When to use the context of application, when to use the context of activity

Transfer from http://www.jcodecraeer.com/a/anzhuokaifa/androidkaifa/2015/0526/2935.html

Single-case mode with application context
See if the period of use is within the activity cycle, if exceeded, must use application; Common scenarios include: Asynctask,thread, third-party library initialization, and so on.

There are also situations where you can only use activity: for example, dialog boxes, various view, startactivity, etc.

If the UI control needs to use activity as the context object, the default toast can actually be used with ApplicationContext.

It is important to note that some numbers have been added to the number, which is actually a yes in terms of ability, but why no. One explanation below:

Number 1: Starting the activity is possible in these classes, but a new task needs to be created. Generally not recommended.

Number 2: It is legal to go to layout inflate in these classes, but use the system default theme style If you customize some styles that might not be used.

Number 3: Allowed when receiver is null, in version 4.2 or later, to get the current value of the sticky broadcast. (Can be ignored)

Note: ContentProvider, broadcastreceiver in the above table, because there is a context in its internal method for use.

OK, here we look at the table, focusing on activity and application, you can see that the UI-related methods are not recommended or not to use application, and the first three operations are almost impossible to appear in application. In fact, as long as the grasp of a point, any UI-related, should use Activity as the context to deal with, and some other operations, service,activity,application and other instances can, of course, attention to the context of the holding of references, Prevent memory leaks.