Workflow for reading and writing files

The workflow for reading and writing files is as follows.

Initialize a File object that points to the path.

This is the path of the file that you want to work with (or a file that you will later create).

var file:File = File.documentsDirectory; 
file = file.resolvePath("AIR Test/testFile.txt"); 

This example uses the File.documentsDirectory property and the resolvePath() method of a File object to initialize the File object. However, there are many other ways to point a File object to a file. For more information, see Pointing a File object to a file.

Initialize a FileStream object.

Call the open() method or the openAsync() method of the FileStream object.

The method you call depends on whether you want to open the file for synchronous or asynchronous operations. Use the File object as the file parameter of the open method. For the fileMode parameter, specify a constant from the FileMode class that specifies the way in which you will use the file.

For example, the following code initializes a FileStream object that is used to create a file and overwrite any existing data:

var fileStream:FileStream = new FileStream();, FileMode.WRITE); 

For more information, see Initializing a FileStream object, and opening and closing files and FileStream open modes.

If you opened the file asynchronously (using the openAsync() method), add and set up event listeners for the FileStream object.

These event listener methods respond to events dispatched by the FileStream object in a variety of situations, such as when data is read in from the file, when I/O errors are encountered, or when the complete amount of data to be written has been written.

For details, see Asynchronous programming and the events generated by a FileStream object opened asynchronously.

Include code for reading and writing data, as needed.

There are many methods of the FileStream class related to reading and writing. (They each begin with "read" or "write".) The method you choose to use to read or write data depends on the format of the data in the target file.

For example, if the data in the target file is UTF-encoded text, you may use the readUTFBytes() and writeUTFBytes() methods. If you want to deal with the data as byte arrays, you may use the readByte(), readBytes(), writeByte(), and writeBytes() methods. For details, see Data formats, and choosing the read and write methods to use.

If you opened the file asynchronously, then be sure that enough data is available before calling a read method. For details, see The read buffer and the bytesAvailable property of a FileStream object.

Before writing to a file, if you want to check the amount of disk space available, you can check the spaceAvailable property of the File object. For more information, see Determining space available on a volume.

Call the close() method of the FileStream object when you are done working with the file.

This makes the file available to other applications.

For details, see Initializing a FileStream object, and opening and closing files.

To see a sample application that uses the FileStream class to read and write files, see the following articles at the Adobe AIR Developer Center: