How to check a file's existence in phone directory with phonegap

Question

I\'m writing an Android application with Phonegap 1.4.1 and Sencha that downloads and reads pdf files. How can I check whether the file exists in the phone directory using e

Answer 1

note:

when I get the filesystem I save it in a var under a macro pg object:

pg = {fs:{}}    // I have a "GOTFS" function... a "fail" function
pg.fs.filesystem = window.requestFileSystem(window.PERSISTENT, 0, pg.fs.GOTFS, pg.fs.fail);

so my code is pretty simple...

var fileExists = function(path, existsCallback, dontExistsCallback){
    pg.fs.fileSystem.root.getFile(path, { create: false }, existsCallback, dontExistsCallback);
        // "existsCallback" will get fileEntry as first param
    }

Answer 2

The trouble with all of the current answers is that they depend on an asynchronous callback which updates a global variable. If you are checking multiple files, there is a risk that the variable will have been set by a different callback.

A basic Javascript XMLHttpRequest check is perfect for synchronously checking the file is accessible to via Javascript.

function checkFileExists(fileName){

    var http = new XMLHttpRequest();
    http.open('HEAD', fileName, false);
    http.send(null);
    return (http.status != 404);
}

Just pass in the full path to the file and then you can reliably use:

if (checkFileExists(fullPathToFile)) {
    // File Exists
} else {
    // File Does Not Exist
}

To store the root path in a variable you can use:

var fileSystemRoot; // Global variable to hold filesystem root

window.requestFileSystem  = window.requestFileSystem || window.webkitRequestFileSystem;
window.requestFileSystem(LocalFileSystem.PERSISTENT, 0, fsSuccess, fsError);

function fsError() {
    console.log("Failed to get Filesystem");
}

function fsSuccess(fileSystem) {
    console.log("Got Filesystem: Root path " + fileSystem.root);

    // save the file to global variable for later access
    window.fileSystemRoot = fileSystem.root;
}   

Answer 3

I had the same problem. I could not manage to get Darkaico's answer to work, but with the answer of Kurt I could make it work.

Here's my code:

function checkIfFileExists(path){
    window.requestFileSystem(LocalFileSystem.PERSISTENT, 0, function(fileSystem){
        fileSystem.root.getFile(path, { create: false }, fileExists, fileDoesNotExist);
    }, getFSFail); //of requestFileSystem
}
function fileExists(fileEntry){
    alert("File " + fileEntry.fullPath + " exists!");
}
function fileDoesNotExist(){
    alert("file does not exist");
}
function getFSFail(evt) {
    console.log(evt.target.error.code);
}

Then you only need to execute like this:

checkIfFileExists("path/to/my/file.txt");

Answer 4

Kurt and Thomas gave better answers, because Darkaico's function not only checks if the file exists but also opens the file and reads it until the end.

This isn't a problem with small files, but if you check a large file then the app may crash.

Anyway, please use .getFile method - it's the best option.

Answer 5

    var fileexist;
function checkIfFileExists(path){
    window.requestFileSystem(LocalFileSystem.PERSISTENT, 0, function(fileSystem){
        fileSystem.root.getFile(path, { create: false }, fileExists, fileDoesNotExist);
    }, getFSFail); //of requestFileSystem
}
function fileExists(fileEntry){
    alert("File " + fileEntry.fullPath + " exists!");
    fileexist = true;
}
function fileDoesNotExist(){
    alert("file does not exist");
   fileexist = false;
}
function getFSFail(evt) {
    console.log(evt.target.error.code);
    fileexist=false;
}

now you can use conditions

if(fileexist=="true"){
//do something;
}
else if(fileexist=="false"){
//do something else
}

Answer 6

This code can be used for custom cases, full documentation here: download if not exist

document.addEventListener("deviceready", init, false);

//The directory to store data
var store;

//Used for status updates
var $status;

//URL of our asset
var assetURL = "https://raw.githubusercontent.com/cfjedimaster/Cordova-Examples/master/readme.md";

//File name of our important data file we didn't ship with the app
var fileName = "mydatafile.txt";

function init() {

$status = document.querySelector("#status");

$status.innerHTML = "Checking for data file.";

store = cordova.file.dataDirectory;

//Check for the file.
window.resolveLocalFileSystemURL(store + fileName, appStart, downloadAsset);

}

function downloadAsset() {
var fileTransfer = new FileTransfer();
console.log("About to start transfer");
fileTransfer.download(assetURL, store + fileName,
function(entry) {
console.log("Success!");
appStart();
},
function(err) {
console.log("Error");
console.dir(err);
});
}

//I'm only called when the file exists or has been downloaded.
function appStart() {
$status.innerHTML = "App ready!";
}