Android-獲取音樂內置圖片，完整解決方案。

代碼功能：獲取系統音樂文件信息，傳入對應ID後獲取對應內置圖片（可選擇大圖或者小圖）。

import java.io.FileDescriptor;
import java.io.FileNotFoundException;
import java.io.IOException;
import java.io.InputStream;
import java.util.ArrayList;
import java.util.HashMap;
import java.util.Iterator;
import java.util.List;

import android.content.ContentResolver;
import android.content.ContentUris;
import android.content.Context;
import android.database.Cursor;
import android.graphics.Bitmap;
import android.graphics.BitmapFactory;
import android.graphics.BitmapFactory.Options;
import android.net.Uri;
import android.os.ParcelFileDescriptor;
import android.provider.MediaStore;

public class MediaInfor {

//獲取專輯封面的Uri
private static final Uri albumArtUri = Uri.parse("content://media/external/audio/albumart");

/**
 * 用於從數據庫中查詢歌曲的信息，保存在List當中
 * 
 * @return
 */
public static List<Music> getMp3Infos(Context context) {
    Cursor cursor = context.getContentResolver().query(
            MediaStore.Audio.Media.EXTERNAL_CONTENT_URI, null, null, null,
            MediaStore.Audio.Media.DEFAULT_SORT_ORDER);

    List<Music> musics = new ArrayList<Music>();
    for (int i = 0; i < cursor.getCount(); i++) {
        cursor.moveToNext();
        Music music = new Music();
        int id = (int)cursor.getLong(cursor
                .getColumnIndex(MediaStore.Audio.Media._ID));   //音樂id
        String title = cursor.getString((cursor 
                .getColumnIndex(MediaStore.Audio.Media.TITLE))); // 音樂標題
        String artist = cursor.getString(cursor
                .getColumnIndex(MediaStore.Audio.Media.ARTIST)); // 藝術家
        String album = cursor.getString(cursor
                .getColumnIndex(MediaStore.Audio.Media.ALBUM)); //專輯
        String displayName = cursor.getString(cursor
                .getColumnIndex(MediaStore.Audio.Media.DISPLAY_NAME));
        int albumId = cursor.getInt(cursor.getColumnIndex(MediaStore.Audio.Media.ALBUM_ID));
        int duration = (int)cursor.getLong(cursor
                .getColumnIndex(MediaStore.Audio.Media.DURATION)); // 時長
        long size = cursor.getLong(cursor
                .getColumnIndex(MediaStore.Audio.Media.SIZE)); // 文件大小
        String url = cursor.getString(cursor
                .getColumnIndex(MediaStore.Audio.Media.DATA)); // 文件路徑
        int isMusic = cursor.getInt(cursor
                .getColumnIndex(MediaStore.Audio.Media.IS_MUSIC)); // 是否爲音樂
        if (isMusic != 0) { // 只把音樂添加到集合當中
            music.setId(id);
            music.setTitle(title);
            music.setArtist(artist);
            music.setAlbum(album);
            music.setDisplayName(displayName);
            music.setAlbumId(albumId);
            music.setDuration(duration);
            music.setSize(size);
            music.setPath(url);
            musics.add(music);
        }
    }
    return musics;
}

/**
 * 往List集合中添加Map對象數據，每一個Map對象存放一首音樂的所有屬性
 * @param musics
 * @return
 */
public static List<HashMap<String, String>> getMusicMaps(
        List<Music> musics) {
    List<HashMap<String, String>> mp3list = new ArrayList<HashMap<String, String>>();
    for (Iterator iterator = musics.iterator(); iterator.hasNext();) {
        Music music = (Music) iterator.next();
        HashMap<String, String> map = new HashMap<String, String>();
        map.put("title", music.getTitle());
        map.put("Artist", music.getArtist());
        map.put("album", music.getAlbum());
        map.put("displayName", music.getDisplayName());
        map.put("albumId", String.valueOf(music.getAlbumId()));
        map.put("duration", formatTime(music.getDuration()));
        map.put("size", String.valueOf(music.getSize()));
        map.put("url", music.getPath());
        mp3list.add(map);
    }
    return mp3list;
}

/**
 * 格式化時間，將毫秒轉換爲分:秒格式
 * @param time
 * @return
 */
public static String formatTime(long time) {
    String min = time / (1000 * 60) + "";
    String sec = time % (1000 * 60) + "";
    if (min.length() < 2) {
        min = "0" + time / (1000 * 60) + "";
    } else {
        min = time / (1000 * 60) + "";
    }
    if (sec.length() == 4) {
        sec = "0" + (time % (1000 * 60)) + "";
    } else if (sec.length() == 3) {
        sec = "00" + (time % (1000 * 60)) + "";
    } else if (sec.length() == 2) {
        sec = "000" + (time % (1000 * 60)) + "";
    } else if (sec.length() == 1) {
        sec = "0000" + (time % (1000 * 60)) + "";
    }
    return min + ":" + sec.trim().substring(0, 2);
}


/**
 * 獲取默認專輯圖片
 * @param context
 * @return
 */
public static Bitmap getDefaultArtwork(Context context,boolean small) {
    BitmapFactory.Options opts = new BitmapFactory.Options();
    opts.inPreferredConfig = Bitmap.Config.RGB_565;
    if(small){  //返回小圖片
        return BitmapFactory.decodeStream(context.getResources().openRawResource(R.drawable.music5), null, opts);
    }
    return BitmapFactory.decodeStream(context.getResources().openRawResource(R.drawable.defaultalbum), null, opts);
}


/**
 * 從文件當中獲取專輯封面位圖
 * @param context
 * @param songid
 * @param albumid
 * @return
 */
private static Bitmap getArtworkFromFile(Context context, long songid, long albumid){
    Bitmap bm = null;
    if(albumid < 0 && songid < 0) {
        throw new IllegalArgumentException("Must specify an album or a song id");
    }
    try {
        BitmapFactory.Options options = new BitmapFactory.Options();
        FileDescriptor fd = null;
        if(albumid < 0){
            Uri uri = Uri.parse("content://media/external/audio/media/"
                    + songid + "/albumart");
            ParcelFileDescriptor pfd = context.getContentResolver().openFileDescriptor(uri, "r");
            if(pfd != null) {
                fd = pfd.getFileDescriptor();
            }
        } else {
            Uri uri = ContentUris.withAppendedId(albumArtUri, albumid);
            ParcelFileDescriptor pfd = context.getContentResolver().openFileDescriptor(uri, "r");
            if(pfd != null) {
                fd = pfd.getFileDescriptor();
            }
        }
        options.inSampleSize = 1;
        // 只進行大小判斷
        options.inJustDecodeBounds = true;
        // 調用此方法得到options得到圖片大小
        BitmapFactory.decodeFileDescriptor(fd, null, options);
        // 我們的目標是在800pixel的畫面上顯示
        // 所以需要調用computeSampleSize得到圖片縮放的比例
        options.inSampleSize = 100;
        // 我們得到了縮放的比例，現在開始正式讀入Bitmap數據
        options.inJustDecodeBounds = false;
        options.inDither = false;
        options.inPreferredConfig = Bitmap.Config.ARGB_8888;

        //根據options參數，減少所需要的內存
        bm = BitmapFactory.decodeFileDescriptor(fd, null, options);
    } catch (FileNotFoundException e) {
        e.printStackTrace();
    }
    return bm;
}

/**
 * 獲取專輯封面位圖對象
 * @param context
 * @param song_id
 * @param album_id
 * @param allowdefalut
 * @return
 */
public static Bitmap getArtwork(Context context, long song_id, long album_id, boolean allowdefalut, boolean small){
    if(album_id < 0) {
        if(song_id < 0) {
            Bitmap bm = getArtworkFromFile(context, song_id, -1);
            if(bm != null) {
                return bm;
            }
        }
        if(allowdefalut) {
            return getDefaultArtwork(context, small);
        }
        return null;
    }
    ContentResolver res = context.getContentResolver();
    Uri uri = ContentUris.withAppendedId(albumArtUri, album_id);
    if(uri != null) {
        InputStream in = null;
        try {
            in = res.openInputStream(uri);
            BitmapFactory.Options options = new BitmapFactory.Options();
            //先制定原始大小
            options.inSampleSize = 1;
            //只進行大小判斷
            options.inJustDecodeBounds = true;
            //調用此方法得到options得到圖片的大小
            BitmapFactory.decodeStream(in, null, options);
            /** 我們的目標是在你N pixel的畫面上顯示。 所以需要調用computeSampleSize得到圖片縮放的比例 **/
            /** 這裏的target爲800是根據默認專輯圖片大小決定的，800只是測試數字但是試驗後發現完美的結合 **/
            if(small){
                options.inSampleSize = computeSampleSize(options, 40);
            } else{
                options.inSampleSize = computeSampleSize(options, 600);
            }
            // 我們得到了縮放比例，現在開始正式讀入Bitmap數據
            options.inJustDecodeBounds = false;
            options.inDither = false;
            options.inPreferredConfig = Bitmap.Config.ARGB_8888;
            in = res.openInputStream(uri);
            return BitmapFactory.decodeStream(in, null, options);
        } catch (FileNotFoundException e) {
            Bitmap bm = getArtworkFromFile(context, song_id, album_id);
            if(bm != null) {
                if(bm.getConfig() == null) {
                    bm = bm.copy(Bitmap.Config.RGB_565, false);
                    if(bm == null && allowdefalut) {
                        return getDefaultArtwork(context, small);
                    }
                }
            } else if(allowdefalut) {
                bm = getDefaultArtwork(context, small);
            }
            return bm;
        } finally {
            try {
                if(in != null) {
                    in.close();
                }
            } catch (IOException e) {
                e.printStackTrace();
            }
        }
    }
    return null;
}

/**
 * 對圖片進行合適的縮放
 * @param options
 * @param target
 * @return
 */
public static int computeSampleSize(Options options, int target) {
    int w = options.outWidth;
    int h = options.outHeight;
    int candidateW = w / target;
    int candidateH = h / target;
    int candidate = Math.max(candidateW, candidateH);
    if(candidate == 0) {
        return 1;
    }
    if(candidate > 1) {
        if((w > target) && (w / candidate) < target) {
            candidate -= 1;
        }
    }
    if(candidate > 1) {
        if((h > target) && (h / candidate) < target) {
            candidate -= 1;
        }
    }
    return candidate;
}

}

本文僅爲備忘，同時歡迎大家交流。