AndEngine Example(8):PathModifierExample

目標：

1. 瞭解場景背景圖片的設置RepeatingSpriteBackground

2.  掌握如何使用PathModifier控制精靈的移動

3. 瞭解如何使用路徑Path得到PathModifier

4. Sprite的animate函數，用於選擇當前幀的動畫

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package org.andengine.examples;

import org.andengine.engine.camera.Camera;
import org.andengine.engine.options.EngineOptions;
import org.andengine.engine.options.ScreenOrientation;
import org.andengine.engine.options.resolutionpolicy.RatioResolutionPolicy;
import org.andengine.entity.IEntity;
import org.andengine.entity.modifier.LoopEntityModifier;
import org.andengine.entity.modifier.PathModifier;
import org.andengine.entity.modifier.PathModifier.IPathModifierListener;
import org.andengine.entity.modifier.PathModifier.Path;
import org.andengine.entity.scene.Scene;
import org.andengine.entity.scene.background.RepeatingSpriteBackground;
import org.andengine.entity.sprite.AnimatedSprite;
import org.andengine.entity.util.FPSLogger;
import org.andengine.opengl.texture.atlas.bitmap.BitmapTextureAtlas;
import org.andengine.opengl.texture.atlas.bitmap.BitmapTextureAtlasTextureRegionFactory;
import org.andengine.opengl.texture.atlas.bitmap.source.AssetBitmapTextureAtlasSource;
import org.andengine.opengl.texture.region.TiledTextureRegion;
import org.andengine.ui.activity.SimpleBaseGameActivity;
import org.andengine.util.debug.Debug;
import org.andengine.util.modifier.ease.EaseSineInOut;

import android.widget.Toast;

/**
 * (c) 2010 Nicolas Gramlich
 * (c) 2011 Zynga
 *
 * @author Nicolas Gramlich
 * @since 11:54:51 - 03.04.2010
 */
public class PathModifierExample extends SimpleBaseGameActivity {
	// ===========================================================
	// Constants
	// ===========================================================

	private static final int CAMERA_WIDTH = 720;
	private static final int CAMERA_HEIGHT = 480;

	// ===========================================================
	// Fields
	// ===========================================================

	private RepeatingSpriteBackground mGrassBackground;

	private BitmapTextureAtlas mBitmapTextureAtlas;
	private TiledTextureRegion mPlayerTextureRegion;

	// ===========================================================
	// Constructors
	// ===========================================================

	// ===========================================================
	// Getter & Setter
	// ===========================================================

	// ===========================================================
	// Methods for/from SuperClass/Interfaces
	// ===========================================================

	@Override
	public EngineOptions onCreateEngineOptions() {
		Toast.makeText(this, "You move my sprite right round, right round...", Toast.LENGTH_LONG).show();

		final Camera camera = new Camera(0, 0, CAMERA_WIDTH, CAMERA_HEIGHT);

		return new EngineOptions(true, ScreenOrientation.LANDSCAPE_FIXED, new RatioResolutionPolicy(CAMERA_WIDTH, CAMERA_HEIGHT), camera);
	}

	@Override
	public void onCreateResources() {
		BitmapTextureAtlasTextureRegionFactory.setAssetBasePath("gfx/");

		this.mGrassBackground = new RepeatingSpriteBackground(CAMERA_WIDTH, CAMERA_HEIGHT, this.getTextureManager(), AssetBitmapTextureAtlasSource.create(this.getAssets(), "gfx/background_grass.png"), this.getVertexBufferObjectManager());

		this.mBitmapTextureAtlas = new BitmapTextureAtlas(this.getTextureManager(), 128, 128);
		this.mPlayerTextureRegion = BitmapTextureAtlasTextureRegionFactory.createTiledFromAsset(this.mBitmapTextureAtlas, this, "player.png", 0, 0, 3, 4);
		this.mBitmapTextureAtlas.load();
	}

	@Override
	public Scene onCreateScene() {
		this.mEngine.registerUpdateHandler(new FPSLogger());

		final Scene scene = new Scene();
		scene.setBackground(this.mGrassBackground);

		/* Create the face and add it to the scene. */
		final AnimatedSprite player = new AnimatedSprite(10, 10, 48, 64, this.mPlayerTextureRegion, this.getVertexBufferObjectManager());

		final Path path = new Path(5).to(10, 10).to(10, CAMERA_HEIGHT - 74).to(CAMERA_WIDTH - 58, CAMERA_HEIGHT - 74).to(CAMERA_WIDTH - 58, 10).to(10, 10);

		/* Add the proper animation when a waypoint of the path is passed. */
		player.registerEntityModifier(new LoopEntityModifier(new PathModifier(30, path, null, new IPathModifierListener() {
			@Override
			public void onPathStarted(final PathModifier pPathModifier, final IEntity pEntity) {
				Debug.d("onPathStarted");
			}

			@Override
			public void onPathWaypointStarted(final PathModifier pPathModifier, final IEntity pEntity, final int pWaypointIndex) {
				Debug.d("onPathWaypointStarted:  " + pWaypointIndex);
				switch(pWaypointIndex) {
					case 0:
						player.animate(new long[]{200, 200, 200}, 6, 8, true);
						break;
					case 1:
						player.animate(new long[]{200, 200, 200}, 3, 5, true);
						break;
					case 2:
						player.animate(new long[]{200, 200, 200}, 0, 2, true);
						break;
					case 3:
						player.animate(new long[]{200, 200, 200}, 9, 11, true);
						break;
				}
			}

			@Override
			public void onPathWaypointFinished(final PathModifier pPathModifier, final IEntity pEntity, final int pWaypointIndex) {
				Debug.d("onPathWaypointFinished: " + pWaypointIndex);
			}

			@Override
			public void onPathFinished(final PathModifier pPathModifier, final IEntity pEntity) {
				Debug.d("onPathFinished");
			}
		}, EaseSineInOut.getInstance())));
		scene.attachChild(player);

		return scene;
	}

	// ===========================================================
	// Methods
	// ===========================================================

	// ===========================================================
	// Inner and Anonymous Classes
	// ===========================================================
}

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使用RepeatingSpriteBackground的好處是：

    使用一張較小的圖，通過重複，就可以得到整個背景。

路徑構造函數中可以指定路徑分爲多少段。然後使用to(x,y)來連接到下一個位置

   你可以使用一個Point數組,然後

Path path = new Path(points.length);
for(Point point:points) {
    path.to(point.x,point.y);
}

這樣就得到一個完整的路徑了。

PathModifier(float,Path,IEntityModiferListener,IPathModiferListener,IEaseFunction)

para1: 整個路徑完成需要的時間

para2: 路徑

para3: 修飾器監聽

para4: 路徑監聽器

para5: 可以理解爲一個插值器(interpolator)

路徑監聽器包含4個回調函數：

onPathStarted(...) 整個路徑的開始

onPathWaypointStarted(final PathModifier pPathModifier, final IEntity pEntity, final int pWaypointIndex)  某段路徑的開始

onPathWaypointFinished(final PathModifier pPathModifier, final IEntity pEntity, final int pWaypointIndex) 某段路徑的結束

onPathFinished(...) 整個路徑的結束

EaseSineInOut 是一個 IEaseFunction，下一節將重點介紹它。