Bits & Bytes

Posts Tagged ‘tutorial’

Responding to Mouse Click Events in Actionscript 3.0

To respond to mouse events of any kind, we create a callback function that takes a MouseEvent and returns void. Then we call addEventListener() with the event and the callback function. Below, we show how this is done for MOUSE_DOWN and MOUSE_UP events, but the same method can be used for all of the mouse event types.

Inside the callback functions, we change the message that is displayed by the TextField and position the message to be displayed where the event occurred. If you click in the box above, you will see the message change and move as you press and release the left mouse button. In this example, we position the message using the stage coordinates. However, we can also use the members localX and localY to get the position based on the object that is listening for the events.

var qMessage:TextField = new TextField();
qMessage.text = "Click In Here";
addChild(qMessage);

stage.addEventListener(MouseEvent.MOUSE_DOWN, OnPress);
function OnPress(e:MouseEvent): void {
	qMessage.text = "Down";
	qMessage.x = e.stageX;
	qMessage.y = e.stageY;
}

stage.addEventListener(MouseEvent.MOUSE_UP, OnRelease);
function OnRelease(e:MouseEvent): void {
	qMessage.text = "Up";
	qMessage.x = e.stageX;
	qMessage.y = e.stageY;
}

Looping Music or Sounds in Actionscript 3.0

For the second example, we demonstrate how to loop a music file using a separate class file. We start with the sound file “XoaxTheme.mp3” in our project and its associated class, XoaxTheme, that we had from our previous post.

To begin, we add an ActionScript code file to the project by selecting File->New from the menubar. This opens the “New Document” dialog shown below, where we left-click “ActionScript File” to select it and left-click the “OK” button to create a new code file.

Next, we paste this code into the new file:

package {

    import flash.media.SoundChannel;
    import flash.events.Event;
	
    public class CMyClass {
		
        var mqMusic:XoaxTheme;
        var mqSoundChannel:SoundChannel;

        public function CMyClass() {
            mqMusic = new XoaxTheme();
        }
		
        public function StartMusic(e:Event):void {
            mqSoundChannel = mqMusic.play();
            mqSoundChannel.addEventListener(Event.SOUND_COMPLETE,
                StartMusic);
        }
    }
}

and then change the code in the main code file to this:

var qMyClass:CMyClass = new CMyClass();
qMyClass.StartMusic(null);

The new code file needs to be saved. So, we select File->Save As… from the menubar and save the file as “CMyClass.as” in the project folder. Finally, we can compile and execute the code, and it will play the music repeatedly.

Let’s review the code above. In our class file, we use an unnamed package and import the SoundChannel and Event files. Inside the class, we have two members: mqMusic and mqSoundChannel, which are used to control the music. The class XoaxTheme is the sound class that we created in the library. We instantiate this class in the constructor.

The function StartMusic() does all of the real work in the program. When we call play(), the music starts playing and a SoundChannel object is created and returned. The SoundChannel controls the sound as it plays. We register a SOUND_COMPLETE event on the SoundChannel to call the function StartMusic() recursively when the music finishes playing. In this manner, we create the loop for repeatedly playing the music.

In the main program, we create an instance of a CMyClass object and then call StartMusic() on it to begin the music loop.

Declaring and Using Arrays in Actionscript 3.0

Arrays in Actionscript are extremely flexible; there are many ways to declare and assign values to an array in Actionscript. We can use functions, bracket notation, or constructors to create an Array object. We also have several ways to fill the entries of an Array object.

It is important to note that an Array in Actionscript is an object. So, an Actionscript Array is very different from say an array in C/C++. In fact, Arraysin Actionscript can hold many different types of data, which is different from arrays in most languages. However, Actionscript does also have a Vector type, which is similar to a traditional array in that, for efficiency, it is limited to holding only one type of data.

One dimensional Arrays are pretty straight-forward in how they can be declared and used. However, there are multiple methods for creating one-dimensional Arrays, which can be put together in numerous combinations to created multi-dimensional Array objects.

One-Dimensional Arrays

Function Notation

  1. var aMyArray:Array = Array();
  2. var aMyArray:Array = Array(3);
  3. var aMyArray:Array = Array(qMyObject);

Bracket Notation

  1. var aMyArray:Array = [“XoaX.net”, 17];

Contructor Notation

  1. var aMyArray:Array = new Array();
  2. var aMyArray:Array = new Array(3);
  3. var aMyArray:Array = new Array(1, 2, 3);

Above, we show several methods for creating an Array. The first three examples use function notation to create an Array of 0, 3, and 1 objects, respectively. Next, we have an Array of two elements that is created via the bracket notation; notice that the Array contains elements of different types: a string and an int. Lastly, we have three Array objects that are created using constructors: the first creates an Array with 0 elements, the second an Array with three elements, and the third an Array of the three elements 1, 2, and 3.

Filling an Array

  1. var aMyArray:Array = new Array();
    aMyArray.push(80, 120, 200, 440);
  2. var aMyArray:Array = new Array(4);
    aMyArray[0] = 80;
    aMyArray[1] = 120;
    aMyArray[2] = 200;
    aMyArray[3] = 440;

Above, we have two examples of how to declare and fill an Array with the four elements 80, 120, 200, and 400. In the first case, the push() function puts an element, or multiple elements, into an Array and extends the size of the Array. In the second case, we use the typical bracket operator [] to set the value of entries that are already allocated. There are many other functions available for removing elements, concatenating Arrays, and altering Arrays in many other different ways, as well; we will cover those later.

Multi-dimensional Arrays

  1. var aRow1:Array = new Array(1, 2, 3);
    var aRow2:Array = new Array(4, 5, 6);
    var aMyArray:Array = new Array(aRow1, aRow2);
  2. var aRow1:Array = [1, 2, 3];
    var aRow2:Array = [4, 5, 6];
    var aMyArray:Array = [aRow1, aRow2];
  3. var aMyArray:Array = new Array(2);
    aMyArray[0] = new Array(1, 2, 3);
    aMyArray[1] = new Array(4, 5, 6);
  4. var aMyArray:Array = new Array(2);
    aMyArray[0] = [1, 2, 3];
    aMyArray[1] = [4, 5, 6];
  5. var aMyArray:Array = [ [1, 2, 3], [4, 5, 6] ];

Here, we have 5 examples of how to create a two-dimensional Array object, by combining the methods for one-dimensional Arrays. We can continue like this and create Arrays with any number of dimensions.