AS3: why does the MC "tremble" when selected?

I'm trying to make a simple function to select and drag a MovieClip, without using the startDrag() function.

I have a few MCs on the stage, when mouse down on a MC, I want the MC to move with the mouse. But when I hold the mouse down, the MC starts to "tremble" and I'm not sure why.

I have the code inside each MC for other reasons. Here is what I have so far:

var selectX:Number; //x coordinate of mouse click (to select right point on mc on mouse down)


this.addEventListener(MouseEvent.MOUSE_DOWN, mouseDownHandler);
this.addEventListener(MouseEvent.MOUSE_UP, mouseUpHandler);

function mouseDownHandler(e:MouseEvent):vo开发者_Python百科id {  
    selectX = this.x - mouseX;
    addEventListener(Event.ENTER_FRAME, onEnterFrameHandler);
}


function mouseUpHandler(e:MouseEvent):void {
    mouseX2 = mouseX;
    removeEventListener(Event.ENTER_FRAME, onEnterFrameHandler);
}

function onEnterFrameHandler(e:Event):void {
    this.x = mouseX + selectX + stage.x;
}

This is happening because you are using mouseX of the inside of the movieclip. but when you are trying to set the x of the movieClip it sets the x on the parent movieclip.

e.g.:

mainClip |-- DragableButton

when you adding DragableButton.x = 100, it is x position insided of the mainClip. and when your code is taking mouseX inside of the DragableButton, the real mouseX = x + mouseX. and since mouseX inside of the DragableButton is equals e.g. 20, and you adding: selectX = this.x - mouseX -> if you have selectX = 100 - 20. but not 100 - 120 as it should be.

so if you still want to keep to your code change it a bit:

var selectX:Number; //x coordinate of mouse click (to select right point on mc on mouse down)
var mouseX2:Number;


this.addEventListener(MouseEvent.MOUSE_DOWN, mouseDownHandler);
this.addEventListener(MouseEvent.MOUSE_UP, mouseUpHandler);

function mouseDownHandler(e:MouseEvent):void {  
    selectX = this.x - parent.mouseX;
    // selectX = this.x - stage.mouseX;
    addEventListener(Event.ENTER_FRAME, onEnterFrameHandler);
}


function mouseUpHandler(e:MouseEvent):void {
    mouseX2 = parent.mouseX;
    removeEventListener(Event.ENTER_FRAME, onEnterFrameHandler);
}

function onEnterFrameHandler(e:Event):void {
    this.x = parent.mouseX + selectX;
    // this.x = stage.mouseX + selectX;
}

p.s. stage.x = 0, it will be always. unless you change the property. p.s.s. stage is only one and same instance no matter from which MC you are trying to get it.

my suggestion draging would be:

this.addEventListener(MouseEvent.MOUSE_DOWN, mouseDownHandler);

function mouseDownHandler(e:MouseEvent):void
{ 
    this.startDrag();
    stage.addEventListener(MouseEvent.MOUSE_UP, mouseUpHandler);
}


function mouseUpHandler(e:MouseEvent):void
{
    this.stopDrag();
    stage.addEventListener(MouseEvent.MOUSE_UP, mouseUpHandler);
}

I think the movieclip is trembling because during your drag, your application keeps calling mouseDownHandler, changing the selectX.

Try removing the MOUSE_DOWN event listener. In mouseDownHandler, make that the first thing you do (this is also a good practice for preventing memory leaks). You can add the listener back when you mouse up (and then remove the mouse up listener).

why are you using Event.ENTER_FRAME event (costly), try to use MouseEvent.MOUSE_MOVE like this.

function mouse_move(e:Event)
{
   this.x = mouseX + selectX + stage.x;
}

and remove this event handler on mouse up.