Java tutorial
/* * Copyright (C) 2014 The Android Open Source Project * * Licensed under the Apache License, Version 2.0 (the "License"); * you may not use this file except in compliance with the License. * You may obtain a copy of the License at * * http://www.apache.org/licenses/LICENSE-2.0 * * Unless required by applicable law or agreed to in writing, software * distributed under the License is distributed on an "AS IS" BASIS, * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. * See the License for the specific language governing permissions and * limitations under the License. */ package com.junnanhao.next.utils; import android.content.Context; import android.support.annotation.NonNull; import android.support.v4.app.FragmentActivity; import android.support.v4.media.MediaBrowserCompat; import android.support.v4.media.session.MediaControllerCompat; import android.text.TextUtils; import java.util.Arrays; /** * Utility class to help on queue related tasks. */ public class MediaIDHelper { // Media IDs used on browseable items of MediaBrowser public static final String MEDIA_ID_EMPTY_ROOT = "__EMPTY_ROOT__"; public static final String MEDIA_ID_ROOT = "__ROOT__"; public static final String MEDIA_ID_MUSICS_BY_GENRE = "__BY_GENRE__"; public static final String MEDIA_ID_MUSICS_BY_SEARCH = "__BY_SEARCH__"; private static final char CATEGORY_SEPARATOR = '/'; private static final char LEAF_SEPARATOR = '|'; /** * Create a String value that represents a playable or a browsable media. * <p> * Encode the media browseable categories, if any, and the unique music ID, if any, * into a single String mediaID. * <p> * MediaIDs are of the form <categoryType>/<categoryValue>|<musicUniqueId>, to make it easy * to find the category (like genre) that a music was selected from, so we * can correctly build the playing queue. This is specially useful when * one music can appear in more than one list, like "by genre -> genre_1" * and "by artist -> artist_1". * * @param musicID Unique music ID for playable items, or null for browseable items. * @param categories hierarchy of categories representing this item's browsing parents * @return a hierarchy-aware media ID */ public static String createMediaID(String musicID, String... categories) { StringBuilder sb = new StringBuilder(); if (categories != null) { for (int i = 0; i < categories.length; i++) { if (!isValidCategory(categories[i])) { throw new IllegalArgumentException("Invalid category: " + categories[i]); } sb.append(categories[i]); if (i < categories.length - 1) { sb.append(CATEGORY_SEPARATOR); } } } if (musicID != null) { sb.append(LEAF_SEPARATOR).append(musicID); } return sb.toString(); } private static boolean isValidCategory(String category) { return category == null || (category.indexOf(CATEGORY_SEPARATOR) < 0 && category.indexOf(LEAF_SEPARATOR) < 0); } /** * Extracts unique musicID from the mediaID. mediaID is, by this sample's convention, a * concatenation of category (eg "by_genre"), categoryValue (eg "Classical") and unique * musicID. This is necessary so we know where the user selected the music from, when the music * exists in more than one music list, and thus we are able to correctly build the playing queue. * * @param mediaID that contains the musicID * @return musicID */ public static String extractMusicIDFromMediaID(String mediaID) { if (mediaID == null) return null; int pos = mediaID.indexOf(LEAF_SEPARATOR); if (pos >= 0) { return mediaID.substring(pos + 1); } return null; } /** * Extracts category and categoryValue from the mediaID. mediaID is, by this sample's * convention, a concatenation of category (eg "by_genre"), categoryValue (eg "Classical") and * mediaID. This is necessary so we know where the user selected the music from, when the music * exists in more than one music list, and thus we are able to correctly build the playing queue. * * @param mediaID that contains a category and categoryValue. */ public static @NonNull String[] getHierarchy(@NonNull String mediaID) { int pos = mediaID.indexOf(LEAF_SEPARATOR); if (pos >= 0) { mediaID = mediaID.substring(0, pos); } return mediaID.split(String.valueOf(CATEGORY_SEPARATOR)); } public static String extractBrowseCategoryValueFromMediaID(@NonNull String mediaID) { String[] hierarchy = getHierarchy(mediaID); if (hierarchy.length == 2) { return hierarchy[1]; } return null; } public static boolean isBrowseable(@NonNull String mediaID) { return mediaID.indexOf(LEAF_SEPARATOR) < 0; } public static String getParentMediaID(@NonNull String mediaID) { String[] hierarchy = getHierarchy(mediaID); if (!isBrowseable(mediaID)) { return createMediaID(null, hierarchy); } if (hierarchy.length <= 1) { return MEDIA_ID_ROOT; } String[] parentHierarchy = Arrays.copyOf(hierarchy, hierarchy.length - 1); return createMediaID(null, parentHierarchy); } /** * Determine if media item is playing (matches the currently playing media item). * * @param context for retrieving the {@link MediaControllerCompat} * @param mediaItem to compare to currently playing {@link MediaBrowserCompat.MediaItem} * @return boolean indicating whether media item matches currently playing media item */ public static boolean isMediaItemPlaying(Context context, MediaBrowserCompat.MediaItem mediaItem) { // Media item is considered to be playing or paused based on the controller's current // media id MediaControllerCompat controller = MediaControllerCompat.getMediaController((FragmentActivity) context); if (controller != null && controller.getMetadata() != null) { String currentPlayingMediaId = controller.getMetadata().getDescription().getMediaId(); String itemMusicId = MediaIDHelper.extractMusicIDFromMediaID(mediaItem.getDescription().getMediaId()); if (currentPlayingMediaId != null && TextUtils.equals(currentPlayingMediaId, itemMusicId)) { return true; } } return false; } }