Android游戏开发十日通（4）-行走，跳跃，碰撞检测

提要

经过前面的三篇文章，我们已经对libgdx有了一定的了解，并且搭建了一个简单的游戏场景，下面我们就继续在之前场景上添加更多的元素。

今天要实现的是精灵的行走、跳跃动画，还有碰撞检测。

行走

今天要实现的东西都是基于物理和数学的原理，首先我们来分析一下行走。

游戏中的动画都是帧动画，比如对Bob的行走一步的动画分解：

当这个序列连续播放的时候，就有了行走的效果。

之前已经有了移动的效果，所以只要在移动的时候循环播放动画就可以了。

现在需要的是决定帧的持续时间。

假设游戏渲染的是60FPS， 那么一帧的持续时间就是1/60s = 0.016 s。

对于一个成年人，每分钟大约走180步，那么每秒走的步数就是180/60 = 3，需要播放的帧为3×5 = 15.

那么每一帧持续时间就是1/15 = 0.066s.及66毫秒，即人物在运动的时候只要以66ms/帧对速度播放帧序列，就可以产生行走的效果了。

下面是代码实现。

首先是加载贴图。

和上一篇不同，这里用的是一次性加载贴图的方式，算是对游戏的一种优化。

需要和贴图textures.png一起添加到Android工程的asset/image/textures文件下的还有一个textures.pack文件，类似于一个xml，用于读取序列。

textures.pngformat: RGBA8888filter: Nearest,Nearestrepeat: noneblock  rotate: false  xy: 1, 11  size: 48, 48  orig: 48, 48  offset: 0, 0  index: -1bob-01  rotate: false  xy: 51, 31  size: 24, 28  orig: 24, 28  offset: 0, 0  index: -1/*..omit..*/

接下来需要修改Bob类。

添加一个statetime成员用于记录Bob生存的时间，后面会用它来决定显示帧序列的哪一帧。

package com.me.testgdxgame.model;import com.badlogic.gdx.math.Rectangle;import com.badlogic.gdx.math.Vector2;public class Bob {public enum State {IDLE, WALKING, JUMPING, DYING}public static final float SPEED = 4f;// unit per secondstatic final float JUMP_VELOCITY = 1f;public static final float SIZE = 0.5f; // half a unitVector2 position = new Vector2();Vector2 acceleration = new Vector2();Vector2 velocity = new Vector2();Rectangle bounds = new Rectangle();Statestate = State.IDLE;booleanfacingLeft = true;floatstateTime = 0;public Bob(Vector2 position) {this.position = position;this.bounds.height = SIZE;this.bounds.width = SIZE;}public boolean isFacingLeft() {return facingLeft;}public void setFacingLeft(boolean facingLeft) {this.facingLeft = facingLeft;}public Vector2 getPosition() {return position;}public Vector2 getAcceleration() {return acceleration;}public Vector2 getVelocity() {return velocity;}public Rectangle getBounds() {return bounds;}public State getState() {return state;}public void setState(State newState) {this.state = newState;}public float getStateTime() {return stateTime;}public void update(float delta) {stateTime += delta;position.add(velocity.cpy().mul(delta));}}

在libgdx中用于处理这种序列图的工具类是TextureAtlas。

getKeyFrame用于获取动画中的关键帧。

修改WorldRender类。

package com.me.testgdxgame.view;import com.me.testgdxgame.*;import com.me.testgdxgame.model.Block;import com.me.testgdxgame.model.Bob;import com.me.testgdxgame.model.Bob.State;import com.me.testgdxgame.model.World;import com.badlogic.gdx.Gdx;import com.badlogic.gdx.graphics.Color;import com.badlogic.gdx.graphics.GL10;import com.badlogic.gdx.graphics.OrthographicCamera;import com.badlogic.gdx.graphics.Texture;import com.badlogic.gdx.graphics.g2d.Animation;import com.badlogic.gdx.graphics.g2d.SpriteBatch;import com.badlogic.gdx.graphics.g2d.TextureAtlas;import com.badlogic.gdx.graphics.g2d.TextureRegion;import com.badlogic.gdx.graphics.glutils.ShapeRenderer;import com.badlogic.gdx.graphics.glutils.ShapeRenderer.ShapeType;import com.badlogic.gdx.math.Rectangle;public class WorldRenderer {private World world;private OrthographicCamera cam;private static final float RUNNING_FRAME_DURATION = 0.06f;private SpriteBatch spriteBatch;private boolean debug=false;private int width;private int height;private float ppuX; // pixels per unit on the X axisprivate float ppuY; // pixels per unit on the Y axisprivate static final float CAMERA_WIDTH = 10f;private static final float CAMERA_HEIGHT = 7f;/** Textures **/private TextureRegion bobIdleLeft;private TextureRegion bobIdleRight;private TextureRegion blockTexture;private TextureRegion bobFrame;/** Animations **/private Animation walkLeftAnimation;private Animation walkRightAnimation;/** for debug rendering **/ShapeRenderer debugRenderer = new ShapeRenderer();public WorldRenderer(World world) {this.world = world;this.cam = new OrthographicCamera(10, 7);this.cam.position.set(5, 3.5f, 0);this.cam.update();spriteBatch=new SpriteBatch();loadTextures();}public void setSize (int w, int h) {this.width = w;this.height = h;ppuX = (float)width / CAMERA_WIDTH;ppuY = (float)height / CAMERA_HEIGHT;}private void loadTextures() {TextureAtlas atlas = new TextureAtlas(Gdx.files.internal("images/textures/textures.pack"));bobIdleLeft = atlas.findRegion("bob-01");bobIdleRight = new TextureRegion(bobIdleLeft);bobIdleRight.flip(true, false);blockTexture = atlas.findRegion("block");TextureRegion[] walkLeftFrames = new TextureRegion[5];for (int i = 0; i < 5; i++) {walkLeftFrames[i] = atlas.findRegion("bob-0" + (i + 2));}walkLeftAnimation = new Animation(RUNNING_FRAME_DURATION, walkLeftFrames);TextureRegion[] walkRightFrames = new TextureRegion[5];for (int i = 0; i < 5; i++) {walkRightFrames[i] = new TextureRegion(walkLeftFrames[i]);walkRightFrames[i].flip(true, false);}walkRightAnimation = new Animation(RUNNING_FRAME_DURATION, walkRightFrames);}public void render() {spriteBatch.begin();drawBlocks();drawBob();spriteBatch.end();if(debug) drawDebug();}private void  drawBlocks(){for (Block block : world.getBlocks()) {spriteBatch.draw(blockTexture, block.getPosition().x * ppuX, block.getPosition().y * ppuY, Block.SIZE * ppuX, Block.SIZE * ppuY);}}private void drawBob(){Bob bob = world.getBob();    bobFrame = bob.isFacingLeft() ? bobIdleLeft : bobIdleRight;//spriteBatch.draw(bobIdleLeft, bob.getPosition().x * ppuX, bob.getPosition().y * ppuY, Bob.SIZE * ppuX, Bob.SIZE * ppuY);if(bob.getState().equals(State.WALKING)){bobFrame = bob.isFacingLeft() ? walkLeftAnimation.getKeyFrame(bob.getStateTime(),true):walkRightAnimation.getKeyFrame(bob.getStateTime(),true);}spriteBatch.draw(bobFrame, bob.getPosition().x * ppuX, bob.getPosition().y * ppuY, Bob.SIZE * ppuX, Bob.SIZE * ppuY);}private void drawDebug(){// render blocksdebugRenderer.setProjectionMatrix(cam.combined);debugRenderer.begin(ShapeType.Rectangle);for (Block block : world.getBlocks()) {Rectangle rect = block.getBounds();float x1 = block.getPosition().x + rect.x;float y1 = block.getPosition().y + rect.y;debugRenderer.setColor(new Color(1, 0, 0, 1));debugRenderer.rect(x1, y1, rect.width, rect.height);}// render BobBob bob = world.getBob();Rectangle rect = bob.getBounds();float x1 = bob.getPosition().x + rect.x;float y1 = bob.getPosition().y + rect.y;debugRenderer.setColor(new Color(0, 1, 0, 1));debugRenderer.rect(x1, y1, rect.width, rect.height);debugRenderer.end();}}

跑一下mian.java,键盘左右键就可以控制小人跑了。

跳跃

首先来复习一下初中的牛顿三定律...

第一定律：倘物体处于静止状态，或呈等速直线运动，只要没外力作用，物体将保持静止状态，或呈等速直线运动之状态。这定律又称为惯性定律。
第二定律：物体的加速度，与所受的净外力成正比。加速度的方向与净外力的方向相同。即 ；其中，是加速度， 是净外力， 是质量。
第三定律：两个物体的相互作用力总是大小相等，方向相反，同时出现或消失。强版第三定律还额外要求两支作用力的方向都处于同一直线。

分析一下Bob的状态。

最初始的时候，Bob处于静止状态，受两个力，一个是重力，一个是地面的支持力，二力平衡。

上图左边是Bob处于起跳状态，此时Bob用力蹬地面，地面给的反作用力大于Bob受的重力，Bob离开地面，起跳。

上图右边是Bob处于空中的状态，只受重力影响。

要用到一个速度计算公式：

v=u+at

u为初速度，a为加速度，t为时间。

下面看具体的代码实现。只需要在WorldController中添加对应的按键事件处理就可以了。

添加一些静态变量作为世界的参数。修改inputProcess和update函数。

注意仔细分析跳跃处理的逻辑。

package com.me.testgdxgame.controller;import java.util.HashMap;import java.util.Map;import com.me.testgdxgame.model.Bob;import com.me.testgdxgame.model.Bob.State;import com.me.testgdxgame.model.World;public class WorldController {enum Keys{LEFT,RIGHT,JUMP,FIRE}private World world;private Bob bob;private long jumpPressedTime;private boolean jumpingPressed;static Map<Keys,Boolean> keys = new HashMap<WorldController.Keys,Boolean>();static {keys.put(Keys.LEFT, false);keys.put(Keys.RIGHT, false);keys.put(Keys.JUMP, false);keys.put(Keys.FIRE, false);};private static final long LONG_JUMP_PRESS = 150l;private static final float ACCELERATION = 20f;private static final float GRAVITY = -20f;private static final float MAX_JUMP_SPEED = 7f;private static final float DAMP = 0.8f;private static final float MAX_VEL = 4f;private static final float WIDTH =10f;public WorldController(World w){world=w;bob=world.getBob();}//Key presses and touchespublic void leftPressed(){keys.get(keys.put(Keys.LEFT, true));}public void rightPressed() {keys.get(keys.put(Keys.RIGHT, true));}public void jumpPressed() {keys.get(keys.put(Keys.JUMP, true));}public void firePressed() {keys.get(keys.put(Keys.FIRE, false));}public void leftReleased() {keys.get(keys.put(Keys.LEFT, false));}public void rightReleased() {keys.get(keys.put(Keys.RIGHT, false));}public void jumpReleased() {keys.get(keys.put(Keys.JUMP, false));jumpingPressed = false;}public void fireReleased() {keys.get(keys.put(Keys.FIRE, false));}public void update(float delta){processInput();bob.getAcceleration().y = GRAVITY;bob.getAcceleration().mul(delta);bob.getVelocity().add(bob.getAcceleration().x, bob.getAcceleration().y);if (bob.getAcceleration().x == 0) bob.getVelocity().x *= DAMP;if (bob.getVelocity().x > MAX_VEL) {bob.getVelocity().x = MAX_VEL;}if (bob.getVelocity().x < -MAX_VEL) {bob.getVelocity().x = -MAX_VEL;}bob.update(delta);//Set Bob's state to State.IDLE when Bob touch edgeif (bob.getPosition().y < 0) {bob.getPosition().y = 0f;bob.setPosition(bob.getPosition());if (bob.getState().equals(State.JUMPING)) {bob.setState(State.IDLE);}}if (bob.getPosition().x < 0) {bob.getPosition().x = 0;bob.setPosition(bob.getPosition());if (!bob.getState().equals(State.JUMPING)) {bob.setState(State.IDLE);}}if (bob.getPosition().x > WIDTH - bob.getBounds().width ) {bob.getPosition().x = WIDTH - bob.getBounds().width;bob.setPosition(bob.getPosition());if (!bob.getState().equals(State.JUMPING)) {bob.setState(State.IDLE);}}}private boolean processInput(){if (keys.get(Keys.JUMP)) {if (!bob.getState().equals(State.JUMPING)) {jumpingPressed = true;jumpPressedTime = System.currentTimeMillis();bob.setState(State.JUMPING);bob.getVelocity().y = MAX_JUMP_SPEED; } else {if (jumpingPressed && ((System.currentTimeMillis() - jumpPressedTime) >= LONG_JUMP_PRESS)) {jumpingPressed = false;} else {if (jumpingPressed) {bob.getVelocity().y = MAX_JUMP_SPEED;}}}}if(keys.get(Keys.LEFT)){bob.setFacingLeft(true);if(!bob.getState().equals(State.JUMPING)){bob.setState(State.WALKING);}bob.getVelocity().x=-ACCELERATION;}else if (keys.get(Keys.RIGHT)) {// left is pressedbob.setFacingLeft(false);if(!bob.getState().equals(State.JUMPING)){bob.setState(State.WALKING);}bob.getVelocity().x=ACCELERATION;}else {if(!bob.getState().equals(State.JUMPING)){bob.setState(State.IDLE);};// acceleration is 0 on the xbob.getAcceleration().x = 0;}return false;}}

在WorldRender中还需要添加与跳跃对应的纹理还有修改drawBob函数。

加载纹理：

private void loadTextures() {TextureAtlas atlas = new TextureAtlas(Gdx.files.internal("images/textures/textures.pack"));bobJumpLeft = atlas.findRegion("bob-up");bobJumpRight = new TextureRegion(bobJumpLeft);bobJumpRight.flip(true, false);bobFallLeft=atlas.findRegion("bob-down");bobFallRight = new TextureRegion(bobFallLeft);bobFallRight.flip(true, false);bobIdleLeft = atlas.findRegion("bob-01");bobIdleRight = new TextureRegion(bobIdleLeft);bobIdleRight.flip(true, false);blockTexture = atlas.findRegion("block");TextureRegion[] walkLeftFrames = new TextureRegion[5];for (int i = 0; i < 5; i++) {walkLeftFrames[i] = atlas.findRegion("bob-0" + (i + 2));}walkLeftAnimation = new Animation(RUNNING_FRAME_DURATION, walkLeftFrames);TextureRegion[] walkRightFrames = new TextureRegion[5];for (int i = 0; i < 5; i++) {walkRightFrames[i] = new TextureRegion(walkLeftFrames[i]);walkRightFrames[i].flip(true, false);}walkRightAnimation = new Animation(RUNNING_FRAME_DURATION, walkRightFrames);}

drawBob函数

private void drawBob(){Bob bob = world.getBob();    bobFrame = bob.isFacingLeft() ? bobIdleLeft : bobIdleRight;    if(bob.getState().equals(State.WALKING)) {bobFrame = bob.isFacingLeft() ? walkLeftAnimation.getKeyFrame(bob.getStateTime(), true) : walkRightAnimation.getKeyFrame(bob.getStateTime(), true);} else if (bob.getState().equals(State.JUMPING)) {if (bob.getVelocity().y > 0) {bobFrame = bob.isFacingLeft() ? bobJumpLeft : bobJumpRight;} else {bobFrame = bob.isFacingLeft() ? bobFallLeft : bobFallRight;}}spriteBatch.draw(bobFrame, bob.getPosition().x * ppuX, bob.getPosition().y * ppuY, Bob.SIZE * ppuX, Bob.SIZE * ppuY);}

运行一下：

碰撞检测

现在的demo是可以穿墙的-_-!,这里的碰撞检测指的是Bob与Blocks之间的碰撞，当Bob撞墙的时候，Bob需要停止前进跳跃或是落下。

最简单的方法就是每update一次就检测Bob与每一个Block是否相撞，当然效率会非常低。

仔细来分析一下：每次与Bob可能发生碰撞的Block只有Bob身边的8块砖，那么在每次Update的时候与检测是否与身边的砖块相碰就可以了。

还可以再简单么？

看下面的图片。

假设Bob正在向右行走，那么在可能与Bob产生碰撞的Block中，只有下面的那个。所以，根据Bob当前的状态进行碰撞检测可以高效地进行碰撞检测。

我们用一个二维数组来保存地形，用于碰撞检测。

首先我们创建一个level，就是关卡，用world来装载，而不是直接在world里面生成。

package com.me.testgdxgame.model;import com.badlogic.gdx.math.Vector2;public class Level {private int width;private int height;private Block[][] blocks;public int getWidth() {return width;}public void setWidth(int width) {this.width = width;}public int getHeight() {return height;}public void setHeight(int height) {this.height = height;}public Block[][] getBlocks() {return blocks;}public void setBlocks(Block[][] blocks) {this.blocks = blocks;}public Level() {loadDemoLevel();}public Block get(int x, int y) {return blocks[x][y];}private void loadDemoLevel() {width = 10;height = 7;blocks = new Block[width][height];for (int col = 0; col < width; col++) {for (int row = 0; row < height; row++) {blocks[col][row] = null;}}for (int col = 0; col < 10; col++) {blocks[col][0] = new Block(new Vector2(col, 0));blocks[col][6] = new Block(new Vector2(col, 6));if (col > 2) {blocks[col][1] = new Block(new Vector2(col, 1));}}blocks[9][2] = new Block(new Vector2(9, 2));blocks[9][3] = new Block(new Vector2(9, 3));blocks[9][4] = new Block(new Vector2(9, 4));blocks[9][5] = new Block(new Vector2(9, 5));blocks[6][3] = new Block(new Vector2(6, 3));blocks[6][4] = new Block(new Vector2(6, 4));blocks[6][5] = new Block(new Vector2(6, 5));}}

World类做对应的修改：

package com.me.testgdxgame.model;import java.util.ArrayList;import java.util.List;import com.badlogic.gdx.math.Rectangle;import com.badlogic.gdx.math.Vector2;import com.badlogic.gdx.utils.Array;public class World {/** Our player controlled hero **/Bob bob;/** A world has a level through which Bob needs to go through **/Level level;/** The collision boxes **/Array<Rectangle> collisionRects = new Array<Rectangle>();// Getters -----------public Array<Rectangle> getCollisionRects() {return collisionRects;}public Bob getBob() {return bob;}public Level getLevel() {return level;}/** Return only the blocks that need to be drawn **/public List<Block> getDrawableBlocks(int width, int height) {int x = (int)bob.getPosition().x - width;int y = (int)bob.getPosition().y - height;if (x < 0) {x = 0;}if (y < 0) {y = 0;}int x2 = x + 2 * width;int y2 = y + 2 * height;if (x2 > level.getWidth()) {x2 = level.getWidth() - 1;}if (y2 > level.getHeight()) {y2 = level.getHeight() - 1;}List<Block> blocks = new ArrayList<Block>();Block block;for (int col = x; col <= x2; col++) {for (int row = y; row <= y2; row++) {block = level.getBlocks()[col][row];if (block != null) {blocks.add(block);}}}return blocks;}// --------------------public World() {createDemoWorld();}private void createDemoWorld() {bob = new Bob(new Vector2(7, 2));level = new Level();}}

然后在WorldController中添加一个checkCollisionWithBlocks函数，函数里面首先检测X方向是否有碰撞，再检测Y方向是否有碰撞。

在update函数中，每运行一次就进行一次检测。

完整的WorldController类如下：

package com.me.testgdxgame.controller;import java.util.HashMap;import java.util.Map;import com.badlogic.gdx.math.Rectangle;import com.badlogic.gdx.utils.Array;import com.badlogic.gdx.utils.Pool;import com.me.testgdxgame.model.Block;import com.me.testgdxgame.model.Bob;import com.me.testgdxgame.model.Bob.State;import com.me.testgdxgame.model.World;public class WorldController {enum Keys {LEFT, RIGHT, JUMP, FIRE}private static final long LONG_JUMP_PRESS = 150l;private static final float ACCELERATION = 20f;private static final float GRAVITY = -20f;private static final float MAX_JUMP_SPEED= 7f;private static final float DAMP = 0.90f;private static final float MAX_VEL = 4f;private World world;private Bob bob;private longjumpPressedTime;private boolean jumpingPressed;private boolean grounded = false;// This is the rectangle pool used in collision detection// Good to avoid instantiation each frameprivate Pool<Rectangle> rectPool = new Pool<Rectangle>() {@Overrideprotected Rectangle newObject() {return new Rectangle();}};static Map<Keys, Boolean> keys = new HashMap<WorldController.Keys, Boolean>();static {keys.put(Keys.LEFT, false);keys.put(Keys.RIGHT, false);keys.put(Keys.JUMP, false);keys.put(Keys.FIRE, false);};// Blocks that Bob can collide with any given frameprivate Array<Block> collidable = new Array<Block>();public WorldController(World world) {this.world = world;this.bob = world.getBob();}// ** Key presses and touches **************** //public void leftPressed() {keys.get(keys.put(Keys.LEFT, true));}public void rightPressed() {keys.get(keys.put(Keys.RIGHT, true));}public void jumpPressed() {keys.get(keys.put(Keys.JUMP, true));}public void firePressed() {keys.get(keys.put(Keys.FIRE, false));}public void leftReleased() {keys.get(keys.put(Keys.LEFT, false));}public void rightReleased() {keys.get(keys.put(Keys.RIGHT, false));}public void jumpReleased() {keys.get(keys.put(Keys.JUMP, false));jumpingPressed = false;}public void fireReleased() {keys.get(keys.put(Keys.FIRE, false));}/** The main update method **/public void update(float delta) {// Processing the input - setting the states of BobprocessInput();// If Bob is grounded then reset the state to IDLE if (grounded && bob.getState().equals(State.JUMPING)) {bob.setState(State.IDLE);}// Setting initial vertical acceleration bob.getAcceleration().y = GRAVITY;// Convert acceleration to frame timebob.getAcceleration().mul(delta);// apply acceleration to change velocitybob.getVelocity().add(bob.getAcceleration().x, bob.getAcceleration().y);// checking collisions with the surrounding blocks depending on Bob's velocitycheckCollisionWithBlocks(delta);// apply damping to halt Bob nicely bob.getVelocity().x *= DAMP;// ensure terminal velocity is not exceededif (bob.getVelocity().x > MAX_VEL) {bob.getVelocity().x = MAX_VEL;}if (bob.getVelocity().x < -MAX_VEL) {bob.getVelocity().x = -MAX_VEL;}// simply updates the state timebob.update(delta);}/** Collision checking **/private void checkCollisionWithBlocks(float delta) {// scale velocity to frame units bob.getVelocity().mul(delta);// Obtain the rectangle from the pool instead of instantiating itRectangle bobRect = rectPool.obtain();// set the rectangle to bob's bounding boxbobRect.set(bob.getBounds().x, bob.getBounds().y, bob.getBounds().width, bob.getBounds().height);// we first check the movement on the horizontal X axisint startX, endX;int startY = (int) bob.getBounds().y;int endY = (int) (bob.getBounds().y + bob.getBounds().height);// if Bob is heading left then we check if he collides with the block on his left// we check the block on his right otherwiseif (bob.getVelocity().x < 0) {startX = endX = (int) Math.floor(bob.getBounds().x + bob.getVelocity().x);} else {startX = endX = (int) Math.floor(bob.getBounds().x + bob.getBounds().width + bob.getVelocity().x);}// get the block(s) bob can collide withpopulateCollidableBlocks(startX, startY, endX, endY);// simulate bob's movement on the XbobRect.x += bob.getVelocity().x;// clear collision boxes in worldworld.getCollisionRects().clear();// if bob collides, make his horizontal velocity 0for (Block block : collidable) {if (block == null) continue;if (bobRect.overlaps(block.getBounds())) {bob.getVelocity().x = 0;world.getCollisionRects().add(block.getBounds());break;}}// reset the x position of the collision boxbobRect.x = bob.getPosition().x;// the same thing but on the vertical Y axisstartX = (int) bob.getBounds().x;endX = (int) (bob.getBounds().x + bob.getBounds().width);if (bob.getVelocity().y < 0) {startY = endY = (int) Math.floor(bob.getBounds().y + bob.getVelocity().y);} else {startY = endY = (int) Math.floor(bob.getBounds().y + bob.getBounds().height + bob.getVelocity().y);}populateCollidableBlocks(startX, startY, endX, endY);bobRect.y += bob.getVelocity().y;for (Block block : collidable) {if (block == null) continue;if (bobRect.overlaps(block.getBounds())) {if (bob.getVelocity().y < 0) {grounded = true;}bob.getVelocity().y = 0;world.getCollisionRects().add(block.getBounds());break;}}// reset the collision box's position on YbobRect.y = bob.getPosition().y;// update Bob's positionbob.getPosition().add(bob.getVelocity());bob.getBounds().x = bob.getPosition().x;bob.getBounds().y = bob.getPosition().y;// un-scale velocity (not in frame time)bob.getVelocity().mul(1 / delta);}/** populate the collidable array with the blocks found in the enclosing coordinates **/private void populateCollidableBlocks(int startX, int startY, int endX, int endY) {collidable.clear();for (int x = startX; x <= endX; x++) {for (int y = startY; y <= endY; y++) {if (x >= 0 && x < world.getLevel().getWidth() && y >=0 && y < world.getLevel().getHeight()) {collidable.add(world.getLevel().get(x, y));}}}}/** Change Bob's state and parameters based on input controls **/private boolean processInput() {if (keys.get(Keys.JUMP)) {if (!bob.getState().equals(State.JUMPING)) {jumpingPressed = true;jumpPressedTime = System.currentTimeMillis();bob.setState(State.JUMPING);bob.getVelocity().y = MAX_JUMP_SPEED; grounded = false;} else {if (jumpingPressed && ((System.currentTimeMillis() - jumpPressedTime) >= LONG_JUMP_PRESS)) {jumpingPressed = false;} else {if (jumpingPressed) {bob.getVelocity().y = MAX_JUMP_SPEED;}}}}if (keys.get(Keys.LEFT)) {// left is pressedbob.setFacingLeft(true);if (!bob.getState().equals(State.JUMPING)) {bob.setState(State.WALKING);}bob.getAcceleration().x = -ACCELERATION;} else if (keys.get(Keys.RIGHT)) {// left is pressedbob.setFacingLeft(false);if (!bob.getState().equals(State.JUMPING)) {bob.setState(State.WALKING);}bob.getAcceleration().x = ACCELERATION;} else {if (!bob.getState().equals(State.JUMPING)) {bob.setState(State.IDLE);}bob.getAcceleration().x = 0;}return false;}}

运行截图：

总结

这篇blog的内容有点多，需要多花时间去体会。

特别是碰撞检测，思路一定要缕清晰。

这个游戏也暂时告一段落了，主要原因是国外的那位大牛也没有更新此系列的文章了...

当然，游戏还在继续。

工程下载

参考：Getting Started in Android Game Development with libgdx-http://obviam.net/