WebMessagePort class Null safety

The representation of the HTML5 message ports.

A Message port represents one endpoint of a Message Channel. In Android webview, there is no separate Message Channel object. When a message channel is created, both ports are tangled to each other and started. See InAppWebViewController.createWebMessageChannel for creating a message channel.

When a message port is first created or received via transfer, it does not have a WebMessageCallback to receive web messages. On Android, the messages are queued until a WebMessageCallback is set.

A message port should be closed when it is not used by the embedder application anymore. A closed port cannot be transferred or cannot be reopened to send messages. Close can be called multiple times.

When a port is transferred to JavaScript, it cannot be used to send or receive messages at the Dart side anymore. Different from HTML5 Spec, a port cannot be transferred if one of these has ever happened: i. a message callback was set, ii. a message was posted on it. A transferred port cannot be closed by the application, since the ownership is also transferred.

It is possible to transfer both ports of a channel to JavaScript, for example for communication between subframes.

Constructors

WebMessagePort({required int index})

Properties

hashCode int
The hash code for this object. [...]
read-only, inherited
runtimeType Type
A representation of the runtime type of the object.
read-only, inherited

Methods

close() Future<void>
Close the message port and free any resources associated with it.
noSuchMethod(Invocation invocation) → dynamic
Invoked when a non-existent method or property is accessed. [...]
inherited
postMessage(WebMessage message) Future<void>
Post a WebMessage to the entangled port.
setWebMessageCallback(WebMessageCallback? onMessage) Future<void>
Sets a callback to receive message events on the main thread.
toJson() Map<String, dynamic>
toMap() Map<String, dynamic>
toString() String
A string representation of this object. [...]
override

Operators

operator ==(Object other) bool
The equality operator. [...]
inherited