Develop Reference

Android: How to get the process id of the foreground app

First of all, please note that this question is not same as all the "android foreground app" questions I found on SO, please read on :-)
I'm trying to write an android app for my own use, using golang, without using android-sdk or ndk (this is the KEY point). It is pretty simple, just use golang to write a http service, compile it for arm CPU and voila my app is running and can be access by simply visit http://localhost.
For the purpose of my app, I need to know the currently running foreground application, to define it precisely:
Foreground application is the application that occupies the screen, or has an "activity" what-so-ever (forgive me I'm not an android developer).
Anything that that is depended by the foreground application (e.g. services) is NOT what I am interested in.
If the phone is LOCKED/screen turned off, I want the solution to tell me there is NO foreground app.
And since I do not use anything android, just treat the phone as a LINUX machine, I want the solution to use native LINUX ways, e.g. by inspect /proc, or by calling any installed android command line tool (including sending messages via these command line tools), but NOT using any SDK/NDK way so that I have to use java or incorporate these thing into my app.

Starting from Android SDK 26 (if I remember well) Apps are executed on -one-User-per-App, so (i.e.) WhatsApp is running on UID=30 and Telegram on UID=76, so executing a ROOT command of "ps -A -o PID,USER,NAME" you can parse output and then Kill all Processes that you don't want to be executed.
36119 u30_a149 <WhatsApp_packagename>
36203 u76_a211 <Telegram_packagename>
37399 root [kworker/1:2H]
37423 u0_a329 su
38069 root sh
Without Root Permissions nothing of what you're trying to achieve is possible simply because is not possibile to denied an application to be executed or to kill it without Superuser privilege.

Android : can native code get broadcast intent from android system? [duplicate]

This question already has answers here:
Listen to own application uninstall event on Android
(3 answers)
Closed 7 years ago.
Recently i've seen a funny app - Photo Wonder.
When this app is uninstalled, it shows a web survey page asking for the reason of app uninstall. Now, here is the problem.
As far as I know, after an app has been removed, the system broadcasts ACTION_PAKAGE_REMOVED intent.
But this funny app was able to show my the web page although the official doc says
"The package that is being installed does not receive this Intent."
Anyhow, I could find a process checking some kind of status of the app.
Now here is the question. Can the native app catch the broadcasted intent from android system?
If it is possible, please let me know how! :-(

I believe I've got the main idea of how they did it. Here is the pieces of the puzzle.
Any Android application can start a process by calling Runtime.exec() function.
Runtime.getRuntime().exec("chmod 755 '/data/data/my.app/files'/native_code");
After this line of code gets executed there is another process spawned. This process runs under the same linux user as the application itself.
When a user opens Settings -> Apps -> My App and presses "Force stop" button, main application process gets killed, but the process hosting native program (see above) still runs. I personally believe this is a security issue and I am going to report it back to AOSP.
Such native program can run infinitely and do nothing - just sleeping. But before going to sleep, it registers a termination signal handler which will be called when process is about to be terminated by the system.
int main(void) {
signal(SIGTERM, termination_handler);
while(1) {
sleep(10);
}
}
void termination_handler(int sig) {
// handle termination signal here
}
Now you should already know what the last piece is, right? My native termination_handler should be able to launch a browser. I didn't try this in code, but I assume this is possible, because I can do it using adb shell as following
adb shell am start -a android.intent.action.VIEW -d http://www.google.com
Now back to the question about how Dolphin Browser does it. Install the app and launch it at least once. Once started, it registers a native uninstall watcher using the principles described above. To see it, connect to the device and open adb shell. Then call ps to see list of processes. You will see two processes similar to following
u0_a109 315 ... mobi.mgeek.TunnyBrowser
u0_a109 371 ... /data/data/mobi.mgeek.TunnyBrowser/files/watch_server
As you can see it starts a watch_server native program, which is a part of its apk-file. Now open App info page of Dolphin Browser and press "Force Stop". Switch back to terminal and call ps again. You will see there is no mobi.mgeek.TunnyBrowser process anymore, but watch_server still runs.
By the way this approach will only work, if watcher server runs all the time. To
make sure it is always up, both apps require "run at startup"
permission, where they start their watchers.
Now, when you uninstall the app, Android stops all processes belonging to this application. Watcher receives termination signal and opens browser with predefined URL and then shuts down.
I might look a bit different in some details, but the main concept behind this hack must be as described.

There could be a tricky thing like that application is also having watcher service.
You can check the permission used by that app may contain INSTALL and UNINSTALL permissions.
HOW IT WORKS:
instead of single app that may have 2 app bundle.
as and when you install it, this app is also installing some service that is watching your app status
When you try to uninstall that app the system broadcast is called which is handled by that service and will check that if your package is exist in installed application or not.
as soon as this service finds that your package is not in the list it calls an intent with action view with the web url to open the brawser.

Stop running application with ADB

is there a simple way to stop a running application using ADB.
Szenario:
Working on App
Have a script which uploads, installs and starts App on change
Problem:
Currently running version gets killed (not shutdown), which make testing cleanup very hard. Option would be to "do cleanup in between", like after a certain time, but I would prefer to do it in the correct location (so like with the OS, as long as the App is still running, so need to save value, as soon as the OS tells me e.g. memory low or calls onDestroy, I want to save stuff)
Chris

I'm not aware of a way to do this. I was hoping there might be a way to send an intent to tell the app to exit using adb shell e.g.
adb shell am start -a [intent] -n [class]
However, I found that somebody asked this question on a Google forum but they haven't got an answer:
http://groups.google.com/group/android-platform/browse_thread/thread/3fd02d01c6c3b41a/56814e518503efd6

How can I get root permissions through the Android SDK?

I'm learning Android programming, and I want to make an application which has to run as root. The logical thing would be to add a root permission in the Android Manifest.
I saw this link in the documentation, and especially noted the FACTORY_TEST permission:
public static final String FACTORY_TEST
Since: API Level 1
Run as a manufacturer test
application, running as the root user.
Only available when the device is
running in manufacturer test mode.
Constant Value:
"android.permission.FACTORY_TEST"
Is that the best way?
If it's not possible using the SDK, how can I make a "root" application work?

What you need to do is something like:
Process root = Runtime.getRuntime().exec("su");
That causes SuperUser to show, which lets you either Allow or Block it from root access. This approach might not work if the user is not rooted. Here is a way you can test it.

First lets us get the basics right. Android run Linux kernel underneath. Now if you have to run your process on it with super user privileges(run it as root) the only way is to execute your process is via command line because it is the only way you can directly interact with the kernel. Also you need to use su before running any command. Also as Chris has mentioned in his comment on the 1st answer
Process process = Runtime.getRuntime().exec("su");
will accomplish nearly nothing. It will just ask for super use privilege using dialog. What you can do is instead of just executing su you can execute your process with su as following
Process process = Runtime.getRuntime().exec(new String[] { "su", "-c", yourCommand});
The -c Option
Among the most commonly used of su's few options is -c, which tells su to execute the command that directly follows it on the same line. Such command is executed as the new user, and then the terminal window or console from which su was run immediately returns to the account of the former user after the command has completed execution or after any program that it has launched has been closed.(More details)
Alternate Option
Alternative to above method one another way that might work is to use command line to copy you app to /system/app/ directory. Then your application will run automatically with root privileges(same as System apps)

The SDK does not offer a way to run an app as root.

android emulating a reboot

I have coded a BroadcastReceiver to enable the resetting of an alarm if a user has to reboot hid device. Is there any way to test this in the emulator, in other words what sequence of events are required to cause the emulator to kick off the BroadcastReceiver .
Ron

I have not tried it yet, but Dianne Hackborn wrote the following yesterday:
You can also use "adb shell am" to
send a BOOT_COMPLETED broadcast to
your app for quick testing. I can't
remember the exact syntax, but "am
help" will tell you. Be sure to
specific your explicit component name
when doing this, or you will cause all
installed apps to re-run their boot
completed receivers, which may not be
fun. :)

I believe that the only way to do it will be to close the emulation window and start it again. If you are running Eclipse, simply close the emulator and then run/debug your project to start it again.