Flash drag and drop tutorial

<pageby nominor="false" comments="false"/>

Overview

Dragging and dropping objects is a popular brick in edutainment programs. This is part of Flash CS3 tutorials. I will expand this article sometimes. - Daniel K. Schneider 18:13, 9 September 2007 (MEST).

Learning goals

Learn how to create simple drag and drop programs with Flash 9 (CS3) components

Learn a little bit of Action Script 3

Prerequisites

Flash CS3 desktop tutorial

Flash drawing tutorial

flash button tutorial

Moving on

The Flash article has a list of other tutorials.

Flash Video component tutorial

Quality

This text should technical people get going and may not be good enough for self-learning beginners. It can be used as handout in a "hands-on" class. That is what Daniel K. Schneider made it for...

Level

It aims at beginners. More advanced features and tricks are not explained here.

Learning materials

Grab the various *.fla files from here:

http://tecfa.unige.ch/guides/flash/ex/drag-and-drop-intro/ (not yet sorry)

The executive summary

• Draw something on the canevas
• Transform it to a movie symbol (buttons don't work)
• Assign an instance name
• Instance_name.startDrag()
• Instance_name.stopDrag()

Introduction - simple dragging code

Step 1 - Draw an object

• Anything you like

Step 2 - Transform it into a Movie Clip

• Select all if you got several objects, then assemble maybe
• Right-click on the object
• Give it a name in the properties panel !

Step 3 - Adapt code below

Most simple drag and drop

// Register mouse event functions
blue_btn.addEventListener(MouseEvent.MOUSE_DOWN, mouseDownHandler);
blue_btn.addEventListener(MouseEvent.MOUSE_UP, mouseUpHandler);

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

// Define a mouse down handler (user is dragging)
function mouseDownHandler(evt:MouseEvent):void {
	var object = evt.target;
	// we should limit dragging to the area inside the canvas
	object.useHandCursor = true;
	object.startDrag();
}

function mouseUpHandler(evt:MouseEvent):void {
	var obj = evt.target;
		obj.stopDrag();
}

Results

• Admire the result
• Get the source from http://tecfa.unige.ch/guides/flash/ex/drag-and-drop-intro/ (files flash-cs3-drag-and-drop-intro.*)

Drag and drop over another object

The goals is to write a little Flash application that will tell the user whether he correctly dragged and dropped an object over another one.

Step 1 - Start from the file above

• I.e. we want to have the user drag the red circle over the blue rectangle.

Step 2 - Add a text box

This textbox should initially display instruction, then display feedback: "made it" and "missed".

• Use the Textool in the tools panel to enter the text.
• Then in the properties panel, change the type to Dynamic Text.

Dynamic Text

Step 3 - Action script code

// Register mouse event functions
blue_btn.addEventListener(MouseEvent.MOUSE_DOWN, mouseDownHandler);
blue_btn.addEventListener(MouseEvent.MOUSE_UP, mouseUpHandler);

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

// Define a mouse down handler (user is dragging)
function mouseDownHandler(evt:MouseEvent):void {
	var object = evt.target;
	// we should limit dragging to the area inside the canvas
	object.useHandCursor = true;
	object.startDrag();
}

function mouseUpHandler(evt:MouseEvent):void {
	var obj = evt.target;
	// obj.dropTarget will give us the reference to the shape of
	// the object over which we dropped the circle.
	var target = obj.dropTarget;
	// If the object exists AND it is the blue button, then we change
	// the text in the TextBox. 
	// Since obj.dropTarget is a Shape, we need its parent.
	if (target != null && target.parent == blue_btn)
	{
		textField.text = "Made it !!";
	}
	else
	{
		textField.text = "Missed :(";
	}
	obj.stopDrag();
}

Results

• Admire the result
• Get the source from http://tecfa.unige.ch/guides/flash/ex/drag-and-drop-intro/ (files flash-cs3-drag-and-drop-intro2.*)

Reference

Sprites and DisplayObjects

Objects that you can drag around are Movie Clips. These are children of Sprites. Sprites have associated graphics.

When you drop a sprite over another sprite, the Flash will give the shape of the target object. This shape is a DisplayObject and from a DisplayObject we can get its parent, i.e. a Movie Clip in our case.

• Sprite (part of the ActionScript 3.0 Language and Components Reference

• DisplayObject

• Graphics

TextFields

The TextField class is used to create display objects for text display and input.

• TextField

• Basics of working with text - for designers.