Activity Context VS getApplicationContext(): Quando utilizar ?

Qualquer desenvolvedor Android já se deparou com o problema de ter que usar a referência da própria Activity ao invés de usar getApplicationContext(). Tanto Activity e getApplicationContext() são  instâncias de Context, porém a diferença é que Activity possui o contexto da própria Activity, e getApplicationContext() é o Context da Aplicação.

Uma aplicação Android possui diversos tipos de Context, tais como:

• Activity
• Application
• Service
• BroadcastReceiver
• ContentProvider

Quando utilizar Activity, getApplicationContext() e etc ?

Depois de pesquisar um pouco, encontrei uma tabela indicando quando utilizar cada caso:

	Application	Activity	Service	ContentProvider	BroadcastReceiver
Show a Dialog	NO	YES	NO	NO	NO
Start an Activity	NO1	YES	NO1	NO1	NO1
Layout Inflation	NO2	YES	NO2	NO2	NO2
Start a Service	YES	YES	YES	YES	YES
Bind to a Service	YES	YES	YES	YES	NO
Send a Broadcast	YES	YES	YES	YES	YES
Register BroadcastReceiver	YES	YES	YES	YES	NO3
Load Resource Values	YES	YES	YES	YES	YES

 

1. An application CAN start an Activity from here, but it requires that a new task be created.  This may fit specific use cases, but can create non-standard back stack behaviors in your application and is generally not recommended or considered good practice.
2. This is legal, but inflation will be done with the default theme for the system on which you are running, not what’s defined in your application.
3. Allowed if the receiver is null, which is used for obtaining the current value of a sticky broadcast, on Android 4.2 and above.

Fonte: https://possiblemobile.com/2013/06/context/