How to limit the number of open activities?

Question

Android

There is an application in which new activities are opened, old activities continue to occupy memory. It is necessary to limit the maximum number of open (for example, up to 4) activities.

Answer 1

In its simplest form, you can do something like this:

fun runNewActivity() {

  val am: ActivityManager = getSystemService(ACTIVITY_SERVICE) as ActivityManager
  var numActivities = 0
  numActivities = if(Build.VERSION.SDK_INT >= Build.VERSION_CODES.M) {
          val tasks = am.appTasks
          tasks[0].taskInfo.numActivities
      } else {
          am.getRunningTasks(10)[0].numActivities
  }

  if(numActivities > 4) {
      startActivity(...)
      // https://developer.android.com/reference/android/app/Activity#finishAffinity()
      finishAffinity()
  }
}

PS: I omitted checks for boundaries intentionally for clarity