在Libgdx中使用SQLite數據庫

Question

我是Libgdx的新手，我在游戲中使用數據庫時遇到了麻煩。

我搜索了一個關於如何使用Libgdx使SQLite在Android和桌面應用程序上工作的教程，但我找不到一個簡單的教程。

我最后一次在Android中使用數據庫時，創建了一個從SQLiteOpenHelper擴展的類。

有沒有一種簡單的方法來使用Libgdx做同樣的事情？ 或者至少，有人能指點我一步一步的教程或類似的東西嗎？

編輯

我忘了說我正在尋找能夠管理SQLiteOpenHelper版本的SQLiteOpenHelper 。 換句話說，當我在代碼上更改我的數據庫版本時，我想在apk安裝上在Android中重新創建我的數據庫。

解

在@42n4回答之后，我設法了如何使用Android應用程序上的SQLiteOpenHelper和桌面應用程序上的JDBC連接到SQLite數據庫。

首先，我為桌面和Android應用程序創建了一個“通用類”：

//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，我為桌面應用程序創建了一個DatabaseDesktop類：

    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;
        }

        [...]

    }

}

和Android應用程序的DatabaseAndroid

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和桌面應用程序的主要類：

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：

我做了一個版本管理一樣，在發生在一個SQLiteOpenHelper使用PRAGMA user_version 。 這樣，我只需要在升級時更改DataBase類的版本。

我沒有把我在Result做的所有方法都放在但是，我認為那些更重要的方法更重要。

Answer 1

我寫了一個擴展（稱為gdx-sqlite），它將完成你需要的大部分工作。 可以從此處下載此擴展程序的最新版本。 源代碼和讀我位於： https ： //github.com/mrafayaleem/gdx-sqlite

此擴展目前支持Android和桌面平台。 此外，不支持打開位於Android應用程序的assets文件夾中的數據庫。 但是，這是一個待處理的功能，很快就會添加。

按照自述文件中的說明設置項目以進行數據庫處理。 以下是一個示例代碼：

package com.mrafayaleem.gdxsqlitetest;

import com.badlogic.gdx.Gdx;
import com.badlogic.gdx.sql.Database;
import com.badlogic.gdx.sql.DatabaseCursor;
import com.badlogic.gdx.sql.DatabaseFactory;
import com.badlogic.gdx.sql.SQLiteGdxException;

public class DatabaseTest {

    Database dbHandler;

    public static final String TABLE_COMMENTS = "comments";
    public static final String COLUMN_ID = "_id";
    public static final String COLUMN_COMMENT = "comment";

    private static final String DATABASE_NAME = "comments.db";
    private static final int DATABASE_VERSION = 1;

    // Database creation sql statement
    private static final String DATABASE_CREATE = "create table if not exists "
            + TABLE_COMMENTS + "(" + COLUMN_ID
            + " integer primary key autoincrement, " + COLUMN_COMMENT
            + " text not null);";

    public DatabaseTest() {
        Gdx.app.log("DatabaseTest", "creation started");
        dbHandler = DatabaseFactory.getNewDatabase(DATABASE_NAME,
                DATABASE_VERSION, DATABASE_CREATE, null);

        dbHandler.setupDatabase();
        try {
            dbHandler.openOrCreateDatabase();
            dbHandler.execSQL(DATABASE_CREATE);
        } catch (SQLiteGdxException e) {
            e.printStackTrace();
        }

        Gdx.app.log("DatabaseTest", "created successfully");

        try {
            dbHandler
                    .execSQL("INSERT INTO comments ('comment') VALUES ('This is a test comment')");
        } catch (SQLiteGdxException e) {
            e.printStackTrace();
        }

        DatabaseCursor cursor = null;

        try {
            cursor = dbHandler.rawQuery("SELECT * FROM comments");
        } catch (SQLiteGdxException e) {
            e.printStackTrace();
        }
        while (cursor.next()) {
            Gdx.app.log("FromDb", String.valueOf(cursor.getString(1)));
        }

        try {
            dbHandler.closeDatabase();
        } catch (SQLiteGdxException e) {
            e.printStackTrace();
        }
        dbHandler = null;
        Gdx.app.log("DatabaseTest", "dispose");
    }
}

Answer 2

http://marakana.com/techtv/android_bootcamp_screencast_series.html第4部分，第1部分：Android Bootcamp - statusData，用於libgdx： http ： //code.google.com/p/libgdx-users/wiki/SQLite

編輯：我應該提到關於Udacity的兩個關於libgdx游戲的新課程： https ： //github.com/udacity/ud405

https://github.com/udacity/ud406