Not Just Rotation: Configuration Changes on Android

Rotation changes aren't the only types of configuration changes you'll see in your Android apps. Let's look at what configurations are, and how to work with, or around, Activity restarts that result from configuration changes.

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1. Not Just Rotation Configuration Changes on Android Nicole Borrelli Developer Programs Engineer for Android at Google
2. Not Just Rotation Configuration Changes on Android Nicole Borrelli Developer Programs Engineer for Android at Google
3. What is a Configuration
4. What is a Configuration • Orientation • Screen width and height • Screen layout • Font Scale • Pixel Density • UI Mode
5. What’s Changing
6. What's Changing • Rotation • Split Screen/Multi-Window • Picture-in-Picture • Multi-Display • Folding
7. Responding to Configuration Changes
8. Responding to Configuration Changes • Do nothing
9. Responding to Configuration Changes • Do nothing
10. Responding to Configuration Changes • Use onSaveInstanceState • Use a ViewModel • Handle the configuration change
11. Saving Instance State Pros: • Always works • Required for maintaining state Cons: • Limited State • Can be slow
12. Cons: • Can't save data through process death Use a ViewModel Pros: • Unrestricted data • Fast updates
13. Use a ViewModel Adapter LiveData Scroll position
14. Handle the Configuration Change Pros • Fastest Cons • Edge cases • Risk of poor UX
15. Handling Configuration Changes <activity
 android:name=".MainActivity"
 android:configChanges="screenSize"
 ...>
 …
 </activity>
16. Handling Configuration Changes <activity
 android:name=".MainActivity"
 android:configChanges="screenSize"
 android:supportsPictureInPicture="true"
 ...>
 …
 </activity>
17. Handling Configuration Changes <activity
 android:name=".MainActivity"
 android:configChanges="screenSize"
 android:supportsPictureInPicture="true"
 ...>
 …
 </activity>
18. Handling Configuration Changes <activity
 android:name=".MainActivity"
 android:configChanges="orientation
 |screenLayout|screenSize"
 android:supportsPictureInPicture="true"
 ...>
 …
 </activity>
19. Handling Configuration Changes <activity
 android:name=".MainActivity"
 android:configChanges="orientation
 |screenLayout|screenSize"
 android:supportsPictureInPicture="true"
 ...>
 …
 </activity>
20. Handling Configuration Changes <activity
 android:name=".MainActivity"
 android:configChanges="orientation
 |screenLayout|screenSize"
 android:supportsPictureInPicture="true"
 ...>
 …
 </activity>
21. Handling Configuration Changes <activity
 android:name=".MainActivity"
 android:configChanges="orientation
 |screenLayout|screenSize"
 android:supportsPictureInPicture="true"
 ...>
 …
 </activity>
22. Handling Configuration Changes class MainActivity : AppCompatActivity() {
 private val config = Configuration()
 override fun onCreate(savedInstanceState: Bundle?) {
 super.onCreate(savedInstanceState)
 // Set the initial configuration.
 config.setTo(resources.configuration)
 // …
 }
 }
23. Handling Configuration Changes override fun onConfigurationChanged(newConfig: Configuration) {
 super.onConfigurationChanged(newConfig)
 
 if (newConfig.screenLayout != config.screenLayout) {
 setContentView(R.layout.activity_main)
 
 val isToolBarShown = supportActionBar?.isShowing ?: true
 toolbar = findViewById(R.id.toolbar)
 setSupportActionBar(toolbar)
 if (!isToolBarShown) supportActionBar?.hide()
 }
 // Save new config
 config.setTo(newConfig)
 }
24. Handling Configuration Changes override fun onConfigurationChanged(newConfig: Configuration) {
 super.onConfigurationChanged(newConfig)
 
 if (newConfig.screenLayout != config.screenLayout) {
 setContentView(R.layout.activity_main)
 
 val isToolBarShown = supportActionBar?.isShowing ?: true
 toolbar = findViewById(R.id.toolbar)
 setSupportActionBar(toolbar)
 if (!isToolBarShown) supportActionBar?.hide()
 }
 // Save new config
 config.setTo(newConfig)
 }
25. How to decide? • Instance state • ViewModel • Handle it yourself
26. Key Take-away Don't take for granted what can and cannot changes after your app has been launched. Anything can change.
27. Thank you! Nicole Borrelli Developer Programs Engineer for Android at Google