YUI Library Examples: Uploader Control: Advanced Uploader Example With Additional POST Variables and Server Data Return

Advanced Uploader Example With Additional POST Variables and Server Data Return

In this example, we allow the user to select a single image or video, and upload it to the server, while tracking progress on the upload. The user can specify custom values for a couple POST vars sent along with the upload, and also get the response from the server (in this case, a simple echo of POSTed variables). Because of security changes in Flash Player 10, the UI for invoking the "Browse" dialog has to be contained within the Flash player. In this example, the Flash player is rendered as a transparent overlay on top of a custom HTML-based UI. The Uploader running in the Flash player dispatches necessary mouse events to the DOM to make visual changes to the overlaid UI.

For starters, let's define the necessary UI styles. We will use regular text links as the UI, and switch their background color when the mouse hovers over them.

Next, we'll place the UI elements on the page. Notice that the selectFilesLink div is overlaid by the uploaderOverlay div. uploaderOverlay is where we'll place the transparent Flash UI layer, that will dispatch various mouse events, based on which we will be able to change the appearance of the UI below.

We are also placing a few input fields for the user to specify two custom POST variables that will be sent along with the file upload, as well as a text field to report back on the upload progress, and a text area to display the response received from the server:

Once the DOM is ready, we can size our container for the transparent UI to the link below it. The following code accomplishes that:

Now we can instantiate the uploader and place it in the container div.

We add handler functions to the uploader events. Note that methods on the uploader should not be called until the "contentReady" event has fired:

These handlers are called when the mouse rolls over and out of the uploader, respectively. They modify the appearance of the UI layer under the transparent Flash layer to match the behavior of the rest of the UI.

Once the contentReady event has fired, we can configure the uploader. In this case, we call a function that turns on logging (so that everything we do is reflected in the YUI logger, as well as in the Flash trace file), disallow multiple file selection, and define a set of filters on the file extensions that the user can choose.

The upload function is called when "Upload Files" link is clicked. It checks whether the fileID variable has been populated, and if so, instructs the upload to send that file to the specified location. Note that we are overriding the default value for the variable submission method (default is "GET", we are making it "POST"). We are also passing an object with two POST variables to submit along with the upload; in this case, their values come from input fields that were presented to the user.

The fileID variable that the upload() function checked for needs to be defined and populated. This happens in the fileSelect event handler, that looks at the list of files passed in the event (they are indexed by the file id, rather than by numerical index, and so an iterator is necessary). Since we know the list will contain only one file, we can simply assign that file id to the fileID variable.

We also update the progress report text field with the information on the selected file

Update the progress report when the upload starts:

Update the progress report on upload progress events:

Update the progress report on upload complete event:

Update the progress report in case of an upload error:

When a response is received from the server, display it in the provided text area:

YUI Logger Output:

Uploader Control Examples:

More Uploader Control Resources:

All YUI 2.x users should review the YUI 2.8.2 security bulletin, which discusses a vulnerability present in YUI 2.4.0-2.8.1.