Read a File in PhoneGap

In the last article we have discussed the Flags and the LocalFileSystem in PhoneGap. To read a file, we require a FileReader object. TheFileReader object is a way to read a file from the device's FileSystem. A file can be read as text, or as a Base64-encoded data string.

This object has the following properties.

• readyState : This is one of the three states (EMPTY, LOADING OR DONE), the reader can be in.
• result : This is used to get the content of the file that has been read.
• error : This is used for an object containing errors.
• onloadstart : This is called when we start reading.
• onload : This is called when the reading has successfully completed.
• onabort : This is called when the read has been aborted.
• onerror : This is called when the read has got failed.
• onloaded : This is called when the request has completed (either in success or failure).

This object has the following methods:

• abort.
• readAsDataUrl.
• readAsText.

abort

By using the abort() method, we can stop reading a file from the FileSystem as shown in the following code:

function success(file) {
var reader_file = new FileReader();
reader_file.onloadend = function (event) {
alert("read success");
alert(event.target.result);
};
reader_file.readAsText(file);
reader_file.abort();
}
function fail(error) {
console.log(error.code);
}
entry.file(success, fail);

readAsDataUrl.

Using the readAsDataUrl() method, we can read a file and return the data as Base64-encoded data, which is ideal for images and other binary files as shown in the following code:

function success(file) {
var file_reader = new FileReader();
file_reader .onloadend = function(evt) {
alert("read success");
alert(evt.target.result);
};
file_reader .readAsDataURL(file);
}
function fail(evt) {
console.log(error.code);
}
entry.file(success, fail);

ReadAsText

By using the ReadAsText() method, we can also read a file and return text, which is most suitable for TXT file as shown in the following code:

function success(file) {
var file_reader = new FileReader();
file_reader .onloadend = function(evt) {
alert("read success");
alert(evt.target.result);
};
file_reader .readAsDataURL(file);
}
function fail(evt) {
console.log(error.code);
}
entry.file(success, fail);

FULL EXAMPLE