ScrollPane and ScrollBar not working - actionscript-3

Question

I have an application I'm trying to build where it will display a large map image (1920x1040 which is set as the base layer of frame one, then all my AS is on the layer above on the first frame too), then draw lines to it by reading in their coordinates from an external file (lines.txt) and associate a particular image with each line.
When a user clicks on a line, a ScrollPane should open, showing the image associated with the line they clicked on. These images are 1040 in height, and at least 4000px wide, so I want the image to fill the screen height, and then allow the user to use a scroll bar along the bottom to scroll left and right to see the full image.
Right now, I have it working where it reads in my lines.txt file, and draws the lines correctly. Then when I click on a line, it will load the corresponding image in the ScrollPane (along with a button to click that will remove the scroll pane and allow them to select a new line).
However, I can't get a horizontal scroll bar to work. I have it so that the space shows up at the bottom where a scroll bar should be, but there's no bar to drag left/right, and no way to scroll around.
I saw that it's possible to use dragging to scroll, which would be nice, but that hasn't worked either (it' now commented out), and when I have it turned on, when I click my Back Button and attempt to click another line, it throws an error saying,
"TypeError: Error #1009: Cannot access a property or method of a null object reference.
at fl.containers::ScrollPane/endDrag()"
Anybody able to help me clean this up and get it figured out what's going wrong here?
My code:
import flash.events.MouseEvent;
import flash.display.Sprite;
import flash.geom.ColorTransform;
import flash.filesystem.File;
import flash.filesystem.FileMode;
import flash.filesystem.FileStream;
import fl.containers.ScrollPane;
import fl.events.ScrollEvent;
import fl.controls.ScrollPolicy;
import fl.controls.DataGrid;
import fl.data.DataProvider;
import flash.display.Loader;
import flash.net.URLRequest;
import flash.net.URLLoader;
import fl.controls.UIScrollBar;
import flash.events.Event;
import fl.controls.ScrollBar;
var worldLines:Array = new Array();
var lineSprites:Array = new Array();
var lineSpritesLength:int;
var basicColorTransform:ColorTransform = new ColorTransform();
basicColorTransform.color = 0x00FF00;
var hoverColorTransform:ColorTransform = new ColorTransform();
hoverColorTransform.color = 0xFFFF00;
populateWorldLines();
function populateWorldLines():void
{
var textFile:File = File.applicationDirectory.resolvePath("lines.txt");
var fileContents:String = getFileData(textFile);
var contentsLength:int = fileContents.split("$").length;
for(var i:int = 0; i < contentsLength; i++)
{
trace(i);
worldLines[i] = new Object();
worldLines[i]["x1"] = fileContents.slice(0, fileContents.indexOf(","));
fileContents = fileContents.slice(fileContents.indexOf(",") + 1, fileContents.length);
worldLines[i]["y1"] = fileContents.slice(0, fileContents.indexOf(","));
fileContents = fileContents.slice(fileContents.indexOf(",") + 1, fileContents.length);
worldLines[i]["x2"] = fileContents.slice(0, fileContents.indexOf(","));
fileContents = fileContents.slice(fileContents.indexOf(",") + 1, fileContents.length);
worldLines[i]["y2"] = fileContents.slice(0, fileContents.indexOf(","));
fileContents = fileContents.slice(fileContents.indexOf(",") + 1, fileContents.length);
worldLines[i]["image"] = fileContents.slice(0, fileContents.indexOf(";"));
fileContents = fileContents.slice(fileContents.indexOf("$") + 1, fileContents.length);
}
drawLines(worldLines);
}
function drawLines(lines:Array):void
{
for(var i:int = 0; i < lines.length; i++)
{
var line:Sprite = new Sprite;
line.graphics.moveTo(lines[i]["x1"], lines[i]["y1"]);
line.graphics.lineStyle(3, basicColorTransform.color);
line.graphics.lineTo(lines[i]["x2"], lines[i]["y2"]);
lineSprites.push(line);
addChild(line);
}
lineSpritesLength = lineSprites.length;
this.addEventListener(MouseEvent.MOUSE_OVER, checkLines);
}
function checkLines(e:MouseEvent):void
{
var targetSprite:* = e.target;
for(var i:int = 0; i < lineSpritesLength; i++)
{
if(targetSprite == lineSprites[i])
{
targetSprite.transform.colorTransform = hoverColorTransform;
targetSprite.addEventListener(MouseEvent.CLICK, lineClicked);
targetSprite.addEventListener(MouseEvent.MOUSE_OUT, resetColorTransform);
}
}
}
function lineClicked(e:MouseEvent):void
{
var targetSprite:* = e.target;
for(var i:int = 0; i < lineSpritesLength; i++)
{
if(targetSprite == lineSprites[i])
{
showImage(worldLines[i]["x1"], worldLines[i]["y1"], worldLines[i]["image"]);
}
}
//e.target.removeEventListener(e.type, lineClicked);
}
function showImage(xPos:int, yPos:int, imageName:String):void
{
var aSp:ScrollPane = new ScrollPane();
var aBox:MovieClip = new MovieClip();
drawBox(aBox, imageName);
aSp.source = aBox;
aSp.setSize(1920, 1040);
aSp.move(0, 0);
aSp.name = "scrollyPaneThing";
//aSp.scrollDrag = true;
aSp.horizontalScrollPolicy=ScrollPolicy.ON;
aSp.addEventListener(ScrollEvent.SCROLL, scrollListener);
addChild(aSp);
}
function scrollListener(event:ScrollEvent):void {
var mySP:ScrollPane = event.currentTarget as ScrollPane;
trace("scrolling");
trace("\t" + "direction:", event.direction);
trace("\t" + "position:", event.position);
trace("\t" + "horizontalScrollPosition:", mySP.horizontalScrollPosition, "of", mySP.maxHorizontalScrollPosition);
trace("\t" + "verticalScrollPosition:", mySP.verticalScrollPosition, "of", mySP.maxVerticalScrollPosition);
};
function drawBox(box:MovieClip,imageName:String):void {
trace(imageName + ":imageName");
var file:File = File.applicationDirectory.resolvePath("dataImages/"+imageName);
var imageLoader:Loader = new Loader();
var image:URLRequest = new URLRequest(file.url);
imageLoader.load(image);
imageLoader.x = 1;
imageLoader.y = 1;
box.addChild (imageLoader);
trace("backButton.png:imageName");
var file2:File = File.applicationDirectory.resolvePath("backButton.png");
var imageLoader2:Loader = new Loader();
var image2:URLRequest = new URLRequest(file2.url);
imageLoader2.load(image2);
imageLoader2.x = 10;
imageLoader2.y = 950;
box.addChild (imageLoader2);
imageLoader2.addEventListener(MouseEvent.CLICK, removeScrollyPaneThing);
}
function removeScrollyPaneThing(MouseEvent):void
{
removeChild(getChildByName("scrollyPaneThing"));
}
function resetColorTransform(e:MouseEvent):void
{
e.target.transform.colorTransform = basicColorTransform;
e.target.removeEventListener(e.type, resetColorTransform);
}
function getFileData(file:File):String
{
var fDataStream:FileStream;
var sContent:String;
fDataStream = new FileStream();
fDataStream.open(file, FileMode.READ);
sContent = fDataStream.readUTFBytes(fDataStream.bytesAvailable);
fDataStream.close();
return sContent;
}

Answer 1

Your Loader Object has a scrollRect property that is built in.
It is MUCH easier to use a simple ScrollBar than a ScrollPane,
but mouse dragging is much cleaner:
see: http://help.adobe.com/en_US/FlashPlatform/reference/actionscript/3/flash/display/DisplayObject.html#scrollRect
To mouse drag:
private var scrollyThingy:Rectangle;
private var map:Loader;
// holders for the location of the view
//(to allow for cancelling the drag):
private var _cx:int = 0;
private var _cy:int = 0;
private var downpoint:Point = null;
public function init():void{
// Load your image:
/* I prefer to use embeded png files
or draw simple line images, but
Loader objects also have a scrollRect property
From this point I will assume your main image ('map') is loaded,
and 'scrollyThingy' is the part you want diplayed
I could not follow the code once you added the
loader to the stage very well...
*/
// to enable mouse dragging:
map.addEventListener(MouseEvent.MOUSE_DOWN, onMouseDown);
var w:int = 100;
var h:int = 100;
scrollyThingy = new Rectangle(_cx, _cy, w, h);
map.scrollRect = scrollyThingy;
AddChild(map);
}
private function onMouseDown(event:MouseEvent):void{
_downpoint = new Point(event.stageX, event.stageY);
map.removeEventListener(MouseEvent.MOUSE_DOWN, onMouseDown);
map.addEventListener(MouseEvent.MOUSE_DRAG, onMouseDrag);
map.addEventListener(MouseEvent.MOUSE_UP, onMouseUp);
map.addEventListener(MouseEvent.RELEASE_OUTSIDE , onReleaseOutside);
}
private function onMouseDrag(event:MouseEvent):void{
if (_downpoint == null)
return;
// the movement delta:
_dx = int((event.stageX - _downpoint.x));
_dy = int((event.stageY - _downpoint.y));
// (if the movement is backwards, use scrollyThingy.x -= _dx)
scrollyThingy.x += _dx;
scrollyThingy.y += _dy;
Loader.scrollRect = scrollyThingy;
}
private function onMouseUp(event:MouseEvent):void{
if (_downpoint == null)
return;
// new corner coords
_cx += int((event.stageX - _downpoint.x));
_cy += int((event.stageY - _downpoint.y));
resetListeners();
}
private function onReleaseOutside(event:MouseEvent):void{
// put it back where it was
resetListeners();
}
private function resetListeners():void{
scrollyThingy.x = _cx;
scrollyThingy.y = _cy;
Loader.scrollRect = scrollyThingy;
_downpoint = null;
if(!map.hasEventListener(MouseEvent.MOUSE_DOWN)
map.addEventListener(MouseEvent.MOUSE_DOWN, onMouseDown);
//(if it has one, it has them all!)
if(map.hasEventListener(MouseEvent.MOUSE_DRAG){
map.removeEventListener(MouseEvent.MOUSE_DRAG, onMouseDrag);
map.removeEventListener(MouseEvent.MOUSE_UP, onMouseUp);
map.removeEventListener(MouseEvent.RELEASE_OUTSIDE , onReleaseOutside);
}
}
if you still want a ScrollBar, just scale it to your Loader dimensions less the
size of the viewport (xScrollBar.maximum = loader.content.width - scrollyThingy.width,
yScrollbar.maximum = loader.content.height - scrollyThingy.height) then you can use the
same listener for both bars:
function onScrollBarChange(e:event):void{
scrollyThingy.x = xScrollBar.value;
scrollyThingy.y = yScrollBar.value;
}
listen for a change Event and set the Loader.scrollRect.x and Loader.scrollRect.y
properties to the scrollBarx.value & scrollBary.value.
Note also that I did not include any value checking.
You should check the values before moving the scrollRect
to avoid rangeErrors
i.e. if (_cx > loader.width - loader.scrollRect.width)
_cx = Loader.width - Loader.scrollRect.width;