Android - Activities Stack Handler

ActivitiesStackHandler.kt

// Manually handle activity stack
// Android has many different mechanism on how to handle activities stack on each version
// Instead rely on native tool, we create this class to handle the stack
//
// How does it work?
//
// Make sure all of your activities is inherited from a `BaseActivity`
// When an activity launched, call `super.onCreate()` method from `BaseActivity`
// `BaseActivity@onCreate` is simple, just call `addActivity(this)` method to add your activity to the stack
// Don't forget to remove it from stack, by calling `removeActivity(this)`, when the activity is destroyed

package com.refactory.sampleapp.app.infrastructures.handlers

import android.app.Activity
import java.util.*

class ActivitiesStackHandler {
    private val activities: Stack<Activity> = Stack()

    // Make it singleton. Because this will be single source of truth for a whole app
    companion object {
        private lateinit var instance: ActivitiesStackHandler

        fun getInstance(): ActivitiesStackHandler {
            if (!::instance.isInitialized) {
                instance = ActivitiesStackHandler()
            }

            return instance
        }
    }

    fun addActivity(activity: Activity) {
        activities.add(activity)
    }

    fun removeActivity(activity: Activity) {
        val removed = findActivity(activity.javaClass)
        activities.remove(removed)
    }

    // get current activity, located in top of the stack
    fun currentActivity(): Class<*>? {
        return if (activities.isEmpty()) null else activities.lastElement()::class.java
    }

    // Counting how many activities is in the stack right now
    fun count(): Int {
        return activities.size
    }

    // find activity by its simple name
    fun findActivity(cls: Class<*>): Activity? {
        var activity: Activity? = null
        for (aClass in activities) {
            if (aClass.javaClass == cls) {
                activity = aClass
                break
            }
        }
        return activity
    }
}