Upload files to a server through webview without using HTTPClient?

I open my website(remote) through titnaium webview url property.

In website having file upload option, when I click on upload option it is not showing any window to select the file from android device.

I want upload file. I was unable find out root cause of it.

Can any one help me out,How can I achieve it.

Here is my sample code:

index.xml

<Alloy>
    <Window class="container" id="mainWindow" platform="android" navBarHidden="false" exitOnClose="true" >
        <View class="viewContainer">
            <WebView id="webid" url="http://www.css-validator.org/#validate_by_upload" />
        </View>
    </Window>
</Alloy>

$.mainWindow.open();