nsIWebProgress 编辑

The nsIWebProgress interface is used to add or remove nsIWebProgressListener instances to observe the loading of asynchronous requests (usually in the context of a DOM window).

nsIWebProgress instances may be arranged in a parent-child configuration, corresponding to the parent-child configuration of their respective DOM windows. However, in some cases a nsIWebProgress instance may not have an associated DOM window. The parent-child relationship of nsIWebProgress instances is not made explicit by this interface, but the relationship may exist in some implementations.

A nsIWebProgressListener instance receives notifications for the nsIWebProgress instance to which it added itself, and it may also receive notifications from any nsIWebProgress instances that are children of that nsIWebProgress instance.

Inherits from: nsISupports

Method overview

Attributes

Constants

The following flags may be combined to form the aNotifyMask parameter for the addProgressListener() method. They limit the set of events that are delivered to an nsIWebProgressListener instance.

These flags indicate the state transistions to observe, corresponding to nsIWebProgressListener.onStateChange().

These flags indicate the other events to observe, corresponding to the other four methods defined on nsIWebProgressListener.

Methods

addProgressListener()

Registers a listener to receive web progress events.

void addProgressListener(
  in nsIWebProgressListener aListener,
  in unsigned long aNotifyMask
);

Parameters

aListener

The listener interface to be called when a progress event occurs. This object must also implement nsISupportsWeakReference.

aNotifyMask

The types of notifications to receive.

Exceptions thrown

NS_ERROR_INVALID_ARG

Indicates that aListener was either null or that it does not support weak references.

NS_ERROR_FAILURE

Indicates that aListener was already registered.

removeProgressListener()

Removes a previously registered listener of progress events.

void removeProgressListener(
  in nsIWebProgressListener aListener
);

Parameters

aListener

The listener interface previously registered with a call to addProgressListener().

Exceptions thrown

NS_ERROR_FAILURE

Indicates that aListener was not registered.