ActivityベースからFragmentベースへの移行

app/build.gradle

@@ -34,6 +34,9 @@ dependencies {
     implementation 'androidx.recyclerview:recyclerview:1.1.0'
     implementation "androidx.cardview:cardview:1.0.0"
     implementation 'com.google.android.material:material:1.1.0'
+    implementation 'androidx.legacy:legacy-support-v4:1.0.0'
+    implementation "androidx.navigation:navigation-fragment-ktx:2.2.1"
+    implementation "androidx.navigation:navigation-ui-ktx:2.2.1"
     testImplementation 'junit:junit:4.12'
     androidTestImplementation 'androidx.test.ext:junit:1.1.1'
     androidTestImplementation 'androidx.test.espresso:espresso-core:3.2.0'

app/src/main/java/hidaka/kotlinstudy/todo/MainActivity.kt

@@ -3,11 +3,9 @@ package hidaka.kotlinstudy.todo
 import android.content.Intent
 import android.os.Bundle
 import androidx.appcompat.app.AppCompatActivity
-import androidx.recyclerview.widget.RecyclerView
-import com.google.android.material.floatingactionbutton.FloatingActionButton
+import hidaka.kotlinstudy.todo.fragment.MainFragment
 import hidaka.kotlinstudy.todo.model.Page
 import hidaka.kotlinstudy.todo.ui.PageNewActivity
-import hidaka.kotlinstudy.todo.ui_component.PagesRecyclerViewComponent
 import java.util.*
 
 /// サンプルデータ
@@ -19,30 +17,22 @@ val pagesList: Array<Page> = arrayOf(
 
 class MainActivity : AppCompatActivity() {
 
-    private lateinit var pagesRecyclerView: RecyclerView
-    private lateinit var pagesRecyclerViewComponent: PagesRecyclerViewComponent
-    private lateinit var floatingActionButton: FloatingActionButton
-
     override fun onCreate(savedInstanceState: Bundle?) {
         super.onCreate(savedInstanceState)
         setContentView(R.layout.activity_main)
 
-        pagesRecyclerView = findViewById<RecyclerView>(R.id.main_recycler_view).also {
-            pagesRecyclerViewComponent =
-                PagesRecyclerViewComponent(pagesList, it.context, ::startActivity)
-
-            it.setHasFixedSize(true)
-            it.layoutManager = pagesRecyclerViewComponent.viewManager
-            it.adapter = pagesRecyclerViewComponent.viewAdapter
+        if (savedInstanceState == null) {
+            val fragment = MainFragment()
+            supportFragmentManager
+                .beginTransaction()
+                .add(R.id.main_fragment_host, fragment)
+                .commit()
         }
-        floatingActionButton =
-            findViewById<FloatingActionButton>(R.id.main_floating_action_button).also {
-                it.setOnClickListener {
-                    val intent = Intent(this, PageNewActivity::class.java)
-                    startActivity(intent)
-                }
-            }
+    }
 
+    fun navigateToPageNew() {
+        val intent = Intent(this, PageNewActivity::class.java)
+        startActivity(intent)
     }
 
 }

app/src/main/java/hidaka/kotlinstudy/todo/fragment/MainFragment.kt

@@ -0,0 +1,60 @@
+package hidaka.kotlinstudy.todo.fragment
+
+import android.content.Intent
+import android.os.Bundle
+import androidx.fragment.app.Fragment
+import android.view.LayoutInflater
+import android.view.View
+import android.view.ViewGroup
+import androidx.lifecycle.Lifecycle
+import androidx.recyclerview.widget.RecyclerView
+import com.google.android.material.floatingactionbutton.FloatingActionButton
+import hidaka.kotlinstudy.todo.MainActivity
+import hidaka.kotlinstudy.todo.R
+import hidaka.kotlinstudy.todo.pagesList
+import hidaka.kotlinstudy.todo.ui.PageNewActivity
+import hidaka.kotlinstudy.todo.ui_component.PagesRecyclerViewComponent
+
+/**
+ * A simple [Fragment] subclass.
+ */
+class MainFragment : Fragment() {
+
+    private lateinit var pagesRecyclerView: RecyclerView
+    private lateinit var pagesRecyclerViewComponent: PagesRecyclerViewComponent
+    private lateinit var floatingActionButton: FloatingActionButton
+
+    override fun onCreateView(
+        inflater: LayoutInflater, container: ViewGroup?,
+        savedInstanceState: Bundle?
+    ): View? {
+        // Inflate the layout for this fragment
+        return inflater.inflate(R.layout.fragment_main, container, false)
+    }
+
+    override fun onViewCreated(view: View, savedInstanceState: Bundle?) {
+        super.onViewCreated(view, savedInstanceState)
+
+        pagesRecyclerView = view.findViewById<RecyclerView>(R.id.main_recycler_view).also {
+            pagesRecyclerViewComponent =
+                PagesRecyclerViewComponent(pagesList, it.context, ::startActivity)
+
+            it.setHasFixedSize(true)
+            it.layoutManager = pagesRecyclerViewComponent.viewManager
+            it.adapter = pagesRecyclerViewComponent.viewAdapter
+        }
+        floatingActionButton =
+            view.findViewById<FloatingActionButton>(R.id.main_floating_action_button).also { it ->
+                it.setOnClickListener {
+                    fabClickCallback()
+                }
+            }
+    }
+
+    private fun fabClickCallback() {
+        if (lifecycle.currentState.isAtLeast(Lifecycle.State.STARTED)) {
+            (requireActivity() as MainActivity).navigateToPageNew()
+        }
+    }
+
+}

app/src/main/java/hidaka/kotlinstudy/todo/fragment/PageDetailFragment.kt

@@ -0,0 +1,68 @@
+package hidaka.kotlinstudy.todo.fragment
+
+import android.os.Bundle
+import androidx.fragment.app.Fragment
+import android.view.LayoutInflater
+import android.view.View
+import android.view.ViewGroup
+import android.widget.TextView
+import androidx.lifecycle.Lifecycle
+import com.google.android.material.floatingactionbutton.FloatingActionButton
+import hidaka.kotlinstudy.todo.R
+import hidaka.kotlinstudy.todo.model.Page
+import hidaka.kotlinstudy.todo.ui.PageDetailActivity
+import hidaka.kotlinstudy.todo.ui_component.PagesRecyclerViewComponent
+import java.text.DateFormat
+import java.util.*
+
+/**
+ * A simple [Fragment] subclass.
+ */
+class PageDetailFragment : Fragment() {
+
+    private lateinit var pageTitle: TextView
+    private lateinit var pageUpdatedAt: TextView
+    private lateinit var pageContent: TextView
+    private lateinit var floatingActionButton: FloatingActionButton
+
+    override fun onCreateView(
+        inflater: LayoutInflater, container: ViewGroup?,
+        savedInstanceState: Bundle?
+    ): View? {
+        // Inflate the layout for this fragment
+        return inflater.inflate(R.layout.fragment_page_detail, container, false)
+    }
+
+    override fun onViewCreated(view: View, savedInstanceState: Bundle?) {
+        super.onViewCreated(view, savedInstanceState)
+
+        val page: Page? =
+            arguments?.getParcelable(PagesRecyclerViewComponent.PUT_EXTRA_KEY_PAGE_DETAIL)
+
+        pageTitle = view.findViewById<TextView>(R.id.page_detail_title).also {
+            it.text = page?.title
+        }
+        pageUpdatedAt = view.findViewById<TextView>(R.id.page_detail_updated_at).also {
+            it.text = getString(
+                R.string.page_detail_activity_updated_at_label,
+                DateFormat.getDateInstance(DateFormat.LONG).format(page?.updatedAt ?: Date())
+            )
+        }
+        pageContent = view.findViewById<TextView>(R.id.page_detail_fragment_host).also {
+            it.text = page?.content
+        }
+        floatingActionButton =
+            view.findViewById<FloatingActionButton>(R.id.page_detail_floating_action_button).also {
+                it.setOnClickListener {
+                    fabClickCallback()
+                }
+            }
+    }
+
+    private fun fabClickCallback() {
+        if (lifecycle.currentState.isAtLeast(Lifecycle.State.STARTED)) {
+            (requireActivity() as PageDetailActivity).navigateToPageEdit()
+        }
+    }
+
+}

app/src/main/java/hidaka/kotlinstudy/todo/fragment/PageEditFragment.kt

@@ -0,0 +1,24 @@
+package hidaka.kotlinstudy.todo.fragment
+
+import android.os.Bundle
+import androidx.fragment.app.Fragment
+import android.view.LayoutInflater
+import android.view.View
+import android.view.ViewGroup
+import hidaka.kotlinstudy.todo.R
+
+/**
+ * A simple [Fragment] subclass.
+ */
+class PageEditFragment : Fragment() {
+
+    override fun onCreateView(
+        inflater: LayoutInflater, container: ViewGroup?,
+        savedInstanceState: Bundle?
+    ): View? {
+        // Inflate the layout for this fragment
+        return inflater.inflate(R.layout.fragment_page_edit, container, false)
+    }
+
+
+}

app/src/main/java/hidaka/kotlinstudy/todo/fragment/PageNewFragment.kt

@@ -0,0 +1,23 @@
+package hidaka.kotlinstudy.todo.fragment
+
+import android.os.Bundle
+import androidx.fragment.app.Fragment
+import android.view.LayoutInflater
+import android.view.View
+import android.view.ViewGroup
+import hidaka.kotlinstudy.todo.R
+
+/**
+ * A simple [Fragment] subclass.
+ */
+class PageNewFragment : Fragment() {
+
+    override fun onCreateView(
+        inflater: LayoutInflater, container: ViewGroup?,
+        savedInstanceState: Bundle?
+    ): View? {
+        // Inflate the layout for this fragment
+        return inflater.inflate(R.layout.fragment_page_new, container, false)
+    }
+
+}

app/src/main/java/hidaka/kotlinstudy/todo/ui/PageDetailActivity.kt

@@ -2,47 +2,31 @@ package hidaka.kotlinstudy.todo.ui
 
 import android.content.Intent
 import android.os.Bundle
-import android.widget.TextView
 import androidx.appcompat.app.AppCompatActivity
-import com.google.android.material.floatingactionbutton.FloatingActionButton
+import hidaka.kotlinstudy.todo.fragment.PageDetailFragment
 import hidaka.kotlinstudy.todo.R
-import hidaka.kotlinstudy.todo.R.string.page_detail_activity_updated_at_label
-import hidaka.kotlinstudy.todo.model.Page
-import hidaka.kotlinstudy.todo.ui_component.PagesRecyclerViewComponent
-import java.text.DateFormat
-import java.util.*
 
 class PageDetailActivity : AppCompatActivity() {
-    private lateinit var pageTitle: TextView
-    private lateinit var pageUpdatedAt: TextView
-    private lateinit var pageContent: TextView
-    private lateinit var floatingActionButton: FloatingActionButton
 
     override fun onCreate(savedInstanceState: Bundle?) {
         super.onCreate(savedInstanceState)
         setContentView(R.layout.activity_page_detail)
 
-        val page: Page? =
-            intent.getParcelableExtra<Page?>(PagesRecyclerViewComponent.PUT_EXTRA_KEY_PAGE_DETAIL)
+        if (savedInstanceState == null) {
+            val fragment = PageDetailFragment()
 
-        pageTitle = findViewById<TextView>(R.id.page_detail_title).also {
-            it.text = page?.title
-        }
-        pageUpdatedAt = findViewById<TextView>(R.id.page_detail_updated_at).also {
-            it.text = getString(
-                page_detail_activity_updated_at_label,
-                DateFormat.getDateInstance(DateFormat.LONG).format(page?.updatedAt ?: Date())
-            )
-        }
-        pageContent = findViewById<TextView>(R.id.page_detail_content).also {
-            it.text = page?.content
+            // Intent extras and Fragment Args are both of type android.os.Bundle.
+            fragment.arguments = intent.extras
+
+            supportFragmentManager
+                .beginTransaction()
+                .add(R.id.page_detail_fragment_host, fragment)
+                .commit()
         }
-        floatingActionButton =
-            findViewById<FloatingActionButton>(R.id.page_detail_floating_action_button).also {
-                it.setOnClickListener {
-                    val intent = Intent(this, PageEditActivity::class.java)
-                    startActivity(intent)
-                }
-            }
+    }
+
+    fun navigateToPageEdit() {
+        val intent = Intent(this, PageEditActivity::class.java)
+        startActivity(intent)
     }
 }

app/src/main/java/hidaka/kotlinstudy/todo/ui/PageEditActivity.kt

@@ -3,11 +3,24 @@ package hidaka.kotlinstudy.todo.ui
 import androidx.appcompat.app.AppCompatActivity
 import android.os.Bundle
 import hidaka.kotlinstudy.todo.R
+import hidaka.kotlinstudy.todo.fragment.PageEditFragment
 
 class PageEditActivity : AppCompatActivity() {
 
     override fun onCreate(savedInstanceState: Bundle?) {
         super.onCreate(savedInstanceState)
         setContentView(R.layout.activity_page_edit)
+
+        if (savedInstanceState == null) {
+            val fragment = PageEditFragment()
+
+            // Intent extras and Fragment Args are both of type android.os.Bundle.
+            fragment.arguments = intent.extras
+
+            supportFragmentManager
+                .beginTransaction()
+                .add(R.id.page_edit_fragment_host, fragment)
+                .commit()
+        }
     }
 }

app/src/main/java/hidaka/kotlinstudy/todo/ui/PageNewActivity.kt

@@ -1,13 +1,26 @@
 package hidaka.kotlinstudy.todo.ui
 
-import androidx.appcompat.app.AppCompatActivity
 import android.os.Bundle
+import androidx.appcompat.app.AppCompatActivity
 import hidaka.kotlinstudy.todo.R
+import hidaka.kotlinstudy.todo.fragment.PageNewFragment
 
 class PageNewActivity : AppCompatActivity() {
 
     override fun onCreate(savedInstanceState: Bundle?) {
         super.onCreate(savedInstanceState)
         setContentView(R.layout.activity_page_new)
+
+        if (savedInstanceState == null) {
+            val fragment = PageNewFragment()
+
+            // Intent extras and Fragment Args are both of type android.os.Bundle.
+            fragment.arguments = intent.extras
+
+            supportFragmentManager
+                .beginTransaction()
+                .add(R.id.page_new_fragment_host, fragment)
+                .commit()
+        }
     }
 }

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

@@ -1,23 +1,4 @@
-<?xml version="1.0" encoding="utf-8"?>
-<androidx.coordinatorlayout.widget.CoordinatorLayout xmlns:android="http://schemas.android.com/apk/res/android"
-    xmlns:app="http://schemas.android.com/apk/res-auto"
-    android:layout_width="match_parent"
-    android:layout_height="match_parent">
-
-    <androidx.recyclerview.widget.RecyclerView
-        android:id="@+id/main_recycler_view"
-        android:layout_width="match_parent"
-        android:layout_height="match_parent"
-        app:layout_constraintStart_toStartOf="parent"
-        app:layout_constraintTop_toTopOf="parent" />
-
-    <com.google.android.material.floatingactionbutton.FloatingActionButton
-        android:id="@+id/main_floating_action_button"
-        android:layout_width="wrap_content"
-        android:layout_height="wrap_content"
-        android:layout_gravity="bottom|end"
-        android:layout_margin="16dp"
-        android:clickable="true"
-        android:focusable="true"
-        android:src="@drawable/ic_add_black_24dp" />
-</androidx.coordinatorlayout.widget.CoordinatorLayout>
+<FrameLayout xmlns:android="http://schemas.android.com/apk/res/android"
+    android:id="@+id/main_fragment_host"
+    android:layout_height="match_parent"
+    android:layout_width="match_parent" />