com.vaadin.client
Class ResourceLoader

java.lang.Object
  com.vaadin.client.ResourceLoader

public class ResourceLoader
extends java.lang.Object

ResourceLoader lets you dynamically include external scripts and styles on the page and lets you know when the resource has been loaded. You can also preload resources, allowing them to get cached by the browser without being evaluated. This enables downloading multiple resources at once while still controlling in which order e.g. scripts are executed.

Since:

7.0.0

Author:

Vaadin Ltd

Nested Class Summary

static class	ResourceLoader.ResourceLoadEvent Event fired when a resource has been loaded.
static interface	ResourceLoader.ResourceLoadListener Event listener that gets notified when a resource has been loaded

Constructor Summary

protected

ResourceLoader() Creates a new resource loader.

Method Summary

static void	addOnloadHandler(Element element, ResourceLoader.ResourceLoadListener listener, ResourceLoader.ResourceLoadEvent event) Adds an onload listener to the given element, which should be a link or a script tag.
static ResourceLoader	get() Returns the default ResourceLoader
void	loadScript(java.lang.String scriptUrl, ResourceLoader.ResourceLoadListener resourceLoadListener) Load a script and notify a listener when the script is loaded.
void	loadScript(java.lang.String scriptUrl, ResourceLoader.ResourceLoadListener resourceLoadListener, boolean async) Load a script and notify a listener when the script is loaded.
void	loadStylesheet(java.lang.String stylesheetUrl, ResourceLoader.ResourceLoadListener resourceLoadListener) Load a stylesheet and notify a listener when the stylesheet is loaded.
void	preloadResource(java.lang.String url, ResourceLoader.ResourceLoadListener resourceLoadListener) Download a resource and notify a listener when the resource is loaded without attempting to interpret the resource.
static boolean	supportsInOrderScriptExecution() The current browser supports script.async='false' for maintaining execution order for dynamically-added scripts.

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Constructor Detail

ResourceLoader

protected ResourceLoader()

Creates a new resource loader. You should generally not create you own resource loader, but instead use get() to get an instance.

Method Detail

get

public static ResourceLoader get()

Returns the default ResourceLoader

Returns:

the default ResourceLoader

loadScript

public void loadScript(java.lang.String scriptUrl,
                       ResourceLoader.ResourceLoadListener resourceLoadListener)

Load a script and notify a listener when the script is loaded. Calling this method when the script is currently loading or already loaded doesn't cause the script to be loaded again, but the listener will still be notified when appropriate.

Parameters:

scriptUrl - the url of the script to load

resourceLoadListener - the listener that will get notified when the script is loaded

loadScript

public void loadScript(java.lang.String scriptUrl,
                       ResourceLoader.ResourceLoadListener resourceLoadListener,
                       boolean async)

Load a script and notify a listener when the script is loaded. Calling this method when the script is currently loading or already loaded doesn't cause the script to be loaded again, but the listener will still be notified when appropriate.

Parameters:

scriptUrl - url of script to load

resourceLoadListener - listener to notify when script is loaded

async - What mode the script.async attribute should be set to

Since:

7.2.4

supportsInOrderScriptExecution

public static boolean supportsInOrderScriptExecution()

The current browser supports script.async='false' for maintaining execution order for dynamically-added scripts.

Returns:

Browser supports script.async='false'

Since:

7.2.4

preloadResource

public void preloadResource(java.lang.String url,
                            ResourceLoader.ResourceLoadListener resourceLoadListener)

Download a resource and notify a listener when the resource is loaded without attempting to interpret the resource. When a resource has been preloaded, it will be present in the browser's cache (provided the HTTP headers allow caching), making a subsequent load operation complete without having to wait for the resource to be downloaded again. Calling this method when the resource is currently loading, currently preloading, already preloaded or already loaded doesn't cause the resource to be preloaded again, but the listener will still be notified when appropriate.

Parameters:

url - the url of the resource to preload

resourceLoadListener - the listener that will get notified when the resource is preloaded

addOnloadHandler

public static void addOnloadHandler(Element element,
                                    ResourceLoader.ResourceLoadListener listener,
                                    ResourceLoader.ResourceLoadEvent event)

Adds an onload listener to the given element, which should be a link or a script tag. The listener is called whenever loading is complete or an error occurred.

Parameters:

element - the element to attach a listener to

listener - the listener to call

event - the event passed to the listener

Since:

7.3

loadStylesheet

public void loadStylesheet(java.lang.String stylesheetUrl,
                           ResourceLoader.ResourceLoadListener resourceLoadListener)

Load a stylesheet and notify a listener when the stylesheet is loaded. Calling this method when the stylesheet is currently loading or already loaded doesn't cause the stylesheet to be loaded again, but the listener will still be notified when appropriate.

Parameters:

stylesheetUrl - the url of the stylesheet to load

resourceLoadListener - the listener that will get notified when the stylesheet is loaded