Q: Android activity state, unable to get information saved There are a bunch of other questions about this topic, but I have not been able to figure this issue out.
In the Android documentation (http://developer.android.com/training/basics/activity-lifecycle/recreating.html) it says:

By default, the system uses the Bundle instance state to save information about each View object in your activity layout (such as the text value entered into an EditText object). So, if your activity instance is destroyed and recreated, the state of the layout is restored to its previous state with no code required by you. 

So I tested this in the emulator by simply creating a view that contains a EditText-view. I then enter information into it and press the home button. When I reopen the app, the information is gone. Shouldnt this be persisted automatically or am I missing something?

A: Well you are partially wrong and partially right. You are wrong, because the quotation in grey is taken out of the context. I'll explain briefly, by making the correct quotations from the link you provided:

When your activity is destroyed because the user presses Back or the
  activity finishes itself, the system's concept of that Activity
  instance is gone forever because the behavior indicates the activity
  is no longer needed. However, if the system destroys the activity due
  to system constraints (rather than normal app behavior), then although
  the actual Activity instance is gone, the system remembers that it
  existed such that if the user navigates back to it, the system creates
  a new instance of the activity using a set of saved data that
  describes the state of the activity when it was destroyed.

Now, after that paragraph we have a clarification:

Caution: Your activity will be destroyed and recreated each time the
  user rotates the screen. When the screen changes orientation, the
  system destroys and recreates the foreground activity because the
  screen configuration has changed and your activity might need to load
  alternative resources (such as the layout).

Another one, several linew below is:

To save additional data about the activity state, you must override
  the onSaveInstanceState() callback method. The system calls this
  method when the user is leaving your activity and passes it the Bundle
  object that will be saved in the event that your activity is destroyed
  unexpectedly. If the system must recreate the activity instance later,
  it passes the same Bundle object to both the onRestoreInstanceState()
  and onCreate() methods.

This Bundle (Bundle savedInstanceState) is used, when the application accidentally crashes OR if the rotation of the screen is enabled (to name few), which is also destoying (then recreating) your foreground.
You can also take a look at the following section "Save Your Activity State", but I would recommend you this link here.
