Lab: Visualizing the Lifecycle

Let's add logging to the lifecycle methods to see what's happening behind the scenes in CalculatorActivity, CalculatorApplication, ButtonFragment, and DisplayFragment.

Tagging

So that we can easily identify our log messages, add a constant field to each class:

private static final String TAG = "Lifecycle " + [ClassName].class.getSimpleName();

Make sure to replace [ClassName] with the name of the class (e.g. CalculatorApplication).

Instrumenting

Use ⌘O to override the lifecycle functions.

Add a log call in each method. For example, your onCreate() should look like this:

@Override
public void onCreate( Bundle savedInstanceState )
{
    super.onCreate( savedInstanceState );
    Log.d(TAG, "onCreate()");
    ...
}

Run

You can filter the IntelliJ logs to show only a specific tag (the first string provided to Log.d()):