chore: add GitHub Actions CI workflow

.github/workflows/android-ci.yml

@@ -0,0 +1,35 @@
+name: Android CI
+
+on:
+  push:
+    branches: [main]
+  pull_request:
+    branches: [main]
+
+concurrency:
+  group: ${{ github.workflow }}-${{ github.ref }}
+  cancel-in-progress: true
+
+jobs:
+  build:
+    runs-on: ubuntu-latest
+    timeout-minutes: 30
+
+    steps:
+      - uses: actions/checkout@v4
+
+      - name: Set up JDK 17
+        uses: actions/setup-java@v4
+        with:
+          java-version: '17'
+          distribution: 'temurin'
+          cache: gradle
+
+      - name: Build with Gradle
+        run: ./gradlew assembleDebug
+
+      - name: Run unit tests
+        run: ./gradlew testDebugUnitTest
+
+      - name: Run lint checks
+        run: ./gradlew lint

app/src/main/java/com/example/calculator_v01/CalculatorEngine.kt

@@ -0,0 +1,15 @@
+package com.example.calculator_v01
+
+import android.util.Log
+import com.udojava.evalex.Expression
+
+private const val TAG = "CALC"
+
+class CalculatorEngine {
+    fun eval(txt: String): String {
+        Log.i(TAG, "eval method -> String to evaluate: $txt")
+        val expression = Expression(txt)
+        expression.setPrecision(12)
+        return expression.eval().toString()
+    }
+}

app/src/main/java/com/example/calculator_v01/MainActivity.kt

@@ -2,19 +2,16 @@ package com.example.calculator_v01
 
 import androidx.appcompat.app.AppCompatActivity
 import android.os.Bundle
-import android.util.Log
 import android.view.View
 import android.widget.Button
 import android.widget.TextView
-import com.udojava.evalex.Expression
 import java.lang.ArithmeticException
 
-private const val TAG = "CALC"
-
 class MainActivity : AppCompatActivity() {
 
     private lateinit var calcOutput : TextView
     private lateinit var calcHist : TextView
+    private val engine = CalculatorEngine()
     private var buildString = ArrayList<String>()
     private var lastNumeric = false
     private var lastEqual = false
@@ -102,7 +99,7 @@ class MainActivity : AppCompatActivity() {
         }
     }
     private fun evalPercent(userInput:String):Double{
-        return eval(buildTextOutput() + "0").toDouble() * (userInput.toDouble() / 100)
+        return engine.eval(buildTextOutput() + "0").toDouble() * (userInput.toDouble() / 100)
     }
 
     fun onEqual(view:View){
@@ -111,7 +108,7 @@ class MainActivity : AppCompatActivity() {
             txt = buildTextOutput()
             txt += calcOutput.text.toString()
             try{
-                calcOutput.text = eval(txt)
+                calcOutput.text = engine.eval(txt)
                 onlyDec = true
             }catch (ex: ArithmeticException){
                 calcOutput.text = getString(R.string.error)
@@ -124,15 +121,7 @@ class MainActivity : AppCompatActivity() {
     }
 
 
-    fun eval(txt:String):String{
-        Log.i(TAG, "eval method -> String to evaluate: $txt")
-        val expression = Expression(txt)
-        expression.setPrecision(12)
-        return expression.eval().toString()
-    }
-
-    fun doNothing(){
-
+    fun doNothing(view: View) {
     }
 
     private fun stringToDbl(input:TextView):Double{

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

@@ -55,7 +55,7 @@
         <Button
                 android:id="@+id/btnLBracket"
                 android:text="@string/btnLBracket"
-                android:onClick=""
+                android:onClick="doNothing"
                 android:layout_width="0dp"
                 android:layout_height="match_parent"
                 android:layout_weight="@dimen/land_weight"

app/src/test/java/com/example/calculator_v01/MainActivityTest.kt

@@ -24,7 +24,7 @@ class TestCalcOutput(val input: String, val expected: String) {
 
     @Test
     fun evaluate_calculator_output() {
-        assertEquals(expected, MainActivity().eval(input))
-
+        val engine = CalculatorEngine()
+        assertEquals(expected, engine.eval(input))
     }
 }