ker*_*ene 5 javascript promise winjs windows-phone-8.1
我有一些奇怪的错误,有时会出现在我的Windows Phone 8.1 512MB RAM仿真器上的WinJS应用程序中.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.当发生这种奇怪的情况时,这三个功能代码都不会到达.
我还把这个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:
创建后台上传器实例(自定义标头+ PUT方法)
StorageFile由URI打开
后台上传器准备上传该文件(uploadOperation的定义)
uploadOperation将开始
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
});
}
谢谢你的帮助!
PS我也有一个弃用的警告,虽然我没有在BackgroundUploader类上使用group/TransferGroup:
不推荐使用Windows.Networking.BackgroundTransfer.IBackgroundTransferBase.put_Group方法.在Windows 8.1之后,组可能会被更改或不可用于发布.而是使用TransferGroup.
也许它与该承诺链错误有关.
也许是一个简单的拼写错误？\n只需检查下面代码
中的注释
var currentUpload; // global\n\n function uploadFile(localFullPath, headers, serverUrl)\n {\n var fileUri = new Windows.Foundation.Uri(\'ms-appdata:///local\' + localFullPath),\n uploader = false;\n\n try\n {\n uploader = new Windows.Networking.BackgroundTransfer.BackgroundUploader();\n uploader.method = \'PUT\';\n\n // set headers to uploader\n for (var key in headers)\n {\n if (headers.hasOwnProperty(key))\n uploader.setRequestHeader(key, headers[key]);\n }\n }\n catch (e)\n {\n // error handling\n return false;\n }\n\n /*\n\n return something it\'s a good practice if you want to chain Promises\n |\n |\n V */ \n return Windows.Storage.StorageFile.getFileFromApplicationUriAsync(fileUri)\n .then(\n function success(file){\n return uploader.createUpload(serverUrl, file);\n },\n function failure(error){\n return WinJS.Promise.wrapError(\'file not found\');\n // |_____________| \n // your are rejecting your promise with ---------^\n }\n ).then(\n function (uploadOperation){\n\n // Just avoid this type of code construction\n // and add brace !\n // adding brace augment readability and prevent errors !\n\n // where do you set this ??? currentUpload = \'Canceled\'\n // is part of winjs ???\n if (currentUpload == \'Canceled\') \n\n // why not handle your rejected promise ?\n // by something like :\n //if( uploadOperation == \'file not found\' )\n return WinJS.Promise.wrapError(\'upload canceled\');\n else\n return ( currentUpload = uploadOperation.startAsync() );\n }\n ).then(\n// Promise resolve handler\n function success(success){\n currentUpload = false;\n // success handling\n return true;\n } , \n// Promise reject handler\n function failure(error){\n currentUpload = false;\n // error handling\n return false;\n }\n/* ^ \n |\nYOU HAVE HERE A DOUBLE CLOSING BRACE }} ???\n \xc2\xb0\n | WHAT IS THIS PART FOR ??????\n |\n +------+---- Ending uploadFile with successive closing brace !\n |\n |+---------------- Declaration separator\n || +--- New function declaration\n || |\n VV V */\n }, function pending(status){\n var progress = status.progress,\n percent = Math.round(progress.bytesSent / progress.totalBytesToSend * 100);\n // progress handling\n });\n }\n\n/*\nALL THAT PART ABOVE IS NOT IN THE PROMISE CHAIN \nAND SHOULD BREAK YOUR CODE !!!\nHOW HAVE YOU EVER COULD RUN THIS ???\n*/\n也许它会错过您代码的一部分以确保这一点，因为在这种状态下您的代码必须中断！
\n\n也许调整可以是：
\n\nvar currentUpload; // global\n\nfunction uploadFile(localFullPath, headers, serverUrl)\n{\n var fileUri = new Windows.Foundation.Uri(\'ms-appdata:///local\' + localFullPath),\n uploader = false;\n\n try\n {\n uploader = new Windows.Networking.BackgroundTransfer.BackgroundUploader();\n uploader.method = \'PUT\';\n\n // set headers to uploader\n for (var key in headers)\n {\n if (headers.hasOwnProperty(key))\n uploader.setRequestHeader(key, headers[key]);\n }\n }\n catch (e)\n {\n // error handling\n return false;\n }\n\n /*\n\n return something it\'s a good practice if you want to chain Promises\n |\n |\n V */ \n return Windows.Storage.StorageFile.getFileFromApplicationUriAsync(fileUri)\n .then(\n function success(file){\n return uploader.createUpload(serverUrl, file);\n },\n function failure(error){\n return WinJS.Promise.wrapError(\'file not found\');// O|--------+\n }// |\n ).then(// |\n function (uploadOperation){// O|-------------------------------|\n // |\n // Just avoid this type of code construction |\n // and add brace ! |\n // adding brace augment readability and prevent errors ! |\n // | \n // EDIT |\n //if (currentUpload == \'Canceled\') { // <--- add brace |\n if (uploadOperation == \'file not found\') { //<---add brace <--+ \n\n return WinJS.Promise.wrapError(\'upload canceled\');\n\n } else { // <---- add braces\n\n // even if it is valid\n // avoid assignement like that\n // so subtil to read / understand / debug ...\n // return ( currentUpload = uploadOperation.startAsync() );\n\n currentUpload = uploadOperation.startAsync();\n // maybe debug here ?\n console.log(\'currentUpload : \' + currentUpload );\n return currentUpload;\n\n } // <---- add brace\n }\n ).then(\n function success(success){\n currentUpload = false;\n // success handling\n return true;\n } , \n function failure(error){\n currentUpload = false;\n // error handling\n return false;\n } ,\n function pending(status){\n var progress = status.progress,\n percent = Math.round(progress.bytesSent / progress.totalBytesToSend * 100);\n // progress handling\n }\n ).done( // it is always a good thing to have a final catcher !!\n function(){\n // things are ok !\n console.log(\'ok\');\n },\n function(err){\n // make something with your error better than\n alert(err);\n console.log(\'ko\');\n\n }\n );\n}\n编辑
\n\n进一步看（我不使用winjs），有一些事情需要澄清：
\n\n.then(\n function success(file) {\n return uploader.createUpload(serverUrl, file);\n },\n function failure(error) {\n return WinJS.Promise.wrapError(\'file not found\');\n\n }\n).then(\n function(uploadOperation) {\n\n if (currentUpload == \'Canceled\')\n return WinJS.Promise.wrapError(\'upload canceled\');\n else\n return (currentUpload = uploadOperation.startAsync());\n }\n).\n你在哪里设置这个：
\n currentUpload = \'Canceled\'
\n你正在检查，但我很确定这部分代码永远不会到达。
\n在你拒绝你的承诺之前：
\n return WinJS.Promise.wrapError(\'file not found\');
\n也许下一个then应该处理类似的事情：
.then(\n function success(file) {\n return uploader.createUpload(serverUrl, file);\n },\n function failure(error) {\n return WinJS.Promise.wrapError(\'file not found\');\n\n }\n).then(\n function(uploadOperation) {\n\n if (uploadOperation == \'file not found\')\n return WinJS.Promise.wrapError(\'upload canceled\');\n else\n return (currentUpload = uploadOperation.startAsync());\n }\n)\n我希望这能帮到您。
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