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POBox2D & Cocos2d level reset issue
 

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  1. POBox2D & Cocos2d level reset issue
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    <p>I have a very simple level that has a single static body (and associated sprite) in it. When the user touches the body, I remove the sprite, destroy the body and replace it with a dynamic body with a new sprite, and then I transition to a new scene. My code works perfectly the first time it is executed, but then when this scene is reloaded it crashes when the user touches the body. </p> <p>I store the filename of the .png file that I use for my sprite in the sprite's userData field. Then when the user presses the button (touches the body) it is a simple matter to retrieve it. The problem is occurring on subsequent reloads of the scene when I try to access the sprite's userData field. Instead of holding the filename it is empty (null). This in turn crashes the program when I try to use the filename.</p> <p>I cannot understand why it works the first time and not the second. I set a breakpoint and watch the filename getting assigned to the sprite's userData field, but it is only retrievable the first time I create the scene. Here is the ccTouchesBegan method. The crash occurs where I try to assign newSpriteFileName because on the second run through oldSpriteFileName is empty.</p> <p>I have just about gone crazy with this one, but I am sure it is something obvious. As always thanks for the help!!</p> <pre><code> (void)ccTouchesBegan:(NSSet *)touches withEvent:(UIEvent *)event { for( UITouch *touch in touches ) { CGPoint touchLocation = [touch locationInView: [touch view]]; touchLocation = [[CCDirector sharedDirector] convertToGL: touchLocation]; touchLocation = [self convertToNodeSpace:touchLocation]; b2Vec2 locationWorld = b2Vec2(touchLocation.x/PTM_RATIO, touchLocation.y/PTM_RATIO); NSLog(@"Location x = %f, y = %f", touchLocation.x, touchLocation.y); b2AABB aabb; b2Vec2 delta = b2Vec2(1.0/PTM_RATIO, 1.0/PTM_RATIO); aabb.lowerBound = locationWorld - delta; aabb.upperBound = locationWorld +delta; SimpleQueryCallback callback(locationWorld); m_world-&gt;QueryAABB(&amp;callback, aabb); //If they have not pressed a button yet, and this touch was actually inside //one of the buttons then we will destroy the static button (and sprite) //that they touched and replace it with a dynamic button //(and new darker sprite) that falls, spinning off of the screen. if(!replaceButtonPushedYet &amp;&amp; callback.fixtureFound) { //Get a reference to the static body of the button they touched and wake it up b2Body *body = callback.fixtureFound-&gt;GetBody(); body-&gt;SetAwake(true); //Get the position of the body (button) they touched and use it to //position the new button. This value is in Box2D coordinates, //so when I position the new button I won't divide by PTM_RATIO. b2Vec2 touchedButtonPosition = body-&gt;GetPosition(); //Get the sprite from the button the user pressed CCSprite *bodySprite = (CCSprite*)body-&gt;GetUserData(); //Then extract the file name of the sprite. I assigned this to //sprite's userData when I loaded the sprite in the method //"placeTheIndividualButton". Now I am going to extract it and //then replace "(up)" with "(down)" in that string //and that becomes the name of the sprite for the new (pressed) //button I am getting ready to create. It is all about the file //naming conventions! NSString *oldSpriteFileName = (NSString*)bodySprite.userData; NSString *newSpriteFileName = [oldSpriteFileName stringByReplacingOccurrencesOfString:@"up" withString:@"down"]; //First remove the sprite tied to the button the user pressed, //then destroy the body of the button. [self removeChild:bodySprite cleanup:YES]; body-&gt;GetWorld()-&gt;DestroyBody(body); //Set the bool to true to keep this code from executing again. //This ensures that once they press a button they can't //press another one. replaceButtonPushedYet = true; //Build the new dynamic button that will fall and spin off the screen b2BodyDef buttonBodyDef2; b2PolygonShape buttonShape2; b2FixtureDef buttonShapeDef2; b2Vec2 vertices2[4]; //load the sprite for the second button (pressed down) and add it to the layer level_down = [CCSprite spriteWithFile:newSpriteFileName]; level_down.userData=newSpriteFileName; [self addChild:level_down]; //Define the polygon that forms the second button (pressed down) buttonBodyDef2.type = b2_dynamicBody; //Not dividing touchedButtonPosition.x or .y by PTM_RATIO because //they are already in Box2D coordinates buttonBodyDef2.position.Set(touchedButtonPosition.x, touchedButtonPosition.y); buttonBodyDef2.angularVelocity = 1.5; buttonBodyDef2.userData = level_down; buttonBody2 = m_world-&gt;CreateBody(&amp;buttonBodyDef2); //Define the vertices for the replacement button vertices2[0].Set(-94/PTM_RATIO, -32/PTM_RATIO); vertices2[1].Set(94/PTM_RATIO, -32/PTM_RATIO); vertices2[2].Set(94/PTM_RATIO, 32/PTM_RATIO); vertices2[3].Set(-94/PTM_RATIO, 32/PTM_RATIO); buttonShape2.Set(vertices2, 4); //Define the shape for the replacement button buttonShapeDef2.shape = &amp;buttonShape2; buttonShapeDef2.density = 50.01f; buttonShapeDef2.friction = 0.75f; buttonShapeDef2.restitution = 0.1f; //The static buttons and the dynamic buttons are both in this groupIndex. //Since it is a negative number they will never collide. If it was //positive they would always collide. buttonShapeDef2.filter.groupIndex = -1; //Put the second button (pressed down) into the world. buttonBody2-&gt;CreateFixture(&amp;buttonShapeDef2); //This starts a timer that fires every second to call the makeTransition //method. The code inside that method will check to see if the button //has fallen off the screen yet. If it has then it will transition to //the new selected level. //The colon after makeTransition sends a ccTime (dt). I don't need it, //but may in the future so I left it in there. buttonFalling = [NSTimer scheduledTimerWithTimeInterval:0.5 target:self selector:@selector(makeTransition:) userInfo:nil repeats:YES]; } } </code></pre> <p>}</p>
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