First Android app in Android Kotlin - Build, Publish & Deploy

Build & Publish - First Android app

Performance Impact

Your first Android app is usually simple, so it has minimal impact on device performance. It typically runs smoothly at 60 frames per second (fps) because it has few UI elements and little background processing.

Memory use is low, often under 50MB, which is safe for all devices. Battery drain is minimal since the app does not do heavy work or use sensors.

💻

How to Optimize for 60fps Rendering

Keep your UI simple and avoid complex animations in your first app. Use Android's recommended layouts like ConstraintLayout for efficient rendering.

Load images and resources efficiently by using optimized formats and sizes. Avoid blocking the main thread with long tasks; use background threads or Kotlin coroutines.

Test your app on real devices and use Android Studio's profiler tools to check frame rates and memory usage.

Impact on App Bundle Size and Startup Time

Your first app is usually very small, often under 5MB, which means it downloads quickly and installs fast.

Keep your app size small by including only necessary resources and libraries. Avoid large images or unused code.

Startup time is usually under 1 second for simple apps, providing a good user experience.

iOS vs Android Differences

Android apps use Kotlin or Java and run on a wide range of devices with different screen sizes and hardware.

iOS apps use Swift or Objective-C and run only on Apple devices with more uniform hardware.

Android apps are packaged as APK or AAB files, while iOS apps use IPA files.

Android apps can be published on Google Play Store, which has a faster review process (hours to days), while iOS apps go through Apple App Store review, which takes 24-48 hours.

Store Review Guidelines and Requirements

• Follow Google Play Store policies: no harmful content, respect user privacy, and use permissions responsibly.
• Sign your app with a secure key before publishing.
• Provide a clear app description, screenshots, and privacy policy.
• Test your app thoroughly to avoid crashes or bugs that cause rejection.
• Ensure your app targets the latest Android SDK version as required by Google Play.

Self-Check: Your app takes 5 seconds to load this screen. What's likely wrong?

Common issues include loading large resources on the main thread, doing heavy work during startup, or inefficient layout rendering.

To fix this, move long tasks to background threads, optimize images and resources, and simplify your UI layout.

Key Result

Your first Android app is lightweight and runs smoothly with minimal memory and battery use. Optimize UI and resource loading to maintain 60fps and fast startup. Follow Google Play guidelines for smooth publishing.

Practice

1. What is the role of the MainActivity class in a simple Android app?

easy

A. It controls what the user sees by loading the layout and handling interactions.

B. It stores user data permanently on the device.

C. It manages network connections for the app.

D. It compiles the app code into machine language.

Solution

1. Step 1: Understand MainActivity's purpose

   MainActivity is the entry point of the app that sets the screen content.

2. Step 2: Identify its function in UI

   It loads the layout file which defines what the user sees and handles user actions.

3. Final Answer:

   It controls what the user sees by loading the layout and handling interactions. -> Option A

4. Quick Check:

   MainActivity controls UI = A [OK]

Hint: MainActivity sets the screen content and user interaction [OK]

Common Mistakes:

• Confusing MainActivity with data storage classes
• Thinking MainActivity handles network tasks
• Believing MainActivity compiles code

2. Which of the following is the correct way to set the content view in MainActivity using Kotlin?

easy

A. setContentView(R.id.activity_main)

B. setContentView(R.layout.activity_main)

C. setContentView(activity_main.xml)

D. setContentView("activity_main")

Solution

1. Step 1: Recall setContentView syntax

   In Kotlin, setContentView expects a layout resource ID, accessed as R.layout.filename.

2. Step 2: Match correct resource reference

   R.layout.activity_main correctly points to the layout XML file named activity_main.xml.

3. Final Answer:

   setContentView(R.layout.activity_main) -> Option B

4. Quick Check:

   Layout resource ID = R.layout.filename [OK]

Hint: Use R.layout.filename to reference layout files [OK]

Common Mistakes:

• Using string names instead of resource IDs
• Confusing layout and id resources
• Including file extensions in code

3. Given this Kotlin code in MainActivity:

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

What will the user see when the app runs?

medium

A. A blank white screen with no text

B. An error message because onCreate is missing a return type

C. Nothing, the app will crash immediately

D. The layout defined in activity_main.xml displayed on screen

Solution

1. Step 1: Understand onCreate behavior

   onCreate is called when the app starts and sets the UI with setContentView.

2. Step 2: Effect of setContentView

   It loads the layout file activity_main.xml, so the user sees that layout on screen.

3. Final Answer:

   The layout defined in activity_main.xml displayed on screen -> Option D

4. Quick Check:

   setContentView loads layout = C [OK]

Hint: onCreate sets UI with setContentView(layout) [OK]

Common Mistakes:

• Thinking onCreate needs a return type
• Assuming no UI appears without extra code
• Confusing layout with id resources

4. What is wrong with this MainActivity code snippet?

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

medium

A. setContentView should be called outside onCreate

B. savedInstanceState should be nullable (Bundle?)

C. super.onCreate(savedInstanceState) must be called before setContentView

D. onCreate must return a value

Solution

1. Step 1: Check onCreate call order

   super.onCreate must be called first to properly initialize the activity.

2. Step 2: Identify correct order

   Calling setContentView before super.onCreate causes errors or unexpected behavior.

3. Final Answer:

   super.onCreate(savedInstanceState) must be called before setContentView -> Option C

4. Quick Check:

   super.onCreate first = B [OK]

Hint: Always call super.onCreate first inside onCreate [OK]

Common Mistakes:

• Calling setContentView before super.onCreate
• Using non-nullable Bundle parameter
• Expecting onCreate to return a value

5. You want your first Android app to show a greeting message centered on a white background. Which layout XML snippet achieves this?

hard

A.

B.

C.

D.

Solution

1. Step 1: Check layout size and background

   uses match_parent for width and height and sets background to white (#FFFFFF).

2. Step 2: Verify text centering

   android:gravity=\"center\" centers the TextView inside the LinearLayout.

3. Final Answer:

   -> Option A

4. Quick Check:

   Center gravity + white background = A [OK]

Hint: Use LinearLayout with gravity=center and background=#FFFFFF [OK]

Common Mistakes:

• Using wrap_content for parent layout size
• Missing gravity=center for centering
• Not setting background color