Use this event to listen for messages from another extension.
To send a message which will be received by the
onMessageExternal
listener, use
runtime.sendMessage()
, passing the ID of the recipient in the
extensionId
参数。
Along with the message itself, the listener is passed:
sender
object giving details about the message sender
sendResponse
function which it can use to send a response back to the sender.
This API can't be used in a content script.
browser.runtime.onMessageExternal.addListener()
browser.runtime.onMessageExternal.removeListener(listener)
browser.runtime.onMessageExternal.hasListener(listener)
Events have three functions:
addListener(callback)
Adds a listener to this event.
removeListener(listener)
Stop listening to this event. The
listener
argument is the listener to remove.
hasListener(listener)
Checks whether a
listener
is registered for this event. Returns
true
if it is listening,
false
否则。
function
A callback function that will be called when this event occurs. The function will be passed the following arguments:
message
对象
. The message itself. This is a JSON-ifiable object.
sender
A
runtime.MessageSender
object representing the sender of the message.
sendResponse
A function to call, at most once, to send a response to the message. The function takes a single argument, which may be any JSON-ifiable object. This argument is passed back to the message sender.
If you have more than one
onMessageExternal
listener in the same document, then only one may send a response.
To send a response synchronously, call
sendResponse
before the listener function returns. To send a response asynchronously:
sendResponse
argument and return
true
from the listener function. You will then be able to call
sendResponse
after the listener function has returned.
Promise
from the listener function and resolve the promise when the response is ready.
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In this example the extension "blue@mozilla.org" sends a message to the extension "red@mozilla.org":
// sender: browser.runtime.id == "blue@mozilla.org"
// Send a message to the extension whose ID is "red@mozilla.org"
browser.runtime.sendMessage(
"red@mozilla.org",
"my message"
);
// recipient: browser.runtime.id == "red@mozilla.org"
function handleMessage(message, sender) {
// check that the message is from "blue@mozilla.org"
if (sender.id === "blue@mozilla.org") {
// process message
}
}
browser.runtime.onMessageExternal.addListener(handleMessage);
注意：
This API is based on Chromium's
chrome.runtime
API. This documentation is derived from
runtime.json
in the Chromium code.
Microsoft Edge compatibility data is supplied by Microsoft Corporation and is included here under the Creative Commons Attribution 3.0 United States License.
最后修改： , 由 MDN 贡献者