How to perform some action from my App when the user opens some other application in his device + Android

Basically I want to do the below through my App,

1. Identify user has opened an application in his device
2. Get the opened application meta data like name,version etc.,
3. Perform some action based on the application he opened

How to perform above steps?

Than开发者_StackOverflow中文版ks, poddroid

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