Please note that the contents of this offline web site may be out of date. To access the most recent documentation visit the online version .
Note that links that point to online resources are green in color and will open in a new window.
We would love it if you could give us feedback about this material by filling this form (You have to be online to fill it)
Android APIs
public final class

PowerManager.WakeLock

extends Object
java.lang.Object
   ↳ android.os.PowerManager.WakeLock

Class Overview

A wake lock is a mechanism to indicate that your application needs to have the device stay on.

Any application using a WakeLock must request the android.permission.WAKE_LOCK permission in an <uses-permission> element of the application's manifest. Obtain a wake lock by calling newWakeLock(int, String) .

Call acquire() to acquire the wake lock and force the device to stay on at the level that was requested when the wake lock was created.

Call release() when you are done and don't need the lock anymore. It is very important to do this as soon as possible to avoid running down the device's battery excessively.

Summary

Public Methods
void acquire ()
Acquires the wake lock.
void acquire (long timeout)
Acquires the wake lock with a timeout.
boolean isHeld ()
Returns true if the wake lock has been acquired but not yet released.
void release ()
Releases the wake lock.
void setReferenceCounted (boolean value)
Sets whether this WakeLock is reference counted.
void setWorkSource ( WorkSource ws)
Sets the work source associated with the wake lock.
String toString ()
Returns a string containing a concise, human-readable description of this object.
Protected Methods
void finalize ()
Invoked when the garbage collector has detected that this instance is no longer reachable.
[Expand]
Inherited Methods
From class java.lang.Object

Public Methods

public void acquire ()

Added in API level 1

Acquires the wake lock.

Ensures that the device is on at the level requested when the wake lock was created.

public void acquire (long timeout)

Added in API level 1

Acquires the wake lock with a timeout.

Ensures that the device is on at the level requested when the wake lock was created. The lock will be released after the given timeout expires.

Parameters
timeout The timeout after which to release the wake lock, in milliseconds.

public boolean isHeld ()

Added in API level 1

Returns true if the wake lock has been acquired but not yet released.

Returns
  • True if the wake lock is held.

public void release ()

Added in API level 1

Releases the wake lock.

This method releases your claim to the CPU or screen being on. The screen may turn off shortly after you release the wake lock, or it may not if there are other wake locks still held.

public void setReferenceCounted (boolean value)

Added in API level 1

Sets whether this WakeLock is reference counted.

Wake locks are reference counted by default. If a wake lock is reference counted, then each call to acquire() must be balanced by an equal number of calls to release() . If a wake lock is not reference counted, then one call to release() is sufficient to undo the effect of all previous calls to acquire() .

Parameters
value True to make the wake lock reference counted, false to make the wake lock non-reference counted.

public void setWorkSource ( WorkSource ws)

Added in API level 9

Sets the work source associated with the wake lock.

The work source is used to determine on behalf of which application the wake lock is being held. This is useful in the case where a service is performing work on behalf of an application so that the cost of that work can be accounted to the application.

Parameters
ws The work source, or null if none.

public String toString ()

Added in API level 1

Returns a string containing a concise, human-readable description of this object. Subclasses are encouraged to override this method and provide an implementation that takes into account the object's type and data. The default implementation is equivalent to the following expression: 

          getClass().getName() + '@' + Integer.toHexString(hashCode())

See Writing a useful toString method if you intend implementing your own toString method.

Returns
  • a printable representation of this object.

Protected Methods

protected void finalize ()

Added in API level 1

Invoked when the garbage collector has detected that this instance is no longer reachable. The default implementation does nothing, but this method can be overridden to free resources.

Note that objects that override finalize are significantly more expensive than objects that don't. Finalizers may be run a long time after the object is no longer reachable, depending on memory pressure, so it's a bad idea to rely on them for cleanup. Note also that finalizers are run on a single VM-wide finalizer thread, so doing blocking work in a finalizer is a bad idea. A finalizer is usually only necessary for a class that has a native peer and needs to call a native method to destroy that peer. Even then, it's better to provide an explicit close method (and implement Closeable ), and insist that callers manually dispose of instances. This works well for something like files, but less well for something like a BigInteger where typical calling code would have to deal with lots of temporaries. Unfortunately, code that creates lots of temporaries is the worst kind of code from the point of view of the single finalizer thread.

If you must use finalizers, consider at least providing your own ReferenceQueue and having your own thread process that queue.

Unlike constructors, finalizers are not automatically chained. You are responsible for calling super.finalize() yourself.

Uncaught exceptions thrown by finalizers are ignored and do not terminate the finalizer thread. See Effective Java Item 7, "Avoid finalizers" for more.

Throws
Throwable