For循环不等待winjs承诺完成 [英] For loop not waiting for winjs promise completion
本文介绍了For循环不等待winjs承诺完成的处理方法,对大家解决问题具有一定的参考价值,需要的朋友们下面随着小编来一起学习吧!
问题描述
for (var j = 0; j < magazineResult[0].data.length; j++) {
downRequest[0].data[j].COVER_PAGE_THUMB = parentUrl + eval(JSON.stringify(downRequest[0].data[j].COVER_PAGE_THUMB));
// Create a new download operation.
downloadFile(eval(magazineResult[0].data[j].COVER_PAGE_THUMB),eval(JSON.stringify(magazineResult[0].data[j].COVER_PAGE_THUMB)));
var url = downRequest[0].data[j].COVER_PAGE_THUMB;
var imgPath = downRequest[0].data[j].ISSUE_ID;
var imgExtension = url.substring(url.lastIndexOf('.') + 1);
var fileName = imgPath + "." + imgExtension;
var promise = Windows.Storage.ApplicationData.current.localFolder.createFileAsync(fileName, Windows.Storage.CreationCollisionOption.replaceExisting);
// Assign the completion handler function.
promise.done(function (newFile) {
MagazineDownLoad.downloadFile(url, fileName, j, newFile);
});
}
推荐答案
如果您试图使MagazineDownLoad.downloadFile
异步运行,则必须修改其定义:
If you're trying to get MagazineDownLoad.downloadFile
to operate asynchronously then you'll have to modify it's definition:
// in MagazineDownload
function downloadFile(url, filename, j, newfile){
return new WinJS.Promise(function (complete, error, progress) {
var returnValue;
//do the stuff that you do and assign something to returnValue
complete(returnValue);
});
}
然后您可以异步使用它:
Then you can use it asynchronously:
for (var j = 0; j < magazineResult[0].data.length; j++) {
downRequest[0].data[j].COVER_PAGE_THUMB = parentUrl + eval(JSON.stringify(downRequest[0].data[j].COVER_PAGE_THUMB));
// Create a new download operation.
downloadFile(eval(magazineResult[0].data[j].COVER_PAGE_THUMB),eval(JSON.stringify(magazineResult[0].data[j].COVER_PAGE_THUMB)));
var url = downRequest[0].data[j].COVER_PAGE_THUMB;
var imgPath = downRequest[0].data[j].ISSUE_ID;
var imgExtension = url.substring(url.lastIndexOf('.') + 1);
var fileName = imgPath + "." + imgExtension;
var promise = Windows.Storage.ApplicationData.current.localFolder.createFileAsync(fileName, Windows.Storage.CreationCollisionOption.replaceExisting);
// Assign the completion handler function.
promise.done(function (newFile) {
MagazineDownLoad.downloadFile(url, fileName, j, newFile).done(function(result){
//do some more stuff with the result
});
});
}
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