/*
* Copyright (C) 2015 The Android Open Source Project
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package android.webkit;
import android.annotation.SystemApi;
import android.os.Handler;
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 WebView.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.
/**
* <p>The Java representation of the
* <a href="https://html.spec.whatwg.org/multipage/comms.html#messageport">
* HTML5 message ports.</a>
*
* <p>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 {@link WebView#createWebMessageChannel}
* for creating a message channel.
*
* <p>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.
*
* <p>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.
*
* <p>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.
*
* <p>It is possible to transfer both ports of a channel to JS, for example for
* communication between subframes.
*/
public abstract class WebMessagePort {
The listener for handling MessagePort events. The message callback methods are called on the main thread. If the embedder application wants to receive the messages on a different thread, it can do this by passing a Handler in WebMessagePort.setWebMessageCallback(WebMessageCallback, Handler). In the latter case, the application should be extra careful for thread safety since WebMessagePort methods should be called on main thread. /**
* The listener for handling MessagePort events. The message callback
* methods are called on the main thread. If the embedder application
* wants to receive the messages on a different thread, it can do this
* by passing a Handler in
* {@link WebMessagePort#setWebMessageCallback(WebMessageCallback, Handler)}.
* In the latter case, the application should be extra careful for thread safety
* since WebMessagePort methods should be called on main thread.
*/
public static abstract class WebMessageCallback {
Message callback for receiving onMessage events.
Params: - port – the WebMessagePort that the message is destined for
- message – the message from the entangled port.
/**
* Message callback for receiving onMessage events.
*
* @param port the WebMessagePort that the message is destined for
* @param message the message from the entangled port.
*/
public void onMessage(WebMessagePort port, WebMessage message) { }
}
Constructor.
@hide
/**
* Constructor.
* @hide
*/
@SystemApi
public WebMessagePort() { }
Post a WebMessage to the entangled port.
Params: - message – the message from Java to JS.
Throws: - IllegalStateException – If message port is already transferred or closed.
/**
* Post a WebMessage to the entangled port.
*
* @param message the message from Java to JS.
*
* @throws IllegalStateException If message port is already transferred or closed.
*/
public abstract void postMessage(WebMessage message);
Close the message port and free any resources associated with it.
/**
* Close the message port and free any resources associated with it.
*/
public abstract void close();
Sets a callback to receive message events on the main thread.
Params: - callback – the message callback.
/**
* Sets a callback to receive message events on the main thread.
*
* @param callback the message callback.
*/
public abstract void setWebMessageCallback(WebMessageCallback callback);
Sets a callback to receive message events on the handler that is provided
by the application.
Params: - callback – the message callback.
- handler – the handler to receive the message messages.
/**
* Sets a callback to receive message events on the handler that is provided
* by the application.
*
* @param callback the message callback.
* @param handler the handler to receive the message messages.
*/
public abstract void setWebMessageCallback(WebMessageCallback callback, Handler handler);
}