Kotlin, how to use getParcelable to keep state across rotation?

Question

I'm trying to use parcelable to maintain state when rotating my device.

val VehiclesParcelable = VehiclesModel()

override fun onSaveInstanceState(outState: Bundle, outPersistentState: PersistableBundle) {
    super.onSaveInstanceState(outState, outPersistentState)
    outState.putParcelable(KEY, VehiclesParcelable)
}

override fun onRestoreInstanceState(savedInstanceState: Bundle) {
    super.onRestoreInstanceState(savedInstanceState)
    if(savedInstanceState != null) {
        savedInstanceState.getParcelable<VehiclesModel>(KEY)
    }
}

I can't figure out how to use the getParcelable, it says it's deprecated, if I try to use the newer version (that says I need to include the class?) getParcelable(KEY, VehiclesModel) I get "type mismatch".

I'm pretty sure I'm putting in the second argument incorrectly.

How do I use the new version? All I find about it just use it like I did in the code above.

Answer 1

I can't figure out how to use the getParcelable, it says it's deprecated

As of API level 33, the one-argument getParcelable (String key) is deprecated. Starting from API level 33, you need to include the class as a second argument using the two-argument version getParcelable (String key, Class<T> clazz)

In Kotlin, the KClass formula is used to represent a class, but to get a Java Class instance corresponding to a given KClass instance, extend that with ".java" suffix (documentation reference). This would be in your model "VehiclesModel::class.java".

So, to fix the deprecation after API level 33:

override fun onRestoreInstanceState(savedInstanceState: Bundle) {
    super.onRestoreInstanceState(savedInstanceState)

    if (Build.VERSION.SDK_INT < Build.VERSION_CODES.TIRAMISU) // API 33
        @Suppress("DEPRECATION")
        savedInstanceState.getParcelable<VehiclesModel>(KEY)
    else
        savedInstanceState.getParcelable(KEY, VehiclesModel::class.java)
}

Side notes:

• The condition if(savedInstanceState != null) has been removed because the savedInstanceState argument is not nullable.
• The VehiclesModel model class is typically a data class, and that expects a constructor with one argument at least, check here. So, you need to fix that in val VehiclesParcelable = VehiclesModel() statement.
• ViewModel would be a typical tool instead of onSaveInstaceState() if you just want to survive configuration changes.

---

Update for the bountied part

how would you solve the bountied part? I'm using Java so I'm using if (savedInstanceState != null) instead of a method onRestoreInstanceState.

Even if you're using Java, the the savedInstanceState is annotated with @NonNull; so it shouldn't be null; instead you'd worry if the getParcelable() returned null in case the key was wrong.

The code in java, you'd use Bitmap.class instead of the OP VehiclesModel:

String KEY = "stateOfImageView";

@Override
protected void onSaveInstanceState(@NonNull Bundle savedInstanceState) {
    super.onSaveInstanceState(savedInstanceState);
    BitmapDrawable drawable = (BitmapDrawable) imageView.getDrawable();
    Bitmap bitmap = drawable.getBitmap();
    savedInstanceState.putParcelable(KEY, bitmap);
}

@Override
protected void onRestoreInstanceState(@NonNull Bundle savedInstanceState) {
    super.onRestoreInstanceState(savedInstanceState);

    Bitmap bitmap;
    if (Build.VERSION.SDK_INT < Build.VERSION_CODES.TIRAMISU) // API 33
        bitmap = savedInstanceState.getParcelable(KEY);
    else
        bitmap = savedInstanceState.getParcelable(KEY, Bitmap.class);
    ...
}