So im quite new to AS3 but have worked with AS2 a lot before.
I have created a button and placed it on my stage then inside my class i have added this:
test.addEventListener(MouseEvent.CLICK, buttonClicked);
function buttonClicked(ev:MouseEvent):void
{
trace("Clicked");
}
Now this does not work as it can't find the stage, the only way i can get this to work is if i put the listener on the same frame as the button & not in the class.
But there must be away around this.
Thank you.
Eli
Update - adding Error messages
If I keep the above code all in the external class these are the errors i get.
Line 22 1120: Access of undefined property test. Line 22 1120: Access
of undefined property myButtonClick.
If you have created a document class with timeline then your "test" button must be in first frame. Because document class starts executing from first frame. You can access your button instance only when its available in stage.
Oh, I forgot to mention. You have to declare those instances as public variable in your document class.
public var test:SimpleButton;
Please go thru below and let me know which of the way you were having.
1) Are you having Document class?
There is a field Class in the Document Properties under the Publish tab of the flash IDE, if you are giving your class name in that field then it is called as Document Class
If you are having document class then you can create listener to your button even in the constructor button. Flash won't throw any errors like you got.
2) If you are instantiated your class in the first frame, it won't have the properties of stage till you add that to the stage using addChild. Also it won't have access to your button. And so it will throw the error, The access of undefined property.
Have you assigned the instance of the button on the stage the name "test"? The error message you posted seems to say there is nothing with the name "test" to assign the event listener to.
To check, click on the button the stage and look at the 'Properties' tab: will show in a text box near the top if it needs assigning.
Now the second error you posted means you're referring to something called "myButtonClick" without first declaring/initialising a variable/function with that name. You will either need to declare it or correct it if you meant to refer to something else.
Fixed.
I was being rava stupid as normal, forgot to put them inside the init :|
For the people who might come across this problem.
Working Code:
public function Main()
{
// constructor code
test.addEventListener(MouseEvent.CLICK, myButtonClick);
}
function myButtonClick(ev:MouseEvent):void
{
trace("button Clicked);
}
Anyway thanks guys for the help sometimes its just the simplest answers are the correct ones.
Eli
Related
I have a class called ChestScene that represents a scene/MovieClip in a .fla file I'm working on. I've had tons of issues that seem to be rooted in a fundamental misunderstanding of how to properly use objects that have code attached to them. It is my understanding that adding the object to the stage automatically instantiates it, so right now all I'm trying to do is instantiate and add to stage ChestScene() in the constructor of my Main method. I thought it would be as simple as this:
public class Main extends MovieClip {
var chest:Chest = new Chest();
public function Main() {
stage.addChild(chest);
}
But I get this error:
TypeError: Error #1009: Cannot access a property or method of a null object reference.
at Chest()/startScene()
at Chest()
at Main()
So my first question is why is Chest null? The object exists in my fla. If I add it to the stage by dragging from the library, the class works as intended. addChild seems to work on other objects that I am using the same way so I don't get why I can't use it on this object.
How to use the Main method to instantiate an object and access/change properties of said object relative to the stage? And how can I do the same thing for the objects nested inside of my initial object?
***** Edit after answer
Thanks for your reply and for teaching me how to read the debug message. startScreen() was indeed the culprit, and the issue there was this:
stage.addEventListener(Event.ENTER_FRAME, gameLoop)
Removing stage and adding the listener to the object fixed that error, so kudos! But I'm still confused; why does trying to add the listener to the stage cause a null error? I don't understand why the stage would be null at this point. Also, removing "stag." from the addEventListener caused the size of the frame that holds the scene to be way smaller, which cropped a lot of my image. Why is an event listener affecting my stageWidth and height? This is why I also asked questions about how to correctly position things relative to the stage width and height, because I know it has something to do with the errors.
why is Chest null?
Chest is not null. It's the constructor of the class and cannot be null.
You should pay attention to the Stack trace attached to the error (the lines with "at …" below the message).
It tells you where the error occurred. Reading it from the bottom up gives you the order of method calls performed.
TypeError: Error #1009: Cannot access a property or method of a null object reference.
at Chest()/startScene()
at Chest()
at Main()
Main() called Chest(), Chest() called startScene() and BOOM! this is where the error occurred.
To debug this error look at startScene() . Something in there is null.
Looking at your current code:
stage.addChild(chest);
I guess that you also try to add something to stage in Chest(). But stage is not available ( null) in Chest().
In general, it's bad practice to add things to stage as can be read in the documentation of addChild()
Simply add to the object and not stage :
addChild(chest);
Complete AS3 noob here - I've tried Googling this, but I can't seem to find what I'm looking for (I stumbled across this, http://ub4.underblob.com/as3-naming-elements-dynamically/, but it doesn't weem to work for me).
I'm trying to dynamically add a Movieclip inside another Movieclip through an external AS3 class
Something like this:
var bullet:Bullet = new Bullet(x, y, "right");
var stageBackground:MovieClip = (stage.getChildByName("back") as MovieClip);
stageBackground.addChild(bullet);
However, while this compiles correctly, at run time, I get error #1009 - Cannot access a property or method of a null object reference.
The debug panel tells me the problem is with this line:
stageBackground.addChild(bullet);
But I can't seem to figure out what's wrong with it. I've tried recasting stageBackground as a Sprite, but that didn't change anything. I know the MovieClip back exists - when I reference it through near identical code in my document class, it works perfectly.
You are accessing stage here to find your container, which is very likely the problem.
You are probably thinking that the stage property refers to "the stage" in Adobe Flash authoring environment.
That's not true.
If you placed a MovieClip on "the stage" in the Flash IDE, it ends up on the main time line, this however, is not the thing the stage property is referencing. stage is the topmost DisplayObjectContainer in the display list. It only exists at runtime. It more or less represents the FlashPlayer window, the runtime environment that executes your .swf file.
In short: you are simply looking for your back MovieClip in the wrong place.
The property of a container that represents the main timeline is root.
Do not use root either.
As you can see, your code becomes dependent on the display list
structure of your application. You are already struggling to find the
container that you are looking for. If you change the structure, your code breaks. Even changing the name of the container (for example to something like "background") will wreak havoc.
Instead, use Events.
You are in another class and you want to fire a bullet.
So you create that bullet same as you do now:
var bullet:Bullet = new Bullet(x, y, "right");
Next, dispatch an Event to notify the rest of your code that a bullet was created and it should be placed in the appropriate container:
dispatchEvent(new BulletEvent(BulletEvent.CREATED, bullet));
(Create a custom event class BulletEvent that extends Event, with the apropriate setter and getter for a Bullet object)
Register a listener on the object of your class that creates the bullets, you will catch this event and place the bullet in the container:
var object:YourClass = new YourClass();
object.addEventListener(BulletEvent.CREATED, addBulletToContainer);
function addBulletToContainer(e:BulletEvent):void
{
// adding the bullet to the container
back.addChild(e.bullet);
}
This code would be placed in the parent of your back MovieClip.
The Flash IDE automatically creates variables behind the scenes that have the same names as the instance names. That's why the variable back is available here.
Using events here allows you to literally fire the bullet into your code with somebody else taking care of it, where it's easy to figure out the container it belongs into.
What I want to do is to add button as a child to a movie clip which is on stage. Get input in a text field and then save that input into String variable. This button should trigger this actions. Only problem I find is that I can't reach the button which is in library. I have set button AS linkage and I am trying to reach it trough that linkage.
This is the line of code which dosen't work:
enterName.addChild(nextButton);
Error I get is: Line 254 1061: Call to a possibly undefined method addChild through a reference with static type Class.
Since your button has a linkage, you should instantiate it, which means:
enterName.addChild(new nextButton());
An even cleaner version would be to have your linkage name with a first letter upper case (this is commonly how classes are named). And you could cast this instance as a DisplayObject to tell the compiler you know this class extends something you can add to a container:
enterName.addChild(new NextButton() as DisplayObject);
I'm trying to call a movieclip called mcMain that's already on the stage. I'm calling it from a class and I've tried googling a whole bunch of possible solutions, none of which appear to work. I've tried stage.mcMain, this.stage.mcMain, MovieClip(root).mcMain, but nothing seems to work. Anyone got any ideas? I don't even get an error message. Just nothing happens.
I don't think that the root of your document timeline is actually the stage. However, you shouldn't be doing this. If the "Class," as you call it, is a DisplayObject, it should not know about anything outside its own scope (unless you've exposed properties or methods on it that would allow for this information to be passed in. If the Class is a data class it shouldn't know about the View at all. If it's a controller class, you'll need to pass a reference to it.
However, given the code you said you tried, I'm guessing your Class instance is some sort of DisplayObject. What you should do is dispatch a bubbling event from your Class, and then in your main Document class, listen for that event. In the event handler function, do whatever you need to do with your mcMain instance, such as adding ketchup. This should work just fine, because your main document Class can receive events from anywhere in the display list, and mcMain is its own instance.
I placed a movie clip instance inside a button, and I want this movie clip to play when the button is released. I'm using this code on the frame containing the button:
function playMovie(event:MouseEvent)
{
this.theButton.theMC.gotoAndPlay(3);
}
theButton.addEventListener(MouseEvent.MOUSE_UP, playMovie);
When I try to test the flash movie, I get this message:
1119: Access of possibly undefined property theMC through a reference with static type flash.display:SimpleButton.
I can somewhat understand why it doesn't like it, but I do not know how to resolve the issue.
if you are inside of theButton already then you won't need to call "this.theButton" because "theButton" is "this"
try
this.theMC.gotoAndPlay(3);
if you are still unsure of the object parent child relation and you are using the flash IDE, in your actions panel, click the blue target at the top of the actions panel and find the MC you are trying to reference and let the flash IDE figure out the relationships for you.
Give the movieclip in your button an instance name of "theMC". Then use the following code:
function playMovie(e:MouseEvent)
{
this.theButton.getChildByName("theMC").gotoAndPlay(3);
}// end function
theButton.addEventListener(MouseEvent.MOUSE_UP, playMovie);