WebMessagePortCompat
abstract class WebMessagePortCompat
| kotlin.Any | |
| ↳ | androidx.webkit.WebMessagePortCompat |
The Java 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, and then returned in a MessagePort array, see WebViewCompat#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. 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 JS, it cannot be used to send or receive messages at the Java 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 JS, for example for communication between subframes.
Summary
Nested classes |
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| abstract |
The listener for handling MessagePort events. |
Public methods |
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| abstract Unit |
close()Close the message port and free any resources associated with it. |
| abstract Unit |
postMessage(@NonNull message: WebMessageCompat)Post a WebMessage to the entangled port. |
| abstract Unit |
setWebMessageCallback(@NonNull callback: WebMessagePortCompat.WebMessageCallbackCompat)Sets a callback to receive message events on the main thread. |
| abstract Unit |
setWebMessageCallback(@Nullable handler: Handler?, @NonNull callback: WebMessagePortCompat.WebMessageCallbackCompat)Sets a callback to receive message events on the handler that is provided by the application. |
Public methods
close
abstract fun close(): Unit
Close the message port and free any resources associated with it.
This method should only be called if WebViewFeature#isFeatureSupported(String) returns true for WebViewFeature#WEB_MESSAGE_PORT_CLOSE.
postMessage
abstract fun postMessage(@NonNull message: WebMessageCompat): Unit
Post a WebMessage to the entangled port.
This method should only be called if WebViewFeature#isFeatureSupported(String) returns true for WebViewFeature#WEB_MESSAGE_PORT_POST_MESSAGE.
| Parameters | |
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message |
WebMessageCompat: the message from Java to JS. |
| Exceptions | |
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IllegalStateException |
If message port is already transferred or closed. |
setWebMessageCallback
abstract fun setWebMessageCallback(@NonNull callback: WebMessagePortCompat.WebMessageCallbackCompat): Unit
Sets a callback to receive message events on the main thread.
This method should only be called if WebViewFeature#isFeatureSupported(String) returns true for WebViewFeature#WEB_MESSAGE_PORT_SET_MESSAGE_CALLBACK.
| Parameters | |
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callback |
WebMessagePortCompat.WebMessageCallbackCompat: the message callback. |
setWebMessageCallback
abstract fun setWebMessageCallback(@Nullable handler: Handler?, @NonNull callback: WebMessagePortCompat.WebMessageCallbackCompat): Unit
Sets a callback to receive message events on the handler that is provided by the application. If the handler is null the message events are received on the main thread.
This method should only be called if WebViewFeature#isFeatureSupported(String) returns true for WebViewFeature#WEB_MESSAGE_PORT_SET_MESSAGE_CALLBACK.
| Parameters | |
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handler |
Handler?: the handler to receive the message events. |
callback |
Handler?: the message callback. |