I have built an app for Android Wear that needs to measure the motion (accelerometer) sensors continuously for an hour or so for data collection purposes. During operation, I have had problems with the device going into ambient mode (or sleep) and slowing down (or shutting off) the sensors.
As a result, I am using the following command to lock the screen on and it seems to work. But it also seems wasteful, since I dont actually need the screen on, just the sensors running.
getWindow().clearFlags(WindowManager.LayoutParams.FLAG_KEEP_SCREEN_ON); // Allow going to sleep
CUrrently, I have the onSensorsChanged() method in the main activity. I am willing to put it in a service, but from what I understand that won't help if it is still in the main UI thread. I could put it in its own thread, but I'm not sure that that will present Ambient Mode from slowing the sensors.
Questions:
1) Is there way to prevent ambient mode? Or if detected to turn it off?
2) If the sensors are in their own service/thread, can I let the activity go to sleep and still maintain sensor collection at full rate?
3) If the sensors are in their own service/thread, can I still send data over the dataapi to the phone?
Thanks.
1) Use a wake lock. To keep the CPU awake but let the screen go dim, you can use code like the following:
PowerManager powerMgr = (PowerManager) getSystemService(Context.POWER_SERVICE);
wakeLock = powerMgr.newWakeLock(PowerManager.PARTIAL_WAKE_LOCK, TAG);
wakeLock.acquire(duration);
where TAG is a string to indicate the component holding the wake lock, and duration is measured in milliseconds.
I assume I don't need to warn you about the adverse battery effects of keeping the device from going into ambient. An average Wear device may or may not last for the solid hour you're proposing.
2) Yes. This is kind of the definition of a Service, "an application component representing either an application's desire to perform a longer-running operation while not interacting with the user" (from https://developer.android.com/reference/android/app/Service.html).
3) Yes. I do this in a number of apps; there's no requirement that Data API calls need to be on the UI thread.
Related
If I have an IntentService that simply updates the SharedPreference, is a (partial) WakeLock needed?
I understand that a WakeLock keeps the CPU awake, but when is it needed?
If you need to keep the CPU running in order to complete some work before the device goes to sleep, you can use a PowerManager system service feature called wake locks. Wake locks allow your application to control the power state of the host device.
Creating and holding wake locks can have a dramatic impact on the host device's battery life. Thus you should use wake locks only when strictly necessary and hold them for as short a time as possible. For example, you should never need to use a wake lock in an activity.
One legitimate case for using a wake lock might be a background service that needs to grab a wake lock to keep the CPU running to do work while the screen is off. Again, though, this practice should be minimized because of its impact on battery life.
Unfortunately, some poorly-coded, malicious, or simply buggy apps might create an abnormal amount of undesirable wakelocks. Other apps require constant Internet access in order to operate in a normal fashion - Facebook and Messenger are probably the most popular representatives. They persistently request information from the web (the so-called "polling" for new events), which is causing subsequent wakelocks.
In other cases, an update to a given app can also cause certain issues, which usually result in partial wakelocks. The latter keep your CPU constantly humming in the background, sometimes without your knowledge, and prevent your device from "going to sleep". That's a pretty substantial prerequisite for anomalous battery drain. Thus, it is advisable to regularly monitor the wakelocks on your device and see which of your apps go harsh on our system's resources.
Read more at:
What-are-wakelocks-how-they-affect-the-battery-life-of-your-Android-device-and-how-to-Greenify
Reference: https://developer.android.com/training/scheduling/wakelock.html
It is needed when you don't want CPU to sleep when user locks the screen for example.
If you have an IntentService without acquired WakeLock it will pause after a while if user locks the screen and it will continue its work when user wakes a device. With WakeLock acquired your service will work even if the screen is locked.
As #My God mentioned, it impacts on battery life a lot, so, use it only when you really need to finish some operation and you cannot wait till user wakes a device.
I have a scenario that the android device exchanges data with a FTP server via Roaming service. I hope to make OS enter proper sleep mode by setting WakeLock type during the data transferring because it really has no interaction with enduser.
I am going through the sleep threads and trying to verifying that what units will be shut down in sleep mode to prevent data sending. So far, no official doc indicates them .
So , Would you please help to enlighten me on the questions: When Android enters sleep mode , what components will stop working , like WIFI , Data Roaming ?
Thanks a lot.
When Android enters sleep mode, almost everything is shut off. Only basic system apps and GSM/CDMA radios are left on to receive texts, calls, push notifications etc. Services, Activities are all shut off, and the CPU is put into a low power mode. Depending on what the user chose in the wifi settings, the wifi connection may or may not switch to mobile data or shut off completely.
If you want to keep processing, but don't need the screen on to interact with the user, you should acquire a PARTIAL_WAKE_LOCK in which the screen and keyboard are off, but the CPU is kept on. However, remember to release the wake lock when you are done, as PARTIAL_WAKE_LOCK is the only one of the four wake locks in which the CPU will continue to run until you release it or your app is killed. Forgetting to release the wake lock can be a huge drain on the user's battery.
When the power off button (lights off) is pressed by user then phone into sleep mode.
Sleep mode means CPU will be in sleep mode and will accept only command from radio interface layer and alarms. Within fraction of seconds the CPU will go into sleep mode.
When we need only CPU on and other things off we use PARTIAL_WAKE_LOCK which suits perfect in your scenario. Weather this lock is generally used in apps like mp3 player etc.
As you want data transfer here in this mode then you have to override already given methods from class PowerManager with specifically by allowing some function to be turned on in this mode.
I am currently developing an app that runs a service from time to time. Currently, the service acquires a wakelock, reads some sensors and sends some information over WIFI (if any). Now what I want to know is weather a wakelock influences sensors and connectivity or not. Is it possible to do these tasks without any wakelock?
Cheers
A wake lock is essentially used to lock the device in an "awake" state, in which the CPU will be on, and the screen may or may not be on.
It is not possible to do these tasks without a wakelock if the phone is in sleep otherwise, as then the CPU is also in sleep mode. However, if the user is using the device for something else, and your app is in the background, you can do these tasks without a wakelock.
Keep in mind that almost everything you're doing is battery intensive (sensors, WiFi, wakelock) and you should not do it too often so that you don't degrade the user's battery life.
I have service running in android to sync files when user wants.
This is not a 24/7 service, only runs for a period of file transfers over wifi, so the user when done transferring files quits the app and therefore the service exits.
So the scenario could be that user has left the mobile and it might get locked/screen off automatically.
Regardless of screen on or off is there a way to ensure wifi is always performing the same with low latency ?
There are multiple apis in relation to this, Wifi lock, Wifi-sleep-policy, screen lock .. People seem to use a combination of them to keep good wireless performance .
Is wifi lock enough to ensure it ? or do I need to use combination of APIs ?
Thank you.
EDIT: this post was helpful
PARTIAL_WAKE_LOCK vs SCREEN_DIM_WAKE_LOCK in download thread
To be on the safe side, a WifiLock as well as a WakeLock would be optimal, with the WakeLock being the more important lock to aquire. The WakeLock ensures the device stays on, and the WifiLock ensures the radio is operating. This should ensure consistent latency. However, you can't expect anything when it comes to data transfers so have your app be ready to handle random connection losses.
I am developing an android application and I want to reduce the power consumption. The method I believe is to put the phone into sleep mode whenever the user activity stops for a certain threshold period. I have three questions regarding this.
If I release the wakeLock and no other application is holding the wakeLock after how much time would the phone go to sleep?
I have multiple HandlerThreads running where I use sendMessageDelayed() function. Would these messages get delivered even after the phone goes to sleep mode?
Does putting the phone into aeroplane mode save more power rather than just putting the phone to sleep. if yes, then why is it because the only difference in those two modes is the use of cellular network.
If I release the wakeLock and no other application is holding the
wakeLock after how much time would the phone go to sleep?
There really is no definitive answer, but, from personal experience, I'd say it is likely that it will happen within 30 seconds to 1 minute.
I have multiple HandlerThreads running where I use
sendMessageDelayed() function. Would these messages get delivered even
after the phone goes to sleep mode?
I really wouldn't count on it because I've never seen anything that says it will wake up the device to send said Message. You can always test it, but I wouldn't trust it to work because the documentation does not claim that it will.
Does putting the phone into aeroplane mode save more power rather than
just putting the phone to sleep. if yes, then why is it because the
only difference in those two modes is the use of cellular network.
If you put it into sleep mode AND airplane mode, then you will save more battery than JUST sleep mode.
The reason for that is that even with the CPU pretty much asleep, the phone must keep a constant connection with the cellular network in order to know if you get a text or phone call. To do this, it must use the battery to constantly keep the antenna turned on. If you put it into airplane mode, it would basically turn the antenna off, and then the phone would not be using battery for that function.