FLEX how to reduce the amount of code to reduce memory consu

发布时间：2020-12-15 05:05:56 所属栏目：百科来源：网络整理

导读：These are some ways to reduce the code or memory,select an author of the network. 1. ?Avoid the new operator when creating Arrays var a = []; NOT: var a = new Array (); 2. ?Arrays are expensive to create,do so conservatively var vanityColl

These are some ways to reduce the code or memory,select an author of the network.

1.?Avoid the new operator when creating Arrays

var a = [];

NOT:var a = new Array();

2.?Arrays are expensive to create,do so conservatively

var vanityCollection01 : Array = Array();
var vanityCollection02 : var vanityCollection03 : var vanityCollection04 : 3.?Fastest way to copy an array:

var copy : Array = sourceArray.concat();

4.?Setting values in Arrays is slow

employees.push( employee );
employees[2] = employee;

5.?Getting values from Arrays is twice as fast as setting

var employee : Employee = employees[2];

6.?Use static for properties methods that do not require an object instance

StringUtils.trim( "text with space at end " );
Class definition:
package
{
public final class StringUtils
public static function trim( s : String ) : String
var trimmed : String;
// implementation...
return trimmed;
}
}

7.?Use const for properties that will never change throughout the lifecycle of the application

public const APPLICATION_PUBLISHER : String = "Company,Inc.";

8.?Use final when no subclasses need to be created of a class

class StringUtils

9.?Length of method/variable names doesn’t matter in ActionScript 3.0 (true in other langs)

someCrazyLongMethodNameDoesntReallyImpactPerformanceTooMuch();

10.?One line assignments DO NOT buy any performance (true in other langs)var i=0; j=10; k=200;

11.?No difference in memory usage between an if statement and a switch statementif ( condition ) // handle condition }

IDENTICAL MEMORY USAGE:

switch ( condition ) {      
case "A":          
// logic to handle case A      
break;            B":          
// logic to handle case B       
break;
}

12.?Rank your if statements in order of comparisons most likely to be true

if ( conditionThatHappensAlot ) { // logic to handle frequently met condition } else if ( conditionThatHappensSomtimes ) {
// handle the case that happens occaisonally } else {
// handle the case that doesn’t happen that often }

13.?AVM promotes int to Number during calculations inside loops (VM has been changing,from 9 to 10,so int,uint and number conversions aren’t as slow as they used to be.)

14.?Resolve issues of promotion,unknown,or incorrect object types

15.?Use uint sparingly,it can be slow (VM has been changing,uint and number conversions aren’t as slow as they used to be.)

var footerHex : uint = 0x00ccff;

16.?Use integers for iterations

(var i: int = 0; i < n; i++) NOT for (Number = 0; i < n; i++)

17.?Don’t use int with decimals

var decimal : Number = 14.654;

NOT:

int = 14.654;

18.?Multiply vs. Divide: instead of 5000/1000 use: 5000*0.001

19.?Locally store function values in for and while statements instead of repeatedly accessing them

for (..){ a * 180 / Math.PI; } declare: toRadians = a*180/PI; outside of the loop

20.?Avoid calculations and method calls in loops

var len : int = myArray.lengh; var i=0;i

var i=0;i< myArray.lengh;i++){ }

21.?Use RegEx for validation,use string methods for searching

// postal code validation example using regular expressions
private var regEx:RegExp = /^[A-Z][0-9][A-Z] [0-9][A-Z][0-9]$/i; function validatePostal( event : Event ) : void {
if( regEx.test( zipTextInput.text ) ) { // handle invalid input case } // search a string using String methods
var string : String = "Search me"; var searchIndex : int = string.indexOf( "me" );
var search : String = string.substring(searchIndex,searchIndex+2);

22.?Reuse objects to maintain a “memory plateau” DisplayObjects,URLLoader objects

23.?Follow the Flex component model:

createChildren(); commitProperties(); updateDisplayList();

24.?Only use Datagrids as a last resort (make sure you can’t implement in a regular List first)

25.?Avoid Repeaters for scrollable data

26.?Avoid the setStyle() method (One of the most expensive calls in the Flex framework)

27.?Using too many containers dramatically reduces the performance of your application

text="Label 1" />
Label 2" />
Label 3" />
Label 4" />

28.?You do not need to always use a container tag as the top-level tag of components Totally valid component,no top level container needed:

width="200" height="200" />

29.?Remove unnecessary container wrappers to reduce container nesting

30.?Avoid: The VBox container inside an tag,(eliminates redundancy)

31.?Avoid: VBox container inside an mx:Application tag,234); border-top-style:solid; border-right-style:solid; border-bottom-style:solid; border-left-style:solid">version="1.0" encoding="utf-8"?>

32.?Set the recycleChildren property to true to improve a Repeater object’s performance (re-uses previously created children instead of creating new ones)

public var repeaterData : Array = ["data 1","data 2"];
]]>
data item: {repeater.currentItem}"/>
33.?Keep framerate set at 60 fps or lower

utf-8"?> Application>

34.?Avoid multiple display manipulations per frame

35.?Code against ENTER_FRAME events instead of Timer events

function onEnterFrame( event : Event ) : void { } init() : void { addEventListener( Event.ENTER_FRAME,onEnterFrame ); }

function onTimerTick( event : Event ) : void { }
private void {
var timer : Timer = new Timer(); timer.start(); timer.addEventListener( TimerEvent.TIMER,onTimerTick ); }

36.?To defer object creation over multiple frames use:

37.?Alpha = 0 is not the same as visible = false (Objects marked invisible are passed over)

loginButton.visible = false;
NOT: loginButton.alpha = 0; From:http://activetofocus.com/blog/flex-how-to-reduce-the-amount-of-code-to-reduce-memory-consumption-7/

（编辑：李大同）

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