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我正在尝试遍历数组中的 3 个图像并将其添加到舞台（使用画架JS）。我也想定位。当我尝试访问数组中的图像时，我收到一条错误消息，提示我无法设置未定义的 x。为什么不能访问easeljs Bitmap的x变量？

function displayPosters() {

    getPosters(); //get all images and assign it to designated array

            console.log(frontPosters);
            console.log(frontPosters.length);

    if(currentCat == Category.HOME) { //if current category is HOME

        for(var i = 0; i < frontPosters.length; i++) { //loop through posters

            frontPosters[i].x = 40; //set x position for testing, also where error occurs
            stage.addChild(frontPosters[i]); //add poster to stage

        }

    }

}

这是加载这些图像并将其推送到 frontPosters 数组中的代码。

var frontPosters = new Array(3);

function getPosters() {

    var games = new Image(); //create 3 images
    var apps = new Image();
    var aboutme = new Image();

    games.onload = function() { //add image to frontImages array on load

        var gamesPost = new createjs.Bitmap(games);
        frontPosters[0] = gamesPost;

    };

    apps.onload = function() {

        var appPost = new createjs.Bitmap(apps);
        frontPosters[1] = appPost;

    };

    aboutme.onload = function() {

        var amPost = new createjs.Bitmap(aboutme);
        frontPosters[2] = amPost;

    };

    games.src = "images/assets/posters/games_poster.jpg"; 
    apps.src = "images/assets/posters/apps_poster.jpg";
    aboutme.src = "images/assets/posters/aboutme_poster.jpg";

}
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1 回答 1

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使用for(poster in frontPosters)是不好的做法，因为您实际上是在迭代数组对象而不是值（也就是数组本身）。改为使用for(var i=0; i<frontPosters.length; i++)。这是最简单的解决方案，IMO。

for(var i = 0; i < frontPosters.length; i++) { //loop through posters
    frontPosters[i].x = 40; //set x position for testing, also where error occurs
    stage.addChild(frontPosters[i]); //add poster to stage
}

编辑

我认为您正在处理竞争条件。在加载所有图像之前，您正在检查您的数组。通过设置var frontPosters = new Array(3);，您会自动设置三个值，将undefined其推入新数组。

在继续执行脚本之前，您应该检查所有图像是否已加载。

这是给你的一个想法。设置仅在加载第三张图像后才会运行的回调。

var frontPosters = new Array(3);

function getPosters(callback) {

    var games   = new Image(),
        apps    = new Image(),
        aboutme = new Image(),
        loaded  = 0;

    games.onload = function() {
        frontPosters[0] = new createjs.Bitmap(this);
        if (++loaded === 3) callback();
    };

    apps.onload = function() {
        frontPosters[1] = new createjs.Bitmap(this);
        if (++loaded === 3) callback();
    };

    aboutme.onload = function() {
        frontPosters[2] = new createjs.Bitmap(this);
        if (++loaded === 3) callback();
    };

    games.src   = "images/assets/posters/games_poster.jpg"; 
    apps.src    = "images/assets/posters/apps_poster.jpg";
    aboutme.src = "images/assets/posters/aboutme_poster.jpg";

}

function displayPosters() {

    getPosters(function() {
        if(currentCat == Category.HOME) { //if current category is HOME
            for(var i = 0; i < frontPosters.length; i++) { //loop through posters
                frontPosters[i].x = 40; //set x position for testing, also where error occurs
                stage.addChild(frontPosters[i]); //add poster to stage
            }
        }
    }); //get all images and assign it to designated array, only after all images were loaded

}
于 2013-02-21T23:44:32.717 回答