AndEngine学习：LevelLoaderExample（加载关卡）

　　我们写游戏的时候需要有地图，比如写迷宫游戏，地图就占了游戏数据的一大部分，AndEngine给我们提供了一个非常实用的类：LevelLoader。我们直接看一个例子。

　　首先在assets目录下新建一个目录，取名为level，该目录下我们要存储关卡数据。然后新建文件：example.lvl，输入以下数据：

<?xml version="1.0" encoding="utf-8"?>
<level width="480" height="320">
    <entity x="0" y="0" width="16" height="16" type="rectangle"/>
    <entity x="100" y="0" width="16" height="16" type="rectangle"/>
    <entity x="200" y="0" width="16" height="16" type="line"/>
</level>

　　然后我们直接看程序：

public class LevelLoaderTestActivity extends BaseGameActivity
{
    // Constants
    private static final int CAMERA_WIDTH = 480;
    private static final int CAMERA_HEIGHT = 320;
    
    private static final String TAG_ENTITY = "entity";
    private static final String TAG_ENTITY_ATTRIBUTE_X = "x";
    private static final String TAG_ENTITY_ATTRIBUTE_Y = "y";
    private static final String TAG_ENTITY_ATTRIBUTE_WIDTH = "width";
    private static final String TAG_ENTITY_ATTRIBUTE_HEIGHT = "height";
    private static final String TAG_ENTITY_ATTRIBUTE_TYPE = "type";
    
    private static final Object TAG_ENTITY_ATTRIBUTE_TYPE_VALUE_RECTANGLE = "rectangle";
    
    @Override
    public Engine onLoadEngine() 
    {
        final Camera camera = new Camera(0, 0, CAMERA_WIDTH, CAMERA_HEIGHT);
        
        return new Engine(new EngineOptions(true, ScreenOrientation.LANDSCAPE,
                new RatioResolutionPolicy(CAMERA_WIDTH, CAMERA_HEIGHT), camera));
        
    }

    @Override
    public void onLoadResources() 
    {
        
    }

    @Override
    public Scene onLoadScene() 
    {
        final Scene scene = new Scene();
        scene.setBackground(new ColorBackground(0, 0, 0));
        
        final LevelLoader levelLoader = new LevelLoader();
        levelLoader.setAssetBasePath("level/");
        
        levelLoader.registerEntityLoader(LevelConstants.TAG_LEVEL, new IEntityLoader()
        {

            @Override
            public void onLoadEntity(String pEntityName, Attributes pAttributes) 
            {
                final int width = SAXUtils.getIntAttributeOrThrow(pAttributes, LevelConstants.TAG_LEVEL_ATTRIBUTE_WIDTH);
                final int height = SAXUtils.getIntAttributeOrThrow(pAttributes, LevelConstants.TAG_LEVEL_ATTRIBUTE_HEIGHT);
                Toast.makeText(LevelLoaderTestActivity.this, "Loaded level with width=" + width + " and height=" + height + ".", Toast.LENGTH_LONG).show();
            }});
        
        levelLoader.registerEntityLoader(TAG_ENTITY, new IEntityLoader()
        {

            @Override
            public void onLoadEntity(String pEntityName, Attributes pAttributes) 
            {
                final int x = SAXUtils.getIntAttributeOrThrow(pAttributes, TAG_ENTITY_ATTRIBUTE_X);
                final int y = SAXUtils.getIntAttributeOrThrow(pAttributes, TAG_ENTITY_ATTRIBUTE_Y);
                final int width = SAXUtils.getIntAttributeOrThrow(pAttributes, TAG_ENTITY_ATTRIBUTE_WIDTH);
                final int height = SAXUtils.getIntAttributeOrThrow(pAttributes, TAG_ENTITY_ATTRIBUTE_HEIGHT);
                final String type = SAXUtils.getAttributeOrThrow(pAttributes, TAG_ENTITY_ATTRIBUTE_TYPE);
                
                addToMap(scene, x, y, width, height, type);
                
            }});
        
        try {
            levelLoader.loadLevelFromAsset(this, "example.lvl");
        } catch (final IOException e) {
            Debug.e(e);
        }
        
        return scene;
    }
    
    private void addToMap(Scene scene, int x, int y, int width, int height, String type)
    {
        if(type.equals(TAG_ENTITY_ATTRIBUTE_TYPE_VALUE_RECTANGLE))
        {
            Rectangle rectangle = new Rectangle(x, y, width, height);
            scene.attachChild(rectangle);
        }
    }

    @Override
    public void onLoadComplete() 
    {
        
    }

}

　　程序依然很简单，就不一句一句地解释了，有问题请留言。