I'm new to coding and AS3. I was reading about adding things to the stage using AS3 and learned about the addChild method. Reading more I found that there are different ways to use it. I also read that some ways are better than others, and that some ways are not good at all and better avoided.
I don't trust those sources though. As a coding newbie I come asking for help, StackOverflow. I'm about to start an addChild heavy project and I want to start it with the right implementations. I trust you, so let me ask you this: What's the correct use of addChild?
I just want to add things to the stage, but I read that it's not good to add them directly to the stage (without further argument though).
stage.addChild()
this.addChild()
addChild()
Are there other ways? Which one should I use?
Thanks for your time. :)
As the top-level container for all display objects in the display list hierarchy, there is only one Stage no matter how many SWF files are loaded into the runtime. So, generally, objects should not be added to the Stage, directly, at all. The only object the Stage should contain is the root object.
Generally, you should not use: stage.addChild()
Adding a DisplayObject to the display list should be performed within the scope of a DisplayObjectContainer.
Each SWF file has an associated ActionScript class, known as the main class of the SWF file which extends a display object. From this class or any child within the hierarchy you may call addChild().
The following are equal, and would add a child within the scope of the current display object container.
this.addChild()
addChild()
The this keyword explicity defines scope; however, is generally implicit when left off.
While a display object added via addChild() is added to the front (top) of all other children, to add a child to a specific index position, use the addChildAt() method.
References:
Display Programming
Basics of display programming
Adding display objects to the display list
Related
I have a game in which I have three different scenes. In the first scene, the objects (movieclips) were added through the flash editor, meaning that no actionscript was used to add them (not added with addChild). After that ive decided that I want to do the second and third scene entirely through actionscript and every object that is added is added with addChild(). The problem with this is that now the objects that have been added through actionscript appear in front of the ones added manually through the editor and I want it to be the other way around. I know that addChildAt() exists but I have over a 100 objects so it doesn't seem like a good option. In short: How do I set the Z-Indexes of movieclips that have been added through the flash editor and not through actionscript.
At first I tell you, this is not a good practice.
I give you some methods:
1.add child at to the back of others:
addChildAt(myDisplayObject,0);
so your added children will go back.
2.set the index of display obects:
first you should give them instance names, then in code:
setChildIndex(myDisplayObect,myIndex);
so you set the index of your display object.
I H☺ P E this helps
i am working with several nested movieclip objects in a project. but i get into trouble with the buttons i created and implemented in the nested movieclips:
to describe it in a simple way:
I have a main movieclip with five frames, including two buttons with listeners to browse between the frames. Then inside of one Frame I have another movieclip with its own buttons. i instanciated it by hand not through code and gave it a specific name like "nestedMc".
Now I dont want to build the Listeners for those buttons inside the class of the nested movieclip class but in its parent class, which works fine until i then goto another frame in the main movieclips timeline and come back.
obviously every time flash enters a frame its contents get created anew (and therefore get new instance names). I could now try solve this through filling the frames via code.
But maybe there is another way to make sure the frame contains the same instance everytime i enter?
Timeline scripting is a dirty business, and really, a carry-over compatibility layer for Actionscript 2 projects. Whenever possible, I highly recommend not doing it, and simply keeping all of your code in your document class. As you're experiencing, timeline code causes headaches.
Consider instead just creating both states of your Stage (it sounds like that's what your two buttons are jumping between) and simply hiding them offstage or setting their alpha to zero and their mouseEnabled state to false. Furthermore, if the purpose of your frames is to play animation (a tween), consider instead switching to a much more powerful suite such as TweenLite. Moving an object over a hundred pixels (smoothly) can be as easy as:
TweenLite.to(redBall, 3, {x:100});
Now, if you're manually adding these items to the stage, as long as the object is a dynamic one, you can assign an instance name to it which will be saved between frame loads. Be aware the object name is not the same as the instanced name. For example:
var redBall:Ball = new Ball();
redBall.name = "bubbles";
The object's name is Ball, but it's represented as a variable called redBall. Its actual DisplayList name will likely be ambiguous (such as "Instance71"), and I can manually define it as "bubbles". 3 different names for the same object, all very different and necessary.
Even if you give the object a displayList name, you may not be able to reference it through code unless you enable Automatically declare stage instances, which basically creates on each object a pointer to the displayList object.
That said, you can always fetch the object by other means. Obviously, your buttons are always appearing, but you're trying to find a very specific object on the stage. At this point, we can use getChildByName() or getChildAt().
Hope that helps.
-Cheers
I have been writing a game in timeline code. I want the different frames (rooms) in the game to be able to share information between each other. Of course, timeline code is limited to the frame it is written in.
After doing quite a bit of reading ("Foundation Game Design with Flash" and a number of articles, tutorials, forums etc) I decided to employ a document class. This did not work either. It seems it only works for frame one but not the rest of the frames (I have four).
How can I have frame four respond to something that happpened in frame one? For example, if the player achieves something in frame one, I want a movie clip in frame four to be visible.
If You are writing your code on the timeline, My suggestion would be to create two layers in the timeline, one for 'frame-actions' - in this layer you insert the code specific to a single frame (will work when the movieclip is stopped on that particular frame).. And also create one more layer called global-actions (for the entire timeline). Only the first frame will be a key frame and there should be empty frames till the end of the timeline.
In this layer actions write the code that you want to access from any keyframe in the same timeline.
If you define a variable in the actions which are written for the whole timeline (global-actions) then that will be available on all the frames.
Now if you want to go to a different frame based on some action, just write some functions in the layer which contains global actions and call that particular function through the frame actions. To go to a different frame use the 'gotoAndStop(frameNumber)' function of flash.
I want to tell you that while it will work, I would not recommend using it in this way.
HTH.
You can use static variables - these are variables which are linked to a class, rather than an instance of it.
Suppose your document class was called Document.as, and you wanted a variable, playerLives, to be visible from any part of the program.
Declare it inside Document.as:
public static var playerLives:int = 3;
You can then reference this directly from anywhere else in your code with:
Document.playerLives
(note that the variable is a member of the class itself, not an instance of it).
You could use a dedicated Statics class to hold these variables if you want to keep your document neat, or attach them to the relevant classes (eg Player.lives)
I've not used timeline/frames for some years but I believe this is how I used to do it!
NB Statics will be fine for your purposes but they are, in some ways, an equivalent to the _global variable in AS2 (at least, they can be used in the same manner) - many would not approve of their use, or over-use, as they are freely accessible from anywhere in your program (thus anathema to the OO concept of encapsulation), but personally I try not to worry about it in small cases - the most important thing to know about the rules of any design pattern is when they can be broken!
They are also slightly slower to access than instance members, but you won't notice this unless you are constantly accessing/changing them (making things like player velocity, which will need to be referenced/changed every frame, static, is not a good idea).
Hope this helps.
You may find the simplest way to link everything with the document class is to move your four frames into a movieclip together and have that on the first frame, then interact with that movieclip.
E.g. in the document class, where the movieclip instance on the timeline is called 'game'.
game.gotoAndStop(4);
game.objectToDisplay.visible = true;
If you encounter reference errors in the IDE then you can avoid these by using [] notation to refer to the properties of game, e.g. game["objectToDisplay"].visible = true;
Note that it's not really best practice to do this, but it will at least help you to finish that first game which is really more important at this stage in your learning. Afterwards, if you want to learn more then I'd recommend "The Essential Guide to Flash Games" by Jeff Fulton from 8bitrocket.com - it will teach you how to use the document class effectively.
When do we need to pass reference to the stage from one as3 class to another like in this tutorial
http://asgamer.com/2009/as3-flash-games-for-beginners-firing-weapons-with-delays
he added a ref to the stage from the bullet class to the ship class
as I understand a reference is needed when we want to use a function in a certain class from another class but why do we have to reference the stage isn't it only one stage for the whole project or each class has it's own stage ?
I am very confused
Thanks
Only objects that are connected to a stage will be shown on screen. In the tutorial he is adding the lasers onto the stage display list so that it appears on screen. Until it is added, it will not be rendered regardless of the visible property.
See this for more info about the display list.
#Geotarget is correct, but the answer is a little bit indirect.
Objects that are not on the display list do not actually have a reference to stage. So if, for example, you create a var mc:MovieClip = new MovieClip(); which is not added to the display list (as in addChild(mc)), then mc.stage will be null. (Also, checking if(mc.stage){[...]} is also a way to verify if the MovieClip is part of the display list yet.)
So you can pass a reference to the stage to non-display-list objects to allow them access to things like stageWidth.
Yes, a reference is needed when you wanna have to access a function present in that particular class ( to which reference belongs). This is one of the uses.
There is only one stage for the whole project.
In the tutorial you are following, both the classes are using the reference of a COMMON Stage, so that both of them can access the Stage.
It's like giving the address of a place to two people. So that both of them can go there. Naturally, giving addresses doesnot mean, we are building two places for each of them.
V.
Consider you have A.swf generated by compiling A.fla. A.fla's document root class is AStage(). Now consider B.swf and it's B.fla. If B.fla loads A.swf. Can it cast A.swf's stage object to AStage()?
If this is not possible, what is the recommended approach for communicating with child SWFs?
Personally I would consider it 'best practice' to use an interface to cast to rather than your SWF's document class itself. Be careful of using the word stage as a Flash application has only one stage regardless of how many SWF's it loads.
I've answered a similar question here:
pass var values from one swf to another swf who is loaded inside the firts one in AS3
Apart from this , it is generally possible for a parent and a child to belong to the same class, consider Sprites for instance.