# 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()):