To develop a Google plug-in, we first need to understand the basic structure and working principle of the plug-in.
Here are the brief steps for writing a Google plug-in:
1. Determine the plug-in type : Google provides many different types of plug-ins, and you need to choose the appropriate type based on the specific needs of the plug-in.
2. Write the manifest.json file : This is the manifest file required by each plug-in, which defines the name, description, version number and other information of the plug-in.
3. Write the background.js file : This file contains the code for the plug-in to run in the background. You can use it to register listeners, handle requests, etc.
4. Write popup.html and popup.js files (if necessary): they are responsible for displaying the user interface of the plug-in and responding to user operations.
5. Package all the above codes into a zip file .
6. Open the extension page in Google Chrome, click " Load unzipped extension ", and then select the zip file you packaged.
The components of Google Plugin include the following main components:
1. manifest.json manifest file : This file defines the basic information of the plug-in, including name, description, version number, etc.
2. Background.js file : This file contains JavaScript code running in the background, which can be used to register listeners, handle requests, etc.
3. Content scripts file : This file is the JavaScript code that the plug-in can inject into the current web page, and can modify the DOM structure and CSS style of the page.
4. Popup.html and Popup.js files (if necessary): They are responsible for displaying the user interface of the plug-in and responding to user operations.
5. Options.html and Options.js files (if required): These are typically used to provide settings options that enable users to change the behavior of the plugin.
In addition to the above core components, there are other optional components, such as icon files, localization files, etc. The most important of these are the manifest file and the Background.js file, which are sufficient to implement the core functionality of most plugins.
Here's an example of a simple Google plugin that displays the current time on a page:
1. First, create a manifest file named "manifest.json" in the project root directory and add the following content:
{
"name": "Simple Clock",
"version": "1.0",
"description": "A simple clock extension",
"manifest_version": 2,
"permissions": ["activeTab"],
"browser_action": {
"default_icon": "icon.png",
"default_popup": "popup.html"
}
}
Here we specify the plugin’s name, version, description, and required permissions. Plug-in icons and pop-ups are also set.
2. Create an HTML file named "popup.html" in the project root directory and add the following content:
<!DOCTYPE html>
<html>
<head>
<meta charset="utf-8">
<title>Simple Clock</title>
<style>
#clock {
font-size: 32px;
font-family: Arial, sans-serif;
text-align: center;
margin: 32px;
}
</style>
</head>
<body>
<div id="clock"></div>
<script src="popup.js"></script>
</body>
</html>
Here, we define a div element to display the time and add a script tag pointing to "popup.js" at the bottom of the page.
3. Create a JavaScript file named "popup.js" in the project root directory and add the following content:
function updateTime() {
var date = new Date();
var hours = date.getHours();
var minutes = date.getMinutes();
var seconds = date.getSeconds();
var time = hours + ":" + minutes + ":" + seconds;
document.getElementById("clock").innerHTML = time;
}
setInterval(updateTime, 1000);
Here, we wrote a JavaScript function to display the current time and call the function regularly to update the time.
4. Create an icon file named "icon.png" in the project root directory as the icon of the plug-in.
Now, we have written a simple Google plug-in that displays an icon in the upper right corner of the browser. Clicking on the icon will pop up a window showing the current time.
5. Install the plug-in in the Chrome browser
Open the "chrome://extensions/" page in the Chrome browser, turn on "Developer Mode" at the top of the page, then click the "Load Unzipped Extension" button and select the root directory of our project. This will allow you to install the plugin.
Now, our simple Google plugin is working successfully!