java.lang.Object | |||||
↳ | android.content.Context | ||||
↳ | android.content.ContextWrapper | ||||
↳ | android.view.ContextThemeWrapper | ||||
↳ | android.app.Activity | ||||
↳ | android.app.ActivityGroup |
Known Direct Subclasses
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A screen that contains and runs multiple embedded activities.
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Inherited Constants | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
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From class
android.app.Activity
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From class
android.content.Context
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Public Constructors | |||||||||||
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Public Methods | |||||||||||
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Protected Methods | |||||||||||
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Called when the activity is starting.
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Perform any final cleanup before an activity is destroyed.
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Called as part of the activity lifecycle when an activity is going into
the background, but has not (yet) been killed.
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Called after
onRestoreInstanceState(Bundle) , onRestart() , or
onPause() , for your activity to start interacting with the user. | |||||||||||
Called to retrieve per-instance state from an activity before being killed
so that the state can be restored in
onCreate(Bundle) or
onRestoreInstanceState(Bundle) (the Bundle populated by this method
will be passed to both). | |||||||||||
Called when you are no longer visible to the user.
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From class android.app.Activity
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From class android.view.ContextThemeWrapper
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From class android.content.ContextWrapper
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From class android.content.Context
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From class java.lang.Object
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From interface android.content.ComponentCallbacks
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From interface android.view.KeyEvent.Callback
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From interface android.view.LayoutInflater.Factory
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From interface android.view.View.OnCreateContextMenuListener
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From interface android.view.Window.Callback
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Called when the activity is starting. This is where most initialization
should go: calling setContentView(int)
to inflate the
activity's UI, using findViewById(int)
to programmatically interact
with widgets in the UI, calling
managedQuery(android.net.Uri, String[], String, String[], String)
to retrieve
cursors for data being displayed, etc.
You can call finish()
from within this function, in
which case onDestroy() will be immediately called without any of the rest
of the activity lifecycle (onStart()
, onResume()
,
onPause()
, etc) executing.
Derived classes must call through to the super class's implementation of this method. If they do not, an exception will be thrown.
savedInstanceState | If the activity is being re-initialized after
previously being shut down then this Bundle contains the data it most
recently supplied in onSaveInstanceState(Bundle) . Note: Otherwise it is null. |
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Perform any final cleanup before an activity is destroyed. This can
happen either because the activity is finishing (someone called
finish()
on it, or because the system is temporarily destroying
this instance of the activity to save space. You can distinguish
between these two scenarios with the isFinishing()
method.
Note: do not count on this method being called as a place for
saving data! For example, if an activity is editing data in a content
provider, those edits should be committed in either onPause()
or
onSaveInstanceState(Bundle)
, not here. This method is usually implemented to
free resources like threads that are associated with an activity, so
that a destroyed activity does not leave such things around while the
rest of its application is still running. There are situations where
the system will simply kill the activity's hosting process without
calling this method (or any others) in it, so it should not be used to
do things that are intended to remain around after the process goes
away.
Derived classes must call through to the super class's implementation of this method. If they do not, an exception will be thrown.
Called as part of the activity lifecycle when an activity is going into
the background, but has not (yet) been killed. The counterpart to
onResume()
.
When activity B is launched in front of activity A, this callback will
be invoked on A. B will not be created until A's onPause()
returns,
so be sure to not do anything lengthy here.
This callback is mostly used for saving any persistent state the activity is editing, to present a "edit in place" model to the user and making sure nothing is lost if there are not enough resources to start the new activity without first killing this one. This is also a good place to do things like stop animations and other things that consume a noticeable mount of CPU in order to make the switch to the next activity as fast as possible, or to close resources that are exclusive access such as the camera.
In situations where the system needs more memory it may kill paused
processes to reclaim resources. Because of this, you should be sure
that all of your state is saved by the time you return from
this function. In general onSaveInstanceState(Bundle)
is used to save
per-instance state in the activity and this method is used to store
global persistent data (in content providers, files, etc.)
After receiving this call you will usually receive a following call
to onStop()
(after the next activity has been resumed and
displayed), however in some cases there will be a direct call back to
onResume()
without going through the stopped state.
Derived classes must call through to the super class's implementation of this method. If they do not, an exception will be thrown.
Called after onRestoreInstanceState(Bundle)
, onRestart()
, or
onPause()
, for your activity to start interacting with the user.
This is a good place to begin animations, open exclusive-access devices
(such as the camera), etc.
Keep in mind that onResume is not the best indicator that your activity
is visible to the user; a system window such as the keyguard may be in
front. Use onWindowFocusChanged(boolean)
to know for certain that your
activity is visible to the user (for example, to resume a game).
Derived classes must call through to the super class's implementation of this method. If they do not, an exception will be thrown.
Called to retrieve per-instance state from an activity before being killed
so that the state can be restored in onCreate(Bundle)
or
onRestoreInstanceState(Bundle)
(the Bundle
populated by this method
will be passed to both).
This method is called before an activity may be killed so that when it
comes back some time in the future it can restore its state. For example,
if activity B is launched in front of activity A, and at some point activity
A is killed to reclaim resources, activity A will have a chance to save the
current state of its user interface via this method so that when the user
returns to activity A, the state of the user interface can be restored
via onCreate(Bundle)
or onRestoreInstanceState(Bundle)
.
Do not confuse this method with activity lifecycle callbacks such as
onPause()
, which is always called when an activity is being placed
in the background or on its way to destruction, or onStop()
which
is called before destruction. One example of when onPause()
and
onStop()
is called and not this method is when a user navigates back
from activity B to activity A: there is no need to call onSaveInstanceState(Bundle)
on B because that particular instance will never be restored, so the
system avoids calling it. An example when onPause()
is called and
not onSaveInstanceState(Bundle)
is when activity B is launched in front of activity A:
the system may avoid calling onSaveInstanceState(Bundle)
on activity A if it isn't
killed during the lifetime of B since the state of the user interface of
A will stay intact.
The default implementation takes care of most of the UI per-instance
state for you by calling onSaveInstanceState()
on each
view in the hierarchy that has an id, and by saving the id of the currently
focused view (all of which is restored by the default implementation of
onRestoreInstanceState(Bundle)
). If you override this method to save additional
information not captured by each individual view, you will likely want to
call through to the default implementation, otherwise be prepared to save
all of the state of each view yourself.
If called, this method will occur before onStop()
. There are
no guarantees about whether it will occur before or after onPause()
.
outState | Bundle in which to place your saved state. |
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Called when you are no longer visible to the user. You will next
receive either onRestart()
, onDestroy()
, or nothing,
depending on later user activity.
Note that this method may never be called, in low memory situations
where the system does not have enough memory to keep your activity's
process running after its onPause()
method is called.
Derived classes must call through to the super class's implementation of this method. If they do not, an exception will be thrown.