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Topic 04: Properties and Events Part I

Topic 04: Properties and Events Part I. Today’s Examples . Simple_Flow.swf and I nteractive_Album.swf in W drive . Review: if Conditional. ... if ( conditionA ) { // process B } . if. Condition A. false. var score : Number = 87 ; if ( score >= 90 ) { trace ( "A+" ); }

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Topic 04: Properties and Events Part I

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  1. Topic 04: Properties and Events Part I SCM-CityU

  2. Today’s Examples • Simple_Flow.swf and Interactive_Album.swf in W drive SCM-CityU

  3. Review: if Conditional ... if(conditionA){ // process B } ... if Condition A false var score:Number=87; if(score >=90){ trace("A+"); } if(score <90&& score >=85) { trace("A"); } true Process B SCM-CityU

  4. Review: if-else Conditional if(conditionA){ // process B }else{ // process C } … if Condition A true false Process C Process B if(currentFrame == 1){ gotoAndStop(totalFrames); }else{ prevFrame(); } SCM-CityU

  5. Review: else-if Conditional if(conditionA){ // process C }elseif(conditionB){ // process D }else{ // process E } if Condition A true false else-if Process C Condition B false true Process D var age:uint =15; if(age >=21){ trace("adult"); }elseif(age >12){ trace("teen"); }elseif(age >7){ trace("child"); }else{ trace("infant"); } Process E second if-else statement SCM-CityU

  6. Review: if Conditional Summary • Requires oneif • Only one optionalelse can be used • Any number of optionalelse-if test can be used if(...){ } if(...){ }elseif(...){ }elseif(...){ } if(...){ }else{ } if(...){ }elseif(...){ }elseif(...){ }else{ } SCM-CityU

  7. Review: Functions • Example: math function f(x, y) = x2+y2 trace(f(1,2)); trace(f(2,3)); trace(f(3,4)); trace(f(4,5)); function f(x:Number, y:Number):Number{ return x*x + y*y; } function calls function definition SCM-CityU

  8. Review: Functions • Position of function definition doesn’t influence program flow function f(x:Number, y:Number):Number{ return x*x + y*y; } trace(f(1,2)); trace(f(2,3)); trace(f(3,4)); trace(f(4,5)); trace(f(1,2)); trace(f(2,3)); function f(x:Number, y:Number):Number{ return x*x + y*y; } trace(f(3,4)); trace(f(4,5)); trace(f(1,2)); trace(f(2,3)); trace(f(3,4)); trace(f(4,5)); function f(x:Number, y:Number):Number{ return x*x + y*y; } SCM-CityU

  9. Review: Statements and Blocks • Simple statements are expressions followed by a semicolon (;) // the following code contains four simple statements var a:int=3; trace(a); a +=5; trace(a); SCM-CityU

  10. Review: Statements and Blocks • Braces { and } group multiple simple statements into a compound statement or block • { and } must be matched • Indentation highly recommended • Blocks can be nested function genderTest(male:Boolean):void{ if(male){ trace("male"); trace("playing games"); }else{ trace("female"); trace("going shopping"); } } genderTest(false); Question 1: How many blocks? Question 2: Output? SCM-CityU

  11. Review: Indent Style var a:Boolean=true; var b:Boolean=false; if(a){ if(b){ trace(10); } trace(5); }else{ trace(20); } var a:Boolean=true; var b:Boolean=false; if(a){ if(b){ trace(10); } trace(5); }else{ trace(20); } Auto Format SCM-CityU

  12. Review: Indent Style • Indentation reveals program structure easily var a:Boolean=true; var b:Boolean=false; if(a){ if(b){ trace(10); }else{ trace(20); } trace(5); } var a:Boolean=true; var b:Boolean=false; if(a){ if(b){ trace(10); }else{ trace(20); } trace(5); } SCM-CityU

  13. Review: Brackets (wiki) • Parentheses: () • Function parameter list • Precedence ordering • Braces: {} • Define a block, which groups a set of statements • Box/square brackets: [] • Array trace(para1, para2, para3, …, paraN); trace((2+3)*4);// 20 if(female){ trace("female"); trace("hobby: shopping"); } var a:Array=[val1, val2, val3]; SCM-CityU

  14. Review: ; : , . var a:int=3; trace(a); • ; • A semicolon ends a simple statement • : • A colon for data type declaration • , • A comma for separate parameters • . • A.B means A contains B (B can be either a property or a method/function) var pi:Number=3.14; function f(x:Number):Number; function f(x:Number, y:Number):Number; trace(a, b, c, d); bird.speed = 5; bird.fly(); btn_prev.addEventListener(MouseEvent.CLICK,onPrevButtonClick); SCM-CityU

  15. Events & Listeners SCM-CityU

  16. Events & Listeners • Multiple parties might be interested in special things, called events (e.g., clicking), happened to a target object(e.g., a button) Hi folks, I have been clicked! SCM-CityU

  17. Got it. I will perform some follow-up task Hi folks, I have been clicked! Who cares! I’m only interested in keyboard events on you SCM-CityU

  18. Got it. I will perform some follow-up task Hi folks, I have been clicked! • In ActionScript, eventTarget.addEventListener ( EventType, eventListener); • btn.addEventListener(MouseEvent.CLICK, clickTask); • btn.addEventListener(KeyboardEvent.KEY_DOWN, keyDownTask); Who cares. I’m only interested in keyboard events on you SCM-CityU

  19. eventTarget.addEventListener (EventType, eventListener); • eventTarget can be • Stage • Any symbol instance you create, e.g., a button! btn_prev.addEventListener(MouseEvent.CLICK, onPrevButtonClick); function onPrevButtonClick(e:MouseEvent):void { prevFrame(); txt_index.text = currentFrame +"/"+ totalFrames; } SCM-CityU

  20. eventTarget.addEventListener (EventType, eventListener); • Listen to an event type you only care! • There are many event types defined in Event, TimerEvent, KeyboardEvent, MouseEvent, … • E.g., MouseEvent.CLICK Event, MouseEvent … are complex data types for events btn_prev.addEventListener(MouseEvent.CLICK, onPrevButtonClick); functiononPrevButtonClick(e:MouseEvent): void { prevFrame(); txt_index.text = currentFrame + "/" + totalFrames; } SCM-CityU

  21. eventTarget.addEventListener (EventType, eventListener); • eventListener is simply a function but always with a single special parameter • Through this parameter you can get the context where the event happens Note: data type of parameter should becompatible with the one used for eventtype btn_prev.addEventListener(MouseEvent.CLICK,onPrevButtonClick); functiononPrevButtonClick(e:MouseEvent): void { prevFrame(); txt_index.text = currentFrame + "/" + totalFrames; } SCM-CityU

  22. Execution Flow • When an event happens to a target, all registered listeners that are listening to this event type are invoked • E.g., when click event happens to btn • clickTask function will be called • But keyDownTask function won’t • btn.addEventListener(MouseEvent.CLICK, clickTask); • btn.addEventListener(KeyboardEvent.KEY_DOWN, • keyDownTask); SCM-CityU

  23. Simple Flow Control • Our previous album demo • A keyframe in every frame • Frame jumping using ActionScript (at Frame 1) SCM-CityU

  24. Simple Flow Control • Today’s first example • Jumping between tween animations SCM-CityU

  25. Basic Steps Image Source • Change stage size to 181 x 380 • Load images (File > Import to Stage) • Select all images of interest • All images will be loaded into single frame and single layer • In previous example, only first image is selected, all images under the same directory are loaded as a sequence, each image placed into individual key frames • Distribute images to individual layers SCM-CityU

  26. Basic Steps • Drag keyframe of 1.jpg and move it to frame 2 Then insert frame at frame 10 SCM-CityU

  27. Basic Steps • Create motion tweens • Convert to symbols first • Why: motion tween requires symbol instances • How: select 1.jpg image on the stage & right click…. SCM-CityU

  28. Basic Steps • Create motion tweens • Convert to symbols first • Change properties of symbol instances • E.g., alpha in our case Alpha = 0 @Frame1 Alpha = 1 @Frame10 SCM-CityU

  29. Timeline SCM-CityU

  30. Class Exercise • Task: create motion tween for images 2-4 31-40 21-30 11-20 2-10 Frame No SCM-CityU

  31. Basic Steps • Add user control • Have a layer for AS and span the entire timeline • Insert frame at Frame 40 • Insert control button (from built-in component) • This button will appear in the entire animation Instance: playBtn SCM-CityU

  32. Basic Steps • Add user control • Add an event listener for the control button I have been clicked! Event Type Got it. I will play the next key frame. Event Listener Event Target SCM-CityU

  33. Basic Steps • Add user control • Add an event listener for the control button • At Frame 1 Event Target Event Type Event Listener playBtn.addEventListener(MouseEvent.CLICK,onButtonClick); functiononButtonClick(e:MouseEvent):void{ if(currentFrame==1){ gotoAndPlay(2); } } SCM-CityU

  34. Basic Steps • Add user control • Stop animation at Frame 10 • Insert a key frame at Frame 10 • Add stop(); to stop animation • Class exercise • Complete the whole animation • Hints • Event listeners are shared among key frames • So the same playBtn can be used for playing control • Add code in onButtonClick (at Frame 1) SCM-CityU

  35. Frame Labels • 10, 20, 30, 40 are like magic numbers in our app • If you change position of key frames, you have to modify the code correspondingly • A better solution: assigning some labels to key frames and accessing those frames in AS by label SCM-CityU

  36. Frame Labels • Example • Select key frame 10 • Assign a frame label in Properties panel • E.g., 1e (end of 1.jpg) SCM-CityU

  37. Frame Labels • Just like currentFrame representing the number of frame being played, currentFrameLabel is the label at the current frame • currentFrameLabel is of String type (ref) • gotoAndPlay and gotoAndStop accept both frame number or label as input (ref) mc1.gotoAndPlay(currentFrame +5); mc1.gotoAndPlay("1e"); SCM-CityU

  38. Properties SCM-CityU

  39. Properties • Symbol instances provide a large set of predefined propertiesfor manipulation, e.g., • x, y • width, height • scaleX, scaleY • alpha • visible • Access properties using dot syntax • E.g., ball.rotation += 30; SCM-CityU

  40. Properties • Why bother property changing in ActionScript? • To support interactivity! • But you can use properties panelto set initial properties SCM-CityU

  41. Properties: x, y • Using dot syntax • Units: pixels X O Note: y-axis is downward! Y SCM-CityU

  42. Properties: width, height X O box.width box.height Y SCM-CityU

  43. Properties: scaleX, scaleY • Multiplies current width/height by a scale factor X O Y box.scaleX = 0.5; box.scaleY = 0.5; SCM-CityU

  44. Properties: rotation • Clockwise; angle in degree X O Y SCM-CityU

  45. Properties: alpha • Range: [0, 1] box.alpha = 0.5; box.alpha = 1; SCM-CityU

  46. Example: Interactive Album • Control multiple objects • Sharing event listeners • All objects have the samebehavior! SCM-CityU

  47. Basic Steps • Load images to the stage • Convert to symbols and assign instance names • E.g., names: s1, s2, s3, s4 • Resize symbol instances and have an initial layout like s4 s1 s2 s3 SCM-CityU

  48. Add User Controls • Add event listeners for s1 • MouseEvent (ref) • Event types: CLICK, DOUBLE_CLICK, MOUSE_DOWN, MOUSE_UP, MOUSE_MOVE • Repeat this for the other images • All images share same event listeners s1.addEventListener(MouseEvent.MOUSE_DOWN, onPhotoDown); s1.addEventListener(MouseEvent.MOUSE_UP,onPhotoUp); SCM-CityU

  49. Add User Controls Note 1: e.targetrefers to event target where event happens. Note 2: as operator does data type conversion (DisplayObject  MovieClip) • Make images draggable • Start to drag when mouse is down • Stop to drag when mouse is up functiononPhotoDown(e:MouseEvent):void{ var photo:MovieClip= e.target as MovieClip; photo.startDrag(); } functiononPhotoUp(e:MouseEvent):void{ var photo:MovieClip= e.target as MovieClip; photo.stopDrag(); } SCM-CityU

  50. Add User Controls • Bring the image being dragged onto topmost (ref) • Each symbol instanceon the stage has an index • numChildren -1 means topmost • 0 means bottommost function onPhotoDown(e:MouseEvent):void{ var photo:MovieClip= e.target as MovieClip; photo.startDrag(); // bring the image being dragged to the top setChildIndex(photo, numChildren -1); } SCM-CityU

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