Navigate Back

NavigateBack.kt

package lavanderia.org.lavanderia

import android.content.Context
import android.content.Intent
import android.os.Bundle
import android.support.v4.app.NavUtils
import android.support.v4.app.TaskStackBuilder
import android.support.v7.app.ActionBarDrawerToggle
import android.support.v7.app.AppCompatActivity
import android.view.MenuItem
import lavanderia.org.lavanderia.UtilityClass.Companion.GO_BACK
import lavanderia.org.lavanderia.UtilityClass.Companion.GO_PARENT
import lavanderia.org.lavanderia.UtilityClass.Companion.GO_UP

class MainActivity : AppCompatActivity() {
    lateinit var drawerToggle: ActionBarDrawerToggle
    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        setContentView(R.layout.activity_main)
    }

    override fun onOptionsItemSelected(menuItem: MenuItem): Boolean {
        when (menuItem.itemId) {
            android.R.id.home -> {
                UtilityClass.hideKeyboard(MainActivity@ this)
                if (!drawerToggle.onOptionsItemSelected(menuItem)) {
                    if (supportFragmentManager.backStackEntryCount <= 0) {
                        navigateBack()
                    } else {
                        onBackPressed()
                    }
                    return true
                }
            }
        }
        return super.onOptionsItemSelected(menuItem)
    }

    private fun navigateBack() {
        val parentIntent = NavUtils.getParentActivityIntent(this)
        when (determineNavBack(parentIntent)) {
            GO_PARENT -> {
                TaskStackBuilder.create(this)
                    .addNextIntentWithParentStack(parentIntent as Intent)
                    .startActivities()
                overridePendingTransition(0, 0)
            }
            GO_UP -> {
                NavUtils.navigateUpTo(this, parentIntent as Intent)
                overridePendingTransition(0, 0)
            }
            GO_BACK -> {
                onBackPressed()
            }
        }
    }

    private fun determineNavBack(parentIntent: Intent?) =
        if (parentIntent != null && NavUtils.shouldUpRecreateTask(this, parentIntent)) {
            GO_PARENT
        } else if (parentIntent != null) {
            GO_UP
        } else {
            GO_BACK
        }

}

class UtilityClass {
    companion object {
        fun hideKeyboard(context: Context) {
            TODO("not implemented") 
        }

        const val GO_PARENT: Int = 0
        const val GO_UP: Int = 1
        const val GO_BACK: Int = 2
    }
}