Alright, let's get started with tracking your app's startup time using Firebase Performance Monitoring. First things first, we need to install the Firebase SDK. Just add this line to your app-level build.gradle file:

    // Add this line
    implementation 'com.google.firebase:firebase-perf:19.0.11'

After that, sync your project with the gradle files to wrap up the SDK installation. Easy peasy, right?

By default, Firebase Performance Monitoring is already enabled. But if you ever need to manually turn it on or off, here's how you can do it:

    // To enable
    FirebasePerformance.getInstance().setPerformanceCollectionEnabled(true);

    // To disable
    FirebasePerformance.getInstance().setPerformanceCollectionEnabled(false);

Simple commands, but super useful when you need them.

Now, let's talk about monitoring your app's startup time. Firebase Performance Monitoring has this neat 'trace' feature that automatically measures how long it takes for your app to start up. This is defined as the time from when the app process kicks off to when the app is fully initialized.

The SDK automatically adds the code to measure this, so you don't have to lift a finger. It tracks the time between the user launching the app and the app being ready for interaction.

For Android, the SDK measures startup time in two scenarios:

• Cold Start: From the moment the app process starts to when the main activity's onResume() method finishes.
• Warm Start: From when the main activity's onStart() method is called to when onResume() method completes.

To see how your app is doing in terms of startup time, head over to the Firebase console:

• Click on Performance from the left-hand menu.
• In the Dashboard tab, scroll down until you find the 'App Start Trace'.
• Click on the 'App Start Trace' to dive into the details.

Here, you'll find the median startup time and a histogram showing the distribution of startup times. This data helps you understand how quickly your app is loading for different segments of your user base.

And there you have it! Happy monitoring!