I'm making a little app for school where you can controll a ball with the Acceleropmeter (for Smartphones) and I want that, if the ball reaches a certain Y coordinate, you lose and you go to another frame (where it says you have lost the game). 've done the ball and the code so far is this:
var fl_Accelerometer:Accelerometer = new Accelerometer();
fl_Accelerometer.addEventListener(AccelerometerEvent.UPDATE, fl_AccelerometerUpdateHandler);
function fl_AccelerometerUpdateHandler(event:AccelerometerEvent):void
{
cBall.x -= event.accelerationX * 40;
cBall.y += event.accelerationY * 40;
}
cBall.addEventListener(Event.ENTER_FRAME, moveBall);
function moveBall(evt:Event){
// this is to stop the ball when it tries to exit the sreen
if(cBall.x > (480-cBall.width/2)){
cBall.x = 480-cBall.width/2;
}
// except for this, that stops the ball not if it touches the end of the screen, but if it reaches a certain Y coordinate
if(cBall.y > (780-cBall.width/2)){
gotoAndStop(3);
}
if(cBall.x < (0+cBall.width/2)){
cBall.x = 0+cBall.width/2;
}
if(cBall.y < (0+cBall.width/2)){
cBall.y = 0+cBall.width/2;
}
}
Whenever I try the app, it says there is an error in the 32nd line (TypeError: Error #1009: Cannot access a property or method of a null object reference.
at ballApp_Scene1_fla::MainTimeline/moveBall()[ballApp_Scene1_fla.MainTimeline::frame1:32) Why? How can i fix this?
Since cball is the only object used in the moveBall-function, the null pointer exception means cBall was not yet initialized. Since this part is not shown there is no big help possible..
But maybe take a look at collision detection and the
BitmapData Class and its method hittest :
http://help.adobe.com/en_US/FlashPlatform/reference/actionscript/3/flash/display/BitmapData.html#hitTest%28%29
or DisplayObject Class offers hitTestPoint and hitTestObject
http://help.adobe.com/en_US/FlashPlatform/reference/actionscript/3/flash/display/DisplayObject.html#hitTestObject%28%29
If you can make different maps and object with image data and transparency it becomes easier to handle than hardcode each x and y coordinate to handle.
another one trying to do similar stuff:
BitmapData Collision
Related
hi im trying to make a basic game on adobe flash as3 to help learn collision dection, the aim is to make your way through traffic. the player (box_MC) has to make it to the other side and the other objects are in the way (cycle) which have collision detection. i did the collision detection by going into cycle movieclip and making other smaller cycles which if you hit creates collision.
the collision error lies with if the player moves down onto the cycle it doesnt run the collision
p.s if there is a better way of doing the collision how is it done?
hitTestObject() and hitTestPoint() aren't very good when it comes to collision detection, which is somewhat ironic since, of course, those are the first things most people look at when trying to implement collisions. However, I've found that simple math (like, really simple) combined with an equally simple while() loop is the best way to go about it.
What I do is:
// the stage collision box
var mStageRect:Rectangle = new Rectangle(/*stage collision box properties here*/);
// create a Point object that holds the location of the bottom center of the player
var mPlayerBase:Point = new Point(player.x + (player.width / 2), player.y + player.height);
// call this function every frame through your game loop (onEnterFrame)
private function checkCollision(e:Event):void
{
// while the player's bottom center point is inside of the stage...
while (rectContainsPoint(mStageRect, mPlayerBase))
{
// decrement the player's y
player.y--;
// set gravity to 0
player.gravity = 0;
// set isOnGround to true
player.isOnGround = true;
}
}
// checks if a point is currently positioned within the bounds of a rectangle object using ultra simple math
private function rectContainsPoint(rect:Rectangle, point:Point):Boolean
{
return point.x > rect.x && point.x < rect.x + rect.width && point.y > rect.y && point.y < rect.y + rect.height;
}
This is waaaaaaay more efficient than hitTestObject/Point, imo, and has given me no problems.
I have an Enemy class that deals with my monster moving and attacking. Within that class, I have another class called enemyMagic, which is a blank movieclip that serves as a masterclass to different movieclips that I will make.
So in the enemyMagic class, I add a movieclip called attack1
public var attack1:Attack1 = new Attack1;
public function EnemyMagic() {
////////////CREATE THE TIMER//////////
masterEnemyAttackTimer.addEventListener(TimerEvent.TIMER, mastertimer);
////////////ATTACKS/////////
//TIER 1//
addChild(attack1);
}
And in the enemy class, I add the enemyMagic when the enemy is attacking a certain position.
for (var k:int = 0; k < Main.tileset.length; k++)
{
if (! Main.tileset[k].tileMiddle.hitTestObject(this.enemyVisionPoint))
{
if (Main.tileset[k].tileHP !== 0)
{
attackoptions.push(Main.tileset[k]);
}
if (Main.tileset[k].tileMiddle.hitTestObject(Main.player.visionPoint))
{
addChild(enemymagic);
Main.tileset[k].outline.gotoAndStop("attack");
this.enemymagic.x = (Main.tileset[k].x);
this.enemymagic.y = (Main.tileset[k].y);
trace(enemymagic.x, enemymagic.y, Main.tileset[k].x, Main.tileset[k].y);
For some reason, the enemymagic is tracing the exact same number as the tile's x and y, but it isn't adding it on the tile. It adds it way off the screen. I think it might be because it starts on the enemy's x and y and then calculates?
So my question is how can I get the enemymagic movie clip to get exactly on the position of the tile?
You can do two things. First, when you do a plain addChild() the base coordinate system of the child is the one of its parent, which is your Enemy instance, which is of course at somewhere nonzero. And then you assign it the coordinates of Main.tileset[k] which has a different parent (most likely instance of Main). This creates the distance you speak of. So, in order to locate your magic over the exact tile, either use this.globalToLocal(Main.tileset[k].localToGlobal(PZERO)) where PZERO is a new Point() constant (or write new Point() instead of PZERO, but this will create another empty Point object and will quickly escalate), or do an addChild() directly to the tile you are attacking with unaltered coordinates.
I'm making a simple game and have a Vector full of enemies in order to do hit-checking on them from my "laser" object (it's a space shmup). Every laser loops through the Vector and checks if it's occluding the hit circle. The problem lies in when one laser destroys an enemy, the rest of the lasers try to also check the same Vector, only to go out of bounds since the enemy's already been spliced out and it's changed the size of the Vector.
for each (var enemy:Enemy in enemies){
var distanceX = this.x - enemy.x;
var distanceY = this.y - enemy.y;
var distance = Math.sqrt( (distanceX*distanceX) + (distanceY*distanceY) );
if (distance <= enemy.hitRadius) {
enemy.removeEnemy();
enemies.splice(enemies.indexOf(enemy),enemies.indexOf(enemy));
}
}
How would I go about collecting the index of individual elements in the Vector to be deleted, then only deleting them when every Laser object is finished its checking?
edit: here's my removeEnemy() function from my Enemy class, just in case:
public function removeEnemy(){
removeEventListener(Event.ENTER_FRAME, move);
parent.removeChild(this);
trace("removed Enemy", enemies.indexOf(this));
}
edit edit: I'm also getting a null reference pointer error to "parent" in my removeEnemy() function... but only sometimes. I have a feeling that if I fix one of these two problems, the other will also be fixed but I'm not sure.
I fixed it! The problem was actually in how I used the "splice()" method. Turns out that the second parameter isn't the end index of where to stop splicing, it's the number of elements to be spliced. So when I was trying to splice element 0, I wasn't splicing anything, and when I was trying to splice element 3, I was also splicing 4 and 5. I feel like such a dunce for not reading the API right and wasting a couple hours on this. Thanks to everyone who commented-- you guys helped me rule out what I thought the problem was.
I'm trying to test for collision between bullets within a vector and enemies within another vector. I can access the data fine, but the problem lies in the actual detection of the collision. Funny thing is, it works perfectly when I use hitTestObject, so I don't see why this shouldn't be working. I might be overlooking something, but I'm having a hard time finding it.
Code:
for each(var i in eManager.enemyArray)
{
for each(var j in gManager.gunVector)
{
for each (var k in j.bManager.bulletVector)
{
// Basically using Pythagorean's theorem but with both sides squared
// to minimize any process-heavy operations
if(((i.x - k.x)*(i.x - k.x))+((i.y - k.y)*(i.y - k.y)) <= 4)
{
// Note that when this happens, the enemy dies
i.kill = true;
}
}
}
}
Whoops. Turns out that I was testing the collision between 2 points, not between a point and a shape. My mistake.
First of all sorry for some english mistakes. Portuguese is my first language(I am from Brazil)
Im trying to make a space game from scratch in AS3 and the way to move the ship is like in the game Air Traffic Chief.
I succeed at some point. But when the ship is very fast it start to shake and its not very smooth and clean as I want.
Here is what i have done: http://megaswf.com/s/2437744
As the code is very big so I pasted in pastebin: pastebin.com/1YVZ23WX
I also wrote some english documentation.
This is my first game and my first post here. I really hope you guys can help me.
Thanks in advance.
Edit:
As the code is very big i will try to clarify here.
When the user MouseDown and MouseMove the ship every coordinate is passed to an array.
When the user MouseUP this array is passed to a function that fix the array.
For example: If the distance between two coordinates is greater than 5px, the function creates a coordinate in the middle of the two coordinates.
if I take this function off the problem seen to be solved. But if the user move the mouse very slow it still happens. It also creates a problem that i was trying to solve with that function. as the distance of the two coordinates are very big when the ship arrive in one coordinate most of the line path disappear.
I uploaded a version without the function that fixes the array. http://megaswf.com/s/2437775
I think there is 2 ways for solving this problem
1- Try to fix the noise in the array of coordinates 2- Take off the function that create an coordinate between two points and try to fix the problem of the line path disappear.
Here is the 2 important functions:
this function moves the ship
private function mover():void
{
if (caminhoCoords[0]!=null) // caminhoCoords is the array that contain the path
{
var angulo:Number = Math.atan2(this.y - caminhoCoords[0][1], this.x - caminhoCoords[0][0]);
this.rotation = angulo / (Math.PI / 180);
this.x = this.x - velocidade * (Math.cos(angulo));
this.y = this.y - velocidade * (Math.sin(angulo));
var testex:Number = Math.abs(this.x - caminhoCoords[0][0]); //test to see the distance between the ship and the position in the array
var testey:Number = Math.abs(this.y - caminhoCoords[0][1]);
if (testey<=velocidade+2 && testex<=velocidade+2) // if is velocidade+2 close then go to the next coordnate
{
caminhoCoords.shift();
}
}
}
This function draw the line:
private function desenhaCaminho():void //draw the black Path
{
if(caminhoCoords.length>=1)
{
caminho.graphics.clear();
caminho.graphics.lineStyle(1, 0x000000, 1,true);
caminho.graphics.moveTo(caminhoCoords[0][0],caminhoCoords[0][1]);
for (var i:int = 1; i < caminhoCoords.length; i++)
{
caminho.graphics.lineTo(caminhoCoords[i][0], caminhoCoords[i][1]);
}
}else
{
caminho.graphics.clear();
}
}
Every time the ship arrive in one coordinate is take that coordinate off the array and redraw the array.
Is there a better way of doing that?
I believe if you set your registration point of the plane to the centre and use .snapto(path), it will improve the action.
Judging from just the look of the stuttering, I would guess you need to smooth out the "line" a fair bit. It's probably picking up a lot of noise in the line, which is then translated into the rotation of the plane. Either smooth out the rotation/position of the plane, or the line itself.