My Ultimate Guide to Android Activities

Starting off in my leveling up of my Android development skills is to "master" the Activity in Android implementation and all its quirkiness and idiosyncrasies.

So far these are the things I would like to cover (I will add others when I discover them):

• Lifecycle
• gotchas
• Passing objects and values between Activities
• Saved instances
• How to test
• Configuration changes
• Starting an activity from a different app
• Intents and its filters
• Tasks and Back Stack

I will not do a tutorial here and put into my own words existing references about Android Activities. Instead I'll just put links here for my future reference. But it is a must that what I have put in here are already read (and digested).

• http://developer.android.com/reference/android/app/Activity.html
• http://developer.android.com/guide/components/activities.html
• http://developer.android.com/guide/components/activities.html#actstate
• http://developer.android.com/guide/topics/resources/runtime-changes.html
• http://developer.android.com/training/basics/activity-lifecycle/index.html
• http://developer.android.com/guide/components/intents-filters.html

Some tidbits that I know now that I missed before:

• the EditText widget saves any text entered by the user and the CheckBox widget saves whether it's checked or not. The only work required by you is to provide a unique ID (with the android:id attribute) for each widget you want to save its state. If a widget does not have an ID, then the system cannot save its state.
• The system will not call onPause() and onStop() if finish() is called within the Activity's onCreate() method. In this case, onDestroy() is called right away.
• I should declare Intent's Extra constant strings with the full package name of my app