Develop Reference

How do I open and display a base64 pdf from inside my Cordova App?

I am creating an App for Android using Cordova, and I would like to open and display a file (PDF or image) that is served from the server as Base64-encoded binary data.
Of course I have read the multiple other posts on the subject that already exist on this website, but none of the proposed solutions have worked for me, more details below.
To be more precise, the server sends a JSON-file to the app, which among many other things contains a string consisting of the base64-encoded contents of a PDF file. I want to convert this data back into the represented PDF and display it to the user.
If this were a pure browser page, I would simply package my base64 data into a data-URL, attach this as the href of some anchor, and add a download-attribute. Optionally I could wrap all of my data into a blob and create an object url for that first.
In Cordova, this does not work. Clicking the <a> does nothing. Here is what I have attempted so far:
Using the file plugin, I can write the binary data to a file on the device. This works, and using a terminal I can see that the file was downloaded correctly, but into an app-private directory which I cannot access normally (e.g. through the file explorer).
Accessing the user's "downloads" folder is blocked by the file system
Using window.open with the file path as the first argument and "_system" as the target does nothing. There is no error but also nothing happens. Setting the target to "_blank" instead, I get an error saying ACCESS_DENIED.
Using cordova.InAppBrowser behaves the same was as window.open
With the plugin file-opener2 installed, the app will not compile, because the plugin is looking for an android4 toolchain, and I am building for android 9 and up
The plugin document-viewer (restricting to PDFs for the time being) suffers the same problem and does not compile.
Passing the data-URI to window.open (or cordova.InAppBrowser) directly loads for a very long time and eventually tells me that the desired page could not be loaded.
The PDF file I am using for testing is roughly 17kb after converting to base64. I know this is technically above the spec for how long data-URIs can be, but Chrome in the browser has no trouble with it whatsoever, and using a much shorter URI (only a few dozen bytes) produces the same behavior.
Ideally, what I would like to do, is download the file and then trigger the user's standard browser to open the file itself. That was, I would not have to deal with MIME types and also it would look exactly how the user expected from their own device.
Alternatively, if that doesn't work, I would be ok with downloading the file into a system-wide directory and prompting the user to open it themselves. This is not optimal, but I would be able to swallow that pill.
And lastly, if there is a plugin or some other solution that solves the problem amazingly, but for PDFs only, then I can also work out something else for images (e.g. embedding a new into my app and assigning the URI to that).
I would be thankful for any suggestion you might have on how to solve this problem. The code I use to download the file currently is shown below.
Thank you for your time.
var filePath = cordova.file.externalDataDirectory; // Note: documentsDirectory is set to "" by Cordova, so I cannot use that
var fileName = "someFileName.pdf";
var mime = "application/pdf";
var dataBlob = /* some blob containing the binary data for a PDF */
function writeFile(fileEntry, dataBlob) {
// Create a FileWriter object for our FileEntry.
// This code is taken directly from the cordova-plugin-file documentation
fileEntry.createWriter(function (fileWriter) {
fileWriter.onwriteend = function() {
console.log("Successful file write...");
readFile(fileEntry);
};
fileWriter.onerror = function (e) {
console.log("Failed file write: " + e.toString());
};
fileWriter.write(dataBlob);
});
}
window.resolveLocalFileSystemURL(
filePath,
function onResolveSuccess (dirEntry) {
dirEntry.getFile(
fileName,
{ create: true },
function onGetFileSuccess (file) (
writeFile(file, dataBlob);
// At this point, the file has been downloaded successfully
window.open(file.toURL(), "_system"); // This line does nothing, and I don't understand why.
}
);
}
);

I managed to solve the problem.
As per the documentation of the file-opener2 plugin, you need to also add the androidx-adapter plugin to correct for the outdated (android 4) packages. With the plugins file, file-opener2 and androidx-adapter installed, the complete code is the following:
var filePath = cordova.file.externalDataDirectory; // Note: documentsDirectory is set to "" by Cordova, so I cannot use that
var fileName = "someFileName.pdf";
var mime = "application/pdf";
var dataBlob = /* some blob containing the binary data for a PDF */
function writeFile(fileEntry, dataBlob) {
// Create a FileWriter object for our FileEntry.
// This code is taken directly from the cordova-plugin-file documentation
fileEntry.createWriter(function (fileWriter) {
fileWriter.onwriteend = function() {
console.log("Successful file write...");
readFile(fileEntry);
};
fileWriter.onerror = function (e) {
console.log("Failed file write: " + e.toString());
};
fileWriter.write(dataBlob);
});
}
window.resolveLocalFileSystemURL(
filePath,
function onResolveSuccess (dirEntry) {
dirEntry.getFile(
fileName,
{ create: true },
function onGetFileSuccess (file) (
writeFile(file, dataBlob);
// At this point, the file has been downloaded successfully
cordova.plugins.fileOpener2.open(
    filepath + filename,
    mime,
    {
     error : function(){ },
success : function(){ }
    }
);
}
);
}
);

save a field value to a file on desktop

I am developing a custom application in "ServiceNow" which requires Javascript and HTML coding. So, I have a field say, "description" on my form. How may I save this field's value to a word document on the desktop?

While JavaScript cannot create a file for you to download by itself, ServiceNow does have a way for you to create one. Creating a Word document is impossible without the use of a MID server and some custom Java code, but if any file type will do you can create an Excel file using an export URL. To test this out, I made a UI Action in a developer instance running Helsinki on the Problem table. I made a list view that contains only the field that I wanted to save, and then used the following code in the UI action:
function startDownload() {
window.open("https://dev13274.service-now.com/problem_list.do?EXCEL&sysparm_query=sys_id%3D" +
g_form.getUniqueValue() + "&sysparm_first_row=1&sysparm_view=download");
}
When the UI action is used, it opens a new tab that will close almost immediately and prompt the user to save or open an Excel file that contains the contents of that single field.
If you want to know more about the different ways you can export data from ServiceNow, check their wiki-page on the subject.

You can use the HTML5 FileSystem API to achieve that
window.requestFileSystem(window.PERSISTENT, 1024*1024, function (fs) {
fs.root.getFile('file.txt', {create: true}, function(fileEntry) {
fileEntry.createWriter(function(fileWriter) {
var blob = new Blob([description.value], {type: 'text/plain'});
fileWriter.write(blob);
});
});
});
FYI, chrome supports webkitRequestFileSystem.
Alternatively, use a Blob and generate download link
var text = document.getElementById("description").value;
var blob = new Blob([text], {type:'text/plain'});
var fileName = "test.txt";
var downloadLink = document.createElement("a");
downloadLink.download = fileName;
downloadLink.href = window.webkitURL.createObjectURL(textFile);
downloadLink.click();

Javascript protects clients against malicious servers who would want to read files on their computer. For that reason, you cannot read or write a file to the client's computer with javascript UNLESS you use some kind of file upload control that implicitely asks for the user's permission.

Phonegap 3.5 fetching audio / video files from external sd card Android

Currently I am not able to fetch video (.mp4) and audio (.wav) files from external sd card, basically I want to fetch the files and convert them to base64 and send them to the server.
Here is my code
window.requestFileSystem(LocalFileSystem.PERSISTENT, 0, function(fileSystem) {
// fileSystem's root is -> file:///storage/emulated/0/
var url = "cdvfile://localhost/root/storage/extSdCard/DCIM/Camera/20141018_143740.mp4";
window.resolveLocalFileSystemURL(url, function(fileObj) {
var fullPath = fileObj.fullPath;
// fullPath -> file:/storage/extSdCard/DCIM/Camera/20141018_143740.mp4
fileSystem.root.getFile(fullPath, null, function(fileEntry) {
fileEntry.file(function(file) {
//.. FileReader function to convert the file to base64 by reader.readAsDataURL(file)
},errorFunc);
},errorFunc);
},errorFunc);
},errorFunc);
Now the problem is I am not able to get the .mp4 file i.e. my fileSystem.root.getFile is giving me the error
Error code 1 i.e. File Not Found
After checking few stack overflow questions and http://rickluna.com/wp/2014/01/accessing-external-storage-in-android-phonegap-3-3/ blog I think my problem lies in "root"
i.e. my fileSystem obj (success callback of requestFileSystem method) looks like this:
filesystem: FileSystem
fullPath: "/"
isDirectory: true
isFile: false
name: ""
nativeURL: "file:///storage/emulated/0/"
__proto__: utils.extend.F
So is it possible to change the root? i.e. from file:///storage/emulated/0/ to file:///storage/ so that I can call getFile and pass the absolute url i.e. /extSdCard/DCIM when( file:///storage/) becomes root
I even tried by changing root i.e.
fileSystem.root.fullPath = 'file:///storage/';
even I tried to change the nativeURL property of fileSystem object but it's not working
ps. solution given in the blog hasn't worked for me
ps ps. The same code is working fine when my absolute url is: file:///storage/emulated/0/MRS/fileName.txt
and I am passing the relative url in function i.e. fileSystem.root.getFile("MRS/fileName.txt",...)

How to access audio fle and upload to server in phonegap

i have one query like i want access to all audio file in phone gap ios and want to upload to server, so any one know how to do get all mp3 files and get upload.
we should need to create a plugin for that .

I don't think you require to create a new plugin. The existing File and File Transfer API should work in your case unless you have more requirements other than the ones stated here.
Use the file API to iterate over all the files in the app.
function success(entries) {
var i;
for (i=0; i<entries.length; i++) {
console.log(entries[i].name);
//Check if the file is in mp3 format. If it is in mp3 format, trigger file upload.
}
}
function fail(error) {
alert("Failed to list directory contents: " + error.code);
}
// Get a directory reader
var directoryReader = dirEntry.createReader();
// Get a list of all the entries in the directory
directoryReader.readEntries(success,fail);
Then use the file upload API to upload the files to the server.
var ft = new FileTransfer();
ft.upload(fileURI, encodeURI("http://some.server.com/upload.php"), win, fail, options);

Filesystem API - Upload from local drive to local filesystem

Ive read a lot about the filesystem API and HTML5, but i just couldn't find a working solution so i ask you guys:
I want to have a file upload form, drag drop or regular input box doesnt matter, however i want to select a file, and after uploading it should take the file or a whole folder and "upload" it to the filesystem located on the clients computer. The upload is in brackets because i actually want to copy the file/folder to the clients local file system.
Is it even possible? Because i want to make an application, where a user can upload his files such as music or large videos and movies to his local filesystem and edit/watch etc them in my application. I know i have to upload those big files i have to cut them into pieces and load them stacked up, but i just want to start little :)
Thanks in advance

There's indeed little information on this subject at the moment, so I put together an example that combines:
Using the webkitdirectory attribute on <input type="file">.
This allows the user to select a directory using an appropriate dialog box.
Using the Filesystem API.
This is about the sandboxed filesystem which allows you to store files on the client's machine.
Using the File API.
This is the API that allows you to read files. The files are accessible through an <input type="file"> element, through a transfer using drag and drop, or through the Filesystem API.
As these are currently only working nicely in Chrome, I used the webkit prefix where necessary.
http://jsfiddle.net/zLna6/3/
The code itself has comments which I hope are clear:
var fs,
err = function(e) {
throw e;
};
// request the sandboxed filesystem
webkitRequestFileSystem(
window.TEMPORARY,
5 * 1024 * 1024,
function(_fs) {
fs = _fs;
},
err
);
// when a directory is selected
$(":file").on("change", function() {
$("ul").empty();
// the selected files
var files = this.files;
if(!files) return;
// this function copies the file into the sandboxed filesystem
function save(i) {
var file = files[i];
var text = file ? file.name : "Done!";
// show the filename in the list
$("<li>").text(text).appendTo("ul");
if(!file) return;
// create a sandboxed file
fs.root.getFile(
file.name,
{ create: true },
function(fileEntry) {
// create a writer that can put data in the file
fileEntry.createWriter(function(writer) {
writer.onwriteend = function() {
// when done, continue to the next file
save(i + 1);
};
writer.onerror = err;
// this will read the contents of the current file
var fr = new FileReader;
fr.onloadend = function() {
// create a blob as that's what the
// file writer wants
var builder = new WebKitBlobBuilder;
builder.append(fr.result);
writer.write(builder.getBlob());
};
fr.onerror = err;
fr.readAsArrayBuffer(file);
}, err);
},
err
);
}
save(0);
});
$("ul").on("click", "li:not(:last)", function() {
// get the entry with this filename from the sandboxed filesystem
fs.root.getFile($(this).text(), {}, function(fileEntry) {
// get the file from the entry
fileEntry.file(function(file) {
// this will read the contents of the sandboxed file
var fr = new FileReader;
fr.onloadend = function() {
// log part of it
console.log(fr.result.slice(0, 100));
};
fr.readAsBinaryString(file);
});
}, err);
});

That is not possible, exactly, but your app can still probably work. Reading the file is possible through a file input form element, but writing the file back to disk is where you'll run into trouble.
The two ways your browser can write to disk are 1) downloading a file and 2) the HTML5 filesystem API. Option #1 obviously doesn't let your application choose the destination and option #2 only works with browser-created sandbox filesystems. That restriction might not be a deal-breaker for you -- it just means that the folders that your app uses will be buried somewhere in your browser's data files.
Also, the Filesystem API is currently Chrome-only (but it is an open standard). If you want cross-platform support, maybe you can use IndexedDB. You could use localStorage, but Chrome has a hard 5MB limit, which would be terrible for a media application.