainable application architecture.