Libgdx学习记录14——数据保存Preferences，XmlReader

在游戏过程过程中，常常需要对某些数据进行保存，以确保下次运行时能够正确读取。如游戏中的金币、道具、游戏分数、已通过的关卡等。

Libgdx中常用的数据保存方式有Preferences和XmlReader。

1. Perferences

Preferences常用来保存一些较短的、使用较频繁的值。

put存入值，存完之后需要flush。

实例：

         Preferences preferences = Gdx.app.getPreferences( "pre1.test" );
         preferences.putString( "name", "Kitty" );
         preferences.putBoolean( "visible", true );
         preferences.putInteger( "age",  );
         preferences.flush();

         String strName1 = preferences.getString( "name" );
         boolean isVisible = preferences.getBoolean( "visible" );
         int age1 = preferences.getInteger( "age" );

2. XmlReader

XmlReader能够读取xml文件，不过此时只能读取，不能写入。

使用Element.get()获取child或者元素的值，示例：

         try{
             XmlReader xmlReader = new XmlReader( );
             Element eleRoot = xmlReader.parse( Gdx.files.internal( "xml/1.xml" ) );
             Element eleStu = eleRoot.getChildByName( "student" );

             String strName2 = eleStu.get( "name" );
             boolean isMale = eleStu.getBoolean( "male" );
             int age2 = eleStu.getInt( "age" );
             strShow2 = strName2 + "  " + isMale + "  " + age2;
         }
         catch(IOException e){
             e.printStackTrace();
         }

3. XmlWriter

XmlWriter能够将Xml的值写入到StringWriter中，然后写入到xml文件中进行保存。

其中.enimate()方法创建子元素，.text()方法插入元素值，.attribute()方法插入元素属性。

示例：

         try{
             stringWriter = new StringWriter();
             //stringWriter.append( "" );
             XmlWriter xmlWriter = new XmlWriter( stringWriter );
             xmlWriter.element("information")
                         .element( "person" ).attribute( "id", "0201" )
                             .element("name").text("Nacy").pop()
                             .element("hobby").text("basketball").pop()
                             .element("age").text("34").pop()
                         .pop()
                     .pop();
             xmlWriter.close();
             FileHandle file = Gdx.files.local( "set.xml" );
             file.writeString( stringWriter.toString(), false );
             System.out.println( stringWriter.toString() );
         }
         catch(IOException e){
             e.printStackTrace();
         }

完整代码：

 package com.fxb.newtest;

 import java.io.IOException;
 import java.io.InputStream;
 import java.io.StringWriter;

 import com.badlogic.gdx.ApplicationAdapter;
 import com.badlogic.gdx.Gdx;
 import com.badlogic.gdx.Preferences;
 import com.badlogic.gdx.files.FileHandle;
 import com.badlogic.gdx.graphics.Color;
 import com.badlogic.gdx.graphics.GL10;
 import com.badlogic.gdx.graphics.g2d.BitmapFont;
 import com.badlogic.gdx.graphics.g2d.SpriteBatch;
 import com.badlogic.gdx.utils.XmlReader;
 import com.badlogic.gdx.utils.XmlReader.Element;
 import com.badlogic.gdx.utils.XmlWriter;

 public class Lib013_XmlReader1 extends ApplicationAdapter{

     //XmlReader reader;
     //Element element;
     BitmapFont font;
     String strShow1, strShow2;
     SpriteBatch batch;
     StringWriter stringWriter;
     String configFileName = "xml/3.xml";

     @Override
     public void create() {
         // TODO Auto-generated method stub
         super.create();

         font = new BitmapFont();
         font.setColor( Color.BLACK );
         batch = new SpriteBatch();

         Preferences preferences = Gdx.app.getPreferences( "pre1.test" );
         preferences.putString( "name", "Kitty" );
         preferences.putBoolean( "visible", true );
         preferences.putInteger( "age", 25 );
         preferences.flush();

         String strName1 = preferences.getString( "name" );
         boolean isVisible = preferences.getBoolean( "visible" );
         int age1 = preferences.getInteger( "age" );
         strShow1 = strName1 + "  " + isVisible + "  " + age1;

         try{
             XmlReader xmlReader = new XmlReader( );
             Element eleRoot = xmlReader.parse( Gdx.files.internal( "xml/1.xml" ) );
             Element eleStu = eleRoot.getChildByName( "student" );

             String strName2 = eleStu.get( "name" );
             boolean isMale = eleStu.getBoolean( "male" );
             int age2 = eleStu.getInt( "age" );
             strShow2 = strName2 + "  " + isMale + "  " + age2;
         }
         catch(IOException e){
             e.printStackTrace();
         }

         try{
             stringWriter = new StringWriter();
             //stringWriter.append( "" );
             XmlWriter xmlWriter = new XmlWriter( stringWriter );
             xmlWriter.element("information")
                         .element( "person" ).attribute( "id", "0201" )
                             .element("name").text("Nacy").pop()
                             .element("hobby").text("basketball").pop()
                             .element("age").text("34").pop()
                         .pop()
                     .pop();
             xmlWriter.close();
             FileHandle file = Gdx.files.local( "set.xml" );
             file.writeString( stringWriter.toString(), false );
             System.out.println( stringWriter.toString() );
         }
         catch(IOException e){
             e.printStackTrace();
         }

     }

     @Override
     public void render() {
         // TODO Auto-generated method stub
         super.render();
         Gdx.gl.glClearColor( 1, 1, 1, 1 );
         Gdx.gl.glClear( GL10.GL_COLOR_BUFFER_BIT );

         batch.begin();
         font.draw( batch, strShow1, 100, 150 );
         font.draw( batch, strShow2, 100, 100 );
         font.drawMultiLine( batch, stringWriter.toString(), 100, 300 );
         batch.end();

     }

     @Override
     public void dispose() {
         // TODO Auto-generated method stub
         super.dispose();
     }

 }

运行结果：