chrome.fileBrowserHandler

Description: Use the chrome.fileBrowserHandler API to extend the Chrome OS file browser. For example, you can use this API to enable users to upload files to your website.
Availability: Since Chrome 14.
Permissions: "fileBrowserHandler"

Important: This API works only on Chrome OS.

The Chrome OS file browser comes up when the user either presses Alt+Shift+M or connects an external storage device, such as an SD card, USB key, external drive, or digital camera. Besides showing the files on external devices, the file browser can also display files that the user has previously saved to the system.

When the user selects one or more files, the file browser adds buttons representing the valid handlers for those files. For example, in the following screenshot, selecting a file with a ".jpg" suffix results in an "Upload to Picasa" button that the user can click.

file browser screenshot

Manifest

You must declare the "fileBrowserHandler" permission in the extension manifest, and you must use the "file_browser_handlers" field to register the extension as a handler of at least one file type. You should also provide a 16x16 icon to be displayed on the button. For example:

      {
        "name": "My extension",
        ...
        "file_browser_handlers": [
          {
            "id": "upload",
            "default_title": "Save to Gallery", // What the button will display
            "file_filters": [
              "filesystem:*.jpg", // To match all files, use "filesystem:*.*"
              "filesystem:*.jpeg",
              "filesystem:*.png"
            ]
          }
        ],
        "permissions" : [
          "fileBrowserHandler"
        ],
        "icons": { "16": "icon16.png",
                   "48": "icon48.png",
                  "128": "icon128.png" },
        ...
      }
      

Note: You can specify locale-specific strings for the value of "default_title". See Internationalization (i18n) for details.

Implementing a file browser handler

To use this API, you must implement a function that handles the onExecute event of chrome.fileBrowserHandler. Your function will be called whenever the user clicks the button that represents your file browser handler. In your function, use the HTML5 FileSystem API to get access to the file contents. Here is an example:

      chrome.fileBrowserHandler.onExecute.addListener(function(id, details) {
        if (id == 'upload') {
          var fileEntries = details.entries;
          for (var i = 0, entry; entry = fileEntries[i]; ++i) {
            entry.file(function(file) {
              // send file somewhere
            });
          }
        }
      });
      

Your event handler is passed two arguments:

id
The "id" value from the manifest file. If your extension implements multiple handlers, you can check the id value to see which handler has been triggered.
details
An object describing the event. You can get the file or files that the user has selected from the entries field of this object, which is an array of FileSystem Entry objects.

Summary

Types
FileHandlerExecuteEventDetails
Methods
selectFile chrome.fileBrowserHandler.selectFile(object selectionParams, function callback)
Events
onExecute

Types

FileHandlerExecuteEventDetails

Event details payload for fileBrowserHandler.onExecute event.
properties
array of any entries

Array of Entry instances representing files that are targets of this action (selected in ChromeOS file browser).

integer (optional) tab_id

The ID of the tab that raised this event. Tab IDs are unique within a browser session.

Methods

selectFile

chrome.fileBrowserHandler.selectFile(object selectionParams, function callback)

Since Chrome 21.

Prompts user to select file path under which file should be saved. When the file is selected, file access permission required to use the file (read, write and create) are granted to the caller. The file will not actually get created during the function call, so function caller must ensure its existence before using it. The function has to be invoked with a user gesture.

Parameters
object selectionParams

Parameters that will be used while selecting the file.

string suggestedName

Suggested name for the file.

array of string (optional) allowedFileExtensions

Since Chrome 23.

List of file extensions that the selected file can have. The list is also used to specify what files to be shown in the select file dialog. Files with the listed extensions are only shown in the dialog. Extensions should not include the leading '.'. Example: ['jpg', 'png']

function callback

Function called upon completion.

The callback parameter should be a function that looks like this:

function(object result) {...};
object result

Result of the method.

boolean success

Whether the file has been selected.

object (optional) entry

Selected file entry. It will be null if a file hasn't been selected.

Events

onExecute

Fired when file system action is executed from ChromeOS file browser.

addListener

chrome.fileBrowserHandler.onExecute.addListener(function callback)
Parameters
function callback

The callback parameter should be a function that looks like this:

function(string id, FileHandlerExecuteEventDetails details) {...};
string id

File browser action id as specified in the listener component's manifest.

FileHandlerExecuteEventDetails details

File handler execute event details.