Develop Reference

Automatically configure Android settings?

At work, we have an Android-based infotainment system that we're constantly deploying new versions to, on a half-dozen different test benches. The deployment script does the moral equivalent of:
for apk in ${apk_files}; do
adb install -r ${apk]
done
After this, we need to manually execute the following steps:
Set the home app to be one of our just-installed applications (Always, not Just Once)
Become a developer, and enable the Stay Awake option
Select the Google TTS engine for text-to-speech functionality rather than Pico
Executing these steps after each deploy is a giant PITA. People often forget one or more steps, and leave the test bench in a non-working state. This results in a bunch of 'bogus' bug reports that waste everbody's time.
Is there some way (using adb, perhaps) that we can automate these steps?

You can disable other home apps with adb shell pm disable .... I don't think there's a command line option to set apps as default. I remember looking into this before and there was a "preferred application" XML file where this was stored. If you want to look into it, the magic happens in PackageManagerService.addPreferredActivityInternal(). Looks like it writes the data to a file on disk: package-restrictions.xml. I suppose it's possible you could figure out the format thereof and write the file (you'd need root).
This is controlled by a system settings, "stay_on_while_plugged_in". You can set it using adb shell settings system put ....
The TTS engine is stored in a secure setting, "tts_default_synth". You can see the value like,
$ adb shell settings get secure tts_default_synth com.svox.pico
com.svox.pico
And you can set it with adb shell settings put secure "tts_default_synth" <the value>.
I noticed that if the value was not been previously set, when you get the value using the settings command you get null and it's not listed in settings list, even though there is a default value. As of Android 6 (I think), settings are no longer in a DB but rather are stored in XML files in /data/system/users/0/settings_*.xml. You can see the values therein.

android 6.0.1 force wifi connection with no internet access

this has many similar questions (google for: "no internet access detected. won't automatically reconnect." or: android force wifi connection programmatically).
i thought i had a answer here, but it stopped working after installing 6.0.1 updates (i have may 1 security patches).
seems like this is a behaviour change.
i have some 2013 nexus 7's with 6.0.1 that run a kiosk type app and want to connect programmatically to a specific wireless network that has no internet connection. each tablet has a unique static ip address of the form: 192.168.0.xx. i use the normal java socket constructors and check to see if the interface is up using: NetworkInterface.getNetworkInterfaces().
a manual connection has been made. sometimes there is a dialog that asks whether or not you want to always connect. i always check yes.
but the wifi says: "no internet access detected. won't automatically reconnect" after the router cycles power.
doing a disconnect, enable, reconnect does not work. at best it gets: ip6-localhost/::1.
has anyone had any luck using a request object, or bindProcessToNetwork?
edit: related.
edit: the problem seems to be with: CAPTIVE_PORTAL_DETECTION_ENABLED - this string seems to be defined in the source:
public static final String
CAPTIVE_PORTAL_DETECTION_ENABLED = "captive_portal_detection_enabled";
...
MOVED_TO_GLOBAL.add(Settings.Global.CAPTIVE_PORTAL_DETECTION_ENABLED);
but throws" android.provider.Settings$SettingNotFoundException: captive_portal_detection_enabled when used explicitly and is not visible to android studio.
also, doing a settings list global does not contain the constant.
edit doing a adb shell settings put global captive_portal_detection_enabled 0 does seem to work, but this can not be done in the field when the router cycles power. this value seems to persist when the tablet cycles power. and now this value shows up in a settings list global. also, using the raw string: Settings.Global.getInt(getContentResolver(),"captive_portal_detection_enabled"); now returns 0.
edit: looks like setting it requires: android.permission.WRITE_SECURE_SETTINGS, but of course this fails when put into the manifest since we are not a system app.
edit: trying to exec the shell command throws: java.lang.SecurityException, so it looks like you need to issue the command from adb :(
thanks

Could you try and set the global setting captive_portal_detection_enabled to 0 (false).
What's actually happening is that by default, everytime you connect to a wifi, the FW will test against a server (typically google) to see if it's a captive wifi (needs login). So if your wifi is not connected to google, this check will fail. After that, the device knows that wifi has no internet connection and simply will not autoconnect to it.
Setting this setting to 0, will avoid this check.
Programatically Settings.Global.putInt(getContentResolver(), Settings.Global.CAPTIVE_PORTAL_DETECTION_ENABLED, 0);
You can do it through adb for testing purposes:
adb shell settings put global captive_portal_detection_enabled 0
And retrieve it's value like this:
adb shell settings list global | grep "captive"
IMHO this is not very nice thing to do, since you are changing a setting for the user and many FWs don't provide even an advanced setting to enable/disable this by the user itself. (Google doesn't). But maybe it suits your needs.
Hope it helps!

A non-root solution which is a kind of hack tech. :P
Reboot phone, connect to the non-Internet Wifi;
Go to Settings and create a new user;
Continue, continue, and continue until you see "Checking connection";
As soon as you see "checking connection", switch off your phone;
Switch on your phone again, you will be in "Owner" user, keep it;
Toggle Wifi, and the exclamation mark should disappear quickly :)
Remove that new user or just leave it there;
I don't know why, but it works...

How to access Power Saving Mode Programmatically in Android?

I need to access to programmatically turn ON & OFF Power Saving Mode in android.
Is there any API for this ? As I can see Power Saving mode option is not available
for all mobile devices, is there any code to check these settings availability and if available then turn it ON and OFF ?
Also is there any work around ?

If you want to test the Power Saving Mode (PSM):
The following works with Android Studio 3.4.1 and a Google Pixel 2 XL phone:
$ adb shell dumpsys battery unplug # a charging device cannot enter PSM
$ adb shell settings put global low_power 1 # enter Power Saving Mode (PSM)
This only works on devices that has the standard Power Saving Mode, like Samsung's, but not Huawei's, for example. On some Samsung devices, this setting is stored in global setting keyed psm_switch, as mentioned above.
You can leave PSM by setting low_power to 0 or by enabling charging again with:
$ adb shell dumpsys battery reset
Source: https://developer.android.com/training/monitoring-device-state/doze-standby#testing_doze_and_app_standby

It's bad practice to control the user's device settings from your app.
Rather consider suspending background services when battery levels are low.
Or to notify the user of low battery power and advising the user to switch of unnecessary settings like Bluetooth or WiFi.

Most devices won't have a built-in power-saver API, so you could try to make your own power-saver mode by turning off the bluetooth if it's on, the wi-fi, etc, deactivating location in settings, or checking for other power-eating options enabled.

There are no available API's to do this in android SDK. however You can control/save the power by Turning off Blutooth,Wi-Fi and other unused sevices inside your coding.

You can't set the power saving mode programmatically. Allowing this would be a bad idea.
On certain Samsung devices you can check if it is enabled:
final String result = Settings.System.getString(getContentResolver(), "psm_switch");
Log.v("Debug", "Powersaving active: " + TextUtils.equals(result, "1"));
See this for more info: https://stackoverflow.com/a/39296959/3600178

Simulate low battery & low memory in Android

In order to generate the notifications i need to know about how to generate the low battery and low memory interrupts programmatically. Can any one please provide your suggestions.I am aware of Intents.

To trigger your onTrimMemory callbacks:
adb shell am send-trim-memory <process-name> <level>
e.g. adb shell am send-trim-memory com.example.app MODERATE

Low memory can also be simulated using Background process limit under the device developer options.
Go to Settings > Developer options. Under the app section change the Background process limit to No background processes
Now your activity will be killed every time you switch to another app. Useful for testing state saving and state restoration.

yes, this api triggers the same callback you would get if you registered a context to ComponentCallback2, specifically the ComponentCallback2#onTrimMemory this wasn't mentioned here, so I thought I'd make it clear. The syntax for this command is:
am send-trim-memory [--user <USER_ID>] <PROCESS> [HIDDEN|RUNNING_MODERATE|BACKGROUND|RUNNING_LOW|MODERATE|RUNNING_CRITICAL|COMPLETE]
Note: this command is only available on devices running Marshmallow+

On the Android Emulator you can set the power status by connecting to the Emulator console and using the power command.
As far as low memory goes, you just need to make sure that your application can handle being killed without warning when it is in the background. Testing this is one of the very few cases that actually call for a Task Manager on Android, or if you're running Android 2.2 you can kill applications via Settings.
There are ways of reducing the memory available to applications but I think they're unnecessary.

To simulate low Battery warning, try this command in the way answered by Frank:
power capacity 10 // It will set the battery level into 10%
For low Memory:
ulimit -Sv 15000 //The current memory limit will set to 15000 Kb

You can use the emulator menu. Just telnet to localhost on the port of your emulator (default is 5554) and then type help. Follow the instructions from there!

To trigger the memory trim event, an app can be used that fills all the RAM of the device, and that triggers the event.
There are many on the Play Store, they can be found by searching for 'fill ram'.

Set Data roaming on/off

How could I programmatically set data roaming on/off in my android application ?

Apologies in advance for reopening a dead post but I have managed to achieve it by calling this executable:
su -c settings put global data_roaming0 1
Also to get the roaming setting for first SIM card:
su -c settings get global data_roaming0

If your app is signatureOrSystem/Privileged app (app resides in /system/priv-app) and your have valid android.permission.WRITE_SECURE_SETTINGS permission in system/etc/permissions. Then you can do it as below.
Enable :
Settings.Global.putInt(context.getContentResolver(), Settings.Global.DATA_ROAMING, 1)
Disable :
Settings.Global.putInt(context.getContentResolver(), Settings.Global.DATA_ROAMING, 0)

I hope that it's not possible to turn on data roaming programmatically as this would be a serious security issue from my point of view ...
Data roaming (i.e. UMTS data transfer via a foreign network) may result in a huge bill from your network provider - at least in europe.

If data roaming is currently on, then I think you can manipulate the Access Points Names in order to make it appear that a data service isn't available. See this post which also links to apndroid. You could browse their source and see the approach they have taken.
If data roaming has been set to off by the user, then this approach won't work. Though you could prompt users to turn it on as part of your install/setup process, which is the route apndroid take.
apndroid also provide an API for changing these kind of settings, which might be more convenient than reimplementing the same functionality.

On rooted devices when using su to enable data roaming, on multi sim devices the data roaming setting is sim specific.
So you need to get the sim number that is active for data calls
sim_num = settings get global multi_sim_data_call
and use this in the data_roaming + sim_num setting. EG sim_num 3
settings get global data_roaming3
if this is null then not multi sim device and use data_roaming otherwise use
settings put global data_roaming3

I was able to enable data roaming on my dual sim Motorola G8 without the need to root it via ADB. I'm posting here the procedure, because the phone has a bug that prevents data roaming from being enabled normally.
You need a computer and to install ADB installed
Enable developer mode and USB debugging in your phone
Connect the phone to the computer via USB and accept the debugging connection.
Start an "adb shell", be sure that it is correctly connected to your phone.
Issue the command
settings put global data_roaming1 1
to enable data roaming for SIM card 1, or
settings put global data_roaming2 1
to enable it for SIM 2
Note: if you do not have the USB cable, this can be done via wifi, but the pairing process is a bit complicated and version dependent.
If you do not have a computer, it may be possible to run the commands directly on the phone using a "local adb" app (there are a few on the play store), but I have not tested any.