How to resume Android app where it was suspended (app not Activity)

Question

How can I have my Android app resume where it last was, i.e. the Activity in view, etc.? If I am showing an Activity and press the Home button and then launch my app again it returns to the startup activity. I'd like it to work like an iPhone app where it suspends in place and resumes back to where the user last was.

Thank you.

Answer 1

You may need to set android:alwaysRetainTaskState="true" for your root activity in the manifest. From the documentation:

Whether or not the state of the task that the activity is in will always be maintained by the system — "true" if it will be, and "false" if the system is allowed to reset the task to its initial state in certain situations. The default value is "false". This attribute is meaningful only for the root activity of a task; it's ignored for all other activities.

Normally, the system clears a task (removes all activities from the stack above the root activity) in certain situations when the user re-selects that task from the home screen. Typically, this is done if the user hasn't visited the task for a certain amount of time, such as 30 minutes.

However, when this attribute is "true", users will always return to the task in its last state, regardless of how they get there. This is useful, for example, in an application like the web browser where there is a lot of state (such as multiple open tabs) that users would not like to lose.

Answer 2

Be sure to save any information you want in your onPause method and check that information in onResume. This will let the app reload any information that was communicated. Some widgets keep state but others don't.

Additionally when an an activity is killed it's onSaveInstanceState method is called. So anything that needs to be stored to persistent memory should be done there.