在Libgdx中使用SQLite数据库 [英] Using a SQLite database in Libgdx
问题描述
我是Libgdx的新手，在使用游戏数据库时遇到麻烦.
I'm new in Libgdx and I'm getting trouble on using a database on my game.
我搜索了一个有关如何使用Libgdx使SQLite在Android和桌面应用程序上运行的教程，但没有找到简单的方法.
I searched for a tutorial on how to make SQLite work on both Android and Desktop applications using Libgdx but I didn't found a easy one.
上次在Android中使用数据库时，我创建了一个从SQLiteOpenHelper扩展的类.
The last time I used a database in Android, I created a class that extends from 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，有人可以指出我的循序渐进教程或类似内容吗?
Is there a simple way to do the same using Libgdx? Or at least, can anyone point me to a step-by-step tutorial or something similar?
编辑
我忘了说我正在寻找可以让我管理诸如SQLiteOpenHelper之类的版本的东西.换句话说，当我更改代码中数据库的版本时，我想在安装apk的Android中重新创建数据库.
I forgot to say that I'm looking for something that let me manage versions like SQLiteOpenHelper. In other words, I want to recreate my database in Android on apk installation, when I change the version of my DB on code.
解决方案
在回答@42n4之后，我设法使用Android应用程序上的SQLiteOpenHelper和桌面应用程序上的JDBC连接到SQLite数据库.
Following @42n4 answer, I managed how to connect to SQLite Database using SQLiteOpenHelper on Android Application and JDBC on Desktop Application.
首先，我为桌面和Android应用程序创建了一个通用类":
First, I created a "common class" for both Desktop and Android Applications:
//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DatabaseDesktop类:
Then, I created a DatabaseDesktop Class for Desktop Application:
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;
}
[...]
}
}
和用于Android应用程序的DatabaseAndroid
And a DatabaseAndroid for Android Application
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:
Finally, I changed the Main Classes of both Android and Desktop Applications:
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进行了类似SQLiteOpenHelper中的版本管理.这样，当我需要升级DataBase类的版本时，就可以更改它.
I made a version management like the one that happens in SQLiteOpenHelper using the PRAGMA user_version. This way, I just change the version of the DataBase class when I need to upgrade it.
我没有将我制作的所有方法都放在Result上，但是我认为我认为更重要的那些方法更重要.
I didn't put all the methods that I made on Result but, I put the ones that I think that are more important.that are more important.
推荐答案
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
http://marakana.com/techtv/android_bootcamp_screencast_series.html Class 4, Part 1: Android Bootcamp - statusData, for libgdx: http://code.google.com/p/libgdx-users/wiki/SQLite
我应该提到Udacity上有关libgdx游戏的两门新课程: https://github.com/udacity/ud405
I should mention about two new courses about libgdx games at Udacity: https://github.com/udacity/ud405
https://github.com/udacity/ud406
这篇关于在Libgdx中使用SQLite数据库的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！
