Any Android developer has encountered the problem of having to use the Activity’s own reference instead of using getApplicationContext(). Both Activity and getApplicationContext() are instances of Context, but the difference is that Activity has the context of the Activity itself, and getApplicationContext() is the Context of the Application.
An Android application has several types of Context, such as:
- Activity
- Application
- Service
- BroadcastReceiver
- ContentProvider
When to use Activity, getApplicationContext() and so on ?
After a bit of research, I found a table indicating when to use each case:
| 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 |
- 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.
- 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.
- Allowed if the receiver is null, which is used for obtaining the current value of a sticky broadcast, on Android 4.2 and above.
Source: https://possiblemobile.com/2013/06/context/
