在Libgdx中使用SQLite数据库

Question

我是Libgdx的新手，在使用游戏数据库时遇到麻烦。

我搜索了有关如何使用Libgdx使SQLite在Android和桌面应用程序上运行的教程，但没有找到一个简单的教程。

我上一次在Android中使用数据库时，创建了一个从扩展的类SQLiteOpenHelper。

有没有一种简单的方法可以使用Libgdx做到这一点？或者至少，有人可以指出我的逐步教程或类似内容吗？

编辑

我忘了说我正在寻找可以让我管理诸如的版本的东西SQLiteOpenHelper。换句话说，当我更改代码数据库的版本时，我想在apk安装中的Android中重新创建数据库。

解

按照@42n4答案，我设法SQLiteOpenHelper在Android应用程序和JDBC桌面应用程序上使用SQLite数据库进行连接。

首先，我为桌面和Android应用程序创建了一个“通用类”：

//General class that needs to be implemented on Android and Desktop Applications
public abstract class DataBase {

    protected static String database_name="recycling_separation";
    protected static DataBase instance = null;
    protected static int version=1;

    //Runs a sql query like "create".
    public abstract void execute(String sql);

    //Identical to execute but returns the number of rows affected (useful for updates)
    public abstract int executeUpdate(String sql);

    //Runs a query and returns an Object with all the results of the query. [Result Interface is defined below]
    public abstract Result query(String sql);

    public void onCreate(){
        //Example of Highscore table code (You should change this for your own DB code creation)
        execute("CREATE TABLE 'highscores' ('_id' INTEGER PRIMARY KEY  NOT NULL , 'name' VARCHAR NOT NULL , 'score' INTEGER NOT NULL );");
        execute("INSERT INTO 'highscores'(name,score) values ('Cris',1234)");
        //Example of query to get DB data of Highscore table
        Result q=query("SELECT * FROM 'highscores'");
        if (!q.isEmpty()){
            q.moveToNext();
            System.out.println("Highscore of "+q.getString(q.getColumnIndex("name"))+": "+q.getString(q.getColumnIndex("score")));
        }
    }

    public void onUpgrade(){
        //Example code (You should change this for your own DB code)
        execute("DROP TABLE IF EXISTS 'highscores';");
        onCreate();
        System.out.println("DB Upgrade maded because I changed DataBase.version on code");
    }

    //Interface to be implemented on both Android and Desktop Applications
    public interface Result{
        public boolean isEmpty();
        public boolean moveToNext();
        public int getColumnIndex(String name);
        public float getFloat(int columnIndex);
        [...]
    }
}

然后，我DatabaseDesktop为桌面应用程序创建了一个类：

    public class DatabaseDesktop extends DataBase{
    protected Connection db_connection;
    protected Statement stmt;
    protected boolean nodatabase=false;

    public DatabaseDesktop() {
        loadDatabase();
        if (isNewDatabase()){
            onCreate();
            upgradeVersion();
        } else if (isVersionDifferent()){
            onUpgrade();
            upgradeVersion();
        }

    }

    public void execute(String sql){
        try {
            stmt.execute(sql);
        } catch (SQLException e) {
            e.printStackTrace();
        }
    }

    public int executeUpdate(String sql){
        try {
            return stmt.executeUpdate(sql);
        } catch (SQLException e) {
            e.printStackTrace();
        }
        return 0;
    }

    public Result query(String sql) {
        try {
            return new ResultDesktop(stmt.executeQuery(sql));
        } catch (SQLException e) {
            e.printStackTrace();
        }
        return null;
    }

    private void loadDatabase(){
        File file = new File (database_name+".db");
        if(!file.exists())
            nodatabase=true;
        try {
            Class.forName("org.sqlite.JDBC");
            db_connection = DriverManager.getConnection("jdbc:sqlite:"+database_name+".db");
            stmt = db_connection.createStatement();
        } catch (ClassNotFoundException e) {
            e.printStackTrace();
        } catch (SQLException e) {
            e.printStackTrace();
        }
    }

    private void upgradeVersion() {
        execute("PRAGMA user_version="+version);
    }

    private boolean isNewDatabase() {
        return nodatabase;
    }

    private boolean isVersionDifferent(){
        Result q=query("PRAGMA user_version");
        if (!q.isEmpty())
            return (q.getInt(1)!=version);
        else 
            return true;
    }

    public class ResultDesktop implements Result{

        ResultSet res;
        boolean called_is_empty=false;

        public ResultDesktop(ResultSet res) {
            this.res = res;
        }

        public boolean isEmpty() {
            try {
                if (res.getRow()==0){
                    called_is_empty=true;
                    return !res.next();
                }
                return res.getRow()==0;
            } catch (SQLException e) {
                e.printStackTrace();
            }
            return false;
        }

        public boolean moveToNext() {
            try {
                if (called_is_empty){
                    called_is_empty=false;
                    return true;
                } else
                    return res.next();
            } catch (SQLException e) {
                e.printStackTrace();
            }
            return false;
        }

        public int getColumnIndex(String name) {
            try {
                return res.findColumn(name);
            } catch (SQLException e) {
                e.printStackTrace();
            }
            return 0;
        }

        public float getFloat(int columnIndex) {
            try {
                return res.getFloat(columnIndex);
            } catch (SQLException e) {
                e.printStackTrace();
            }
            return 0;
        }

        [...]

    }

}

并DatabaseAndroid为Android应用程序

public class DatabaseAndroid extends DataBase{
    protected SQLiteOpenHelper db_connection;
    protected SQLiteDatabase stmt;

    public DatabaseAndroid(Context context) {
        db_connection = new AndroidDB(context, database_name, null, version);
        stmt=db_connection.getWritableDatabase();
    }

    public void execute(String sql){
        stmt.execSQL(sql);
    }

    public int executeUpdate(String sql){
        stmt.execSQL(sql);
        SQLiteStatement tmp = stmt.compileStatement("SELECT CHANGES()");
        return (int) tmp.simpleQueryForLong();
    }

    public Result query(String sql) {
        ResultAndroid result=new ResultAndroid(stmt.rawQuery(sql,null));
        return result;
    }

    class AndroidDB extends SQLiteOpenHelper {

        public AndroidDB(Context context, String name, CursorFactory factory,
                int version) {
            super(context, name, factory, version);
        }

        public void onCreate(SQLiteDatabase db) {
            stmt=db;
            DatabaseAndroid.this.onCreate();
        }

        public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
            stmt=db;
            DatabaseAndroid.this.onUpgrade();
        }

    }

    public class ResultAndroid implements Result{
        Cursor cursor;

        public ResultAndroid(Cursor cursor) {
            this.cursor=cursor;
        }

        public boolean isEmpty() {
            return cursor.getCount()==0;
        }

        public int getColumnIndex(String name) {
            return cursor.getColumnIndex(name);
        }

        public String[] getColumnNames() {
            return cursor.getColumnNames();
        }

        public float getFloat(int columnIndex) {
            return cursor.getFloat(columnIndex);
        }

        [...]

    }

}

最后，我更改了Android和桌面应用程序的主要类：

public class Main extends AndroidApplication {

    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        initialize(new MyGame(new DatabaseAndroid(this.getBaseContext())), false);
    }
}

public class Main {

    public static void main(String[] args) {
        new LwjglApplication(new MyGame(new DatabaseDesktop()), "Example", MyGame.SCREEN_WIDTH, MyGame.SCREEN_HEIGHT,false);
    }

}

注意：

我做了一个版本管理，就像SQLiteOpenHelper使用时发生的那样PRAGMA user_version。这样，我仅DataBase在需要升级时更改类的版本。

我并没有把我做的所有方法都放在上面，Result而是我认为更重要的方法也更重要。

Answer 1

http://marakana.com/techtv/android_bootcamp_screencast_series.html

第4类，第1部分：Android Bootcamp-

用于libgdx的statusData： http

//code.google.com/p/libgdx-
users/wiki/SQLite

编辑：我应该提到有关Udacity的libgdx游戏的两门新课程：https :
//github.com/udacity/ud405

https://github.com/udacity/ud406