小编zzx*_*anw的帖子

我正在尝试从图像输出像素值.图像正确加载; 这里的另一个答案表明,浏览器试图在图像加载完成之前读取像素,但我可以看到它在alert()触发时加载.

function initContext(canvasID, contextType)
{
   var canvas = document.getElementById(canvasID);
   var context = canvas.getContext(contextType);
   return context;
}

function loadImage(imageSource, context)
{
    var imageObj = new Image();
    imageObj.onload = function()
    {
        context.drawImage(imageObj, 0, 0);
    };
    imageObj.src = imageSource;
    return imageObj;
}

function readImage(imageData)
{
    console.log();
    console.log(imageData.data[0]);
}

var context = initContext('canvas','2d');
var imageObj = loadImage('images/color-test.png',context);
var imageData = context.getImageData(0,0,10,10);
alert();
readImage(imageData);

我正在尝试检查属性是否为null,但我得到一个空指针异常.这样做的正确方法是什么？

private void recursePrintList(myNode head)
{
    if(head.next == null) //NullPointerException on this line
    {
        System.out.println(head.value);
    }
    else
    {
        System.out.println(head.value);
        recursePrintList(head.next);
    }
}

我有两个slideToggles的奇怪问题.#bannerChoice幻灯片工作得很好,但是#search幻灯片,打开时应该重叠#bannerChoice,从不打开多个中途.相反,它会强制页面重新加载.

这是我的代码:

function bannerChoice()
{
    $('#bannerChoice').slideToggle(function()
    {
        if($('#bannerChoice').is(':visible'))
        {
            $('html').css({overflow:"hidden",height:"100%"});
        }
        else
        {
            $('html').css({overflow:"auto",height:"2171px"});
        }
    });
}

function toggleForm()
{
    $('#search').slideToggle(350);
    return false;
}

和

<div id="bannerChoice">
    <div id="bcText">Select a banner graphic:<br/></div>
    <div id="bcImages">
        <form action="#" method="post">
            <input type="hidden" name="setBanner" id="setBanner" value="">
            <img src="/media/profile/images/bgs/bg1_thumb.png"
                 onClick="setBanner(1,event);"/>
            <img src="/media/profile/images/bgs/bg2_thumb.png"
                 onClick="setBanner(2,event);"/>
            <img src="/media/profile/images/bgs/bg3_thumb.png"
                 onClick="setBanner(3,event)" />
            <img src="/media/profile/images/bgs/bg4_thumb.png"
                 onClick="setBanner(4,event)" /><br/>
            <span id="bcBttns">
                <input type="submit" value="Submit" class="submit"
                 name="bttnSubmit" /><input type="button" value="Cancel"
                 onClick="bannerChoice()">
            </span>
        </form>
    </div>

    <div id="bcBG">&nbsp;</div>
</div>

和

<span onClick="toggleForm()">
    <a href="" style="display:inline-block; color:#bbb; …

我试图通过动态设置文本颜色以匹配背景颜色来在颜色选择器中创建透明文本的错觉.

jquery的最后一行似乎有问题.到目前为止,我所拥有的是:

$('.color').blur(function()
{
    id = $(this).attr('id');
    id = id.substring(0,id.length-6);
    $(id).css('color',$(this).css('background-color'));
});

和

<div id="header-wrapper">
    <input class="color" id="header-wrapper-color" value="#303030">
    <div id="header">
        ...
    </div>
</div>

<cfset stateList = "Alabama,Alaska,Arizona, ..., Wyoming">
<cfset stateAbbrList = "AL,AK,AR, ..., WY">

<cfset stateAbbr = #ListGetAt("stateAbbrList",ListFind("stateList",form.state))#>

当form.state是Alabama时,我希望stateAbbrList是AL.但相反,我得到一个错误,说ListGetAt返回零.

我究竟做错了什么？