将数据插入到表中，如果已经存在，则将其带到顶部SQLite

Question

我正在我的音乐应用程序中创建一个“最近播放过的”播放列表。我已经创建了一个数据库来存储与歌曲相关的信息。我当前的代码所做的是，每当我播放一首歌曲时，它会将它添加到数据库中，然后我就可以成功地显示它。但问题是，当我播放同一首歌两次时，数据库没有更新。例如，我分别播放歌曲A、歌曲B、歌曲C、歌曲D。然后它将显示歌曲A，歌曲B，歌曲C，歌曲D。但是如果我分别播放歌曲A，歌曲B，歌曲C，歌曲D和歌曲B。然后它再次显示相同的内容(歌曲A、歌曲B、歌曲C、歌曲D)。但我想要的是:歌曲A，歌曲C，歌曲D，歌曲B。它应该更新并显示最新播放的歌曲，这就是我的意思。我想不出该怎么做。

创建表的代码：

 public void onCreate(SQLiteDatabase sqLiteDatabase) {

    String CREATE_TABLE = "CREATE TABLE " + TABLE_NAME+ "("
            + KEY_ID + " INTEGER PRIMARY KEY,"
            + KEY_NAME + " TEXT,"
            + KEY_ARTIST + " TEXT,"
            + KEY_DURATION + " INTEGER,"
            + KEY_ART + " TEXT"
            + ");";

    sqLiteDatabase.execSQL(CREATE_TABLE);

}

获取和显示数据的代码：

   public ArrayList<SongInfoModel> getRecentlyPlayed(){

    ArrayList<SongInfoModel> rpList = new ArrayList<>();
    String selectQuery  = "SELECT * FROM " + TABLE_NAME;
    SQLiteDatabase db = this.getWritableDatabase();
    Cursor cursor = db.rawQuery(selectQuery,null);
    if(cursor.moveToFirst()){

        do{

            long id = cursor.getLong(0);
            String SongName = cursor.getString(1);
            String artistName = cursor.getString(2);
            long dur = cursor.getLong(3);
            String Art = cursor.getString(4);

            SongInfoModel sh = new SongInfoModel(id,SongName,artistName,dur,null,Art);

            rpList.add(sh);
        }while (cursor.moveToNext());
    }

    return rpList;

添加数据的代码：

 public void addSong(SongInfoModel songInfoModel){

        SQLiteDatabase db = this.getWritableDatabase();
        ContentValues values = new ContentValues();
        values.put(KEY_ID, songInfoModel.getSongID());
        values.put(KEY_NAME, songInfoModel.getSongName());
        values.put(KEY_ARTIST, songInfoModel.getArtistName());
        values.put(KEY_DURATION, songInfoModel.getDuration());
        values.put(KEY_ART, songInfoModel.getAlbumIDArtwork());

        db.insert(TABLE_NAME,null,values);
        db.close();

    }

Answer 1

在create query ")";中更改表查询的尾部分号

String CREATE_TABLE = "CREATE TABLE " + TABLE_NAME+ "("
            + KEY_ID + " INTEGER PRIMARY KEY,"
            + KEY_NAME + " TEXT,"
            + KEY_ARTIST + " TEXT,"
            + KEY_DURATION + " INTEGER,"
            + KEY_ART + " TEXT"
            + ")";

    sqLiteDatabase.execSQL(CREATE_TABLE);

Answer 2

我想到的是添加一个表示播放次数的字段，比方说KEY_TIMES。

添加歌曲时检查

• ，如果已经存在，则更新字段
• ，如果不存在，则使用字段默认值添加它。

最后，为了获得值，只需使用相同的查询，但按这个新字段排序：

String selectQuery  = "SELECT * FROM " + TABLE_NAME + " ORDER BY " + KEY_TIMES;

要创建表，请使用以下命令：

public void onCreate(SQLiteDatabase sqLiteDatabase) {
    String CREATE_TABLE = 
    "CREATE TABLE " + TABLE_NAME+ "(" +
        KEY_ID + " INTEGER PRIMARY KEY," +
        KEY_NAME + " TEXT," + 
        KEY_ARTIST + " TEXT," +
        KEY_DURATION + " INTEGER," +
        KEY_LAST_PLAYED + " INTEGER," +
        KEY_TIMES + " INTEGER," +
        KEY_ART + " TEXT" + ");";

    sqLiteDatabase.execSQL(CREATE_TABLE); 
}

然后，当您要添加歌曲时，使用您要添加的ID进行查询，如果查询返回表中的条目，则进行查询以更新KEY_TIMES字段。如果它没有返回条目，请像现在这样插入，但要添加新字段。(目前无法为此提供代码)

Answer 3

您可以做的是在代码中添加一个lastPlayed日期字段。所以它看起来像这样。

public void onCreate(SQLiteDatabase sqLiteDatabase) {
    String CREATE_TABLE = 
    "CREATE TABLE " + TABLE_NAME+ "(" +
        KEY_ID + " INTEGER PRIMARY KEY," +
        KEY_NAME + " TEXT," + 
        KEY_ARTIST + " TEXT," +
        KEY_DURATION + " INTEGER," +
        KEY_LAST_PLAYED + " INTEGER," +
        KEY_ART + " TEXT" + ");";

    sqLiteDatabase.execSQL(CREATE_TABLE); 
}

您用于显示数据的代码将如下所示，并确保按上次播放的时间排序：

public ArrayList<SongInfoModel getRecentlyPlayed() { 
    ArrayList<SongInfoModel> rpList = new ArrayList<>();
    String selectQuery = "SELECT * FROM " + TABLE_NAME + " ORDER BY " + KEY_LAST_PLAYED + " ASC;";
    SQLiteDatabase db = this.getWritableDatabase(); 
    Cursor cursor = db.rawQuery(selectQuery,null);
    if(cursor.moveToFirst()){ 
        do{ 
            long id = cursor.getLong(0); 
            String SongName = cursor.getString(1); 
            String artistName = cursor.getString(2); 
            long dur = cursor.getLong(3); 
            String Art = cursor.getString(5); 
            SongInfoModel sh = new SongInfoModel(id,SongName,artistName,dur,null,Art); 
            rpList.add(sh);
       }while (cursor.moveToNext()); 
} 
return rpList;
}

以及用于添加数据的代码：

public void addSong(SongInfoModel songInfoModel){
    SQLiteDatabase db = this.getWritableDatabase(); 
    ContentValues values = new ContentValues(); 
    values.put(KEY_ID, songInfoModel.getSongID()); 
    values.put(KEY_NAME, songInfoModel.getSongName()); 
    values.put(KEY_ARTIST, songInfoModel.getArtistName()); 
    values.put(KEY_DURATION, songInfoModel.getDuration()); 
    values.put(KEY_LAST_PLAYED, new Date().getTime());
    values.put(KEY_ART, songInfoModel.getAlbumIDArtwork()); 
    db.insert(TABLE_NAME,null,values); 
    db.close();
}

此组合将按上次播放的顺序获取数据。