Java Swing实时汇率货币转换器开发指南

import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.net.HttpURLConnection;
import java.net.URL;
import java.util.HashMap;
import java.util.Map;
import org.json.JSONObject;

public class ExchangeRateFetcher {

    // 存储实时汇率，键为货币代码，值为相对于基础货币的汇率
    private Map<String, Double> liveExchangeRates = new HashMap<>();
    private String baseCurrency = "EUR"; // 假设API的基础货币是EUR

    /**
     * 从API获取实时汇率。
     * 建议在非EDT（事件调度线程）中调用此方法，以避免UI冻结。
     *
     * @throws IOException 如果网络请求失败
     * @throws org.json.JSONException 如果JSON解析失败
     */
    public void fetchLiveExchangeRates() throws IOException, org.json.JSONException {
        // 示例API URL。请根据实际API调整，可能需要API Key。
        // 假设API返回以EUR为基准的USD, BGN, BTC, ADA汇率
        URL url = new URL("https://api.exchangerate.host/latest?base=" + baseCurrency + "&symbols=USD,BGN,BTC,ADA"); // 示例使用 exchangerate.host
        HttpURLConnection connection = (HttpURLConnection) url.openConnection();
        connection.setRequestMethod("GET");

        int responseCode = connection.getResponseCode();
        if (responseCode == HttpURLConnection.HTTP_OK) { // 检查HTTP响应码
            BufferedReader in = new BufferedReader(new InputStreamReader(connection.getInputStream()));
            String jsonText = readAll(in);
            in.close();

            JSONObject jsonResponse = new JSONObject(jsonText);
            if (jsonResponse.has("rates")) {
                JSONObject rates = jsonResponse.getJSONObject("rates");
                // 将基础货币自身也加入汇率Map，汇率为1.0
                liveExchangeRates.put(baseCurrency, 1.0);
                for (String key : rates.keySet()) {
                    liveExchangeRates.put(key, rates.getDouble(key));
                }
                System.out.println("实时汇率已更新: " + liveExchangeRates);
            } else {
                throw new org.json.JSONException("API响应中未找到'rates'字段。");
            }
        } else {
            throw new IOException("API请求失败，响应码: " + responseCode);
        }
    }

    /**
     * 读取BufferedReader中的所有内容并返回字符串。
     */
    private String readAll(BufferedReader rd) throws IOException {
        StringBuilder sb = new StringBuilder();
        int cp;
        while ((cp = rd.read()) != -1) {
            sb.append((char) cp);
        }
        return sb.toString();
    }

    public Map<String, Double> getLiveExchangeRates() {
        return liveExchangeRates;
    }

    public String getBaseCurrency() {
        return baseCurrency;
    }
}

package currencyConverterGUI;

import javax.swing.*;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.text.DecimalFormat;
import java.io.IOException;
import java.util.Map;
import org.json.JSONException; // 确保导入

public class currencyGUI extends JFrame {

    private static final DecimalFormat df = new DecimalFormat("0.00000");
    private JButton btnConvert;
    private JPanel JPanelMain;
    private JTextField textAmount;
    private JComboBox<String> textFrom; // 明确泛型
    private JComboBox<String> textTo;   // 明确泛型
    private JLabel result;

    private ExchangeRateFetcher rateFetcher; // 汇率获取器实例

    public currencyGUI() {
        // 初始化汇率获取器
        rateFetcher = new ExchangeRateFetcher();

        // 尝试在构造函数中获取汇率。
        // 注意：在实际应用中，这应该在后台线程中完成，例如使用SwingWorker。
        // 为简化示例，这里直接调用，但可能会短暂阻塞UI。
        try {
            rateFetcher.fetchLiveExchangeRates();
        } catch (IOException | JSONException e) {
            e.printStackTrace();
            JOptionPane.showMessageDialog(this, "无法获取实时汇率: " + e.getMessage(), "错误", JOptionPane.ERROR_MESSAGE);
            // 可以考虑在此处禁用转换功能或使用默认/旧汇率
        }

        // 初始化货币下拉列表
        // 假设我们支持的货币包括API返回的货币和基础货币
        String[] currencies = {"EUR", "USD", "BGN", "BTC", "ADA"}; 
        for (String currency : currencies) {
            textFrom.addItem(currency);
            textTo.addItem(currency);
        }

        btnConvert.addActionListener(new ActionListener() {
            @Override
            public void actionPerformed(ActionEvent e) {
                performConversion();
            }
        });
    }

    private void performConversion() {
        try {
            double amount = Double.parseDouble(textAmount.getText());
            String fromCurrency = (String) textFrom.getSelectedItem();
            String toCurrency = (String) textTo.getSelectedItem();

            Map<String, Double> rates = rateFetcher.getLiveExchangeRates();
            String baseCurrency = rateFetcher.getBaseCurrency();

            if (rates.isEmpty()) {
                JOptionPane.showMessageDialog(this, "汇率数据不可用，请稍后再试或检查网络连接。", "错误", JOptionPane.ERROR_MESSAGE);
                return;
            }

            // 确保所有参与转换的货币都有汇率数据
            if (!rates.containsKey(fromCurrency) || !rates.containsKey(toCurrency)) {
                JOptionPane.showMessageDialog(this, "所选货币的汇率数据不可用。", "错误", JOptionPane.ERROR_MESSAGE);
                return;
            }

            double fromRate = rates.get(fromCurrency);
            double toRate = rates.get(toCurrency);

            // 如果源货币或目标货币是基础货币，其汇率应为1.0
            // ExchangeRateFetcher已经将baseCurrency的汇率设置为1.0

            double amountInBase;
            if (fromCurrency.equals(baseCurrency)) {
                amountInBase = amount; // 如果源货币就是基础货币
            } else {
                amountInBase = amount / fromRate; // 将源货币金额转换为基础货币金额
            }

            double total;
            if (toCurrency.equals(baseCurrency)) {
                total = amountInBase; // 如果目标货币就是基础货币
            } else {
                total = amountInBase * toRate; // 将基础货币金额转换为目标货币金额
            }

            result.setText(df.format(total) + " " + toCurrency);

        } catch (NumberFormatException ex) {
            JOptionPane.showMessageDialog(this, "请输入有效的数字金额。", "输入错误", JOptionPane.ERROR_MESSAGE);
        } catch (Exception ex) {
            ex.printStackTrace();
            JOptionPane.showMessageDialog(this, "转换过程中发生错误: " + ex.getMessage(), "错误", JOptionPane.ERROR_MESSAGE);
        }
    }

    public static void main(String[] args) {
        // GUI初始化必须在事件调度线程(EDT)上运行
        SwingUtilities.invokeLater(() -> {
            JFrame frame = new JFrame("实时货币转换器");
            currencyGUI gui = new currencyGUI();
            frame.setContentPane(gui.JPanelMain);
            frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
            frame.pack();
            frame.setVisible(true);
        });
    }
}