我在Windows Phone 8.1 512MB RAM仿真器上的WinJS应用程序上有时会出现奇怪的错误。我无法在其他仿真器实例或设备上重现它。
执行通过promise链运行并完成以下return语句：
return ( currentUpload = uploadOperation.startAsync() );
之后没有任何反应。 我在.then定义的所有三个函数（成功，失败，待定）中设置了断点。当出现这种奇怪的情况时，这三个功能代码都不会到达。
我也把这个return语句放在try catch块上，但是没有异常可以捕获。
代码的简短说明：
后台创建了上传器实例（自定义标头+ PUT方法）
StorageFile由URI
后台上传程序准备上传该文件（uploadOperation的定义）
将启动uploadOperation
查看完整代码：
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;
}
Windows.Storage.StorageFile.getFileFromApplicationUriAsync(fileUri)
.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() );
})
.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
});
}
感谢您的帮助！
P.S。我也有一个弃用的警告，虽然我没有在BackgroundUploader类上使用group / TransferGroup：
方法Windows.Networking.BackgroundTransfer.IBackgroundTransferBase.put_Group 已被弃用。组可能被更改或不可用于发布 在Windows 8.1之后。相反，请使用TransferGroup。
可能与承诺链错误有关。
答案 0 :(得分：2)
也许一个简单的拼写错误？
只需查看下面代码 s 中的评论
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 ???
*/
也许它错过了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破坏！
也许调整可能是：
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');
}
);
}
<强> 修改
进一步观察（我不使用winjs），有一些事情要澄清：
.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());
}
).
你在哪里设置这个：
currentUpload = 'Canceled'
你正在检查，但我很确定这部分代码永远不会到达
在此之前，你拒绝承诺：
return WinJS.Promise.wrapError('file not found');
也许下一个then应该处理这样的事情：
.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());
}
)
我希望这会对你有所帮助。