android.content.ComponentCallbacks2 |
Known Indirect Subclasses |
Extended ComponentCallbacks
interface with a new callback for
finer-grained memory management. This interface is available in all application components
(Activity
, Service
,
ContentProvider
, and Application
).
You should implement onTrimMemory(int)
to incrementally release memory based on current
system constraints. Using this callback to release your resources helps provide a more
responsive system overall, but also directly benefits the user experience for
your app by allowing the system to keep your process alive longer. That is,
if you don't trim your resources based on memory levels defined by this callback,
the system is more likely to kill your process while it is cached in the least-recently used
(LRU) list, thus requiring your app to restart and restore all state when the user returns to it.
The values provided by onTrimMemory(int)
do not represent a single linear progression of
memory limits, but provide you different types of clues about memory availability:
TRIM_MEMORY_RUNNING_MODERATE
TRIM_MEMORY_RUNNING_LOW
TRIM_MEMORY_RUNNING_CRITICAL
TRIM_MEMORY_UI_HIDDEN
TRIM_MEMORY_BACKGROUND
TRIM_MEMORY_MODERATE
TRIM_MEMORY_COMPLETE
To support API levels lower than 14, you can use the onLowMemory()
method as a
fallback that's roughly equivalent to the TRIM_MEMORY_COMPLETE
level.
Note: When the system begins killing processes in the LRU list, although it primarily works bottom-up, it does give some consideration to which processes are consuming more memory and will thus provide more gains in memory if killed. So the less memory you consume while in the LRU list overall, the better your chances are to remain in the list and be able to quickly resume.
More information about the different stages of a process lifecycle (such as what it means to be placed in the background LRU list) is provided in the Processes and Threads document.
Constants | |||||||||||
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int | TRIM_MEMORY_BACKGROUND | Level for onTrimMemory(int) : the process has gone on to the
LRU list. |
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int | TRIM_MEMORY_COMPLETE | Level for onTrimMemory(int) : the process is nearing the end
of the background LRU list, and if more memory isn't found soon it will
be killed. |
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int | TRIM_MEMORY_MODERATE | Level for onTrimMemory(int) : the process is around the middle
of the background LRU list; freeing memory can help the system keep
other processes running later in the list for better overall performance. |
|||||||||
int | TRIM_MEMORY_RUNNING_CRITICAL | Level for onTrimMemory(int) : the process is not an expendable
background process, but the device is running extremely low on memory
and is about to not be able to keep any background processes running. |
|||||||||
int | TRIM_MEMORY_RUNNING_LOW | Level for onTrimMemory(int) : the process is not an expendable
background process, but the device is running low on memory. |
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int | TRIM_MEMORY_RUNNING_MODERATE | Level for onTrimMemory(int) : the process is not an expendable
background process, but the device is running moderately low on memory. |
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int | TRIM_MEMORY_UI_HIDDEN | Level for onTrimMemory(int) : the process had been showing
a user interface, and is no longer doing so. |
Public Methods | |||||||||||
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Called when the operating system has determined that it is a good
time for a process to trim unneeded memory from its process.
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[Expand]
Inherited Methods | |||||||||||
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From interface
android.content.ComponentCallbacks
|
Level for onTrimMemory(int)
: the process has gone on to the
LRU list. This is a good opportunity to clean up resources that can
efficiently and quickly be re-built if the user returns to the app.
Level for onTrimMemory(int)
: the process is nearing the end
of the background LRU list, and if more memory isn't found soon it will
be killed.
Level for onTrimMemory(int)
: the process is around the middle
of the background LRU list; freeing memory can help the system keep
other processes running later in the list for better overall performance.
Level for onTrimMemory(int)
: the process is not an expendable
background process, but the device is running extremely low on memory
and is about to not be able to keep any background processes running.
Your running process should free up as many non-critical resources as it
can to allow that memory to be used elsewhere. The next thing that
will happen after this is onLowMemory()
called to report that
nothing at all can be kept in the background, a situation that can start
to notably impact the user.
Level for onTrimMemory(int)
: the process is not an expendable
background process, but the device is running low on memory.
Your running process should free up unneeded resources to allow that
memory to be used elsewhere.
Level for onTrimMemory(int)
: the process is not an expendable
background process, but the device is running moderately low on memory.
Your running process may want to release some unneeded resources for
use elsewhere.
Level for onTrimMemory(int)
: the process had been showing
a user interface, and is no longer doing so. Large allocations with
the UI should be released at this point to allow memory to be better
managed.
Called when the operating system has determined that it is a good time for a process to trim unneeded memory from its process. This will happen for example when it goes in the background and there is not enough memory to keep as many background processes running as desired. You should never compare to exact values of the level, since new intermediate values may be added -- you will typically want to compare if the value is greater or equal to a level you are interested in.
To retrieve the processes current trim level at any point, you can
use ActivityManager.getMyMemoryState(RunningAppProcessInfo)
.
level | The context of the trim, giving a hint of the amount of
trimming the application may like to perform. May be
TRIM_MEMORY_COMPLETE , TRIM_MEMORY_MODERATE ,
TRIM_MEMORY_BACKGROUND , TRIM_MEMORY_UI_HIDDEN ,
TRIM_MEMORY_RUNNING_CRITICAL , TRIM_MEMORY_RUNNING_LOW ,
or TRIM_MEMORY_RUNNING_MODERATE .
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