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What is the method to write code in Java to draw a pie chart on the map through Baidu Map API?

王林Original: 2023-07-29 15:01:341417browse

With the development of the Internet, the application of maps is becoming more and more widespread. As one of the most popular map service providers in China, Baidu Maps provides a wealth of APIs that developers can use to implement various functions. This article will introduce how to write code in Java and draw a pie chart on the map through Baidu Map API.

First, we need to obtain the developer key of Baidu Maps. You can apply by visiting Baidu Map Open Platform (https://lbsyun.baidu.com/). Once we have the key, we can start writing code.

The basic idea of code implementation is: use the JavaScript API provided by Baidu Maps to create a custom overlay on the map, and then draw a pie chart in the custom overlay. The specific steps are as follows:

Create an HTML file and introduce the JavaScript API of Baidu Maps. The code is as follows:

<!DOCTYPE html>
<html>
<head>
    <meta charset="utf-8">
    <title>绘制饼图</title>
</head>
<body>
    <div id="map" style="width: 100%; height: 100%;"></div>
    <script type="text/javascript" src="http://api.map.baidu.com/api?v=2.0&ak=your_ak"></script>
<script src="https://code.jquery.com/jquery-3.6.0.min.js"></script>
</body>
</html>

You need to pay attention to replacing your_ak with your own Baidu Map developer key.

Create a Java class that generates a JSON string containing pie chart data. The code is as follows:

import java.util.HashMap;
import java.util.Map;

public class PieChartDataGenerator {
    public static String generateJsonData() {
        Map<String, Integer> data = new HashMap<>();
        data.put("A", 10);
        data.put("B", 20);
        data.put("C", 30);

        StringBuilder sb = new StringBuilder();
        sb.append("[");
        boolean isFirst = true;
        for (Map.Entry<String, Integer> entry : data.entrySet()) {
            if (!isFirst) {
                sb.append(",");
            }
            sb.append("{"name":"")
              .append(entry.getKey())
              .append("","value":")
              .append(entry.getValue())
              .append("}");
            isFirst = false;
        }
        sb.append("]");

        return sb.toString();
    }
}

This class will generate a JSON string containing pie chart data, where the key is the pie chart sector name and the value is the value of the pie chart sector.

Create a Java class to handle HTTP requests and return the generated HTML file. The code is as follows:

import java.io.File;
import java.io.IOException;
import java.nio.file.Files;
import java.util.stream.Collectors;

public class HttpRequestHandler {
    public static String handleRequest() throws IOException {
        String jsonData = PieChartDataGenerator.generateJsonData();
        String htmlTemplate = Files.lines(new File("path_to_html_template_file").toPath())
                .collect(Collectors.joining(System.lineSeparator()));

        return htmlTemplate.replace("${json_data}", jsonData);
    }
}

You need to replace path_to_html_template_file with the path to the file containing the HTML template.

Create a Java class to start an HTTP server and handle HTTP requests. The code is as follows:

import com.sun.net.httpserver.HttpExchange;
import com.sun.net.httpserver.HttpHandler;
import com.sun.net.httpserver.HttpServer;

import java.io.IOException;
import java.io.OutputStream;
import java.net.InetSocketAddress;

public class HttpServerLauncher {
    public static void main(String[] args) throws IOException {
        HttpServer server = HttpServer.create(new InetSocketAddress(8080), 0);
        server.createContext("/", new HttpHandler() {
            @Override
            public void handle(HttpExchange exchange) throws IOException {
                String response = HttpRequestHandler.handleRequest();
                exchange.sendResponseHeaders(200, response.length());
                OutputStream os = exchange.getResponseBody();
                os.write(response.getBytes());
                os.close();
            }
        });
        server.setExecutor(null);
        server.start();
    }
}

This class will start an HTTP server, listen to the local 8080 port, and when receiving an HTTP request, call HttpRequestHandler to process the request and return the corresponding HTML file.

Run the HttpServerLauncher class, and then visit http://localhost:8080 in the browser to see the pie chart drawn on the map .

Through the above steps, we have successfully implemented the method of drawing a pie chart on the map through Baidu Map API. In actual applications, you can modify the code as needed and customize the data and style of the pie chart to achieve richer functions.

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