Welcome
Android Application Development

Table of Contents

Course Intro, Android Studio Setup, Interface Walkthrough

Mobile OS History: Android vs. iOS

Android vs. iOS: Key Numbers (2024)

Top 3 Apps (2024)

*Based on total global downloads (2024)

Top Tools for Android and iOS Development

• Android Studio – Official IDE for Android development
• Xcode – Official IDE for iOS/macOS development
• Flutter – Cross-platform UI toolkit by Google
• React Native – JavaScript framework for building native apps
• Firebase – Backend services for real-time apps
• CocoaPods – Dependency manager for iOS projects
• Fastlane – Automation tool for app releases

Links open in new tabs. Most tools support both platforms or offer platform-specific advantages.

Regular vs Android Software

Android Architecture

Image source: GeeksforGeeks

Android Project Structure, Calculator

Android Project Structure

• src/main/java/ - Kotlin files
• src/main/res/layout/ - XML UI files
• AndroidManifest.xml - Declare Activities

One activity + layout for calculator app.

Layout XML (activity_main.xml)

    <LinearLayout
        android:orientation="vertical"
        android:padding="16dp"
        android:layout_width="match_parent"
        android:layout_height="match_parent">

        <EditText android:id="@+id/etNumber1" ... />
        <EditText android:id="@+id/etNumber2" ... />
        <Button android:id="@+id/btnAdd" ... />
        <TextView android:id="@+id/tvResult" ... />
    </LinearLayout>
                    

Where to Store Layout

Save XML at:

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

Used by MainActivity via setContentView().

MainActivity.kt Location

Path:

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

Basic activity code skeleton:

    class MainActivity : AppCompatActivity() {
        override fun onCreate(savedInstanceState: Bundle?) {
            super.onCreate(savedInstanceState)
            setContentView(R.layout.activity_main)
        }
    }
                    

onCreate() & setContentView()

onCreate() // : Activity start point

setContentView() // : Load UI from XML.

Accessing Views

    val et1 = findViewById<EditText>(R.id.etNumber1)
    val et2 = findViewById<EditText>(R.id.etNumber2)
    val btn = findViewById<Button>(R.id.btnAdd)
    val tv = findViewById<TextView>(R.id.tvResult)
                    

Use these to read inputs and update output.

Button Click Listener

    btn.setOnClickListener {
    // code when clicked
    }
      

Put calculation logic here.

Read Input Values

    val num1 = et1.text.toString().toDoubleOrNull() ?: 0.0
    val num2 = et2.text.toString().toDoubleOrNull() ?: 0.0
      

Safe conversion with default 0.0

Calculate & Show Result

    val result = num1 + num2
    tv.text = "Result: $result"
      

override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        setContentView(R.layout.activity_main)
        val et1 = findViewById<EditText>(R.id.etNumber1)
        val et2 = findViewById<EditText>(R.id.etNumber2)
        val btn = findViewById<Button>(R.id.btnAdd)
        val tv = findViewById<TextView>(R.id.tvResult)
        btn.setOnClickListener {
            val num1 = et1.text.toString().toDoubleOrNull() ?: 0.0
            val num2 = et2.text.toString().toDoubleOrNull() ?: 0.0
            val result = num1 + num2
            tv.text = "Result: $result"
        }
    }

<LinearLayout
    android:orientation="vertical"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    xmlns:android="http://schemas.android.com/apk/res/android">
    <TextView
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="Vertical Layout Example" />
    <LinearLayout
        android:orientation="horizontal"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:paddingTop="16dp">
        <Button
            android:layout_width="0dp"
            android:layout_weight="1"
            android:layout_height="wrap_content"
            android:text="Button 1" />
        <Button
            android:layout_width="0dp"
            android:layout_weight="1"
            android:layout_height="wrap_content"
            android:text="Button 2" />
    </LinearLayout>
</LinearLayout>

Common Kotlin Syntax in Android

<manifest xmlns:android="http://schemas.android.com/apk/res/android" package="com.example.app">
    <application
        android:allowBackup="true"
        android:label="@string/app_name"
        android:icon="@mipmap/ic_launcher"
        android:roundIcon="@mipmap/ic_launcher_round"
        android:supportsRtl="true"
        android:theme="@style/AppTheme">
        <activity android:name=".MainActivity">
            <intent-filter>
                <action android:name="android.intent.action.MAIN" />
                <category android:name="android.intent.category.LAUNCHER" />
            </intent-filter>
        </activity>
    </application>
</manifest>