[wip]Update sample

app/build.gradle

@@ -1,4 +1,6 @@
 apply plugin: 'com.android.application'
+apply plugin: 'kotlin-android-extensions'
+apply plugin: 'kotlin-android'
 
 android {
     compileSdkVersion 28
@@ -9,7 +11,6 @@ android {
         targetSdkVersion 28
         versionCode 1
         versionName "1.0"
-        testInstrumentationRunner "androidx.test.runner.AndroidJUnitRunner"
     }
     buildTypes {
         release {
@@ -23,9 +24,10 @@ dependencies {
     implementation project(':library')
     implementation 'androidx.appcompat:appcompat:1.1.0'
     implementation 'androidx.constraintlayout:constraintlayout:1.1.3'
-    testImplementation 'junit:junit:4.12'
-    androidTestImplementation 'androidx.test.ext:junit:1.1.1'
-    androidTestImplementation('androidx.test.espresso:espresso-core:3.1.0', {
-        exclude group: 'com.android.support', module: 'support-annotations'
-    })
+    implementation 'com.ToxicBakery.viewpager.transforms:view-pager-transforms:2.0.24'
+    implementation "org.jetbrains.kotlin:kotlin-stdlib-jdk7:$kotlin_version"
+    implementation 'com.jakewharton.timber:timber:4.7.1'
+}
+repositories {
+    mavenCentral()
 }

app/src/main/AndroidManifest.xml

@@ -1,16 +1,16 @@
 <?xml version="1.0" encoding="utf-8"?>
 <manifest xmlns:android="http://schemas.android.com/apk/res/android"
+    xmlns:tools="http://schemas.android.com/tools"
     package="jp.shts.android.storyprogressbar">
 
-    <uses-permission android:name="android.permission.INTERNET" />
-
     <application
         android:allowBackup="true"
         android:icon="@mipmap/ic_launcher"
         android:label="@string/app_name"
         android:roundIcon="@mipmap/ic_launcher_round"
         android:supportsRtl="true"
-        android:theme="@style/AppTheme">
+        android:theme="@style/AppTheme"
+        tools:ignore="GoogleAppIndexingWarning">
         <activity android:name=".MainActivity">
             <intent-filter>
                 <action android:name="android.intent.action.MAIN" />
@@ -20,4 +20,6 @@
         </activity>
     </application>
 
+    <uses-permission android:name="android.permission.INTERNET" />
+
 </manifest>

app/src/main/java/jp/shts/android/storyprogressbar/MainActivity.kt

@@ -0,0 +1,141 @@
+package jp.shts.android.storyprogressbar
+
+import android.animation.Animator
+import android.animation.ValueAnimator
+import android.os.Bundle
+import android.util.SparseIntArray
+import android.view.WindowManager
+import androidx.appcompat.app.AppCompatActivity
+import androidx.fragment.app.Fragment
+import androidx.fragment.app.FragmentManager
+import androidx.fragment.app.FragmentStatePagerAdapter
+import androidx.interpolator.view.animation.FastOutSlowInInterpolator
+import androidx.viewpager.widget.ViewPager
+import com.ToxicBakery.viewpager.transforms.CubeOutTransformer
+import timber.log.Timber
+
+interface PageViewOperator {
+    fun backPageView()
+    fun nextPageView()
+}
+
+class MainActivity : AppCompatActivity(), PageViewOperator {
+
+    companion object {
+        private const val PAGE_COUNT = 5
+        /* key: page-count, value: story-count */
+        val progressState = SparseIntArray()
+    }
+
+    private lateinit var viewPager: ViewPager
+    private lateinit var pageAdapter: PageAdapter
+
+    private var currentPage: Int = 0
+
+    override fun onCreate(savedInstanceState: Bundle?) {
+        super.onCreate(savedInstanceState)
+        window.addFlags(WindowManager.LayoutParams.FLAG_FULLSCREEN)
+        setContentView(R.layout.activity_main)
+
+        Timber.plant(Timber.DebugTree())
+
+        pageAdapter = PageAdapter(supportFragmentManager)
+        viewPager = findViewById(R.id.viewpager)
+        viewPager.adapter = pageAdapter
+        viewPager.setPageTransformer(true, CubeOutTransformer())
+        viewPager.addOnPageChangeListener(object : PageChangeListener() {
+            override fun onPageScrollCanceled() {
+                Timber.d("onPageScrollCanceled()")
+                currentFragment()?.resume()
+            }
+            override fun onPageSelected(position: Int) {
+                super.onPageSelected(position)
+                currentPage = position
+//                currentFragment()?.resume()
+            }
+        })
+    }
+
+    private fun currentFragment(): StoryFragment? {
+        return pageAdapter.findFragmentByPosition(viewPager, currentPage) as StoryFragment
+    }
+
+    override fun backPageView() {
+        if (viewPager.currentItem > 0) {
+            fakeDrag(false)
+        }
+    }
+
+    override fun nextPageView() {
+        if (viewPager.currentItem + 1 < viewPager.adapter?.count ?: 0) {
+            fakeDrag(true)
+        }
+    }
+
+    private var prevDragPosition = 0
+
+    /**
+     * Change ViewPage sliding programmatically(not using reflection).
+     * https://tech.dely.jp/entry/2018/12/13/110000
+     * What for?
+     * setCurrentItem(int, boolean) changes too fast. And it cannot set animation duration.
+     */
+    private fun fakeDrag(forward: Boolean) {
+        if (prevDragPosition == 0 && viewPager.beginFakeDrag()) {
+            ValueAnimator.ofInt(0, viewPager.width).apply {
+                duration = 500L
+                interpolator = FastOutSlowInInterpolator()
+                addListener(object : Animator.AnimatorListener {
+
+                    override fun onAnimationStart(animation: Animator?) = Unit
+
+                    override fun onAnimationEnd(animation: Animator?) {
+                        removeAllUpdateListeners()
+                        if (viewPager.isFakeDragging) {
+                            viewPager.endFakeDrag()
+                        }
+                        prevDragPosition = 0
+                    }
+
+                    override fun onAnimationCancel(animation: Animator?) {
+                        removeAllUpdateListeners()
+                        if (viewPager.isFakeDragging) {
+                            viewPager.endFakeDrag()
+                        }
+                        prevDragPosition = 0
+                    }
+
+                    override fun onAnimationRepeat(animation: Animator?) = Unit
+                })
+                addUpdateListener {
+                    if (!viewPager.isFakeDragging) {
+                        return@addUpdateListener
+                    }
+                    val dragPosition: Int = it.animatedValue as Int
+                    val dragOffset: Float = ((dragPosition - prevDragPosition) * if (forward) -1 else 1).toFloat()
+                    prevDragPosition = dragPosition
+                    viewPager.fakeDragBy(dragOffset)
+                }
+            }.start()
+        }
+    }
+
+    private class PageAdapter internal constructor(fragmentManager: FragmentManager) :
+            FragmentStatePagerAdapter(fragmentManager, BEHAVIOR_RESUME_ONLY_CURRENT_FRAGMENT) {
+        override fun getItem(position: Int): Fragment = StoryFragment.createIntent(position)
+        override fun getCount(): Int {
+            return PAGE_COUNT
+        }
+        /**
+         * https://qiita.com/chooblarin/items/88b4accac0cbb6944d4b#%E6%96%B9%E6%B3%953-instantiateitem%E3%82%92%E4%BD%BF%E3%81%86
+         */
+        fun findFragmentByPosition(viewPager: ViewPager, position: Int): Fragment? {
+            try {
+                val f = instantiateItem(viewPager, position)
+                return f as? Fragment
+            } finally {
+                finishUpdate(viewPager)
+            }
+        }
+    }
+}

app/src/main/java/jp/shts/android/storyprogressbar/PageChangeListener.kt

@@ -0,0 +1,54 @@
+package jp.shts.android.storyprogressbar
+
+import android.os.Handler
+import android.os.HandlerThread
+import android.os.Message
+import androidx.viewpager.widget.ViewPager.*
+import timber.log.Timber
+
+abstract class PageChangeListener : OnPageChangeListener {
+
+    companion object {
+        private const val DEBOUNCE_TIMES = 500L
+    }
+
+    private var pageBeforeDragging = 0
+    private var currentPage = 0
+    private var lastTime = DEBOUNCE_TIMES + 1L
+
+    override fun onPageScrollStateChanged(state: Int) {
+        when (state) {
+            SCROLL_STATE_IDLE -> {
+                Timber.d("onPageScrollStateChanged(): SCROLL_STATE_IDLE")
+                // 500ms 以下間隔のリクエストは破棄する
+                val now = System.currentTimeMillis()
+                if (now - lastTime < DEBOUNCE_TIMES) {
+                    return
+                }
+                lastTime = now
+                Handler().postDelayed({
+                    if (pageBeforeDragging == currentPage) {
+                        onPageScrollCanceled()
+                    }
+                }, 300L)
+            }
+            SCROLL_STATE_DRAGGING -> {
+                Timber.d("onPageScrollStateChanged(): SCROLL_STATE_DRAGGING")
+                pageBeforeDragging = currentPage
+            }
+            SCROLL_STATE_SETTLING -> {
+                Timber.d("onPageScrollStateChanged(): SCROLL_STATE_SETTLING")
+            }
+        }
+    }
+
+    override fun onPageScrolled(position: Int, positionOffset: Float, positionOffsetPixels: Int) {
+    }
+
+    override fun onPageSelected(position: Int) {
+        Timber.d("onPageSelected(): position($position)")
+        currentPage = position
+    }
+
+    abstract fun onPageScrollCanceled()
+}