MACROMEDIA FLEX - DEVELOPING COMPONENTS AND THEMES Instrukcja Użytkownika Pobierz pdf (Strona 33)

UNDERSTANDING+THE+FLEX+3+COMPONENT+AND+FRAMEWORK+LIFECYCLE!

33!

©!2009!DevelopmentArc!LLC,!All!rights!reserved.!

private var _chartDirty:Boolean = false;

override protected function commitProperties():void {

super.commitProperties();

if(_dataValueDirty) {

_dataValueDirty = false;

// calculate the total

var len:int = __dataValue.length;

var _total:Number = 0;

for(var i:uint=0; i < len; i++) {

_total += Number(__dataValue[i]);

}

// set the total

total = _total;

_chartDirty= true;

}

override protected function updateDisplayList(

unscaledWidth:Number,

unscaledHeight:Number):void {

super.updateDisplayList(unscaledWidth, unscaledHeight);

if(_chartDirty) {

_chartDirty= false;

// draw the data

drawChart();

}

Figure'14')'Overri ding't he'Validation'Me thods'Exam ple'

The!validation!methods!are!always!called!in!an!explicit!order:!commitProperties(),!

measure(),!layoutChrome(),!and!finally!updateDisplayList().!!As!we!have!

previously!mentioned,!this!order!is!important!because!calculations!and!properties!

set!in!the!commitProperties()!may!affect!the!size!or!the!display!list.!!!

Looking!at!Figure!14!‐!Overriding!the!Validation!Methods!Example,!its!possible!that!

we!may!need!the!total!value!to!be!drawn!or!updated!in!the!display!list,!so!it!should!

be!calculated!first.!!This!is!why!we!use!the!invalidate!methods.!!Because!we!need!to!

calculate!a!total!and!also!draw!our!chart!we!need!to!make!sure!that!both!

invalidateProperites()!and!invalidateDisplayList()!are!called!by!the!setter!in!

Figure!13!‐!Using!Dirty!Flags!Example#so!that!commitProperties()!and!then!

updateDisplayList()!are!called.!

When!commitProperties()!is!called,!we!check!to!see!if!the!_dataValueDirty!flag!

has!been!set!to!true.!!We!want!to!make!this!check!because!if!the!value!has!not!

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MACROMEDIA FLEX - DEVELOPING COMPONENTS AND THEMES Instrukcja Użytkownika Strona 33