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From "Alan Neveu (JIRA)" <>
Subject [jira] [Created] (CB-2084) CordovaWP7 FileEntry.write Intermittent Errors
Date Tue, 18 Dec 2012 13:52:12 GMT
Alan Neveu created CB-2084:

             Summary: CordovaWP7 FileEntry.write Intermittent Errors
                 Key: CB-2084
             Project: Apache Cordova
          Issue Type: Bug
          Components: WP7, WP8
    Affects Versions: 2.3.0
         Environment: Windows Phone 7, Windows Phone 8
            Reporter: Alan Neveu
            Assignee: Jesse MacFadyen

I have found problems due to strange behavior with writing new files to the device.  I found
that the File.cs function called:

public void write(string options)

is intermittently losing the filePath value that comes in via options. This happens a lot
when the file is being created and does not exist.  It does not happen 100% of the time, however.
 What seems to be happening is that the call to getMetaData while getting a FileEntry object
fails because the file does not exist and when the FileEntry is then used to write a new file
to the device the filePath is null.  My application needs to downloads maybe 30 files from
a web service and write them all to disk.  While I am looping through the files I downloaded
and attempting to write them to disk, maybe 2 or 3 out of 30 will experience this problem.
I wrote a simple function for writing files called write2, and it lives in my File.cs file.
 This is what it looks like:
        public void write2(string options)
            string[] optStrings = JSON.JsonHelper.Deserialize<string[]>(options);
            string filename = optStrings[0];
            string data = optStrings[1];
                using (IsolatedStorageFile isoFile = IsolatedStorageFile.GetUserStoreForApplication())
                    bool booExists = isoFile.FileExists(filename);
                    if (booExists)
                    IsolatedStorageFileStream myNewIsoFS = isoFile.CreateFile(filename);
                    byte[] bytData = System.Text.Encoding.UTF8.GetBytes(data);
                    myNewIsoFS.Write(bytData, 0, bytData.Length);
            catch (Exception ex)
                string whaa = ex.Message;
 It’s really lame and limited, I know, but it works every time.  I also had to modify cordova-2.3.0.js
to shim my function in there.  All I did was copy the FileWriter.prototype.write function
and name mine write2, and I also made mine so that it accepts two parameters - the first being
the filename and the second being the data.  This allows me to pass these arguments to my
write2 function in File.cs, and from there I definitely have the filename every time, which
then allows me to simply write the file to disk.  I spent many hours trying to figure out
how/why the normal write call is sometimes losing the filename and filePath, but I just can’t
figure it out.  Here is what my FileWriter.prototype.write2 javascript function looks like:
FileWriter.prototype.write2 = function (targetfilename, text) {
    // Throw an exception if we are already writing a file
    console.log("targetfilename=" + targetfilename);
    if (this.readyState === FileWriter.WRITING) {
        throw new FileError(FileError.INVALID_STATE_ERR);
    // WRITING state
    this.readyState = FileWriter.WRITING;
    var me = this;
    // If onwritestart callback
    if (typeof me.onwritestart === "function") {
        me.onwritestart(new ProgressEvent("writestart", { "target": me }));
    // Write file
        // Success callback
        function (r) {
            // If DONE (cancelled), then don't do anything
            if (me.readyState === FileWriter.DONE) {
            // position always increases by bytes written because file would be extended
            me.position += r;
            // The length of the file is now where we are done writing.
            me.length = me.position;
            // DONE state
            me.readyState = FileWriter.DONE;
            // If onwrite callback
            if (typeof me.onwrite === "function") {
                me.onwrite(new ProgressEvent("write", { "target": me }));
            // If onwriteend callback
            if (typeof me.onwriteend === "function") {
                me.onwriteend(new ProgressEvent("writeend", { "target": me }));
        // Error callback
        function (e) {
            // If DONE (cancelled), then don't do anything
            if (me.readyState === FileWriter.DONE) {
            // DONE state
            me.readyState = FileWriter.DONE;
            // Save error
            me.error = new FileError(e);
            // If onerror callback
            if (typeof me.onerror === "function") {
                me.onerror(new ProgressEvent("error", { "target": me }));
            // If onwriteend callback
            if (typeof me.onwriteend === "function") {
                me.onwriteend(new ProgressEvent("writeend", { "target": me }));
        }, "File", "write2", [targetfilename, text]);

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