Android 9 Development Cookbook - Third Edition

How it works...

All activities go through multiple states during their lifetime. By setting up callbacks to handle the events, we can have our code save important information before the activity is destroyed.

Step 3 is where the actual saving and restoring occurs. The OS sends a Bundle (a data object that also uses name/value pairs) to the methods. We use the onSaveInstanceState() callback to save the data and pull it out in the onRestoreInstanceState() callback.

But wait! Did you try typing text in the EditText view before rotating the device? If so, you'd have noticed that the text was also restored, but we don't have any code to handle that view. By default, the system will automatically save the state, provided it has a unique ID.

Note ...