Mastering Kotlin

Handling savedInstanceState

Kotlin allows us to perform null-safe method calls on variables that may, or may not, be null. One example of how this can reduce boilerplate in our code is in the handling of savedInstanceState.

A common pattern is to check whether savedInstanceState is non-null within onCreate(), and if it is, handle the restoration of that state. We can see an example of this in the following code snippet:

override fun onCreate(savedInstanceState: Bundle?) {    super.onCreate(savedInstanceState)    setContentView(R.layout.activity_details)        savedInstanceState?.let { it }}fun restoreSavedState(savedInstanceState: Bundle) {    // restore state}

Using a null-safe call to the let() function, we can safely restore our state only if savedInstanceState ...