也许是一个简单的错字错误？
只需选中注释代码小号下面
var currentUpload; // global
function uploadFile(localFullPath, headers, serverUrl)
{
var fileUri = new Windows.Foundation.Uri('ms-appdata:///local' + localFullPath),
uploader = false;
try
{
uploader = new Windows.Networking.BackgroundTransfer.BackgroundUploader();
uploader.method = 'PUT';
// set headers to uploader
for (var key in headers)
{
if (headers.hasOwnProperty(key))
uploader.setRequestHeader(key, headers[key]);
}
}
catch (e)
{
// error handling
return false;
}
/*
return something it's a good practice if you want to chain Promises
|
|
V */
return Windows.Storage.StorageFile.getFileFromApplicationUriAsync(fileUri)
.then(
function success(file){
return uploader.createUpload(serverUrl, file);
},
function failure(error){
return WinJS.Promise.wrapError('file not found');
// |_____________|
// your are rejecting your promise with ---------^
}
).then(
function (uploadOperation){
// Just avoid this type of code construction
// and add brace !
// adding brace augment readability and prevent errors !
// where do you set this ??? currentUpload = 'Canceled'
// is part of winjs ???
if (currentUpload == 'Canceled')
// why not handle your rejected promise ?
// by something like :
//if(uploadOperation == 'file not found')
return WinJS.Promise.wrapError('upload canceled');
else
return (currentUpload = uploadOperation.startAsync());
}
).then(
// Promise resolve handler
function success(success){
currentUpload = false;
// success handling
return true;
} ,
// Promise reject handler
function failure(error){
currentUpload = false;
// error handling
return false;
}
/* ^
|
YOU HAVE HERE A DOUBLE CLOSING BRACE }} ???
°
| WHAT IS THIS PART FOR ??????
|
+------+---- Ending uploadFile with successive closing brace !
|
|+---------------- Declaration separator
|| +--- New function declaration
|| |
VV V */
}, function pending(status){
var progress = status.progress,
percent = Math.round(progress.bytesSent/progress.totalBytesToSend * 100);
// progress handling
});
}
/*
ALL THAT PART ABOVE IS NOT IN THE PROMISE CHAIN
AND SHOULD BREAK YOUR CODE !!!
HOW HAVE YOU EVER COULD RUN THIS ???
*/
也许是想念你的代码的一部分，以确保这一点，因为在这种状态下你的代码必须打破！
也许一个adjustement可能是：
var currentUpload; // global
function uploadFile(localFullPath, headers, serverUrl)
{
var fileUri = new Windows.Foundation.Uri('ms-appdata:///local' + localFullPath),
uploader = false;
try
{
uploader = new Windows.Networking.BackgroundTransfer.BackgroundUploader();
uploader.method = 'PUT';
// set headers to uploader
for (var key in headers)
{
if (headers.hasOwnProperty(key))
uploader.setRequestHeader(key, headers[key]);
}
}
catch (e)
{
// error handling
return false;
}
/*
return something it's a good practice if you want to chain Promises
|
|
V */
return Windows.Storage.StorageFile.getFileFromApplicationUriAsync(fileUri)
.then(
function success(file){
return uploader.createUpload(serverUrl, file);
},
function failure(error){
return WinJS.Promise.wrapError('file not found');// O|--------+
}// |
).then(// |
function (uploadOperation){// O|-------------------------------|
// |
// Just avoid this type of code construction |
// and add brace ! |
// adding brace augment readability and prevent errors ! |
// |
// EDIT |
//if (currentUpload == 'Canceled') { // <--- add brace |
if (uploadOperation == 'file not found') { //<---add brace <--+
return WinJS.Promise.wrapError('upload canceled');
} else { // <---- add braces
// even if it is valid
// avoid assignement like that
// so subtil to read/understand/debug ...
// return (currentUpload = uploadOperation.startAsync());
currentUpload = uploadOperation.startAsync();
// maybe debug here ?
console.log('currentUpload : ' + currentUpload);
return currentUpload;
} // <---- add brace
}
).then(
function success(success){
currentUpload = false;
// success handling
return true;
} ,
function failure(error){
currentUpload = false;
// error handling
return false;
} ,
function pending(status){
var progress = status.progress,
percent = Math.round(progress.bytesSent/progress.totalBytesToSend * 100);
// progress handling
}
).done(// it is always a good thing to have a final catcher !!
function(){
// things are ok !
console.log('ok');
},
function(err){
// make something with your error better than
alert(err);
console.log('ko');
}
);
}
编辑
寻找进一步（我不使用winjs），有一些需要澄清：
.then(
function success(file) {
return uploader.createUpload(serverUrl, file);
},
function failure(error) {
return WinJS.Promise.wrapError('file not found');
}
).then(
function(uploadOperation) {
if (currentUpload == 'Canceled')
return WinJS.Promise.wrapError('upload canceled');
else
return (currentUpload = uploadOperation.startAsync());
}
).
你在哪里设置：
currentUpload = 'Canceled'
你正在检查，但我很确定这部分代码是永远不会到达的。
在此之前，你拒绝与你的承诺：
return WinJS.Promise.wrapError('file not found');
说不定下then应该处理成才这样的：
.then(
function success(file) {
return uploader.createUpload(serverUrl, file);
},
function failure(error) {
return WinJS.Promise.wrapError('file not found');
}
).then(
function(uploadOperation) {
if (uploadOperation == 'file not found')
return WinJS.Promise.wrapError('upload canceled');
else
return (currentUpload = uploadOperation.startAsync());
}
)
我希望这会帮助你。
我坦率地不明白你想用'return（currentUpload = uploadOperation.startAsync（））;'实现。你也搞砸了你承诺链接。当链接承诺时，我必须在最后完成错误处理和所有错误处理。这就是承诺链的美妙之处。 – sebagomez
该声明将当前上载保存在全局变量中。想象一下，它会返回uploadOperation.startAsync（） - 测试它，然后出错。 “搞砸”是什么意思？你是在谈论最佳做法和风格，还是可能导致错误？我这样做的原因是它只给了我一个“WinRT错误”，所以我无法正确区分这些错误（有一个文本，但这是一种特定的语言）。 – kerosene
根据[MSDN文档]（https://msdn.microsoft.com/en-us/library/windows/apps/windows.networking.backgroundtransfer.downloadoperation.startasync.aspx），该函数可能会降低性能。也许你正在经历一个放缓。他们建议“你在后台工作线程上调用StartAsync ...”这可能是你问题的根源吗？ – Jimmy