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Working with the file system
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• Moving files and directories
• Deleting files and directories (or moving them to the trash)
• Listing files and directories contained in a directory
• Creating temporary files and folders
Once a File object points to a file path, you can use it to read and write file data, using the FileStream class.
A File object can point to the path of a file or directory that does not yet exist. You can use such a File object in creating
a file or directory.
Paths of File objects
Adobe AIR 1.0 and later
Each File object has two properties that each define its path:
The File class includes static properties for pointing to standard directories on Mac OS, Windows, and Linux. These
properties include:
•
File.applicationStorageDirectory
—a storage directory unique to each installed AIR application. This
directory is an appropriate place to store dynamic application assets and user preferences. Consider storing large
amounts of data elsewhere.
•
File.applicationDirectory
—the directory where the application is installed (along with any installed assets).
On some operating systems, the application is stored in a single package file rather than a physical directory. In this
case, the contents may not be accessible using the native path. The application directory is read-only.
•
File.desktopDirectory
—the user’s desktop directory. If a platform does not define a desktop directory, another
location on the file system is used.
•
File.documentsDirectory
—the user’s documents directory. If a platform does not define a documents
directory, another location on the file system is used.
•
File.userDirectory
—the user directory. If a platform does not define a user directory, another location on the
file system is used.
Note: When a platform does not define standard locations for desktop, documents, or user directories,
File.documentsDirectory
,
File.desktopDirectory
, and
File.userDirectory
can reference the same directory.
These properties have different values on different operating systems. For example, Mac and Windows each have a
different native path to the user’s desktop directory. However, the
File.desktopDirectory
property points to an
appropriate directory path on every platform. To write applications that work well across platforms, use these
properties as the basis for referencing other directories and files used by the application. Then use the
resolvePath()
method to refine the path. For example, this code points to the preferences.xml file in the application storage directory:
Property
Description
nativePath
Specifies the platform-specific path to a file. For example, on Windows a path might be "c:\Sample
directory\test.txt" whereas on Mac OS it could be "/Sample directory/test.txt". A nativePath
property uses the backslash (\) character as the directory separator character on Windows, and it uses
the forward slash (/) character on Mac OS and Linux.
url
This may use the file URL scheme to point to a file. For example, on Windows a path might be
"file:///c:/Sample%20directory/test.txt" whereas on Mac OS it could be
"file:///Sample%20directory/test.txt". The runtime includes other special URL schemes besides file
and are described in “Supported AIR URL schemes” on page
153
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Working with the file system
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var prefsFile:File = air.File.applicationStorageDirectory;
prefsFile = prefsFile.resolvePath("preferences.xml");
Although the File class lets you point to a specific file path, doing so can lead to applications that do not work across
platforms. For example, the path C:\Documents and Settings\joe\ only works on Windows. For these reasons, it is best
to use the static properties of the File class, such as
File.documentsDirectory
.
Common directory locations
The actual native paths for these directories vary based on the operating system and computer configuration. The
paths shown in this table are typical examples. You should always use the appropriate static File class properties to refer
to these directories so that your application works correctly on any platform. In an actual AIR application, the values
for
applicationID
and
filename
shown in the table are taken from the application descriptor. If you specify a
publisher ID in the application descriptor, then the publisher ID is appended to the application ID in these paths. The
value for
userName
is the account name of the installing user.
Pointing a File object to a directory
Adobe AIR 1.0 and later
There are different ways to set a File object to point to a directory.
Platform
Directory type
Typical file system location
Linux
Application
/opt/filename/share
Application-storage
/home/userName/.appdata/applicationID/Local Store
Desktop
/home/userName/Desktop
Documents
/home/userName/Documents
Temporary
/tmp/FlashTmp.randomString
User
/home/userName
Mac
Application
/Applications/filename.app/Contents/Resources
Application-storage
/Users/userName/Library/Preferences/applicationID/Local Store
Desktop
/Users/userName/Desktop
Documents
/Users/userName/Documents
Temporary
/private/var/folders/JY/randomString/TemporaryItems/FlashTmp
User
/Users/userName
Windows Application
C:\Program Files\filename
Application-storage
C:\Documents and
settings\userName\ApplicationData\applicationID\Local Store
Desktop
C:\Documents and settings\userName\Desktop
Documents
C:\Documents and settings\userName\My Documents
Temporary
C:\Documents and settings\userName\Local
Settings\Temp\randomString.tmp
User
C:\Documents and settings\userName
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Working with the file system
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Pointing to the user’s home directory
Adobe AIR 1.0 and later
You can point a File object to the user’s home directory. The following code sets a File object to point to an AIR Test
subdirectory of the home directory:
var file = air.File.userDirectory.resolvePath("AIR Test");
Pointing to the user’s documents directory
Adobe AIR 1.0 and later
You can point a File object to the user's documents directory. The following code sets a File object to point to an AIR
Test subdirectory of the documents directory:
var file = air.File.documentsDirectory.resolvePath("AIR Test");
Pointing to the desktop directory
Adobe AIR 1.0 and later
You can point a File object to the desktop. The following code sets a File object to point to an AIR Test subdirectory
of the desktop:
var file = air.File.desktopDirectory.resolvePath("AIR Test");
Pointing to the application storage directory
Adobe AIR 1.0 and later
You can point a File object to the application storage directory. For every AIR application, there is a unique associated
path that defines the application storage directory. This directory is unique to each application and user. You can use
this directory to store user-specific, application-specific data (such as user data or preferences files). For example, the
following code points a File object to a preferences file, prefs.xml, contained in the application storage directory:
var file = air.File.applicationStorageDirectory;
file = file.resolvePath("prefs.xml");
The application storage directory location is typically based on the user name and the application ID. The following
file system locations are given here to help you debug your application. You should always use the
File.applicationStorage
property or
app-storage:
URI scheme to resolve files in this directory:
• On Mac OS—In:
/Users/
user name
/Library/Preferences/
applicationID
/Local Store/
For example:
/Users/babbage/Library/Preferences/com.example.TestApp/Local Store
• On Windows—In the documents and Settings directory, in:
C:\Documents and Settings\user name
\Application Data\
applicationID
\Local Store\
For example:
C:\Documents and Settings\babbage\Application Data\com.example.TestApp\Local Store
• On Linux—In:
/home/
user name
/.appdata/
applicationID
/Local Store/
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Working with the file system
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For example:
/home/babbage/.appdata/com.example.TestApp/Local Store
Note: If an application has a publisher ID, then the publisher ID is also used as part of the path to the application storage
directory.
The URL (and
url
property) for a File object created with
File.applicationStorageDirectory
uses the
app-
storage
URL scheme (see “Supported AIR URL schemes” on page 153), as in the following:
var dir = air.File.applicationStorageDirectory;
dir = dir.resolvePath("prefs.xml");
air.trace(dir.url); // app-storage:/preferences
Pointing to the application directory
Adobe AIR 1.0 and later
You can point a File object to the directory in which the application was installed, known as the application directory.
You can reference this directory using the
File.applicationDirectory
property. You can use this directory to
examine the application descriptor file or other resources installed with the application. For example, the following
code points a File object to a directory named images in the application directory:
var dir = air.File.applicationDirectory;
dir = dir.resolvePath("images");
The URL (and
url
property) for a File object created with
File.applicationDirectory
uses the
app
URL scheme
(see “Supported AIR URL schemes” on page 153), as in the following:
var dir = air.File.applicationDirectory;
dir = dir.resolvePath("images");
air.trace(dir.url); // app:/images
Pointing to the file system root
Adobe AIR 1.0 and later
The
File.getRootDirectories()
method lists all root volumes, such as C: and mounted volumes, on a Windows
computer. On Mac OS and Linux, this method always returns the unique root directory for the machine (the "/"
directory). The
StorageVolumeInfo.getStorageVolumes()
method provides more detailed information on
mounted storage volumes (see “Working with storage volumes” on page 163).
Pointing to an explicit directory
Adobe AIR 1.0 and later
You can point the File object to an explicit directory by setting the
nativePath
property of the File object, as in the
following example (on Windows):
var file = new air.File();
file.nativePath = "C:\\AIR Test";
Important: Pointing to an explicit path this way can lead to code that does not work across platforms. For example,
the previous example only works on Windows. You can use the static properties of the File object, such as
File.applicationStorageDirectory
, to locate a directory that works cross-platform. Then use the
resolvePath()
method (see the next section) to navigate to a relative path.
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Navigating to relative paths
Adobe AIR 1.0 and later
You can use the
resolvePath()
method to obtain a path relative to another given path. For example, the following
code sets a File object to point to an "AIR Test" subdirectory of the user's home directory:
var file = air.File.userDirectory;
file = file.resolvePath("AIR Test");
You can also use the
url
property of a File object to point it to a directory based on a URL string, as in the following:
var urlStr = "file:///C:/AIR Test/";
var file = new air.File()
file.url = urlStr;
For more information, see “Modifying File paths” on page 153.
Letting the user browse to select a directory
Adobe AIR 1.0 and later
The File class includes the
browseForDirectory()
method, which presents a system dialog box in which the user can
select a directory to assign to the object. The
browseForDirectory()
method is asynchronous. The File object
dispatches a
select
event if the user selects a directory and clicks the Open button, or it dispatches a
cancel
event if
the user clicks the Cancel button.
For example, the following code lets the user select a directory and outputs the directory path upon selection:
var file = new air.File();
file.addEventListener(air.Event.SELECT, dirSelected);
file.browseForDirectory("Select a directory");
function dirSelected(event) {
alert(file.nativePath);
}
Pointing to the directory from which the application was invoked
Adobe AIR 1.0 and later
You can get the directory location from which an application is invoked, by checking the
currentDirectory
property
of the InvokeEvent object dispatched when the application is invoked. For details, see “Capturing command line
arguments” on page 297.
Pointing a File object to a file
Adobe AIR 1.0 and later
There are different ways to set the file to which a File object points.
Pointing to an explicit file path
Adobe AIR 1.0 and later
Important: Pointing to an explicit path can lead to code that does not work across platforms. For example, the path
C:/foo.txt only works on Windows. You can use the static properties of the File object, such as
File.applicationStorageDirectory
, to locate a directory that works cross-platform. Then use the
resolvePath()
method (see “Modifying File paths” on page 153) to navigate to a relative path.
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You can use the
url
property of a File object to point it to a file or directory based on a URL string, as in the following:
var urlStr = "file:///C:/AIR Test/test.txt";
var file = new air.File()
file.url = urlStr;
You can also pass the URL to the
File()
constructor function, as in the following:
var urlStr = "file:///C:/AIR Test/test.txt";
var file = new air.File(urlStr);
The
url
property always returns the URI-encoded version of the URL (for example, blank spaces are replaced with
"%20
):
file.url = "file:///c:/AIR Test";
alert(file.url); // file:///c:/AIR%20Test
You can also use the
nativePath
property of a File object to set an explicit path. For example, the following code, when
run on a Windows computer, sets a File object to the test.txt file in the AIR Test subdirectory of the C: drive:
var file = new air.File();
file.nativePath = "C:/AIR Test/test.txt";
You can also pass this path to the
File()
constructor function, as in the following:
var file = new air.File("C:/AIR Test/test.txt");
Use the forward slash (/) character as the path delimiter for the
nativePath
property. On Windows, you can also use
the backslash (\) character, but doing so leads to applications that do not work across platforms.
For more information, see “Modifying File paths” on page 153.
Enumerating files in a directory
Adobe AIR 1.0 and later
You can use the
getDirectoryListing()
method of a File object to get an array of File objects pointing to files and
subdirectories at the root level of a directory. For more information, see “Enumerating directories” on page 159.
Letting the user browse to select a file
Adobe AIR 1.0 and later
The File class includes the following methods that present a system dialog box in which the user can select a file to
assign to the object:
•
browseForOpen()
•
browseForSave()
•
browseForOpenMultiple()
These methods are each asynchronous. The
browseForOpen()
and
browseForSave()
methods dispatch the select
event when the user selects a file (or a target path, in the case of browseForSave()). With the
browseForOpen()
and
browseForSave()
methods, upon selection the target File object points to the selected files. The
browseForOpenMultiple
() method dispatches a
selectMultiple
event when the user selects files. The
selectMultiple
event is of type FileListEvent, which has a
files
property that is an array of File objects (pointing
to the selected files).
For example, the following code presents the user with an “Open” dialog box in which the user can select a file:
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Working with the file system
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var fileToOpen = air.File.documentsDirectory;
selectTextFile(fileToOpen);
function selectTextFile(root)
{
var txtFilter = new air.FileFilter("Text", "*.as;*.css;*.html;*.txt;*.xml");
root.browseForOpen("Open", new window.runtime.Array(txtFilter));
root.addEventListener(air.Event.SELECT, fileSelected);
}
function fileSelected(event)
{
trace(fileToOpen.nativePath);
}
If the application has another browser dialog box open when you call a browse method, the runtime throws an Error
exception.
Modifying File paths
Adobe AIR 1.0 and later
You can also modify the path of an existing File object by calling the
resolvePath()
method or by modifying the
nativePath
or
url
property of the object, as in the following examples (on Windows):
file1 = air.File.documentsDirectory;
file1 = file1.resolvePath("AIR Test");
alert(file1.nativePath); // C:\Documents and Settings\userName\My Documents\AIR Test
var file2 = air.File.documentsDirectory;
file2 = file2.resolvePath("..");
alert(file2.nativePath); // C:\Documents and Settings\userName
var file3 = air.File.documentsDirectory;
file3.nativePath += "/subdirectory";
alert(file3.nativePath); // C:\Documents and Settings\userName\My Documents\subdirectory
var file4 = new air.File();
file4.url = "file:///c:/AIR Test/test.txt";
alert(file4.nativePath); // C:\AIR Test\test.txt
When using the
nativePath
property, use the forward slash (/) character as the directory separator character. On
Windows, you can use the backslash (\) character as well, but you should not do so, as it leads to code that does not
work cross-platform.
Supported AIR URL schemes
Adobe AIR 1.0 and later
In AIR, you can use any of the following URL schemes in defining the
url
property of a File object:
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Working with the file system
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Finding the relative path between two files
Adobe AIR 1.0 and later
You can use the
getRelativePath()
method to find the relative path between two files:
var file1 = air.File.documentsDirectory
file1 = file1.resolvePath("AIR Test");
var file2 = air.File.documentsDirectory
file2 = file2.resolvePath("AIR Test/bob/test.txt");
alert(file1.getRelativePath(file2)); // bob/test.txt
The second parameter of the
getRelativePath()
method, the
useDotDot
parameter, allows for
..
syntax to be
returned in results, to indicate parent directories:
var file1 = air.File.documentsDirectory;
file1 = file1.resolvePath("AIR Test");
var file2 = air.File.documentsDirectory;
file2 = file2.resolvePath("AIR Test/bob/test.txt");
var file3 = air.File.documentsDirectory;
file3 = file3.resolvePath("AIR Test/susan/test.txt");
alert(file2.getRelativePath(file1, true)); // ../..
alert(file3.getRelativePath(file2, true)); // ../../bob/test.txt
Obtaining canonical versions of file names
Adobe AIR 1.0 and later
File and path names are not case sensitive on Windows and Mac OS. In the following, two File objects point to the
same file:
File.documentsDirectory.resolvePath("test.txt");
File.documentsDirectory.resolvePath("TeSt.TxT");
However, documents and directory names do include capitalization. For example, the following assumes that there is
a folder named AIR Test in the documents directory, as in the following examples:
URL scheme
Description
file
Use to specify a path relative to the root of the file system. For example:
file:///c:/AIR Test/test.txt
The URL standard specifies that a file URL takes the form file://<host>/<path>. As a special
case,<host> can be the empty string, which is interpreted as "the machine from which the URL is being
interpreted." For this reason, file URLs often have three slashes (///).
app
Use to specify a path relative to the root directory of the installed application (the directory that contains
the application.xml file for the installed application). For example, the following path points to an images
subdirectory of the directory of the installed application:
app:/images
app-storage
Use to specify a path relative to the application store directory. For each installed application, AIR defines
a unique application store directory, which is a useful place to store data specific to that application. For
example, the following path points to a prefs.xml file in a settings subdirectory of the application store
directory:
app-storage:/settings/prefs.xml
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