我正在制作一个滑板游戏，你必须使用box2D和AndEngine来跳过障碍。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！以下是一些代码段 -
当我创建精灵/边界时，我将一个JSONObject附加到包含精灵的主体和精灵的类型，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;
}
构建障碍精灵的代码与构建玩家的代码非常相似，但是我设置了移动速度：
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);
}
答案 0 :(得分：8)
在google搜索box2D和sprite / body删除后，你发现你无法从contactListener中删除一个sprite / body，但你可以做的是在body或sprite中设置一个标志来删除它并检查这些在contactListener之外的单独更新方法中的标志。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中（我已经在我的onLoadScene方法中有一个更新得分）我添加了一个调用另一个方法来迭代我物理世界中的物体寻找这个标志：
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，因此在添加/删除/移动物体时需要非常小心，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）我把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，我用尸体进行编码，我可以确认这可以阻止我的随机崩溃：）