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PowerManager

public final class PowerManager
extends Object

java.lang.Object
   ↳ android.os.PowerManager


This class gives you control of the power state of the device.

Device battery life will be significantly affected by the use of this API. Do not acquire PowerManager.WakeLocks unless you really need them, use the minimum levels possible, and be sure to release them as soon as possible.

You can obtain an instance of this class by calling Context.getSystemService().

The primary API you'll use is newWakeLock(). This will create a PowerManager.WakeLock object. You can then use methods on the wake lock object to control the power state of the device.

In practice it's quite simple:

PowerManager pm = (PowerManager) getSystemService(Context.POWER_SERVICE);
 PowerManager.WakeLock wl = pm.newWakeLock(PowerManager.SCREEN_DIM_WAKE_LOCK, "My Tag");
 wl.acquire();
   ..screen will stay on during this section..
 wl.release();
 

The following wake lock levels are defined, with varying effects on system power. These levels are mutually exclusive - you may only specify one of them.

Flag Value CPU Screen Keyboard
PARTIAL_WAKE_LOCK On* Off Off
SCREEN_DIM_WAKE_LOCK On Dim Off
SCREEN_BRIGHT_WAKE_LOCK On Bright Off
FULL_WAKE_LOCK On Bright Bright

*If you hold a partial wake lock, the CPU will continue to run, regardless of any display timeouts or the state of the screen and even after the user presses the power button. In all other wake locks, the CPU will run, but the user can still put the device to sleep using the power button.

In addition, you can add two more flags, which affect behavior of the screen only. These flags have no effect when combined with a PARTIAL_WAKE_LOCK.

Flag Value Description
ACQUIRE_CAUSES_WAKEUP Normal wake locks don't actually turn on the illumination. Instead, they cause the illumination to remain on once it turns on (e.g. from user activity). This flag will force the screen and/or keyboard to turn on immediately, when the WakeLock is acquired. A typical use would be for notifications which are important for the user to see immediately.
ON_AFTER_RELEASE If this flag is set, the user activity timer will be reset when the WakeLock is released, causing the illumination to remain on a bit longer. This can be used to reduce flicker if you are cycling between wake lock conditions.

Any application using a WakeLock must request the android.permission.WAKE_LOCK permission in an <uses-permission> element of the application's manifest.

Summary

Nested classes

class PowerManager.WakeLock

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

Constants

int ACQUIRE_CAUSES_WAKEUP

Wake lock flag: Turn the screen on when the wake lock is acquired.

String ACTION_DEVICE_IDLE_MODE_CHANGED

Intent that is broadcast when the state of isDeviceIdleMode() changes.

String ACTION_POWER_SAVE_MODE_CHANGED

Intent that is broadcast when the state of isPowerSaveMode() changes.

int FULL_WAKE_LOCK

This constant was deprecated in API level 17. Most applications should use FLAG_KEEP_SCREEN_ON instead of this type of wake lock, as it will be correctly managed by the platform as the user moves between applications and doesn't require a special permission.

int ON_AFTER_RELEASE

Wake lock flag: When this wake lock is released, poke the user activity timer so the screen stays on for a little longer.

int PARTIAL_WAKE_LOCK

Wake lock level: Ensures that the CPU is running; the screen and keyboard backlight will be allowed to go off.

int PROXIMITY_SCREEN_OFF_WAKE_LOCK

Wake lock level: Turns the screen off when the proximity sensor activates.

int RELEASE_FLAG_WAIT_FOR_NO_PROXIMITY

Flag for WakeLock.release(int): Defer releasing a PROXIMITY_SCREEN_OFF_WAKE_LOCK wake lock until the proximity sensor indicates that an object is not in close proximity.

int SCREEN_BRIGHT_WAKE_LOCK

This constant was deprecated in API level 13. Most applications should use FLAG_KEEP_SCREEN_ON instead of this type of wake lock, as it will be correctly managed by the platform as the user moves between applications and doesn't require a special permission.

int SCREEN_DIM_WAKE_LOCK

This constant was deprecated in API level 17. Most applications should use FLAG_KEEP_SCREEN_ON instead of this type of wake lock, as it will be correctly managed by the platform as the user moves between applications and doesn't require a special permission.

Public methods

boolean isDeviceIdleMode()

Returns true if the device is currently in idle mode.

boolean isIgnoringBatteryOptimizations(String packageName)

Return whether the given application package name is on the device's power whitelist.

boolean isInteractive()

Returns true if the device is in an interactive state.

boolean isPowerSaveMode()

Returns true if the device is currently in power save mode.

boolean isScreenOn()

This method was deprecated in API level 20. Use isInteractive() instead.

boolean isSustainedPerformanceModeSupported()

This function checks if the device has implemented Sustained Performance Mode.

boolean isWakeLockLevelSupported(int level)

Returns true if the specified wake lock level is supported.

PowerManager.WakeLock newWakeLock(int levelAndFlags, String tag)

Creates a new wake lock with the specified level and flags.

void reboot(String reason)

Reboot the device.

Inherited methods

From class java.lang.Object

Constants

ACQUIRE_CAUSES_WAKEUP

Added in API level 1
int ACQUIRE_CAUSES_WAKEUP

Wake lock flag: Turn the screen on when the wake lock is acquired.

Normally wake locks don't actually wake the device, they just cause the screen to remain on once it's already on. Think of the video player application as the normal behavior. Notifications that pop up and want the device to be on are the exception; use this flag to be like them.

Cannot be used with PARTIAL_WAKE_LOCK.

Constant Value: 268435456 (0x10000000)

ACTION_DEVICE_IDLE_MODE_CHANGED

Added in API level 23
String ACTION_DEVICE_IDLE_MODE_CHANGED

Intent that is broadcast when the state of isDeviceIdleMode() changes. This broadcast is only sent to registered receivers.

Constant Value: "android.os.action.DEVICE_IDLE_MODE_CHANGED"

ACTION_POWER_SAVE_MODE_CHANGED

Added in API level 21
String ACTION_POWER_SAVE_MODE_CHANGED

Intent that is broadcast when the state of isPowerSaveMode() changes. This broadcast is only sent to registered receivers.

Constant Value: "android.os.action.POWER_SAVE_MODE_CHANGED"

FULL_WAKE_LOCK

Added in API level 1
int FULL_WAKE_LOCK

This constant was deprecated in API level 17.
Most applications should use FLAG_KEEP_SCREEN_ON instead of this type of wake lock, as it will be correctly managed by the platform as the user moves between applications and doesn't require a special permission.

Wake lock level: Ensures that the screen and keyboard backlight are on at full brightness.

If the user presses the power button, then the FULL_WAKE_LOCK will be implicitly released by the system, causing both the screen and the CPU to be turned off. Contrast with PARTIAL_WAKE_LOCK.

Constant Value: 26 (0x0000001a)

ON_AFTER_RELEASE

Added in API level 1
int ON_AFTER_RELEASE

Wake lock flag: When this wake lock is released, poke the user activity timer so the screen stays on for a little longer.

Will not turn the screen on if it is not already on. See ACQUIRE_CAUSES_WAKEUP if you want that.

Cannot be used with PARTIAL_WAKE_LOCK.

Constant Value: 536870912 (0x20000000)

PARTIAL_WAKE_LOCK

Added in API level 1
int PARTIAL_WAKE_LOCK

Wake lock level: Ensures that the CPU is running; the screen and keyboard backlight will be allowed to go off.

If the user presses the power button, then the screen will be turned off but the CPU will be kept on until all partial wake locks have been released.

Constant Value: 1 (0x00000001)

PROXIMITY_SCREEN_OFF_WAKE_LOCK

Added in API level 21
int PROXIMITY_SCREEN_OFF_WAKE_LOCK

Wake lock level: Turns the screen off when the proximity sensor activates.

If the proximity sensor detects that an object is nearby, the screen turns off immediately. Shortly after the object moves away, the screen turns on again.

A proximity wake lock does not prevent the device from falling asleep unlike FULL_WAKE_LOCK, SCREEN_BRIGHT_WAKE_LOCK and SCREEN_DIM_WAKE_LOCK. If there is no user activity and no other wake locks are held, then the device will fall asleep (and lock) as usual. However, the device will not fall asleep while the screen has been turned off by the proximity sensor because it effectively counts as ongoing user activity.

Since not all devices have proximity sensors, use isWakeLockLevelSupported(int) to determine whether this wake lock level is supported.

Cannot be used with ACQUIRE_CAUSES_WAKEUP.

Constant Value: 32 (0x00000020)

RELEASE_FLAG_WAIT_FOR_NO_PROXIMITY

Added in API level 21
int RELEASE_FLAG_WAIT_FOR_NO_PROXIMITY

Flag for WakeLock.release(int): Defer releasing a PROXIMITY_SCREEN_OFF_WAKE_LOCK wake lock until the proximity sensor indicates that an object is not in close proximity.

Constant Value: 1 (0x00000001)

SCREEN_BRIGHT_WAKE_LOCK

Added in API level 1
int SCREEN_BRIGHT_WAKE_LOCK

This constant was deprecated in API level 13.
Most applications should use FLAG_KEEP_SCREEN_ON instead of this type of wake lock, as it will be correctly managed by the platform as the user moves between applications and doesn't require a special permission.

Wake lock level: Ensures that the screen is on at full brightness; the keyboard backlight will be allowed to go off.

If the user presses the power button, then the SCREEN_BRIGHT_WAKE_LOCK will be implicitly released by the system, causing both the screen and the CPU to be turned off. Contrast with PARTIAL_WAKE_LOCK.

Constant Value: 10 (0x0000000a)

SCREEN_DIM_WAKE_LOCK

Added in API level 1
int SCREEN_DIM_WAKE_LOCK

This constant was deprecated in API level 17.
Most applications should use FLAG_KEEP_SCREEN_ON instead of this type of wake lock, as it will be correctly managed by the platform as the user moves between applications and doesn't require a special permission.

Wake lock level: Ensures that the screen is on (but may be dimmed); the keyboard backlight will be allowed to go off.

If the user presses the power button, then the SCREEN_DIM_WAKE_LOCK will be implicitly released by the system, causing both the screen and the CPU to be turned off. Contrast with PARTIAL_WAKE_LOCK.

Constant Value: 6 (0x00000006)

Public methods

isDeviceIdleMode

Added in API level 23
boolean isDeviceIdleMode ()

Returns true if the device is currently in idle mode. This happens when a device has been sitting unused and unmoving for a sufficiently long period of time, so that it decides to go into a lower power-use state. This may involve things like turning off network access to apps. You can monitor for changes to this state with ACTION_DEVICE_IDLE_MODE_CHANGED.

Returns
boolean Returns true if currently in active device idle mode, else false. This is when idle mode restrictions are being actively applied; it will return false if the device is in a long-term idle mode but currently running a maintenance window where restrictions have been lifted.

isIgnoringBatteryOptimizations

Added in API level 23
boolean isIgnoringBatteryOptimizations (String packageName)

Return whether the given application package name is on the device's power whitelist. Apps can be placed on the whitelist through the settings UI invoked by ACTION_IGNORE_BATTERY_OPTIMIZATION_SETTINGS.

Parameters
packageName String
Returns
boolean

isInteractive

Added in API level 20
boolean isInteractive ()

Returns true if the device is in an interactive state.

When this method returns true, the device is awake and ready to interact with the user (although this is not a guarantee that the user is actively interacting with the device just this moment). The main screen is usually turned on while in this state. Certain features, such as the proximity sensor, may temporarily turn off the screen while still leaving the device in an interactive state. Note in particular that the device is still considered to be interactive while dreaming (since dreams can be interactive) but not when it is dozing or asleep.

When this method returns false, the device is dozing or asleep and must be awoken before it will become ready to interact with the user again. The main screen is usually turned off while in this state. Certain features, such as "ambient mode" may cause the main screen to remain on (albeit in a low power state) to display system-provided content while the device dozes.

The system will send a screen on or screen off broadcast whenever the interactive state of the device changes. For historical reasons, the names of these broadcasts refer to the power state of the screen but they are actually sent in response to changes in the overall interactive state of the device, as described by this method.

Services may use the non-interactive state as a hint to conserve power since the user is not present.

Returns
boolean True if the device is in an interactive state.

See also:

isPowerSaveMode

Added in API level 21
boolean isPowerSaveMode ()

Returns true if the device is currently in power save mode. When in this mode, applications should reduce their functionality in order to conserve battery as much as possible. You can monitor for changes to this state with ACTION_POWER_SAVE_MODE_CHANGED.

Returns
boolean Returns true if currently in low power mode, else false.

isScreenOn

Added in API level 7
boolean isScreenOn ()

This method was deprecated in API level 20.
Use isInteractive() instead.

Returns true if the device is in an interactive state.

For historical reasons, the name of this method refers to the power state of the screen but it actually describes the overall interactive state of the device. This method has been replaced by isInteractive().

The value returned by this method only indicates whether the device is in an interactive state which may have nothing to do with the screen being on or off. To determine the actual state of the screen, use getState().

Returns
boolean True if the device is in an interactive state.

isSustainedPerformanceModeSupported

Added in API level 24
boolean isSustainedPerformanceModeSupported ()

This function checks if the device has implemented Sustained Performance Mode. This needs to be checked only once and is constant for a particular device/release. Sustained Performance Mode is intended to provide a consistent level of performance for prolonged amount of time. Applications should check if the device supports this mode, before using setSustainedPerformanceMode(boolean).

Returns
boolean Returns True if the device supports it, false otherwise.

See also:

isWakeLockLevelSupported

Added in API level 21
boolean isWakeLockLevelSupported (int level)

Returns true if the specified wake lock level is supported.

Parameters
level int: The wake lock level to check.
Returns
boolean True if the specified wake lock level is supported.

newWakeLock

Added in API level 1
PowerManager.WakeLock newWakeLock (int levelAndFlags, 
                String tag)

Creates a new wake lock with the specified level and flags.

The levelAndFlags parameter specifies a wake lock level and optional flags combined using the logical OR operator.

The wake lock levels are: PARTIAL_WAKE_LOCK, FULL_WAKE_LOCK, SCREEN_DIM_WAKE_LOCK and SCREEN_BRIGHT_WAKE_LOCK. Exactly one wake lock level must be specified as part of the levelAndFlags parameter.

The wake lock flags are: ACQUIRE_CAUSES_WAKEUP and ON_AFTER_RELEASE. Multiple flags can be combined as part of the levelAndFlags parameters.

Call acquire() on the object to acquire the wake lock, and release() when you are done.

PowerManager pm = (PowerManager)mContext.getSystemService(
                                          Context.POWER_SERVICE);
 PowerManager.WakeLock wl = pm.newWakeLock(
                                      PowerManager.SCREEN_DIM_WAKE_LOCK
                                      | PowerManager.ON_AFTER_RELEASE,
                                      TAG);
 wl.acquire();
 // ... do work...
 wl.release();
 

Although a wake lock can be created without special permissions, the WAKE_LOCK permission is required to actually acquire or release the wake lock that is returned.

If using this to keep the screen on, you should strongly consider using FLAG_KEEP_SCREEN_ON instead. This window flag will be correctly managed by the platform as the user moves between applications and doesn't require a special permission.

Parameters
levelAndFlags int: Combination of wake lock level and flag values defining the requested behavior of the WakeLock.
tag String: Your class name (or other tag) for debugging purposes.
Returns
PowerManager.WakeLock

See also:

reboot

Added in API level 8
void reboot (String reason)

Reboot the device. Will not return if the reboot is successful.

Requires the REBOOT permission.

Parameters
reason String: code to pass to the kernel (e.g., "recovery") to request special boot modes, or null.
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