我正在制作一个滑板游戏,你必须使用box2D和AndEngine跳过障碍.我试图这样做,以便当玩家与一个物体碰撞时,物体被移除并且物体旧位置会发生爆炸,但精灵移除代码中的某些东西会冻结我的程序导致它结束(甚至不是强制关闭消息它只是关闭自己并进入我的主屏幕)并且没有错误/异常信息出现在logcat中所以我不知道是什么导致它！以下是一些代码片段 –
当我创建精灵/边界时,我将JSONObject附加到包含精灵和精灵类型的主体,并将类似的JSONOBject附加到具有正文和类型的精灵：
/** method to construct our player (takes an x and y position)*/
private void constructPlayer(final float pX, final float pY) {
final Body body;
/* construct the sprite of our player and set the animation */
this.player = new AnimatedSprite(pX, pY, this.mSkaterTextureRegion);
long[] frameDurations = {100, 100};
player.animate(frameDurations, 4, 5, true);
body = PhysicsFactory.createBoxBody(this.mPhysicsWorld, player, BodyType.DynamicBody, PLAYER_FIXTURE_DEF);
this.mPhysicsWorld.registerPhysicsConnector(new PhysicsConnector(player, body, true, false));
body.setUserData(makeUserDataForBody(PLAYER_TYPE,player));
player.setUserData(makeUserDataForSprite(PLAYER_TYPE,body));
this.mScene.registerTouchArea(player);
//attach our player to the scene
this.mScene.attachChild(player);
}
private JSONObject makeUserDataForBody(int type, Object sprite)
{
JSONObject myObject = new JSONObject();
try {
myObject.put("type", type);
myObject.put("sprite", sprite);
} catch (JSONException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
return myObject;
}
private JSONObject makeUserDataForSprite(int type, Body body)
{
JSONObject myObject = new JSONObject();
try {
myObject.put("body", body);
myObject.put("type", type);
} catch (JSONException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
return myObject;
}
构建阻塞精灵的代码与构造玩家的代码几乎相同,但我设置了移动速度：
private void addObstruction(final float pX, final float pY) {
final Body body;
final Sprite myObstruction;
myObstruction = new Sprite(pX, pY, this.mCrateTextureRegion);
body = PhysicsFactory.createBoxBody(this.mPhysicsWorld, myObstruction, BodyType.DynamicBody, OBJECT_FIXTURE_DEF);
this.mPhysicsWorld.registerPhysicsConnector(new PhysicsConnector(myObstruction, body, true, true));
body.setUserData(makeUserDataForBody(OBSTRUCTION_TYPE,myObstruction));
myObstruction.setUserData(makeUserDataForSprite(OBSTRUCTION_TYPE,body));
body.setLinearVelocity(-150f, 0);
//attach our Obstruction to the scene
this.mScene.attachChild(myObstruction);
}
这是我的物理世界的contactListener：
this.mPhysicsWorld.setContactListener(new ContactListener() {
@Override
public void preSolve(Contact contact, Manifold oldManifold) {
}
@Override
public void postSolve(Contact contact, ContactImpulse impulse) {
}
@Override
public void endContact(Contact contact) {
// TODO Auto-generated method stub
Body obj1Data = contact.getFixtureA().getBody();
Body obj2Data = contact.getFixtureB().getBody();
JSONObject obj1UserData;
JSONObject obj2UserData;
int obj1Type = 0;
int obj2Type = 0;
if(obj1Data.getUserData()!=null)
{
obj1UserData =(JSONObject) obj1Data.getUserData();
try {
obj1Type = obj1UserData.getInt("type");
}catch (JSONException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
if(obj2Data.getUserData()!=null)
{
obj2UserData=(JSONObject) obj2Data.getUserData();
try {
obj2Type = obj2UserData.getInt("type");
} catch (JSONException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
switch (obj1Type)
{
case PLAYER_TYPE:
break;
case GRINDRAIL_TYPE:
if(isGrinding)
{
endGrind();
if(!isJumping)
fall(player);
}
break;
case GROUND_TYPE:
break;
case OBSTRUCTION_TYPE:
break;
case WALL_TYPE:
break;
}
switch (obj2Type)
{
case PLAYER_TYPE:
break;
case GRINDRAIL_TYPE:
if(isGrinding)
{
endGrind();
if(!isJumping)
fall(player);
}
break;
case GROUND_TYPE:
break;
case OBSTRUCTION_TYPE:
break;
case WALL_TYPE:
break;
}
}
@Override
public void beginContact(Contact contact) {
Body obj1Data = contact.getFixtureA().getBody();
Body obj2Data = contact.getFixtureB().getBody();
JSONObject obj1UserData;
JSONObject obj2UserData;
int obj1Type = 0;
int obj2Type = 0;
if(obj1Data.getUserData()!=null)
{
obj1UserData =(JSONObject) obj1Data.getUserData();
try {
obj1Type = obj1UserData.getInt("type");
}catch (JSONException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
if(obj2Data.getUserData()!=null)
{
obj2UserData=(JSONObject) obj2Data.getUserData();
try {
obj2Type = obj2UserData.getInt("type");
} catch (JSONException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
//deal with things colliding with the player
if(obj1Type==PLAYER_TYPE)
{
playerCollisionHandler(obj2Data);
}
else if(obj2Type==PLAYER_TYPE)
{
playerCollisionHandler(obj1Data);
}
}
});
这是我的playerCollisionHandler方法：
private void playerCollisionHandler(Body secondBody)
{
JSONObject secondBodyData = null;
if(secondBody.getUserData()!=null)
{
secondBodyData=(JSONObject) secondBody.getUserData();
}
JSONObject userdata = (JSONObject) player.getUserData();
Body playerBody = null;
try {
playerBody = (Body) userdata.get("body");
} catch (JSONException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
int objType = 0;
try {
if(secondBodyData!=null)
objType = secondBodyData.getInt("type");
} catch (JSONException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
if(objType == GROUND_TYPE)
{
if(playerBody.getLinearVelocity().y<0)
{
/* If the sprites y velocity is negative the sprite is jumping,
* don't reset the values!!!*/
}
else
{
if((isJumping)||(isFalling))
{
//play landing sound
AndEngineTestActivity.this.mLandSound.play();
isJumping = false;
isFalling = false;
//player.setPosition(player.getX(), GROUND_LEVEL-player.getHeight());
//animate landing
player.animate(createFrameDurations(LAND_ANIM_FRAMES.length), LAND_ANIM_FRAMES, 0);
}
if(!rollSoundIsPlaying)
{
playRollSound();
}
}
}
else if(objType == GRINDRAIL_TYPE)
{
Sprite grindRail=null;
try {
grindRail = (Sprite) secondBodyData.get("sprite");
} catch (JSONException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
/*create a rectangle at the upper bound of the grind rail to test collision*/
grindRailUpperBound = new Rectangle(grindRail.getX(), grindRail.getY(), mGrindRailTextureRegion.getWidth(), COLLISION_BOUNDS_PIXEL_ACCURACY);
playerLowerBound = new Rectangle(player.getX(), player.getY()+player.getHeight(), player.getWidth(), COLLISION_BOUNDS_PIXEL_ACCURACY);
grindRailUpperBound.setColor(1.0f, 0f, 0f,1f);
playerLowerBound.setColor(1.0f, 1.0f, 0f,1f);
mScene.attachChild(playerLowerBound);
mScene.attachChild(grindRailUpperBound);
if(grindRailUpperBound.collidesWith(playerLowerBound))
{
if(!isGrinding)
{
mScene.detachChild(grindRailUpperBound);
mScene.detachChild(playerLowerBound);
grindPlayer(player);
}
}
if(!isGrinding)
{
/* if it reaches this point and the custom rectangle bounds did not collide
* it means the player has collided with the grind rail another way, so we hurt the player*/
playerHitByObject();
destroyObstruction(secondBody);
}
}
else if(objType == OBSTRUCTION_TYPE)
{
playerHitByObject();
destroyObstruction(secondBody);
}
}
这里是destroyObtruction方法,它似乎是崩溃的罪魁祸首(如果我注释掉我对destroyObstruction的调用,我的代码运行正常,但我不确定为什么这个方法导致崩溃……)：
private void destroyObstruction(Body obstructionBody)
{
obstructionBody.setActive(false);
try{
JSONObject secondBodyData = null;
if(obstructionBody.getUserData()!=null)
{
secondBodyData=(JSONObject) obstructionBody.getUserData();
}
explodeObstruction(((IEntity) secondBodyData.get("sprite")).getX(),((IEntity) secondBodyData.get("sprite")).getY());
final PhysicsConnector obstructionPhysicsConnector = this.mPhysicsWorld.getPhysicsConnectorManager().findPhysicsConnectorByShape((IShape) secondBodyData.get("sprite"));
this.mPhysicsWorld.unregisterPhysicsConnector(obstructionPhysicsConnector);
this.mPhysicsWorld.destroyBody(obstructionPhysicsConnector.getBody());
//this.mPhysicsWorld.destroyBody(obstructionBody);
this.mScene.detachChild((IEntity) secondBodyData.get("sprite"));
}catch(Exception e)
{
Log.d(TAG, "Exception:"+e);
}
catch(Error e)
{
Log.d(TAG, "Error:"+e);
}
}
private void explodeObstruction(float pX, float pY)
{
PointParticleEmitter obstructionExplosion = new PointParticleEmitter(pX, pY);
ParticleSystem ExplosionParticleSystem = new ParticleSystem(obstructionExplosion, 45, 60, 60, this.mCrateParticleTextureRegion);
ExplosionParticleSystem.addParticleInitializer(new AlphaInitializer(1f));
ExplosionParticleSystem.setBlendFunction(GL10.GL_SRC_ALPHA, GL10.GL_ONE);
ExplosionParticleSystem.addParticleInitializer(new VelocityInitializer(-175, 175, -175, 175));
ExplosionParticleSystem.addParticleInitializer(new RotationInitializer(0.0f, 360.0f));
ExplosionParticleSystem.addParticleInitializer(new RotationInitializer(0f, -20f));
ExplosionParticleSystem.addParticleModifier(new ScaleModifier(1.0f, 0.5f, 0, MAX_PARTICLE_LIFE/2));
ExplosionParticleSystem.addParticleModifier(new AlphaModifier(1, 0.35f, 0, MAX_PARTICLE_LIFE));
ExplosionParticleSystem.addParticleModifier(new ExpireModifier(MAX_PARTICLE_LIFE, MAX_PARTICLE_LIFE));
this.mScene.attachChild(ExplosionParticleSystem);
}
解决方法:
关于box2D和sprite / body删除后,你发现你无法从contactListener中删除一个sprite / body,但是你可以做的是在body或sprite中设置一个标志来删除它并检查这些标志. contactListener之外的单独更新方法.我这样做是通过制作一个’makeUserData’方法来创建一个带有sprite / body / type的JSONObject,另外还有一个布尔’deleteStatus’来确定它是否标记为删除：
private JSONObject makeUserData(int type, Body body, Object sprite)
{
JSONObject myObject = new JSONObject();
try {
myObject.put("type", type);
myObject.put("sprite", sprite);
myObject.put("body", body);
myObject.put("deleteStatus", false);
} catch (JSONException e) {
// TODO Auto-generated catch block
Log.d(TAG,"Exception creating user data:"+e);
}
return myObject;
}
然后我不是在碰撞后调用destroyObstruction()而是调用我创建的方法来将body中的删除标志设置为true：
private void setForDestruction(Body myBody) throws JSONException
{
if(myBody.getUserData()!=null)
{
((JSONObject)myBody.getUserData()).put("deleteStatus", true);
}
}
然后在一个单独的更新处理程序(我已经在我的onLoadScene方法中有一个更新分数)我添加了一个调用另一个方法,我迭代通过物理世界中的主体寻找这个标志：
this.mScene.registerUpdateHandler(new IUpdateHandler() {
@Override
public void reset() { }
@Override
public void onUpdate(final float pSecondsElapsed) {
//update the players score
updateScore();
//update the text on the screen
playerScoreText.setText( "Score: "+PLAYER_SCORE);
playerLivesText.setText("Lives:"+PLAYER_LIVES);
//remove any sprites flagged for deletion
try{
removeObjectsSetForDestruction();
}catch(Exception e)
{
Log.d(TAG,"Exception removing objects from update:"+e);
}
catch(Error e)
{
Log.d(TAG,"Error removing objects from update:"+e);
}
}
});
这是removeObjectsSetForDestruction方法：
private void removeObjectsSetForDestruction()
{
if(this.mPhysicsWorld!=null)
{
Iterator<Body> allMyBodies = this.mPhysicsWorld.getBodies();//gets all the bodies in my physics world
boolean isDelete = false;
JSONObject currentBodyData;
while(allMyBodies.hasNext())
{
try {
//this code is in a try/catch bracket because some of my bodies don't have the extra data attached
currentBodyData = (JSONObject)allMyBodies.next().getUserData();//gets the next JSONOBject from the body
if(currentBodyData!=null)
{
isDelete = (Boolean) currentBodyData.get("deleteStatus");
if(isDelete)
{
destroyObstruction((Body) currentBodyData.get("body"));
}
}
} catch (JSONException e) {
// TODO Auto-generated catch block
Log.d(TAG,"Error getting world bodies data:"+e);
}
}
}
}
编辑：The AndEngine wiki on box2D很好地解释了世界物理计算是如何脆弱的,所以你需要在添加/删除/移动物体时要非常小心,因为在某些地方它可能与世界物理计算同时发生,最终导致程序崩溃.它还概述了将代码放入’this.runOnUpdateThread’的解决方案.所以例如在我的代码中,当我在我的代码中添加一个障碍精灵时(它们是从CountDownTimer添加的,所以很可能在世界步骤计算的同时添加它们)我将它包装在一个线程中：
private void addObstruction(final float pX, final float pY) {
runOnUpdateThread(new Runnable() {
@Override
public void run() {
final Body body;
final Sprite myObstruction;
myObstruction = new Sprite(pX, pY-mCrateTextureRegion.getHeight(), mCrateTextureRegion);
body = PhysicsFactory.createBoxBody(mPhysicsWorld, myObstruction, BodyType.DynamicBody, OBJECT_FIXTURE_DEF);
//body.setLinearDamping(10);
//body.setAngularDamping(10);
mPhysicsWorld.registerPhysicsConnector(new PhysicsConnector(myObstruction, body, true, true));
body.setUserData(makeUserData(OBSTRUCTION_TYPE,body,myObstruction));
myObstruction.setUserData(makeUserData(OBSTRUCTION_TYPE,body,myObstruction));
myObstruction.registerUpdateHandler(new IUpdateHandler() {
@Override
public void reset() {
}
@Override
public void onUpdate(float pSecondsElapsed) {
runOnUpdateThread(new Runnable() {
@Override
public void run() {
final Vector2 velocity = Vector2Pool.obtain(-10f, 0f);
body.setLinearVelocity(velocity);
Vector2Pool.recycle(velocity);
}
});
}
});
//attach our Obstruction to the scene
mScene.attachChild(myObstruction);
}
});
}
我在大多数地方都使用过这些线程,我用机身编码,我可以确认这阻止了我的随机崩溃:)