Day53 of #100DaysOfCode

#CodeTogether Day 53/100

Hii folks 🙌

Today I will be continuing the same pathway in which I will build Kotlin words app.

Unit 3: Navigation

Pathway 1: Navigate between screens

Source: https://developer.android.com/courses/android-basics-kotlin/course

Activities and intents

We will start by downloading the repo from the given link in the course and setting it up in Android Studio.

Words app overview

We will be specifically working on LetterAdapter, WordAdapter and MainActivity files

• Intro to Intents

An intent is an object representing some action to be performed. The most common use for intent is to launch an activity. There are two types of intents — implicit and explicit.

• An explicit intent is highly specific, where we know the exact activity to be launched, often a screen in our own app.
• An implicit intent is an a bit more abstract, where we tell the system the type of action, such as opening a link, composing an email, or making a phone call, and the system is responsible for figuring out how to fulfill the request.

• Setting up Explicit Intent

In the LetterAdapter.kt we will set the onClickListener for holder.button in onBindViewHolder() and Create an Intent, passing in the context, as well as the class name of the destination activity.

holder.button.setOnClickListener {
val context = holder.view.context
val intent = Intent(context, DetailActivity::class.java)
}

Now we will call the putExtra method passing in the letter as the first argument and the button text as the second argument

intent.putExtra("letter", holder.button.text.toString())

Then, we will Call the startActivity() method on the context object, passing in the intent.

context.startActivity(intent)

Now we will move forward and set up a DetailActivity. In the onCreate method of DetailActivity, after the call to setContentView, we replace the hardcoded letter with code to get the letterId passed in from the intent.

val letterId = intent?.extras?.getString("letter").toString()

Now in the DetailActivity we will add the following just above the OnCreate

companion object {
const val LETTER = "letter"
val letterId = intent?.extras?.getString(Letter).toString()
intent.putExtra(DetailActivity.LETTER, holder.button.text.toString())
}

• Setting up Implicit Intent

companion object {
   const val LETTER = "letter"
   const val SEARCH_PREFIX = "https://www.google.com/search?q="
}

Then we will set up the menu and icons in the res/Menu/layou_menu . We will replace the contents of layout_menu.xml with the following:

<menu xmlns:android="http://schemas.android.com/apk/res/android"
   xmlns:app="http://schemas.android.com/apk/res-auto">
   <item android:id="@+id/action_switch_layout"
       android:title="@string/action_switch_layout"
       android:icon="@drawable/ic_linear_layout"
       app:showAsAction="always" />
</menu>

• Now we will implement the Menu button

private var isLinearLayoutManager = true
private fun chooseLayout() {
    if (isLinearLayoutManager) {
        recyclerView.layoutManager = LinearLayoutManager(this)
    } else {
        recyclerView.layoutManager = GridLayoutManager(this, 4)
    }
    recyclerView.adapter = LetterAdapter()
}

• We will conditionally set the isLinearLayoutManager

private fun setIcon(menuItem: MenuItem?) {
   if (menuItem == null)
       return
   // Set the drawable for the menu icon based on which LayoutManager is currently in use
   menuItem.icon =
       if (isLinearLayoutManager)
           ContextCompat.getDrawable(this, R.drawable.ic_grid_layout)
       else ContextCompat.getDrawable(this, R.drawable.ic_linear_layout)
}

• Override onCreateOptionsMenu as follows:

override fun onCreateOptionsMenu(menu: Menu?): Boolean {
   menuInflater.inflate(R.menu.layout_menu, menu)

   val layoutButton = menu?.findItem(R.id.action_switch_layout)
   // Calls code to set the icon based on the LinearLayoutManager of the RecyclerView
   setIcon(layoutButton)

   return true
}

Before we run the app. Since the layout manager and adapter are now set in chooseLayout(), we should replace that code in onCreate() to call our new method. onCreate() should look like the following after the change.

override fun onCreate(savedInstanceState: Bundle?) {
   super.onCreate(savedInstanceState)

   val binding = ActivityMainBinding.inflate(layoutInflater)
   setContentView(binding.root)

   recyclerView = binding.recyclerView
   // Sets the LinearLayoutManager of the recyclerview
   chooseLayout()
}

This is how app looks like

App preview

Today I Learned:

• Explicit intents are used to navigate to specific activities in our app.
• Implicit intents correspond to specific actions (like opening a link, or sharing an image) and let the system determine how to fulfill the intent.
• Menu options allow us to add buttons and menus to the app bar.
• Companion objects provide a way to associate reusable constants with a type, rather than an instance of that type.

That is all for Day53 ✅

Thanks for reading, See you tomorrow!

If you are reading my #100Days Journey, feel free to drop by ;)

The Journey of #100DaysOfCode (@im_Kushagra)