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Android, Detect when other apps are launched

Posted by: admin March 11, 2020 Leave a comment


I’m trying to develop an app that prevents a user from getting to a specified app without a password. The scenario is…

  1. user clicks on “Email” app (for example)
  2. my app detects launch of an app
  3. my app confirms it is the “Email” app
  4. my app opens a view over the top, asking for a password
  5. user enters a password, if correct, my app disappears, leaving the “Email” app on top

I’m ok doing the rest of it, just part 2 is puzzling me, and after many days reading up on Broadcast Intents etc and trying to listen for “android.intent.action.MAIN” etc in my trial projects I can’t seem to detect when an app other than mine is started.

Can anyone help? Am I going about it the right way, in looking for new apps broadcasting an intent to start, or should I be reading the system log for new intents, or doing something in native code?

Any pointers would help, even if you can’t answer it fully I’ll be able to do some more research. Thanks a lot. Ian

How to&Answers:

I think we can use logcat and analyze it’s output.

In all similar programs I have found this permission :


It means all of them use it but it seems the program starts and after that our program (app protector) will start and bring front.

Use below code :

        Process mLogcatProc = null;
        BufferedReader reader = null;
        mLogcatProc = Runtime.getRuntime().exec(new String[]{"logcat", "-d"});

        reader = new BufferedReader(new InputStreamReader(mLogcatProc.getInputStream()));

        String line;
        final StringBuilder log = new StringBuilder();
        String separator = System.getProperty("line.separator"); 

        while ((line = reader.readLine()) != null)
        String w = log.toString();
        Toast.makeText(getApplicationContext(),w, Toast.LENGTH_LONG).show();
    catch (Exception e) 
        Toast.makeText(getApplicationContext(), e.getMessage(), Toast.LENGTH_LONG).show();

And do not forget to add it’s permission in Manifest file.


A gimmicky way to do it is have a service with a timed loop that checks

ActivityManager am = (ActivityManager)getSystemService(Context.ACTIVITY_SERVICE);
List<ActivityManager.RunningAppProcessInfo> runningAppProcessInfo = am.getRunningAppProcesses();

You run through that list to look at what is running on the phone.
Now you can identify them with ids and processName, so for standard activity this is easy for custom ones well unless you stop them all its hard to discriminate…

Note: this isnt a list of whats is actually on the screen, just a list of whats is running…kinda nullifying your goal maybe but at least you will know when something is starting to run… it will keep being in that list even when in background though.

For the password thing you can just start your activity when you found an app
thats protected or whatever.


I think and hope this is not possible. Consider how easily such functionality could be abused by malicious software. You can listen to intents directed at you, and those that are broadcast, but application launching should not be a broadcast event.

What you may be able to do is replace the launcher. If the user agrees to it.


class CheckRunningActivity extends Thread{
    ActivityManager am = null;
    Context context = null;

    public CheckRunningActivity(Context con){
        context = con;
        am = (ActivityManager) context.getSystemService(Context.ACTIVITY_SERVICE);

    public void run(){

            // Return a list of the tasks that are currently running,
            // with the most recent being first and older ones after in order.
            // Taken 1 inside getRunningTasks method means want to take only
            // top activity from stack and forgot the olders.
            List< ActivityManager.RunningTaskInfo > taskInfo = am.getRunningTasks(1);

            String currentRunningActivityName = taskInfo.get(0).topActivity.getClassName();

            if (currentRunningActivityName.equals("PACKAGE_NAME.ACTIVITY_NAME")) {
                // show your activity here on top of PACKAGE_NAME.ACTIVITY_NAME

You can get current running Activity and check if this Activity corresponds to Email application.

Run CheckRunningActivity Thread on Application start (or on device boot).

new CheckRunningActivity().start();

This class need android.permission.GET_TASKS permission, so add next line to the Manifest:

<uses-permission android:name="android.permission.GET_TASKS" />


The main issue is you are trying to listen for implicit intents when the Launcher (home screen) is typically using explicit intents.

An implicit intent is when you want to say “Somebody play this video” and Android picks an app that can handle that intent.

An explicit intent is what happens when you click the “Email” icon on the home screen. It is specifically telling Android to open that specific app by fully qualified name (i.e. com.android.mail or something).

There is no way AFAIK to intercept such explicit intents. It is a security measure built into Android that no two Activities can have the same fully qualified package name. This prevents a third party from cloning the app and masquerading as that app. If what you wish to do was possible, you could theoretically install an app that could block all of your competition’s apps from working.

What you are trying to do goes against the Android security model.

One thing you could do is partner with specific app developers to forward the intents to your security system, but that’s probably not something you want to deal with.


getRunningTasks() is deprecated in Android L.

To obtain app usage statistics you can use UsageStats class from android.app.usage package.

The new App usage statistics API allows app developers to collect statistics related to usage of the applications. This API provides more detailed usage information than the deprecated getRecentTasks() method.

To use this API, you must first declare the android.permission.PACKAGE_USAGE_STATS permission in your manifest. The user must also enable access for this app through Settings > Security > Apps with usage access.

Here is a basic app example showing how to use App usage statistics API to let users collect statistics related to usage of the applications.


Perhaps you need a service, something that will run in the background constantly. Than have your service do what you said. Listen for the android.intent.action.MAIN also with the category android.intent.category.LAUNCHER. Then have that broadcast receiver override the onReceive method and do check to see the name of the application etc.