我目前有一个chrome打包的应用程序，我们也已经移植到了iPad，但是我想使用node-webkit（nw.js）将其安装为可安装的程序，并且我需要抽象该chrome打包的应用程序API以便与chrome.fileSystem一起使用。我当前用于保存的代码如下。
var downloadFile = function (readUrl, next) {
var xhr = new XMLHttpRequest();
xhr.open('GET', readUrl);
xhr.responseType = 'arraybuffer';
xhr.onload = function (e) {
if (this.status == 200) {
var response = this.response;
var params = {
type : 'saveFile',
suggestedName : fileNameNoExtension,
//my code will inject the extension but in this case i just put in txt
accepts : [{
extensions : ['.txt']
}
]
}
chrome.fileSystem.chooseEntry(params, function (writableFileEntry) {
debugger;
writableFileEntry.createWriter(function (writer) {
debugger;
writer.onwriteend = function (e) {
return next(null)
};
writer.onerror = function (e) {};
writer.write(new Blob([response], {
type : 'application/octet-stream'
}));
});
});
} else {
//alert
}
};
xhr.onprogress = function (evt) {
if (evt.lengthComputable) {
console.log('progress: ' + Math.round(evt.loaded * 100 / evt.total));
}
}
xhr.addEventListener("error", function () {
return next('error')
}, false);
xhr.addEventListener("abort", function () {
return next('abort')
}, false);
xhr.send();
}
我创建了一个名为interop.js的文件，并将此脚本加载到index.html中，如果它是nw.js项目，它将处理文件存储的所有Chrome打包应用API调用。如果它是chrome打包的应用，则chrome将处理它自己的API。
//if process is undefined then it is not an nw.js project and we can ignore the rest of the code;
if (typeof process == 'undefined') {}
//this is a nw.js project, spoof the chrome packaged app API
else {
var fs = require('fs')
chrome = new function () {
var fileSystem = {
//callback return readableFileEntry, which has a
chooseEntry : function (params, callback) {
if (params.type == 'openFile') {
//open file choose
chooseFile(params, function (files) {
//this is technically an html5 "filelist" we need to turn it into an array if there is more
//than one, and just return the single file if there isn't
if (!files) {
return callback(null)
}
async.map(files, function (file, cb) {
//normally chrome provides a 'readablefileentry' that will only give you the file
//asynchronously using the file() function
file.file = function (next) {
return next(this);
}
cb(null, file)
}, function (err, files) {
if (files.length > 1) {
return callback(files);
} else {
return callback(files[0]);
}
})
})
} else if (params.type == 'saveFile') {
chooseFile(params, function (files) {
var file = files[0];
debugger;
file.createWriter = function (next) {
var writer = {
write : function (blob) {
debugger;
var reader = new FileReader()
reader.readAsArrayBuffer(blob)
reader.addEventListener('loadend', function (e) {
var binary = new Uint8Array(reader.result)
debugger;
fs.writeFile(file.path, new Buffer(binary), function (err) {
//if the on error and writeend has been defined then callback, otherwise throw the error and log success
if (err && writer.onerror) {
writer.onerror(err)
} else if (err) {
throw err
} else if (writer.onwriteend) {
writer.onwriteend()
} else {
console.log('file was written but no callback was defined')
}
})
});
}
}
return next(writer)
}
return callback(file)
})
}
function chooseFile(params, next) {
var fileHtml = '<input type="file"'
debugger;
if (params.acceptsMultiple)
fileHtml += ' multiple';
if (params.accepts && params.accepts.length > 0 && params.accepts[0].extensions) {
fileHtml += ' accept="'
for (var i = 0; i < params.accepts[0].extensions.length; i++) {
if (i != 0)
fileHtml += ','
fileHtml += '.' + params.accepts[0].extensions[i]
}
fileHtml += '"'
}
if (params.suggestedName) {
fileHtml += ' nwsaveas="' + params.suggestedName + '"'
}
fileHtml += '>'
var chooser = $(fileHtml);
chooser.change(function (evt) {
debugger;
return next(chooser[0].files)
});
chooser.click();
}
}
}
return {
fileSystem : fileSystem,
}
};
}
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