android 在Libgdx中使用SQLite数据库

xmd2e60i  于 2023-09-28  发布在  Android
关注(0)|答案(2)|浏览(106)

我是Libgdx的新手,我在游戏中使用数据库时遇到了麻烦。
我搜索了一个关于如何使用Libgdx使SQLite在Android和桌面应用程序上工作的教程,但我没有找到一个简单的教程。
上次在Android中使用数据库时,我创建了一个从SQLiteOpenHelper扩展的类。
有没有一种简单的方法可以使用Libgdx来做同样的事情?或者至少,有人能给我一个循序渐进的教程或类似的东西吗?

编辑

我忘了说,我正在寻找的东西,让我管理的版本,如SQLiteOpenHelper。换句话说,我想在Android上的apk安装中重新创建我的数据库,当我在代码上更改数据库的版本时。

解决方案

根据@42n4的回答,我管理了如何在Android应用程序上使用SQLiteOpenHelper和桌面应用程序上使用JDBC连接到SQLite数据库。
首先,我为桌面和Android应用程序创建了一个“公共类”:

//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,我为桌面应用程序创建了一个DatabaseDesktop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;
        }

        [...]

    }

}

和一个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);
    }

}

请注意:
我使用PRAGMA user_version做了一个类似于SQLiteOpenHelper的版本管理。这样,当我需要升级DataBase类时,我只需要更改它的版本。
我没有把所有的方法都放在Result上,但是我把我认为更重要的方法放在Result上。

odopli94

odopli941#

我写了一个扩展(名为gdx-sqlite),它可以完成你所需要的大部分工作。此扩展的最新版本可以从here下载。源代码和read me位于:https://github.com/mrafayaleem/gdx-sqlite
此扩展目前支持Android和桌面平台。此外,不支持打开位于Android应用程序资产文件夹中的数据库。但是,这是一个待定的功能,将很快添加。
按照自述中的说明设置项目以进行数据库处理。下面是一个示例代码:

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");
    }
}
hkmswyz6

hkmswyz62#

http://marakana.com/techtv/android_bootcamp_screencast_series.html第4类,第1部分:Android Bootcamp - statusData,对于libgdx:http://code.google.com/p/libgdx-users/wiki/SQLite
编辑:我应该提到Udacity的两个关于libgdx游戏的新课程:https://github.com/udacity/ud405
https://github.com/udacity/ud406

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