Add help dialog to feed screen

Help to a possible confusion or simply awareness that NewPipe has both
ways to load the feed.

app/src/main/java/org/schabi/newpipe/local/feed/FeedFragment.kt

@@ -23,8 +23,10 @@ import android.content.Intent
 import android.os.Bundle
 import android.os.Parcelable
 import android.view.*
+import androidx.appcompat.app.AlertDialog
 import androidx.lifecycle.Observer
 import androidx.lifecycle.ViewModelProviders
+import androidx.preference.PreferenceManager
 import icepick.State
 import kotlinx.android.synthetic.main.error_retry.*
 import kotlinx.android.synthetic.main.fragment_feed.*
@@ -101,6 +103,38 @@ class FeedFragment : BaseListFragment<FeedState, Unit>() {
         super.onCreateOptionsMenu(menu, inflater)
         activity.supportActionBar?.setTitle(R.string.fragment_feed_title)
         activity.supportActionBar?.subtitle = groupName
+
+        inflater.inflate(R.menu.menu_feed_fragment, menu)
+
+        if (useAsFrontPage) {
+            menu.findItem(R.id.menu_item_feed_help).setShowAsAction(MenuItem.SHOW_AS_ACTION_NEVER);
+        }
+    }
+
+    override fun onOptionsItemSelected(item: MenuItem): Boolean {
+        if (item.itemId == R.id.menu_item_feed_help) {
+            val sharedPreferences = PreferenceManager.getDefaultSharedPreferences(requireContext())
+
+            val usingDedicatedMethod = sharedPreferences.getBoolean(getString(R.string.feed_use_dedicated_fetch_method_key), false)
+            val enableDisableButtonText = when {
+                usingDedicatedMethod -> R.string.feed_use_dedicated_fetch_method_disable_button
+                else -> R.string.feed_use_dedicated_fetch_method_enable_button
+            }
+
+            AlertDialog.Builder(requireContext())
+                    .setMessage(R.string.feed_use_dedicated_fetch_method_help_text)
+                    .setNeutralButton(enableDisableButtonText) { _, _ ->
+                        sharedPreferences.edit()
+                                .putBoolean(getString(R.string.feed_use_dedicated_fetch_method_key), !usingDedicatedMethod)
+                                .apply()
+                    }
+                    .setPositiveButton(android.R.string.ok, null)
+                    .create()
+                    .show()
+            return true
+        }
+
+        return super.onOptionsItemSelected(item)
     }
 
     override fun onDestroyOptionsMenu() {

app/src/main/res/drawable/ic_help_black_24dp.xml

@@ -0,0 +1,9 @@
+<vector xmlns:android="http://schemas.android.com/apk/res/android"
+        android:width="24dp"
+        android:height="24dp"
+        android:viewportWidth="24.0"
+        android:viewportHeight="24.0">
+    <path
+        android:fillColor="#FF000000"
+        android:pathData="M12,2C6.48,2 2,6.48 2,12s4.48,10 10,10 10,-4.48 10,-10S17.52,2 12,2zM13,19h-2v-2h2v2zM15.07,11.25l-0.9,0.92C13.45,12.9 13,13.5 13,15h-2v-0.5c0,-1.1 0.45,-2.1 1.17,-2.83l1.24,-1.26c0.37,-0.36 0.59,-0.86 0.59,-1.41 0,-1.1 -0.9,-2 -2,-2s-2,0.9 -2,2L8,9c0,-2.21 1.79,-4 4,-4s4,1.79 4,4c0,0.88 -0.36,1.68 -0.93,2.25z"/>
+</vector>

app/src/main/res/drawable/ic_help_white_24dp.xml

@@ -0,0 +1,9 @@
+<vector xmlns:android="http://schemas.android.com/apk/res/android"
+        android:width="24dp"
+        android:height="24dp"
+        android:viewportWidth="24.0"
+        android:viewportHeight="24.0">
+    <path
+        android:fillColor="#FFFFFFFF"
+        android:pathData="M12,2C6.48,2 2,6.48 2,12s4.48,10 10,10 10,-4.48 10,-10S17.52,2 12,2zM13,19h-2v-2h2v2zM15.07,11.25l-0.9,0.92C13.45,12.9 13,13.5 13,15h-2v-0.5c0,-1.1 0.45,-2.1 1.17,-2.83l1.24,-1.26c0.37,-0.36 0.59,-0.86 0.59,-1.41 0,-1.1 -0.9,-2 -2,-2s-2,0.9 -2,2L8,9c0,-2.21 1.79,-4 4,-4s4,1.79 4,4c0,0.88 -0.36,1.68 -0.93,2.25z"/>
+</vector>

app/src/main/res/menu/menu_feed_fragment.xml

@@ -0,0 +1,10 @@
+<?xml version="1.0" encoding="utf-8"?>
+<menu xmlns:android="http://schemas.android.com/apk/res/android"
+    xmlns:app="http://schemas.android.com/apk/res-auto">
+
+    <item
+        android:id="@+id/menu_item_feed_help"
+        android:icon="?attr/ic_help"
+        android:title="@string/help"
+        app:showAsAction="always" />
+</menu>

app/src/main/res/values/attrs.xml

@@ -80,6 +80,7 @@
     <attr name="ic_telescope" format="reference"/>
     <attr name="ic_megaphone" format="reference"/>
     <attr name="ic_sort" format="reference"/>
+    <attr name="ic_help" format="reference"/>
 
     <attr name="progress_horizontal_drawable" format="reference"/>
     <!-- Can't refer to colors directly in drawable's xml-->

app/src/main/res/values/strings.xml

@@ -191,6 +191,7 @@
     <string name="clear_search_history_summary">Deletes history of search keywords</string>
     <string name="delete_search_history_alert">Delete entire search history?</string>
     <string name="search_history_deleted">Search history deleted.</string>
+    <string name="help">Help</string>
     <!-- error strings -->
     <string name="general_error">Error</string>
     <string name="download_to_sdcard_error_title">External storage unavailable</string>
@@ -640,4 +641,7 @@
     <string name="feed_update_threshold_option_always_update">Always update</string>
     <string name="feed_use_dedicated_fetch_method_title">Fetch from dedicated feed when available</string>
     <string name="feed_use_dedicated_fetch_method_summary">Available in some services, it is usually much faster but may return a limited amount of items and often incomplete information (e.g. no duration, item type, no live status).</string>
+    <string name="feed_use_dedicated_fetch_method_enable_button">Enable fast mode</string>
+    <string name="feed_use_dedicated_fetch_method_disable_button">Disable fast mode</string>
+    <string name="feed_use_dedicated_fetch_method_help_text">Do you think feed loading is too slow? If so, try enabling fast loading (you can change it in settings or by pressing the button below).\n\nNewPipe offers two feed loading strategies:\n• Fetching the whole subscription channel, which is slow but complete.\n• Using a dedicated service endpoint, which is fast but usually not complete.\n\nThe difference between the two is that the fast one usually lacks some information, like the item\'s duration or type (can\'t distinguish between live videos and normal ones) and it may return less items.\n\nYouTube is an example of a service that offers this fast method with its RSS feed.\n\nSo the choice boils down to what you prefer: speed or precise information.</string>
 </resources>

app/src/main/res/values/styles.xml

@@ -95,6 +95,7 @@
         <item name="ic_telescope">@drawable/ic_telescope_black_24dp</item>
         <item name="ic_megaphone">@drawable/ic_megaphone_black_24dp</item>
         <item name="ic_sort">@drawable/ic_sort_black_24dp</item>
+        <item name="ic_help">@drawable/ic_help_black_24dp</item>
 
         <item name="separator_color">@color/light_separator_color</item>
         <item name="contrast_background_color">@color/light_contrast_background_color</item>
@@ -200,6 +201,7 @@
         <item name="ic_telescope">@drawable/ic_telescope_white_24dp</item>
         <item name="ic_megaphone">@drawable/ic_megaphone_white_24dp</item>
         <item name="ic_sort">@drawable/ic_sort_white_24dp</item>
+        <item name="ic_help">@drawable/ic_help_white_24dp</item>
 
         <item name="separator_color">@color/dark_separator_color</item>
         <item name="contrast_background_color">@color/dark_contrast_background_color</item>