I am running an accelerometer based android app that will run for a few months while phone is on and does nothing else. Some phone allow display not to go to sleep at all which allows my app run fine infinitely. The screen also has only a black display and nothing else apart from background accelerometer listener and occasional http posts. My question is if I remove the display screen while the app is running, would that stop the operating system and/or my app?
My question is if I remove the display screen while the app is running, would that stop the operating system and/or my app?
In short, it depends on your app architecture (otherwise i.e. music players would require to keep screen on to work). Depending on task you are really doing you may use Alarm Manager to periodically fire your code, or use Service.
I'm developing a security program that prevent moving phone without knowing its owner. When program is running when phone moves alarm will fire and show unlock screen to spot the alarm. The alarm can be stop by a password. But the problem is when use press and hold the power button, phone will shutdown. So is there any way to disable power button action?
So is there any way to disable power button action?
There is no way for an ordinary Android application to prevent the power button from functioning, for blindingly obvious security reasons.
It is conceivable that there are ways to accomplish this on rooted devices. Also, if you create your own custom ROM, you can integrate your alarm feature into it, blocking the power button operation while in the alarm state.
There is no way to work around this, because even if it was possible to prevent a shutdown, there would still be the option of simply removing the battery.
I have a very simple question. Can you force an app (from a development point of view) to run while the phone is off and plugged in. I know with my phone there is a battery display that shows while the phone is off and charging which I assume is controlled by software but I was wondering if that is possible with an app. After research my gut is telling me no but I want to make sure.
I know with my phone there is a battery display that shows while the phone is off and charging which I assume is controlled by software but I was wondering if that is possible with an app.
This is not possible from an app, only from firmware.
If you are not looking to update the screen, you can use a WakeLock to keep the CPU on. Or, use a different WakeLock and keep the screen on all of the time. Neither of these will make the user very happy, unless it is done completely under their control.
You will need create Service and on create or when you are about to do whatever your app does, create and acquire WakeLock. Once it's done you can startForeground to let user know that you are doing some important job and let Android to keep you alive/process and let your app finish work.
I read this unable to detect shake event when my phones screen is off in android article. But this question is differ from this.
I created an application which speak (using TextToSpeach API) time when I shake device. For that I have created a "Service" in which "ShakeListener" was registered. While I shake device, it will speak current time.
But this works fine while my device is "ON". When I lock my device, it stops working. Can any one elaborate what is the problem behind?
I think the problem here is that when you lock the device, it goes to sleep mode. And your ShakeListener doesn't receive shake events. The best way to implement what you want would be to register broadcast receiver to receive shake events. But as I know, android doesn't provide such broadcast. Another solution is to acuire a partial WakeLock. It'll prevent android from sleep. But of course it'll cause battery issues. Also take a look on this thread: Android accelerometer not working when screen is turned off
Probably you can not receive this notification until you patch some kernel implementation. Android doesn't broadcast such notification.
For this question I'm going to quote another user who got no response to their question:
I've written an Andoid app that uses the hardware Volume buttons for another purpose.
It works fine if the app is running and visible, but when I turn the
screen off or let it time out, the button clicks don't get into my
handlers.
Does anyone know if there is a way to detect these button clicks when
the screen is off?
Source: AV695's question
I'm working on an app myself that makes use of the volume buttons, but as this user also noted, the normal behavior of checking buttons with onKeyPress stops working once the screen is off. This is because the Activity gets paused on screen off.
Is there a way to keep the activity running while the screen is off, or check for the usage of the volume buttons when the screen is off? I tried using a Service for this before but it's impossible to check for the volume keys like that as noted by Commonsware.
I doubt that this is supported (without resorting to a battery-draining wakelock) at either the platform, kernel, or underlying radio firmware levels without modifications to the last to bring volume presses during sleep to the attention of the kernel.
Within the realm of reasonable system-ROM modifications, a more reasonable one might be to modify an existing open source ROM for the device to insert some custom platform level code into the handling of the power button usually used to wake up the device preparatory to unlocking it - that at least we know does get the attention of the kernel. That code could then inform the user by sound or vibration if there are unacknowledged notifications.
You could optionally wait briefly, check device orientation, or look for another key press to avoid doing this in an annoying way when the user is holding the device outside their pocket and trying to unlock it.
Or you could not use the volume key and just set a timer to wake up every 15 minutes and vibrate if there are unacknowledged notifications, avoiding the need to fumble in ones pockets.
You mention it's a custom request: if implies it's one off or low-volume, another option to consider would be that a few vendors have "bluetooth watches" out with an SDK that lets you push notifications from an android device.
If you can capture the notification when it's generated, you could push it to the user's wrist, and then let the phone go back to sleep.
You cannot intercept the key while your application is in background, but instead of listening to the KeyPress itself. You can register a ContentObserver, as described in this question.
As Chris Stratton mentioned, the only way to keep your App alive is by using battery-draining wake locks.
However, since I found myself in the same situation, I came up with another solution. Unfortunately, you'll need a rooted device as well as the Xposed framework.
With Xposed, which replaces the zygot process so you can hook yourself into any constructor and method of the system, you will be able to catch the raw KeyEvents before the system handles them.
This is done in PhoneWindowManager.interceptKeyBeforeQueueing(). By using a XC_MethodHook, you can use beforeHookedMethod() on the afore mentioned method to catch every hardware button event, even if the device is in deep sleep.
After catching events you are interested in, you can create a temporary wake lock to do your things but don't forget to release the wake lock after you finished your work.
A good example of how to accomplish this is the Xposed Torch Module.
If you, however, rely on a non rooted system, the bad news is that it's simply not possible without draining the battery...
I was also trying to implement volume button press detection in my app and I left that part to be developed later once the core part is done. I was able to detect volume key press while screen is on even when phone is locked, from a background service.
Background Video Recorder 2 (BVR2) (and possible BVR1 also, I did not try) is one of the apps that can detect volume key press even when screen is off. While trying to implement volume key detection while screen is off in my app, I installed BVR2, hoping to find how it works. To my surprise it gave my app the ablity to detect volume keys even when screen is off. My app had a ContentObserver to monitor volume changes, but was not working when screen is off. When BVR2 is active my app also could detect volume key press when screen is off. Still digging.
But BVR2 has its own trigger action, that is to record video, an action you may not want to occur just for the sake of you application detecting volume key presses.
Another app is QuickClick. This app can give your app what it lacks, the power to detect volume key presses even when screen is off, without extra unwanted actions. Just install QuickClick and do not configure any action. Create a ContentObserver to monitor for stream volume changes and you are ready. You app will now be able to detect volume key presses even when screen is off.
Please note that my app runs as a background service.
Both of the apps mentioned above are meant for other uses, but uses volume key detection to perform action. I am in no way connected to any of the apps mentioned.
If these apps, and possibly dozens others, can detect volume key press, it can be done. I request experts to find out how to do it, so that we can implement in our app without relying on another app.
If you find this answer useful, please up-vote.
I am not sure if it is as simple as this but check this android blog:
Allowing applications to play nice(r) with each other: Handling remote control buttons
It explains the usage of a broadcast receiver that receives the up/down volume controls and other music controls.
In summary you should use registerMediaButtonEventReceiver