create tasks 0,1,2

app/src/main/AndroidManifest.xml

@@ -12,8 +12,15 @@
         android:supportsRtl="true"
         android:theme="@style/Theme.Fragments"
         tools:targetApi="31">
+        <activity
+            android:name=".SecondActivity"
+            android:exported="false" />
+        <activity
+            android:name=".FirstActivity"
+            android:exported="false" />
         <activity
             android:name=".MainActivity"
+            android:launchMode="singleTask"
             android:exported="true">
             <intent-filter>
                 <action android:name="android.intent.action.MAIN" />

app/src/main/java/otus/gpb/homework/fragments/FirstActivity.kt

@@ -0,0 +1,16 @@
+package otus.gpb.homework.fragments
+
+import android.os.Bundle
+import androidx.appcompat.app.AppCompatActivity
+
+class FirstActivity : AppCompatActivity() {
+    override fun onCreate(savedInstanceState: Bundle?) {
+        super.onCreate(savedInstanceState)
+        setContentView(R.layout.activity_first)
+
+        supportFragmentManager
+            .beginTransaction()
+            .add(R.id.container, FragmentA())
+            .commit()
+    }
+}

app/src/main/java/otus/gpb/homework/fragments/FragmentA.kt

@@ -0,0 +1,60 @@
+package otus.gpb.homework.fragments
+
+import android.content.Context
+import android.os.Bundle
+import android.view.LayoutInflater
+import android.view.View
+import android.view.View.GONE
+import android.view.View.VISIBLE
+import android.view.ViewGroup
+import android.widget.Button
+import androidx.activity.OnBackPressedCallback
+import androidx.core.os.bundleOf
+import androidx.fragment.app.Fragment
+
+class FragmentA : Fragment() {
+
+    override fun onCreateView(
+        inflater: LayoutInflater, container: ViewGroup?,
+        savedInstanceState: Bundle?
+    ): View? {
+        return inflater.inflate(R.layout.fragment_a, container, false)
+    }
+
+    private lateinit var button: Button
+
+    override fun onAttach(context: Context) {
+        super.onAttach(context)
+        val callback = object : OnBackPressedCallback(true) {
+            override fun handleOnBackPressed() {
+                if (childFragmentManager.backStackEntryCount == 1) {
+                    activity?.title = getString(R.string.fragment_a)
+                    button.visibility = VISIBLE
+                }
+                if (childFragmentManager.backStackEntryCount >= 1) {
+                    childFragmentManager.popBackStack()
+                } else {
+                    requireActivity().finish()
+                }
+            }
+        }
+        requireActivity().onBackPressedDispatcher.addCallback(this, callback)
+    }
+
+    override fun onViewCreated(view: View, savedInstanceState: Bundle?) {
+        super.onViewCreated(view, savedInstanceState)
+        activity?.title = getString(R.string.fragment_a)
+
+        button = view.findViewById(R.id.button_aa)
+        button.setOnClickListener {
+            button.visibility = GONE
+            childFragmentManager
+                .beginTransaction()
+                .replace(R.id.container, FragmentAA().apply {
+                    arguments = bundleOf(KEY_COLOR to ColorGenerator.generateColor())
+                })
+                .addToBackStack(null)
+                .commit()
+        }
+    }
+}

app/src/main/java/otus/gpb/homework/fragments/FragmentAA.kt

@@ -0,0 +1,37 @@
+package otus.gpb.homework.fragments
+
+import android.os.Bundle
+import androidx.fragment.app.Fragment
+import android.view.LayoutInflater
+import android.view.View
+import android.view.ViewGroup
+import android.widget.Button
+import androidx.core.os.bundleOf
+
+class FragmentAA : Fragment() {
+    private lateinit var button: Button
+
+    override fun onCreateView(
+        inflater: LayoutInflater, container: ViewGroup?,
+        savedInstanceState: Bundle?
+    ): View? {
+        return inflater.inflate(R.layout.fragment_a_a, container, false)
+    }
+
+    override fun onViewCreated(view: View, savedInstanceState: Bundle?) {
+        super.onViewCreated(view, savedInstanceState)
+        activity?.title = getString(R.string.fragment_aa)
+
+        view.setBackgroundColor(requireArguments().getInt(KEY_COLOR))
+        button = view.findViewById(R.id.button_a_b)
+        button.setOnClickListener {
+            parentFragmentManager
+                .beginTransaction()
+                .replace(R.id.container, FragmentAB().apply {
+                    arguments = bundleOf(KEY_COLOR to ColorGenerator.generateColor())
+                })
+                .addToBackStack(null)
+                .commit()
+        }
+    }
+}

app/src/main/java/otus/gpb/homework/fragments/FragmentAB.kt

@@ -0,0 +1,24 @@
+package otus.gpb.homework.fragments
+
+import android.os.Bundle
+import androidx.fragment.app.Fragment
+import android.view.LayoutInflater
+import android.view.View
+import android.view.ViewGroup
+
+class FragmentAB : Fragment() {
+
+    override fun onCreateView(
+        inflater: LayoutInflater, container: ViewGroup?,
+        savedInstanceState: Bundle?
+    ): View? {
+        return inflater.inflate(R.layout.fragment_a_b, container, false)
+    }
+
+    override fun onViewCreated(view: View, savedInstanceState: Bundle?) {
+        super.onViewCreated(view, savedInstanceState)
+        activity?.title = getString(R.string.fragment_ab)
+
+        view.setBackgroundColor(requireArguments().getInt(KEY_COLOR))
+    }
+}

app/src/main/java/otus/gpb/homework/fragments/FragmentBA.kt

@@ -0,0 +1,46 @@
+package otus.gpb.homework.fragments
+
+import android.content.res.Configuration.ORIENTATION_LANDSCAPE
+import android.content.res.Configuration.ORIENTATION_PORTRAIT
+import android.os.Bundle
+import android.view.LayoutInflater
+import android.view.View
+import android.view.View.GONE
+import android.view.View.VISIBLE
+import android.view.ViewGroup
+import android.widget.Button
+import android.widget.FrameLayout
+import androidx.fragment.app.Fragment
+
+class FragmentBA : Fragment() {
+    private lateinit var button: Button
+
+    override fun onCreateView(
+        inflater: LayoutInflater, container: ViewGroup?,
+        savedInstanceState: Bundle?
+    ): View? {
+        return inflater.inflate(R.layout.fragment_b_a, container, false)
+    }
+
+    override fun onViewCreated(view: View, savedInstanceState: Bundle?) {
+        super.onViewCreated(view, savedInstanceState)
+        val orientation = resources.configuration.orientation
+        view.setBackgroundColor(requireArguments().getInt(KEY_COLOR))
+
+        button = view.findViewById(R.id.button_bb)
+        if (orientation == ORIENTATION_PORTRAIT) {
+            requireActivity().findViewById<FrameLayout>(R.id.container_ba).visibility = VISIBLE
+            requireActivity().findViewById<FrameLayout>(R.id.container_bb).visibility = GONE
+            button.visibility = VISIBLE
+            button.setOnClickListener {
+                parentFragmentManager
+                    .beginTransaction()
+                    .replace(R.id.container_bb, FragmentBB())
+                    .commit()
+            }
+        } else if (orientation == ORIENTATION_LANDSCAPE) {
+            button.visibility = GONE
+        }
+    }
+
+}

app/src/main/java/otus/gpb/homework/fragments/FragmentBB.kt

@@ -0,0 +1,41 @@
+package otus.gpb.homework.fragments
+
+import android.content.res.Configuration.ORIENTATION_PORTRAIT
+import android.os.Bundle
+import androidx.fragment.app.Fragment
+import android.view.LayoutInflater
+import android.view.View
+import android.view.View.GONE
+import android.view.View.VISIBLE
+import android.view.ViewGroup
+import android.widget.Button
+import android.widget.FrameLayout
+import androidx.core.os.bundleOf
+
+class FragmentBB : Fragment() {
+    private lateinit var button: Button
+
+    override fun onCreateView(
+        inflater: LayoutInflater, container: ViewGroup?,
+        savedInstanceState: Bundle?
+    ): View? {
+        return inflater.inflate(R.layout.fragment_b_b, container, false)
+    }
+
+    override fun onViewCreated(view: View, savedInstanceState: Bundle?) {
+        super.onViewCreated(view, savedInstanceState)
+
+        button = view.findViewById(R.id.button_color)
+        if (resources.configuration.orientation == ORIENTATION_PORTRAIT) {
+            requireActivity().findViewById<FrameLayout>(R.id.container_ba).visibility = GONE
+            requireActivity().findViewById<FrameLayout>(R.id.container_bb).visibility = VISIBLE
+        }
+        button.setOnClickListener {
+            parentFragmentManager.beginTransaction()
+                .replace(R.id.container_ba, FragmentBA().apply {
+                    arguments = bundleOf(KEY_COLOR to ColorGenerator.generateColor())
+                })
+                .commit()
+        }
+    }
+}

app/src/main/java/otus/gpb/homework/fragments/MainActivity.kt

@@ -1,12 +1,28 @@
 package otus.gpb.homework.fragments
 
+import android.content.Intent
 import android.os.Bundle
+import android.widget.Button
 import androidx.appcompat.app.AppCompatActivity
 
+
+const val KEY_COLOR = "color"
+
 class MainActivity : AppCompatActivity() {
 
     override fun onCreate(savedInstanceState: Bundle?) {
         super.onCreate(savedInstanceState)
         setContentView(R.layout.activity_main)
+
+        val buttonFirst = findViewById<Button>(R.id.container_a)
+        val buttonSecond = findViewById<Button>(R.id.container_b)
+
+        buttonFirst.setOnClickListener {
+            startActivity(Intent(this, FirstActivity::class.java))
+        }
+
+        buttonSecond.setOnClickListener {
+            startActivity(Intent(this, SecondActivity::class.java))
+        }
     }
 }

app/src/main/java/otus/gpb/homework/fragments/SecondActivity.kt

@@ -0,0 +1,35 @@
+package otus.gpb.homework.fragments
+
+import android.content.res.Configuration.ORIENTATION_LANDSCAPE
+import android.content.res.Configuration.ORIENTATION_PORTRAIT
+import android.os.Bundle
+import androidx.appcompat.app.AppCompatActivity
+import androidx.core.os.bundleOf
+
+class SecondActivity : AppCompatActivity() {
+    override fun onCreate(savedInstanceState: Bundle?) {
+        super.onCreate(savedInstanceState)
+        setContentView(R.layout.activity_second)
+
+        val orientation = resources.configuration.orientation
+
+        if (orientation == ORIENTATION_PORTRAIT) {
+            supportFragmentManager
+                .beginTransaction()
+                .add(R.id.container_ba, FragmentBA().apply {
+                    arguments = bundleOf(KEY_COLOR to ColorGenerator.generateColor())
+                })
+                .commit()
+        } else if (orientation == ORIENTATION_LANDSCAPE) {
+            supportFragmentManager
+                .beginTransaction()
+                .add(R.id.container_ba, FragmentBA().apply {
+                    arguments = bundleOf(KEY_COLOR to ColorGenerator.generateColor())
+                })
+                .add(R.id.container_bb, FragmentBB().apply {
+                    arguments = bundleOf(KEY_COLOR to ColorGenerator.generateColor())
+                })
+                .commit()
+        }
+    }
+}

app/src/main/res/layout/activity_first.xml

@@ -0,0 +1,13 @@
+<?xml version="1.0" encoding="utf-8"?>
+<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
+    xmlns:tools="http://schemas.android.com/tools"
+    android:layout_width="match_parent"
+    android:layout_height="match_parent"
+    tools:context=".FirstActivity">
+
+    <FrameLayout
+        android:id="@+id/container"
+        android:layout_width="match_parent"
+        android:layout_height="match_parent" />
+
+</LinearLayout>

app/src/main/res/layout/activity_main.xml

@@ -1,18 +1,22 @@
 <?xml version="1.0" encoding="utf-8"?>
-<androidx.constraintlayout.widget.ConstraintLayout xmlns:android="http://schemas.android.com/apk/res/android"
-    xmlns:app="http://schemas.android.com/apk/res-auto"
+<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
     xmlns:tools="http://schemas.android.com/tools"
     android:layout_width="match_parent"
     android:layout_height="match_parent"
+    android:gravity="center"
+    android:orientation="vertical"
     tools:context=".MainActivity">
 
-    <TextView
+    <Button
+        android:id="@+id/container_a"
         android:layout_width="wrap_content"
         android:layout_height="wrap_content"
-        android:text="Hello World!"
-        app:layout_constraintBottom_toBottomOf="parent"
-        app:layout_constraintEnd_toEndOf="parent"
-        app:layout_constraintStart_toStartOf="parent"
-        app:layout_constraintTop_toTopOf="parent" />
+        android:text="@string/task_first" />
 
-</androidx.constraintlayout.widget.ConstraintLayout>
+    <Button
+        android:id="@+id/container_b"
+        android:layout_width="wrap_content"
+        android:layout_height="wrap_content"
+        android:text="@string/task_second" />
+
+</LinearLayout>

app/src/main/res/layout/activity_second.xml

@@ -0,0 +1,22 @@
+<?xml version="1.0" encoding="utf-8"?>
+<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
+    xmlns:tools="http://schemas.android.com/tools"
+    android:id="@+id/layout"
+    android:layout_width="match_parent"
+    android:layout_height="match_parent"
+    android:baselineAligned="false"
+    tools:context=".SecondActivity">
+
+    <FrameLayout
+        android:id="@+id/container_ba"
+        android:layout_width="match_parent"
+        android:layout_height="match_parent"
+        android:layout_weight="1" />
+
+    <FrameLayout
+        android:id="@+id/container_bb"
+        android:layout_width="match_parent"
+        android:layout_height="match_parent"
+        android:layout_weight="1" />
+
+</LinearLayout>