html代码:

<tr>
    <td><label for="pic" style="font-weight:normal;">图片</label>:</td>
    <td colspan="3">
        <div class="file-box">
            <input type="text" maxlength="50" value="<?php echo $threadinfo['pic']?>" name="pic" style="display:inline-block;width:200px;" class="form-control" id="pic">
            <a href='javascript:;' class="upload" style="display:inline-block;width:60px;" οnclick="click_up()">上传</a>
            <div style="display:none"><input type="file" id="upload" name="UploadForm[file]" /></div>
        </div>
    </td>
</tr>

<?=Html::jsFile('/static/admin/js/ajaxfileupload.js')?>

js代码1 [有bug:点击上传一次图片后,再次点击上传图片无效:原因input框的change事件只触发了一次]

这个问题并不是由change事件失效造成的，而是ajaxFileUpload插件造成的，它会把原来的file元素替换成新的file元素，所以之前绑定的change事件就失效了，需要重新绑定一下

<script>

$("input#upload").change(function () {
        $.ajaxFileUpload({
            url: "/index.php?r=public/upload/upload",
            secureuri: false,
            data:{'type':'forum','cid':<?php echo intval($threadinfo['cid'])?>},
            fileElementId:'upload',
            dataType: 'json',
            success: function (data, status) {
                if (data && data.result == 'Success') {
                    $("#pic").val(data.url);
                    $("#pic_show").attr('src',data.url);
                    return ;
                }else{
                    alert("上传失败");
                    return ;
                }
            },
            error: function (data, status, e) {
                return;
            }
        });
    });

</script>

js代码2[解决办法,再次点击上传时给input框重新绑定change事件]

<script>
function click_up(){
    $("input#upload").click();       //添加一个点击事件来触发$(input#upload)的change事件
    $("input#upload").change(function () {
        $.ajaxFileUpload({
            url: "/index.php?r=public/upload/upload",
            secureuri: false,
            data:{'type':'forum','cid':<?php echo intval($threadinfo['cid'])?>},
            fileElementId:'upload',
            dataType: 'json',
            success: function (data, status) {
                if (data && data.result == 'Success') {
                    $("#pic").val(data.url);
                    $("#pic_show").attr('src',data.url);
                    return ;
                }else{
                    alert("上传失败");
                    return ;
                }
            },
            error: function (data, status, e) {
                return;
            }
        });
    });
}    
</script>