空对象引用actionscript 3
空对象引用actionscript 3
提问于 2014-01-23 18:32:07
我做了一个这样的类：
package
{
import flash.display.Sprite;
import flash.text.TextField;
public class Hint extends Sprite
{
public static var _instance:Hint = null;
public function Hint()
{
_instance = this;
}
public function DrawHintText():void
{
Const._scoreText = new TextField();
Const._scoreTextHolder = new TextField();
Const._highScoreText = new TextField();
Const._highScoreTextHolder = new TextField();
Const._timeLeft = new TextField();
Const._timeLeftHolder = new TextField();
Const._scoreTextHolder.textColor = 0xFFFFFF;
Const._scoreTextHolder.x = stage.stageWidth - 350;
Const._scoreTextHolder.y = 100;
Const._scoreTextHolder.text = "Score: ";
Const._scoreTextHolder.selectable = false;
Const._scoreText.textColor = 0xFFFFFF;
Const._scoreText.x = stage.stageWidth - 250;
Const._scoreText.y = 100;
Const._scoreText.text = "--";
Const._scoreText.selectable = false;
Const._highScoreTextHolder.textColor = 0xFFFFFF;
Const._highScoreTextHolder.x = stage.stageWidth - 350;
Const._highScoreTextHolder.y = 150;
Const._highScoreTextHolder.text = "High Score: ";
Const._highScoreTextHolder.selectable = false;
Const._highScoreText.textColor = 0xFFFFFF;
Const._highScoreText.x = stage.stageWidth - 250;
Const._highScoreText.y = 150;
Const._highScoreText.text = "--";
Const._highScoreText.selectable = false;
Const._timeLeftHolder.textColor = 0xFF0000;
Const._timeLeftHolder.x = stage.stageWidth - 350;
Const._timeLeftHolder.y = 200;
Const._timeLeftHolder.text = "Time Left: ";
Const._timeLeftHolder.selectable = false;
Const._timeLeft.textColor = 0xFF0000;
Const._timeLeft.x = stage.stageWidth - 275;
Const._timeLeft.y = 200;
Const._timeLeft.text = "00:00";
Const._timeLeft.selectable = false;
addChild(Const._scoreText);
addChild(Const._scoreTextHolder);
addChild(Const._highScoreText);
addChild(Const._highScoreTextHolder);
addChild(Const._timeLeft);
addChild(Const._timeLeftHolder);
}
}
}然后我调用了GameManager：
package
{
import flash.display.Sprite;
import flash.events.Event;
import flash.text.TextField;
[SWF(width='1366',height='768',backgroundColor='#000000',frameRate='30')]
public class GameManager extends Sprite
{
public function GameManager():void
{
DrawHintText();
GenerateField();
ShowField();
GenerateGems();
}
private function GenerateField():void
{
Const._gridField = new Array();
for (var i:uint = 0; i < Const._gridSizeY; i++)
{
Const._gridField[i] = new Array();
for (var j:uint = 0; j < Const._gridSizeX; j++)
{
Const._gridField[i][j] = 0;
}
}
}
private function ShowField():void
{
Const._fieldSprite = new Sprite();
addChild(Const._fieldSprite);
Const._fieldSprite.graphics.lineStyle(1, 0xFFFFFF);
for (var i:uint = 0; i < Const._gridSizeY; i++)
{
for (var j:uint = 0; j < Const._gridSizeX; j++)
{
Const._fieldSprite.graphics.beginFill(0x666666);
Const._fieldSprite.graphics.drawRect(25 + 65 * j, 80 + 60 * i, 65, 60);
Const._fieldSprite.graphics.endFill();
}
}
}
private function DrawHintText():void
{
Hint._instance.DrawHintText();
}
private function GenerateGems():void
{
}
}
}下面是常量：
package
{
import flash.display.Sprite;
import flash.text.TextField;
public class Const
{
public static var _gridField:Array;
public static var _fieldSprite:Sprite;
public static var _scoreText:TextField;
public static var _scoreTextHolder:TextField;
public static var _highScoreText:TextField;
public static var _highScoreTextHolder:TextField;
public static var _timeLeft:TextField;
public static var _timeLeftHolder:TextField;
public static const _gridSizeX:Number = 10;
public static const _gridSizeY:Number = 10;
public function Const()
{
}
}
}当我运行代码时，我得到了错误：
我在哪里遗漏了一些代码？
回答 4
Stack Overflow用户
发布于 2014-01-23 18:41:37
在Hint._instance.DrawHintText();中调用函数DrawHintText()不会创建类Hint的实例。
尝试用public getter替换您的public变量。
private static var __instance:Hint = null;
public static function get _instance():Hint {
if (!__instance) {
__instance = new Hint();
}
return __instance;
}并删除构造函数，因为getter使它变得不必要。
Stack Overflow用户
发布于 2014-01-23 18:39:49
这可能是一个愚蠢的问题，但您实际上是在某处创建Hint的实例吗？因为只要你不做new Hint()，Hint._instance就会是空的。
Stack Overflow用户
发布于 2014-01-23 18:43:33
尝试如下所示：
public class Hint extends Sprite
{
private static var _instance:Hint;
public function Hint()
{
if (_instance) throw new Error("Hint... use getInstance()");
_instance = this;
}
public static function getInstance():Hint
{
if (!_instance) new Hint();
return _instance;
}
//DrawHintText >> rename to drawHintText
public function drawHintText():void
{
//your code here
}
}并使用：
Hint.getInstance().drawHintText();页面原文内容由Stack Overflow提供。腾讯云小微IT领域专用引擎提供翻译支持
原文链接：
https://stackoverflow.com/questions/21305531
复制相关文章
相似问题
腾讯云开发者
