使用纯Javascript在Android上使用mosync / phonegap从SD卡读取文件

Question

I know this question was asked many times before but I cannot figure it out anyhow. I'm able to write a text file to a directory on the sdcard (android 4), but no way to read it back again, using this code:

function get_file () {  
window.requestFileSystem(LocalFileSystem.PERSISTENT, 0, getFilesystem, fail);
}   
function getFilesystem(fs) {
alert("getFilesystem -> backup.txt");  // OK !
// alert("filesystem.name: "+fileSystem.name);  // = persistent
// alert("filesystem.root.name: "+fileSystem.root.name);  // = long number
    // 
fs.root.getFile("../../../../../../sdcard/test/backup.txt", {create: false, exclusive: false}, 
    function(fileEntry) {
      alert(fileEntry.fullPath); // shows that my path is appended to "data/.."
      fileEntry.file(function(file) {
      var reader = new FileReader();
      reader.onloadend = function(evt) {
        alert(+evt.target.result);  // NOT SHOWING !        
          };
        reader.readAsText(file);
    }, fail);
}, fail);
}

I wrote the file using the writer function into the directory sdcard/test using this sequence of ../ - this is an ugly code but working !

But fs.root.getFile does not work in the same way - the fullPath information it returns shows that my path given is APPENDED to "/data/data/com.appname/files" but does not replace it !

The onloadend function obviously isn't working since i never got the alert message, neither did I get an error message. Change of path to "file:///sdcard/test" or "sdcard/test" has no effect either.

Any help is highly appreciated - thank you in advance ! Chris

Answer 1

Please refer PHONEGAP DOCUMENT

From this you will get working example of getting file from sdcard. And if you have problem in downloading a file please refer LINK

I think in Place of "/sdcard/backup.txt" try to use only "backup.txt".

It seems to work fine.

PhoneGap takes care of the details of the path ,also works with directories.

Answer 2

So finally I could figure it out: To access the directory (on Android 4.0, Samsung Note 8) I had to go up literally all directories from /data/data/com.app-name/files/apps/(random no.)/ back to the sdcard by choosing:

 fs.root.getFile("../../../../../../sdcard/test/backup.txt", ...

in mosync Reload client.

"Compiling" the app with mosync apk would require only 4 times "../" because the file hierarchy there is lower than in the Reload Client. In any case have to check in file explorer (root access required). Different from that is when you compile in the cloud with phonegap - then indeed the root path is sdcard ! You then cannot go to the data directory as far as I could find out.

This path works with write and read in mosync - my mistake was that I had line break character "\\n" inside the text file. In this case I could write it, but the reader stops without error message.

Hope that will help someone else as well !

Chris