我有一个多文件输入字段:
<input type="file" class="image_file" multiple>
我正在使用FileReader在上传图像时显示图像的预览。
我现在还想在每个图像上载时显示进度条。这是我尝试过的:
$('.image_file').change(function() {
var input = $(this);
var files = this.files;
var total = files.length;
var url = input.attr('data-url');
for (var i = 0; i < total; i++) {
var formData = new FormData();
var file = files[i];
formData.append('image_file', file);
var reader = new FileReader();
reader.onload = function(e) {
var container = $('.photos .photo:not(.active):first');
if (container.length) {
container.css('background-image', 'url(' + e.target.result + ')').addClass('active uploading');
}
};
reader.readAsDataURL(file);
$.ajax({
type: 'post',
url: url,
data: formData,
cache: false,
processData: false,
contentType: false,
xhr: function() {
var myXhr = $.ajaxSettings.xhr();
var progressElem = container.find('progress');
if (myXhr.upload) {
myXhr.upload.addEventListener('progress', function(e) {
if (e.lengthComputable) {
progressElem.attr({
value: e.loaded,
max: e.total
});
}
}, false);
}
return myXhr;
},
success: function(result) {
if (result.status == true) {
$('.success-message').show();
}
else {
alert('There was an error uploading your file.);
}
}
});
}
});
我遇到的问题是xhr
函数中的这一行:
var progressElem = container.find('progress');
出现图像预览,但AJAX上传不起作用。控制台中也不会显示任何错误。我想是因为var container
是在reader.onload
函数中设置的,所以xhr
函数无法访问它。
如果我将该var移到函数外部,则可以上传图像,但仅显示一个图像预览和一个进度条。
有人知道正确的方法吗?
答案 0 :(得分:3)
问题在于,运行for循环时会创建并删除一个xhr。一旦代码完成,先前的xhr将被销毁,因此它将永远无法运行。
解决这个问题的方法是不使用jQuery和/或为每个for循环创建一个新的 xmlhttprequest 。
var array = []; //ADDED HERE
$('.image_file').change(function() {
var input = $(this);
var files = this.files;
var total = files.length;
var url = input.attr('data-url');
for (var i = 0; i < total; i++) {
var formData = new FormData();
var file = files[i];
formData.append('image_file', file);
var reader = new FileReader();
reader.onload = function(e) {
var container = $('.photos .photo:not(.active):first');
if (container.length) {
container.css('background-image', 'url(' + e.target.result + ')').addClass('active uploading');
}
};
reader.readAsDataURL(file);
array[array.Length] = $.ajax({ //ADDED HERE
type: 'post',
url: url,
data: formData,
cache: false,
processData: false,
contentType: false,
xhr: function() {
var myXhr = $.ajaxSettings.xhr();
var progressElem = container.find('progress');
if (myXhr.upload) {
myXhr.upload.addEventListener('progress', function(e) {
if (e.lengthComputable) {
progressElem.attr({
value: e.loaded,
max: e.total
});
}
}, false);
}
return myXhr;
},
success: function(result) {
if (result.status == true) {
$('.success-message').show();
} else {
alert('There was an error uploading your file.);
}
}
});
}
});
我需要强调的是,我还没有完全阅读过您的代码,但希望这会引导您朝着正确的方向前进。
答案 1 :(得分:1)
根据您的问题描述,我认为:
问题出在哪里?
问题是您在变量container
中无法访问变量xhr()
,就像您已经提到的那样。
解决方案是什么?
可以为您解决许多问题,但是我认为将ajax请求块移到reader.onload
内是更好的主意,因为子功能可以访问变量container
并将其调用仅当上传有效文件时。
$('.image_file').change(function() {
var input = $(this);
var files = this.files;
var total = files.length;
var url = input.attr('data-url');
for (var i = 0; i < total; i++) {
var formData = new FormData();
var file = files[i];
formData.append('image_file', file);
var reader = new FileReader();
reader.onload = function(e) {
var container = $('.photos .photo:not(.active):first');
if (container.length) {
var ajaxFunction = function() {
var myXhr = $.ajaxSettings.xhr();
var progressElem = this.find('progress');
if (myXhr.upload) {
myXhr.upload.addEventListener('progress', function(e) {
if (e.lengthComputable) {
progressElem.attr({
value: e.loaded,
max: e.total
});
}
}, false);
}
return myXhr;
};
container.css('background-image', 'url(' + e.target.result + ')').addClass('active uploading');
$.ajax({
type: 'post',
url: url,
data: formData,
cache: false,
processData: false,
contentType: false,
xhr: ajaxFunction.bind(container),
success: function(result) {
if (result.status == true) {
$('.success-message').show();
} else {
alert('There was an error uploading your file.');
}
}
});
}
};
reader.readAsDataURL(file);
}
});
.photo {
display: none;
height: 200px;
width: 200px;
float: left;
}
.active {
display: block;
}
<script src="https://ajax.googleapis.com/ajax/libs/jquery/2.1.1/jquery.min.js"></script>
<input type="file" class="image_file" multiple data-url="http://httpbin.org/post">
<div class="photos">
<div class="photo">
<progress></progress>
</div>
<div class="photo">
<progress></progress>
</div>
</div>
已更新:使用了bind()
函数将变量container
的当前值传递给ajaxFunction()