Lab 5

🖥 Lab 5: Working with Activities and Fragments

In this lab, we will setup a basic navigation infrastructure for a new Study app

📝 Objectives

0. Create a new Android Studio project named Android Study Guide

1. Ensure you have an empty Kotlin Activity named MainActivity

   1. This should be set as the app's launcher activity in AndroidManifest.xml

2. Create a second Kotlin Activity named TwitterActivity

   1. This will be used later this week to integrate with Twitter's PWA

3. Create 4 Fragments that will become the core screens in our app

   1. CreateNoteFragment
   2. NoteDetailFragment
   3. MyNotesFragment
   4. StudyGuideFragment

4. For each Activity & Fragment add a TextView to the layout that uniquely identifies that screen

5. Add a Button to MainActivity that shows TwitterActivity when clicked

6. Add 4 Buttons to MainActivity that show each of the new Fragments when clicked

   1. To show a Fragment, you'll need to add a FrameLayout to activity_main.xml to act as the Fragment container.
   2. Give the FrameLayout an id of fragmentContainer
   3. Make the FrameLayout fill the layout.
   4. Give the FrameLayout an elevation of 4dp.
      1. This is just temporary to ensure the buttons aren't drawn above the container. We'll replace this in the next lab.
   5. Add the 4 Buttons and give each a label to indicate which Fragment they will show.
   6. Add click handlers to each button within MainActivity
   7. Within each click handler, perform a replace() FragmentTransaction to show the desired Fragment

✨ Challenges

Logging the Android Activity and Fragment lifecycles

Using Logcat, add log messages to key lifecycle events in an Activity and Fragment to observe lifecycle changes as you interact with your app.

Changing Launcher Activities

Temporarily change your app's launcher Activity to TwitterActivity and observe the impact on your app

 

🖥 Lab 5: Working with Activities and Fragments

💡 Helpful Resources

• How to Create a Fragment?
• TextView Documentation
• Button Documentation
• Material Design Button Guidance

 

💡 Creating new Activities and Fragments

Android Studio can help us create a new Activity or Fragment.
Right-click on your main package within src/main, select New -> Activity/Fragment and select the template you want to use.

However, the IDE often presents us with a handful of different templates such as EmptyActivity, Fragment with ViewModel, List Activity, etc

These can be kind of fun to play with when starting out, but more most situations you're going to want to choose EmptyActivity and BlankFragment so you can customize exactly how you want without having to remove stubbed out code.

 

💡 Showing a Fragment in an Activity

To show a Fragment we need 2 things:

• We need a ViewGroup to act as a container for the Fragment. In this case, we could use a FrameLayout that fills activity_main.xml.
• We need to use the FragmentManager to create FragmentTransactions that add/remove Fragments from the container.

Here is a sample method that you can add to MainActivity to allow for showing Fragments within a container with an id of fragmentContainer.

private fun showFragment(fragment: Fragment, name: String) {
    supportFragmentManager
      .beginTransaction()
      .replace(R.id.fragmentContainer, fragment)
      .addToBackStack(name)
      .commit()
  }

 

💡 Creating an Intent to show the TwitterActivity

Intents are a very general-purpose tool in Android. We can create them in a variety of ways to achieve a desired result. In this case, we want to create an "explicit Intent" to open a specific Activity - our TwitterActivity. To do that, we need 2 things:

• a Context. This is usually going to be an instance of an Activity.
• the class name for the Activity we want to start.

Once we've created an Intent, we can use Activity.startActivity(intent) to start the desired Activity

binding.showTwitterButton.setOnClickListener {
  val showTwitterIntent = Intent(this@MainActivity, TwitterActivity::class.java)
  startActivity(showTwitterIntent)
}

 

💡 Logging to Logcat

The Android SDK provides a default set of logging functions:

• Log.d()
• Log.e()
• Log.i()
• etc

Adding these to your code can be a helpful way to observe the lifecycle of your application or to help track down bugs.

Output from these functions will go to Logcat which can be observed in the Locat tool window or using adb