Android SDK and API levels in Android Kotlin - Cheat Sheet & Quick Revision

Recall & Review

beginner

What is the Android SDK?

The Android SDK is a set of tools and libraries that developers use to build Android apps. It includes things like the Android platform, emulator, and build tools.

beginner

What does API level mean in Android development?

API level is a number that represents the version of the Android platform. It helps developers know which features and behaviors are available on a device.

intermediate

Why is it important to set a minimum SDK version in your Android app?

Setting a minimum SDK version ensures your app only runs on devices that support the features you use. It prevents crashes on older devices.

intermediate

What is the difference between compileSdkVersion and targetSdkVersion?

compileSdkVersion is the Android version you use to build your app. targetSdkVersion tells the system which Android version your app is designed for, affecting runtime behavior.

intermediate

How can you check the API level of a device programmatically in Kotlin?

You can check the API level using: val apiLevel = android.os.Build.VERSION.SDK_INT. This returns the device's API level as an integer.

What does the API level number represent in Android?

A The number of apps installed

B The version of the Android platform

C The device screen size

D The app's version code

API level corresponds to the Android platform version, indicating available features.

Which SDK version should you set to ensure your app uses the latest Android features during build?

A compileSdkVersion

B targetSdkVersion

C minSdkVersion

D maxSdkVersion

compileSdkVersion defines the Android version used to compile your app.

If your app's minSdkVersion is 21, what does this mean?

A The app supports all API levels

B The app targets API level 21

C The app only runs on devices with API level 21 or higher

D The app compiles with API level 21

minSdkVersion sets the lowest API level your app supports.

What happens if you run an app on a device with an API level lower than minSdkVersion?

A The app crashes or won't install

B The app runs normally

C The app updates the device's API level

D The app runs in compatibility mode

Devices with API levels below minSdkVersion cannot install or run the app.

How do you get the current device API level in Kotlin?

A android.device.apiLevel

B System.getApiLevel()

C Build.VERSION_CODE

D android.os.Build.VERSION.SDK_INT

android.os.Build.VERSION.SDK_INT returns the device's API level.

Explain the roles of minSdkVersion, targetSdkVersion, and compileSdkVersion in Android app development.

Think about compatibility and build process.

Describe why understanding API levels is important when developing Android apps.

Consider how devices differ by Android version.

Practice

1. What does the minSdk version specify in an Android app?

easy

A. The latest Android version available

B. The Android version you compile your app against

C. The Android version your app is optimized for

D. The oldest Android version your app can run on

Solution

1. Step 1: Understand minSdk meaning

   minSdk defines the minimum Android version that can run the app.

2. Step 2: Differentiate from other SDK versions

   compileSdk is for building, targetSdk is optimization, but minSdk is the oldest supported version.

3. Final Answer:

   The oldest Android version your app can run on -> Option D

4. Quick Check:

   minSdk = oldest supported version [OK]

Hint: minSdk means minimum Android version supported [OK]

Common Mistakes:

• Confusing minSdk with compileSdk
• Thinking minSdk is the target optimization version
• Assuming minSdk is the latest Android version

2. Which of the following is the correct way to set the compileSdk version to 33 in a Kotlin DSL Gradle file?

easy

A. compileSdkVersion 33

B. compileSdkVersion = 33

C. compileSdk = 33

D. compileSdk(33)

Solution

1. Step 1: Identify Kotlin DSL syntax for compileSdk

   In Kotlin DSL, compileSdk is assigned directly with =.

2. Step 2: Compare options

   compileSdkVersion 33 is Groovy syntax without assignment, compileSdkVersion = 33 uses the wrong property name, and compileSdk(33) is invalid function call syntax. Only compileSdk = 33 is correct.

3. Final Answer:

   compileSdk = 33 -> Option C

4. Quick Check:

   Kotlin DSL uses compileSdk = 33 [OK]

Hint: Kotlin DSL uses equals sign for assignments [OK]

Common Mistakes:

• Using Groovy syntax in Kotlin DSL
• Omitting equals sign
• Using method call syntax incorrectly

3. Given this Gradle configuration snippet:

android {
  compileSdk = 31
  minSdk = 21
  targetSdk = 30
}

What is the highest Android version your app is optimized for?

medium

A. 30

B. 21

C. 31

D. Cannot determine from this

Solution

1. Step 1: Identify meaning of targetSdk

   targetSdk is the Android version the app is optimized for and tested against.

2. Step 2: Check given values

   Here, targetSdk is 30, so the app is optimized for Android 30.

3. Final Answer:

   30 -> Option A

4. Quick Check:

   targetSdk = 30 means optimized for Android 30 [OK]

Hint: targetSdk shows optimization version, not compileSdk [OK]

Common Mistakes:

• Confusing compileSdk with targetSdk
• Thinking minSdk is optimization version
• Choosing compileSdk as optimization version

4. You set minSdk = 30 but want your app to run on Android 21 devices. What is the problem in this Gradle config?

android {
  compileSdk = 33
  minSdk = 30
  targetSdk = 33
}

medium

A. compileSdk must be lower than minSdk

B. minSdk is too high, app won't run on Android 21

C. targetSdk must be equal to minSdk

D. No problem, app runs on all versions

Solution

1. Step 1: Understand minSdk role

   minSdk sets the lowest Android version the app supports.

2. Step 2: Check compatibility with Android 21

   Since minSdk is 30, devices with Android 21 cannot run the app.

3. Final Answer:

   minSdk is too high, app won't run on Android 21 -> Option B

4. Quick Check:

   minSdk = 30 excludes Android 21 devices [OK]

Hint: minSdk must be ≤ lowest Android version supported [OK]

Common Mistakes:

• Thinking compileSdk affects device compatibility
• Assuming targetSdk limits device support
• Believing app runs on all versions regardless of minSdk

5. You want to use a new Android feature introduced in API level 31 but still support devices running API level 21. How should you configure your Gradle file to safely use this feature?

hard

A. Set minSdk = 21, targetSdk = 31, and use runtime checks for API 31 features

B. Set minSdk = 21 and targetSdk = 21

C. Set minSdk = 31 and targetSdk = 31

D. Set compileSdk = 21 and minSdk = 31

Solution

1. Step 1: Understand minSdk and targetSdk roles

   minSdk is the oldest supported version; targetSdk is the optimized version.

2. Step 2: Use runtime checks for new features

   To support API 21 devices but use API 31 features, keep minSdk = 21, set targetSdk = 31, and check API level at runtime before using new features.

3. Step 3: Evaluate options

   Set minSdk = 21, targetSdk = 31, and use runtime checks for API 31 features correctly sets minSdk and targetSdk and mentions runtime checks. Others either restrict support or use wrong compileSdk.

4. Final Answer:

   Set minSdk = 21, targetSdk = 31, and use runtime checks for API 31 features -> Option A

5. Quick Check:

   minSdk low + targetSdk high + runtime checks = safe feature use [OK]

Hint: Use runtime API checks to support older devices safely [OK]

Common Mistakes:

• Raising minSdk and losing older device support
• Not using runtime checks for new APIs
• Setting compileSdk lower than targetSdk