feat: implement App Introduction System

* Displays the App Introduction System
* Handles only displaying it once
* Handles syncing if the app intro loads an existing AnkiWeb account
* (special case) Handles an upgrade from 2.15 -> 2.16 where
  the preference for the app intro was unset.

AnkiDroid/src/main/java/com/ichi2/anki/DeckPicker.kt

@@ -149,6 +149,9 @@ import kotlin.math.roundToLong
  * * A custom image as a background can be added: [applyDeckPickerBackground]
  */
 @KotlinCleanup("lots to do")
+@NeedsTest("On a new startup, the App Intro is displayed")
+@NeedsTest("If the collection has been created, the app intro is not displayed")
+@NeedsTest("If the user selects 'Sync Profile' in the app intro, a sync starts immediately")
 open class DeckPicker :
     NavigationDrawerActivity(),
     StudyOptionsListener,
@@ -382,6 +385,19 @@ open class DeckPicker :
 
         // Then set theme and content view
         super.onCreate(savedInstanceState)
+
+        // handle the first load: display the app introduction
+        if (!hasShownAppIntro()) {
+            val appIntro = Intent(this, IntroductionActivity::class.java)
+            appIntro.addFlags(Intent.FLAG_ACTIVITY_CLEAR_TOP or Intent.FLAG_ACTIVITY_NEW_TASK)
+            startActivityWithoutAnimation(appIntro)
+            finish() // calls onDestroy() immediately
+            return
+        }
+        if (intent.hasExtra(INTENT_SYNC_FROM_LOGIN)) {
+            mSyncOnResume = true
+        }
+
         setContentView(R.layout.homescreen)
         handleStartup()
         val mainView = findViewById<View>(android.R.id.content)
@@ -463,6 +479,23 @@ open class DeckPicker :
         Onboarding.DeckPicker(this, mRecyclerViewLayoutManager).onCreate()
     }
 
+    private fun hasShownAppIntro(): Boolean {
+        val prefs = AnkiDroidApp.getSharedPrefs(this)
+
+        // if moving from 2.15 to 2.16 then we do not want to show the intro
+        // remove this after ~2.17 and default to 'false' if the pref is not set
+        if (!prefs.contains(IntroductionActivity.INTRODUCTION_SLIDES_SHOWN)) {
+            return if (!InitialActivity.wasFreshInstall(prefs)) {
+                prefs.edit { putBoolean(IntroductionActivity.INTRODUCTION_SLIDES_SHOWN, true) }
+                true
+            } else {
+                false
+            }
+        }
+
+        return prefs.getBoolean(IntroductionActivity.INTRODUCTION_SLIDES_SHOWN, false)
+    }
+
     /**
      * The first call in showing dialogs for startup - error or success.
      * Attempts startup if storage permission has been acquired, else, it requests the permission
@@ -861,7 +894,8 @@ open class DeckPicker :
 
     fun refreshState() {
         mActivityPaused = false
-        if (mSyncOnResume) {
+        // Due to the App Introduction, this may be called before permission has been granted.
+        if (mSyncOnResume && hasStorageAccessPermission(this)) {
             Timber.i("Performing Sync on Resume")
             sync()
             mSyncOnResume = false
@@ -2684,6 +2718,14 @@ open class DeckPicker :
         const val RESULT_DB_ERROR = 203
         const val UPGRADE_VERSION_KEY = "lastUpgradeVersion"
 
+        /**
+         * If passed into the intent, the user should have been logged in and DeckPicker
+         * should sync immediately.
+         *
+         * This is for the 'download existing collection from AnkiWeb' use case
+         */
+        const val INTENT_SYNC_FROM_LOGIN = "syncFromLogin"
+
         /**
          * Available options performed by other activities (request codes for onActivityResult())
          */

AnkiDroid/src/main/java/com/ichi2/anki/IntroductionActivity.kt

@@ -96,7 +96,7 @@ class IntroductionActivity : AppIntro() {
         val deckPicker = Intent(this, DeckPicker::class.java)
         deckPicker.addFlags(Intent.FLAG_ACTIVITY_CLEAR_TOP or Intent.FLAG_ACTIVITY_NEW_TASK)
         if (result == RESULT_SYNC_PROFILE) {
-            deckPicker.putExtra("syncFromLogin", true)
+            deckPicker.putExtra(DeckPicker.INTENT_SYNC_FROM_LOGIN, true)
         }
 
         startActivity(deckPicker)

AnkiDroid/src/test/java/com/ichi2/anki/DeckPickerTest.kt

@@ -5,6 +5,7 @@ import android.content.Intent
 import android.content.SharedPreferences
 import android.content.pm.PackageManager
 import android.view.Menu
+import androidx.core.content.edit
 import androidx.test.core.app.ActivityScenario
 import com.ichi2.anki.dialogs.DatabaseErrorDialog
 import com.ichi2.anki.dialogs.DeckPickerConfirmDeleteDeckDialog
@@ -54,6 +55,7 @@ class DeckPickerTest : RobolectricTest() {
     @Before
     fun before() {
         RuntimeEnvironment.setQualifiers(mQualifiers)
+        getPreferences().edit { putBoolean(IntroductionActivity.INTRODUCTION_SLIDES_SHOWN, true) }
     }
 
     @Test

AnkiDroid/src/test/java/com/ichi2/anki/dialogs/CreateDeckDialogTest.kt

@@ -17,6 +17,7 @@
 package com.ichi2.anki.dialogs
 
 import android.widget.EditText
+import androidx.core.content.edit
 import androidx.lifecycle.Lifecycle
 import androidx.test.core.app.ActivityScenario
 import com.afollestad.materialdialogs.WhichButton
@@ -24,6 +25,7 @@ import com.afollestad.materialdialogs.actions.getActionButton
 import com.afollestad.materialdialogs.input.getInputField
 import com.ichi2.anki.CollectionManager.withCol
 import com.ichi2.anki.DeckPicker
+import com.ichi2.anki.IntroductionActivity
 import com.ichi2.anki.R
 import com.ichi2.anki.RobolectricTest
 import com.ichi2.libanki.DeckManager
@@ -51,6 +53,7 @@ class CreateDeckDialogTest : RobolectricTest() {
     private var mActivityScenario: ActivityScenario<DeckPicker>? = null
     override fun setUp() {
         super.setUp()
+        getPreferences().edit { putBoolean(IntroductionActivity.INTRODUCTION_SLIDES_SHOWN, true) }
         ensureCollectionLoadIsSynchronous()
         mActivityScenario = ActivityScenario.launch(DeckPicker::class.java)
         val activityScenario: ActivityScenario<DeckPicker>? = mActivityScenario