Move PlayerType into its own class and add documentation

Also replace some `isPlayerOpen` with direct `playerType == null` checks.

app/src/main/java/org/schabi/newpipe/player/Player.java

@@ -32,7 +32,6 @@ import static org.schabi.newpipe.extractor.utils.Utils.isNullOrEmpty;
 import static org.schabi.newpipe.player.helper.PlayerHelper.isPlaybackResumeEnabled;
 import static org.schabi.newpipe.player.helper.PlayerHelper.nextRepeatMode;
 import static org.schabi.newpipe.player.helper.PlayerHelper.retrievePlaybackParametersFromPrefs;
-import static org.schabi.newpipe.player.helper.PlayerHelper.retrievePlayerTypeFromIntent;
 import static org.schabi.newpipe.player.helper.PlayerHelper.retrieveSeekDurationFromPreferences;
 import static org.schabi.newpipe.player.helper.PlayerHelper.savePlaybackParametersToPrefs;
 import static org.schabi.newpipe.player.notification.NotificationConstants.ACTION_CLOSE;
@@ -95,7 +94,6 @@ import org.schabi.newpipe.extractor.stream.StreamType;
 import org.schabi.newpipe.extractor.stream.VideoStream;
 import org.schabi.newpipe.fragments.detail.VideoDetailFragment;
 import org.schabi.newpipe.local.history.HistoryRecordManager;
-import org.schabi.newpipe.player.PlayerService.PlayerType;
 import org.schabi.newpipe.player.event.PlayerEventListener;
 import org.schabi.newpipe.player.event.PlayerServiceEventListener;
 import org.schabi.newpipe.player.helper.AudioReactor;
@@ -308,7 +306,7 @@ public final class Player implements PlaybackListener, Listener {
         }
 
         final PlayerType oldPlayerType = playerType;
-        playerType = retrievePlayerTypeFromIntent(intent);
+        playerType = PlayerType.retrieveFromIntent(intent);
         initUIsForCurrentPlayerType();
         // We need to setup audioOnly before super(), see "sourceOf"
         isAudioOnly = audioPlayerSelected();

app/src/main/java/org/schabi/newpipe/player/PlayerService.java

@@ -42,11 +42,6 @@ public final class PlayerService extends Service {
 
     private final IBinder mBinder = new PlayerService.LocalBinder();
 
-    public enum PlayerType {
-        MAIN,
-        AUDIO,
-        POPUP
-    }
 
     /*//////////////////////////////////////////////////////////////////////////
     // Service's LifeCycle

app/src/main/java/org/schabi/newpipe/player/PlayerType.java

@@ -0,0 +1,32 @@
+package org.schabi.newpipe.player;
+
+import static org.schabi.newpipe.player.Player.PLAYER_TYPE;
+
+import android.content.Intent;
+
+public enum PlayerType {
+    MAIN,
+    AUDIO,
+    POPUP;
+
+    /**
+     * @return an integer representing this {@link PlayerType}, to be used to save it in intents
+     * @see #retrieveFromIntent(Intent) Use retrieveFromIntent() to retrieve and convert player type
+     *                                  integers from an intent
+     */
+    public int valueForIntent() {
+        return ordinal();
+    }
+
+    /**
+     * @param intent the intent to retrieve a player type from
+     * @return the player type integer retrieved from the intent, converted back into a {@link
+     *         PlayerType}, or {@link PlayerType#MAIN} if there is no player type extra in the
+     *         intent
+     * @throws ArrayIndexOutOfBoundsException if the intent contains an invalid player type integer
+     * @see #valueForIntent() Use valueForIntent() to obtain valid player type integers
+     */
+    public static PlayerType retrieveFromIntent(final Intent intent) {
+        return values()[intent.getIntExtra(PLAYER_TYPE, MAIN.valueForIntent())];
+    }
+}

app/src/main/java/org/schabi/newpipe/player/helper/PlayerHelper.java

@@ -3,7 +3,6 @@ package org.schabi.newpipe.player.helper;
 import static com.google.android.exoplayer2.Player.REPEAT_MODE_ALL;
 import static com.google.android.exoplayer2.Player.REPEAT_MODE_OFF;
 import static com.google.android.exoplayer2.Player.REPEAT_MODE_ONE;
-import static org.schabi.newpipe.player.Player.PLAYER_TYPE;
 import static org.schabi.newpipe.player.helper.PlayerHelper.AutoplayType.AUTOPLAY_TYPE_ALWAYS;
 import static org.schabi.newpipe.player.helper.PlayerHelper.AutoplayType.AUTOPLAY_TYPE_NEVER;
 import static org.schabi.newpipe.player.helper.PlayerHelper.AutoplayType.AUTOPLAY_TYPE_WIFI;
@@ -14,7 +13,6 @@ import static java.lang.annotation.RetentionPolicy.SOURCE;
 
 import android.annotation.SuppressLint;
 import android.content.Context;
-import android.content.Intent;
 import android.content.SharedPreferences;
 import android.provider.Settings;
 import android.view.accessibility.CaptioningManager;
@@ -44,7 +42,6 @@ import org.schabi.newpipe.extractor.stream.StreamInfoItem;
 import org.schabi.newpipe.extractor.stream.SubtitlesStream;
 import org.schabi.newpipe.extractor.utils.Utils;
 import org.schabi.newpipe.player.Player;
-import org.schabi.newpipe.player.PlayerService;
 import org.schabi.newpipe.player.playqueue.PlayQueue;
 import org.schabi.newpipe.player.playqueue.PlayQueueItem;
 import org.schabi.newpipe.player.playqueue.SinglePlayQueue;
@@ -428,12 +425,6 @@ public final class PlayerHelper {
     // Utils used by player
     ////////////////////////////////////////////////////////////////////////////
 
-    public static PlayerService.PlayerType retrievePlayerTypeFromIntent(final Intent intent) {
-        // If you want to open popup from the app just include Constants.POPUP_ONLY into an extra
-        return PlayerService.PlayerType.values()[
-                intent.getIntExtra(PLAYER_TYPE, PlayerService.PlayerType.MAIN.ordinal())];
-    }
-
     public static boolean isPlaybackResumeEnabled(final Player player) {
         return player.getPrefs().getBoolean(
                 player.getContext().getString(R.string.enable_watch_history_key), true)

app/src/main/java/org/schabi/newpipe/player/helper/PlayerHolder.java

@@ -18,6 +18,7 @@ import org.schabi.newpipe.MainActivity;
 import org.schabi.newpipe.extractor.stream.StreamInfo;
 import org.schabi.newpipe.player.PlayerService;
 import org.schabi.newpipe.player.Player;
+import org.schabi.newpipe.player.PlayerType;
 import org.schabi.newpipe.player.event.PlayerServiceEventListener;
 import org.schabi.newpipe.player.event.PlayerServiceExtendedEventListener;
 import org.schabi.newpipe.player.playqueue.PlayQueue;
@@ -46,13 +47,13 @@ public final class PlayerHolder {
     @Nullable private Player player;
 
     /**
-     * Returns the current {@link PlayerService.PlayerType} of the {@link PlayerService} service,
-     * otherwise `null` if no service running.
+     * Returns the current {@link PlayerType} of the {@link PlayerService} service,
+     * otherwise `null` if no service is running.
      *
      * @return Current PlayerType
      */
     @Nullable
-    public PlayerService.PlayerType getType() {
+    public PlayerType getType() {
         if (player == null) {
             return null;
         }