Getting Started Example - First Data Interaction

In the previous two documents Getting Started Example - Menu and Getting Started Example - Panel, we introduced:

• How to create extensions
• How to define menus in extensions
• how to define messages in an extension
• How to define a panel in an extension

This article demonstrates how two extensions can communicate with each other and will cover three topics:

• How to open a panel of another extension
• How to send a message to another extension
• How to send and listen to broadcast messages

Open Another Extension's Panel

Sometimes we need to open another extension in an extension we wrote, so next we'll try to modify the extension example in Getting Started Example - Menu so that it opens the panel defined in Getting Started Example - Panel.

The modified package.json looks like this:

{
    "package_version": 2,
    "version": "1.0.0",
    "name": "hello-world",
    ...
    "contributions": {
        "menu": [
            {
                "path": "Develop/HelloWorld",
                "label": "test",
                "message": "log"
            },
            {
                "path": "Develop/HelloWorld",
                "label": "open other",
                "message": "open-other"
            }
        ],
        "messages": {
            "log": {
                "methods": [
                    "log"
                ]
            },
            "open-other": {
                "methods": [
                    "openOther"
                ]
            }
        }
    }
}

We modified contributions.menu, added open other menu item, and put all the menus of this extension under Develop/HelloWorld. After refreshing the extension, you can find the menu items in the top menu bar as shown below.

In contributions.messages, we add an open-other message and let the openOther function in main.ts handle this message.

The extension in Getting Started Example - Panel is first-panel, so we use Editor.Panel.open('extension') to open its default panel, as follows:

openOther(){
    Editor.Panel.open('first-panel');
}

After executing the npm run build command at the root of hello-world, go to Extension Manager to refresh the hello-world extension.

Click on the Develop -> HelloWorld -> open other menu item and you will see the example panel open.

Communication with other extensions

Directional communication

In the above example, we open the first-panel panel in hello-world with Editor.Panel.open('extension'). But if we are trying to do something else, this solution won't work.

When an extension wants to call the function of another extension, this can be done by sending a message to one of the extensions with the following function:

Editor.Message.send(extensionName:string,messasge:string,...args:any[])

The messages defined in contributions.messages of each extension are available to the public by default. In first-panel we find the open-panel message, which is used to open its own default panel. For simplicity, we replace the openOther function in main.ts in hello-world with the following:

openOther(){
    Editor.Message.send('first-panel','open-panel');
}

After recompiling the hello-world extension and refreshing it, click Develop -> HelloWorld -> open other menu item again, you can see the default panel of first-panel is opened.

Broadcast communication

When an extension wants to notify all extensions across the system of the completion of an event, it can do so by broadcasting a message with the following function.

Editor.Message.broadcast(message:string, ...args:any[])`

Next, we define a broadcast message called first-panel:open, which is broadcast by the first-panel extension and listened to by the hello-world extension.

In hello-world, we add a new message listener and specify the handler function, with the following modified contributions.messages:

{
    "messages": {
        "log": {
            "methods": [
                "log"
            ]
        },
        "open-other": {
            "methods": [
                "openOther"
            ]
        },
        "first-panel:open":{
            "methods": [
                "onFirstPanelOpen"
            ]
        }
    }
}

Then add the following handler function to main.ts of hello-world:

onFirstPanelOpen(){
    console.log("hello-world knows first-panel is open");
}

The transformation as a listener is done, next we modify the broadcast side first-panel.

Add the following broadcast message code to the src/panels/default/index.ts :ready function in the ``first-panel` project.

Editor.Message.broadcast("first-panel:open");

The ready function will be called when the default panel of first-panel is opened, at which point the first-panel:open message will be broadcast.

Note: Broadcasters can also listen for their own broadcast messages in messages, but this is usually not necessary.

Compile and refresh the two extensions separately, click again on the Develop -> HelloWorld -> open other menu item, and you will see the sample panel opened, in addition to the following print in the Cocos Creator console window.

hello-world knows first-panel is open

This means that the hello-world extension has received a broadcast message from the first-panel extension.

For more message-related details, please refer to the documentation Message System.