Activities & Application Components

package com.devascent.lifecycle

import android.os.Bundle
import android.util.Log
import androidx.appcompat.app.AppCompatActivity
import com.devascent.databinding.ActivityLifecycleBinding

class LifecycleLoggingActivity : AppCompatActivity() {

    private lateinit var binding: ActivityLifecycleBinding
    private var timerSeconds: Int = 0
    private val tag = "ActivityLifecycle"

    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        binding = ActivityLifecycleBinding.inflate(layoutInflater)
        setContentView(binding.root)

        // Restore transient state after configuration change / process kill
        if (savedInstanceState != null) {
            timerSeconds = savedInstanceState.getInt("KEY_TIMER", 0)
            Log.d(tag, "onCreate: Restored timer state = $timerSeconds")
        } else {
            Log.d(tag, "onCreate: Fresh activity initialization")
        }
    }

    override fun onStart() {
        super.onStart()
        Log.d(tag, "onStart: Activity becoming visible")
    }

    override fun onResume() {
        super.onResume()
        Log.d(tag, "onResume: Activity interactive and in foreground")
    }

    override fun onPause() {
        super.onPause()
        Log.d(tag, "onPause: Losing input focus")
    }

    override fun onSaveInstanceState(outState: Bundle) {
        super.onSaveInstanceState(outState)
        outState.putInt("KEY_TIMER", timerSeconds)
        Log.d(tag, "onSaveInstanceState: Transient state saved to Bundle")
    }

    override fun onStop() {
        super.onStop()
        Log.d(tag, "onStop: Activity hidden from view")
    }

    override fun onDestroy() {
        super.onDestroy()
        Log.d(tag, "onDestroy: Activity resource teardown")
    }
}

package com.devascent.navigation

import android.content.Intent
import android.net.Uri
import android.os.Bundle
import android.os.Parcelable
import androidx.activity.result.contract.ActivityResultContracts
import androidx.appcompat.app.AppCompatActivity
import kotlinx.parcelize.Parcelize

@Parcelize
data class StudentEnrollment(
    val studentId: String,
    val courseTitle: String,
    val tuitionFee: Double
) : Parcelable

class EnrollmentHostActivity : AppCompatActivity() {

    // 1. Modern Activity Result API (replaces deprecated startActivityForResult)
    private val paymentLauncher = registerForActivityResult(
        ActivityResultContracts.StartActivityForResult()
    ) { result ->
        if (result.resultCode == RESULT_OK) {
            val transactionId = result.data?.getStringExtra("KEY_TXN_ID")
            // Process confirmed enrollment
        }
    }

    fun launchExplicitCheckout() {
        val enrollment = StudentEnrollment("STU-882", "Android Mobile Track", 499.00)
        
        // Explicit Intent: Directly targets destination class
        val intent = Intent(this, PaymentCheckoutActivity::class.java).apply {
            putExtra("EXTRA_ENROLLMENT_DATA", enrollment)
        }
        paymentLauncher.launch(intent)
    }

    fun launchImplicitBrowser() {
        // Implicit Intent: System resolves web browser app
        val webIntent = Intent(Intent.ACTION_VIEW, Uri.parse("https://devascentacademy.me"))
        if (webIntent.resolveActivity(packageManager) != null) {
            startActivity(webIntent)
        }
    }
}

package com.devascent.checkout

import android.content.Intent
import android.os.Bundle
import android.os.Parcelable
import android.util.Log
import androidx.activity.result.contract.ActivityResultContracts
import androidx.appcompat.app.AppCompatActivity
import com.devascent.databinding.ActivityOrderBinding
import com.devascent.databinding.ActivityPaymentBinding
import kotlinx.parcelize.Parcelize

// 1. Parcelable Domain Model
@Parcelize
data class CourseOrder(
    val orderId: String,
    val courseTitle: String,
    val amount: Double
) : Parcelable

// 2. Primary Order Activity
class OrderActivity : AppCompatActivity() {

    private lateinit var binding: ActivityOrderBinding
    private val logTag = "DevAscentComponent"

    // Register Activity Result Contract for modern callback handling
    private val checkoutLauncher = registerForActivityResult(
        ActivityResultContracts.StartActivityForResult()
    ) { result ->
        if (result.resultCode == RESULT_OK) {
            val paymentRef = result.data?.getStringExtra("EXTRA_PAYMENT_REF") ?: "UNKNOWN"
            binding.statusLabel.text = "Enrollment Complete! Ref: $paymentRef"
            Log.i(logTag, "OrderActivity: Payment acknowledged with reference: $paymentRef")
        } else {
            binding.statusLabel.text = "Checkout Cancelled by Student"
            Log.w(logTag, "OrderActivity: Checkout aborted")
        }
    }

    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        binding = ActivityOrderBinding.inflate(layoutInflater)
        setContentView(binding.root)

        binding.btnProceedCheckout.setOnClickListener {
            val order = CourseOrder("ORD-2026-99", "Unit 5: Android Components", 199.99)
            
            // Build Explicit Intent with Parcelable Payload
            val intent = Intent(this, PaymentActivity::class.java).apply {
                putExtra("EXTRA_ORDER_PARCEL", order)
            }
            Log.d(logTag, "OrderActivity: Launching PaymentActivity for result")
            checkoutLauncher.launch(intent)
        }
    }
}

// 3. Secondary Destination Activity
class PaymentActivity : AppCompatActivity() {

    private lateinit var binding: ActivityPaymentBinding

    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        binding = ActivityPaymentBinding.inflate(layoutInflater)
        setContentView(binding.root)

        // Retrieve Parcelable object
        val order: CourseOrder? = intent.getParcelableExtra("EXTRA_ORDER_PARCEL")
        binding.txtCourseTitle.text = order?.courseTitle ?: "No Order Data"
        binding.txtTotalDue.text = "Total Due: $${order?.amount}"

        binding.btnConfirmPayment.setOnClickListener {
            // Return result intent to caller
            val resultIntent = Intent().apply {
                putExtra("EXTRA_PAYMENT_REF", "TXN-SUCCESS-7718")
            }
            setResult(RESULT_OK, resultIntent)
            finish() // Destroy activity and pop off backstack
        }
    }
}