Not flashy, but functional

app/build.gradle

@@ -16,6 +16,10 @@ android {
         testInstrumentationRunner "androidx.test.runner.AndroidJUnitRunner"
     }
 
+    viewBinding {
+        enabled = true
+    }
+
     buildTypes {
         release {
             minifyEnabled false

app/src/main/java/dev/andrewkemp/diceroller/MainActivity.kt

@@ -2,11 +2,31 @@ package dev.andrewkemp.diceroller
 
 import androidx.appcompat.app.AppCompatActivity
 import android.os.Bundle
+import dev.andrewkemp.diceroller.databinding.ActivityMainBinding
+import kotlinx.android.synthetic.main.activity_main.*
+import java.util.*
 
 class MainActivity : AppCompatActivity() {
+    private lateinit var binding: ActivityMainBinding
+
+    companion object {
+        const val DICE_SIDES = 6
+    }
 
     override fun onCreate(savedInstanceState: Bundle?) {
         super.onCreate(savedInstanceState)
-        setContentView(R.layout.activity_main)
+        binding = ActivityMainBinding.inflate(layoutInflater)
+        val view = binding.root
+        setContentView(view)
+
+        roll_button.setOnClickListener() {
+            rollDice()
+        }
     }
+
+    private fun rollDice() {
+        val rollResult = Random().nextInt(DICE_SIDES + 1)
+        dice_result.text = rollResult.toString()
+    }
+
 }

app/src/main/res/layout/activity_main.xml

@@ -1,18 +1,25 @@
 <?xml version="1.0" encoding="utf-8"?>
-<androidx.constraintlayout.widget.ConstraintLayout xmlns:android="http://schemas.android.com/apk/res/android"
-    xmlns:app="http://schemas.android.com/apk/res-auto"
+<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
     xmlns:tools="http://schemas.android.com/tools"
     android:layout_width="match_parent"
-    android:layout_height="match_parent"
+    android:layout_height="wrap_content"
+    android:orientation="vertical"
+    android:layout_gravity="center_vertical"
     tools:context=".MainActivity">
 
     <TextView
+        android:id="@+id/dice_result"
         android:layout_width="wrap_content"
         android:layout_height="wrap_content"
-        android:text="Hello World!"
-        app:layout_constraintBottom_toBottomOf="parent"
-        app:layout_constraintLeft_toLeftOf="parent"
-        app:layout_constraintRight_toRightOf="parent"
-        app:layout_constraintTop_toTopOf="parent" />
+        android:layout_gravity="center_horizontal"
+        android:text="1"
+        android:textSize="30sp" />
 
-</androidx.constraintlayout.widget.ConstraintLayout>
+    <Button
+        android:id="@+id/roll_button"
+        android:layout_width="wrap_content"
+        android:layout_height="wrap_content"
+        android:layout_gravity="center_horizontal"
+        android:text="@string/roll" />
+
+</LinearLayout>

app/src/main/res/values/strings.xml

@@ -1,3 +1,4 @@
 <resources>
     <string name="app_name">Dice Roller</string>
+    <string name="roll">Roll</string>
 </resources>