AS3 - TypeError: Error #1009 "null" at MethodInfo

Question

I have this small project. Frames that change every time I click button, and a simulation of progress bar inside arrows.

stop();
/** initializtios **/
var trans:ColorTransform = next_arrow.transform.colorTransform;
var p:int = 1;

var myColorTransform = new ColorTransform();
myColorTransform.color = 0x42f498;
var trans1:ColorTransform = back_arrow.transform.colorTransform;

/** actual code **/
btn_next_arrow.addEventListener(MouseEvent.CLICK, function goNextLectFrame(e:MouseEvent):void {
    if (p==1) {
        fill_1.transform.colorTransform = myColorTransform;
        fill_22.alpha = 0.00001;
        fill_3.alpha = 0.00001;
        fill_33.alpha = 0.00001;
        fill_5.alpha = 0.00001;
        fill_6.alpha = 0.00001;
        fill_7.alpha = 0.00001;
        fill_8.alpha = 0.00001;
        fill_9.alpha = 0.00001;
        fill_10.alpha = 0.00001;
        fill_11.alpha = 0.00001;
        fill_12.alpha = 0.00001;
        fill_13.alpha = 0.00001;
        fill_14.alpha = 0.00001;
        fill_151.alpha = 0.00001;
        ++p;
    }
    switch (currentFrame) {
        case 1:
            gotoAndStop(2);
            break;
        case 2:
            fill_22.transform.colorTransform = myColorTransform;
            gotoAndStop(3);
            break;
        case 3:
            fill_3.transform.colorTransform = myColorTransform;
            gotoAndStop(4);
            break;
        case 4:
            fill_33.transform.colorTransform = myColorTransform;
            gotoAndStop(5);
            break;
        case 5:
            fill_5.transform.colorTransform = myColorTransform;
            gotoAndStop(6);
            break;
        case 6:
            fill_6.transform.colorTransform = myColorTransform;
            gotoAndStop(7);
            break;
        case 7:
            fill_7.transform.colorTransform = myColorTransform;
            gotoAndStop(8);
            break;
        case 8:
            fill_8.transform.colorTransform = myColorTransform;
            gotoAndStop(9);
            break;
        case 9:
            fill_9.transform.colorTransform = myColorTransform;
            gotoAndStop(10);
            break;
        case 10:
            fill_10.transform.colorTransform = myColorTransform;
            gotoAndStop(11);
            break;
        case 11:
            fill_11.transform.colorTransform = myColorTransform;
            gotoAndStop(12);
            break;
        case 12:
            fill_12.transform.colorTransform = myColorTransform;
            gotoAndStop(13);
            break;
        case 13:
            fill_13.transform.colorTransform = myColorTransform;
            gotoAndStop(14);
            break;
        case 14:
            fill_14.transform.colorTransform = myColorTransform;
            gotoAndStop(15);
            break;
        case 15:
            fill_151.transform.colorTransform = myColorTransform;
            gotoAndStop(16);
            break;
        case 16:
            gotoAndStop(17);
            break;
    }
});

btn_next_arrow.addEventListener(MouseEvent.MOUSE_OVER, function hovering(e:MouseEvent):void {
    trans.color = uint(0x606266);
    next_arrow.transform.colorTransform = trans;
});

btn_back_arrow.addEventListener(MouseEvent.MOUSE_OVER, function hovering1(e:MouseEvent):void {
    trans1.color = uint(0x606266);
    back_arrow.transform.colorTransform = trans1;
});

btn_next_arrow.addEventListener (MouseEvent.MOUSE_OUT, function hideShadow(event:MouseEvent):void {
    trans.color = uint(0x999999);
    next_arrow.transform.colorTransform = trans;
});

btn_back_arrow.addEventListener (MouseEvent.MOUSE_OUT, function hideShadow1(event:MouseEvent):void {
    trans1.color = uint(0x999999);
    back_arrow.transform.colorTransform = trans1;
});

btn_back_arrow.addEventListener(MouseEvent.CLICK, function goPrevLectFrame(e:MouseEvent):void {
        switch(currentFrame){
        case 2:
            gotoAndStop(1);
            break;
        case 3:
            gotoAndStop(2);
            break;
        case 4:
            gotoAndStop(3);
            break;
        case 5:
            gotoAndStop(4);
            break;
        case 6:
            gotoAndStop(5);
            break;
        case 7:
            gotoAndStop(6);
            break;
        case 8:
            gotoAndStop(7);
            break;
        case 9:
            gotoAndStop(8);
            break;
        case 10:
            gotoAndStop(9);
            break;
        case 11:
            gotoAndStop(10);
            break;
        case 12:
            gotoAndStop(11);
            break;
        case 13:
            gotoAndStop(12);
            break;
        case 14:
            gotoAndStop(13);
            break;
        case 15:
            gotoAndStop(14);
            break;
        case 16:
            gotoAndStop(15);
            break;
        }
});

btn_main_menu.addEventListener(MouseEvent.CLICK, function goPrevLectFrame1(e:MouseEvent):void {
    gotoAndStop(17);
});

The problem is when I get to the last frame and click the next button, it says:

TypeError: Error #1009: ... "null". at Function/()[RECOVER_shitty_fla.MainTimeline::frame1:114]

That's a problem causing function:

btn_next_arrow.addEventListener (MouseEvent.MOUSE_OUT, function hideShadow(event:MouseEvent):void {
    trans.color = uint(0x999999);
    next_arrow.transform.colorTransform = trans; // LINE 114
});

I'm really struggling here, will appreciate any help, thank in advance.

Answer 1

You need to remove the event listeners before entering the final frame. Your program is still listening for MouseEvents on objects that do not exist on that frame.

Additionally, I'd heed @BadFeelingAboutThis's advice. Inline functions are bad practice and should generally be avoided.

There are other problems with this code (mostly minor). I've tweaked your code from the FLA document to get the program working. See the changes below.

---

Frames 1-16

stop();

import flash.events.MouseEvent;
import flash.system.fscommand;
import flash.display.StageScaleMode; 
import flash.events.TimerEvent;
import flash.utils.Timer;
import flash.geom.ColorTransform;

/** initializtios **/
var trans:ColorTransform = next_arrow.transform.colorTransform;
var p:int = 1;
var myColorTransform = new ColorTransform();
myColorTransform.color = 0x42f498;
var trans1:ColorTransform = back_arrow.transform.colorTransform;

/** actual code **/
btn_next_arrow.addEventListener(MouseEvent.CLICK, goNextLectFrame);
function goNextLectFrame(e:MouseEvent):void {
    if (p==1) {

        fill_1.transform.colorTransform = myColorTransform;
        fill_22.alpha = 0.00001;
        fill_3.alpha = 0.00001;
        fill_33.alpha = 0.00001;
        fill_5.alpha = 0.00001;
        fill_6.alpha = 0.00001;
        fill_7.alpha = 0.00001;
        fill_8.alpha = 0.00001;
        fill_9.alpha = 0.00001;
        fill_10.alpha = 0.00001;
        fill_11.alpha = 0.00001;
        fill_12.alpha = 0.00001;
        fill_13.alpha = 0.00001;
        fill_14.alpha = 0.00001;
        fill_151.alpha = 0.00001;
        ++p;
    }
    switch (currentFrame) {
        case 1:
            gotoAndStop(2);
            break;
        case 2:
            fill_22.transform.colorTransform = myColorTransform;
            gotoAndStop(3);
            break;
        case 3:
            fill_3.transform.colorTransform = myColorTransform;
            gotoAndStop(4);
            break;
        case 4:
            fill_33.transform.colorTransform = myColorTransform;
            gotoAndStop(5);
            break;
        case 5:
            fill_5.transform.colorTransform = myColorTransform;
            gotoAndStop(6);
            break;
        case 6:
            fill_6.transform.colorTransform = myColorTransform;
            gotoAndStop(7);
            break;
        case 7:
            fill_7.transform.colorTransform = myColorTransform;
            gotoAndStop(8);
            break;
        case 8:
            fill_8.transform.colorTransform = myColorTransform;
            gotoAndStop(9);
            break;
        case 9:
            fill_9.transform.colorTransform = myColorTransform;
            gotoAndStop(10);
            break;
        case 10:
            fill_10.transform.colorTransform = myColorTransform;
            gotoAndStop(11);
            break;
        case 11:
            fill_11.transform.colorTransform = myColorTransform;
            gotoAndStop(12);
            break;
        case 12:
            fill_12.transform.colorTransform = myColorTransform;
            gotoAndStop(13);
            break;
        case 13:
            fill_13.transform.colorTransform = myColorTransform;
            gotoAndStop(14);
            break;
        case 14:
            fill_14.transform.colorTransform = myColorTransform;
            gotoAndStop(15);
            break;
        case 15:
            fill_151.transform.colorTransform = myColorTransform;
            btn_next_arrow.removeEventListener(MouseEvent.MOUSE_OVER, hovering);
            btn_next_arrow.removeEventListener(MouseEvent.MOUSE_OUT, hideShadow);
            btn_back_arrow.removeEventListener(MouseEvent.MOUSE_OVER, hovering1);
            btn_back_arrow.removeEventListener(MouseEvent.MOUSE_OUT, hideShadow1);
            gotoAndStop(16);
            break;
        case 16:
            gotoAndStop(17);
            break;
    }
}

btn_next_arrow.addEventListener(MouseEvent.MOUSE_OVER, hovering);
function hovering(e:MouseEvent):void {
    trans.color = uint(0x606266);
    next_arrow.transform.colorTransform = trans;
}

btn_back_arrow.addEventListener(MouseEvent.MOUSE_OVER, hovering1);
function hovering1(e:MouseEvent):void {
    trans1.color = uint(0x606266);
    back_arrow.transform.colorTransform = trans1;
}

btn_next_arrow.addEventListener (MouseEvent.MOUSE_OUT, hideShadow);
function hideShadow(event:MouseEvent):void {
    trans.color = uint(0x999999);
    next_arrow.transform.colorTransform = trans;
}

btn_back_arrow.addEventListener (MouseEvent.MOUSE_OUT, hideShadow1);
function hideShadow1(event:MouseEvent):void {
    trans1.color = uint(0x999999);
    back_arrow.transform.colorTransform = trans1;
}

btn_back_arrow.addEventListener(MouseEvent.CLICK, goPrevLectFrame);
function goPrevLectFrame(e:MouseEvent):void {
        switch(currentFrame){
        case 2:
            gotoAndStop(1);
            break;
        case 3:
            gotoAndStop(2);
            break;
        case 4:
            gotoAndStop(3);
            break;
        case 5:
            gotoAndStop(4);
            break;
        case 6:
            gotoAndStop(5);
            break;
        case 7:
            gotoAndStop(6);
            break;
        case 8:
            gotoAndStop(7);
            break;
        case 9:
            gotoAndStop(8);
            break;
        case 10:
            gotoAndStop(9);
            break;
        case 11:
            gotoAndStop(10);
            break;
        case 12:
            gotoAndStop(11);
            break;
        case 13:
            gotoAndStop(12);
            break;
        case 14:
            gotoAndStop(13);
            break;
        case 15:
            gotoAndStop(14);
            break;
        case 16:
            gotoAndStop(15);
            break;
        }
}

btn_main_menu.addEventListener(MouseEvent.CLICK, goPrevLectFrame1);
function goPrevLectFrame1(e:MouseEvent):void {
    gotoAndStop(17);
}

Frame 17

stop();
import flash.events.MouseEvent;

btn_goto_lect1.alpha = 0.00001;
btn_goto_pract.alpha = 0.00001;

btn_goto_lect1.addEventListener (MouseEvent.MOUSE_OVER, showShadow);
function showShadow(event:MouseEvent):void {
    btn_goto_lect1.alpha = 1;
}

btn_goto_lect1.addEventListener (MouseEvent.MOUSE_OUT, hideShadow_);
function hideShadow_(event:MouseEvent):void {
    btn_goto_lect1.alpha = 0.00001;
}

btn_goto_pract.addEventListener (MouseEvent.MOUSE_OVER, showShadow1);
function showShadow1(event:MouseEvent):void {
    btn_goto_pract.alpha = 1;
}

btn_goto_pract.addEventListener (MouseEvent.MOUSE_OUT, hideShadow2);
function hideShadow2(event:MouseEvent):void {
    btn_goto_pract.alpha = 0.00001;
}

btn_goto_lect1.addEventListener (MouseEvent.CLICK, showShadow3);

function showShadow3(event:MouseEvent):void {
    btn_goto_lect1.removeEventListener (MouseEvent.MOUSE_OVER, showShadow);
    btn_goto_lect1.removeEventListener (MouseEvent.MOUSE_OUT, hideShadow_);
    btn_goto_pract.removeEventListener (MouseEvent.MOUSE_OVER, showShadow1);
    btn_goto_pract.removeEventListener (MouseEvent.MOUSE_OUT, hideShadow2);
    gotoAndStop(1);
}