Java - 线程 "AWT-EventQueue-0"java.lang.NumberFormatException : create a URL from User Input using JComboBox 中的异常

Question

我正在构建一个 GUI 来检索历史天气数据。我有 2 个 JFrame，第一个框架要求用户输入他/她想要检索给定天气数据的日期。

单击“确定”按钮后，应将数据传递给 urlString，并应从该 URL 检索天气数据并显示在第二帧上。

frame1 中的代码:

okButton.addActionListener(new ActionListener() {
    public void actionPerformed(ActionEvent event) {
        String s = event.getActionCommand();
        if (s.equals("OK")) {
            String a = (String) airportBox.getSelectedItem();
            String d = (String) dayBox.getSelectedItem();
            String m = (String) monthBox.getSelectedItem();
            String y = (String) yearBox.getSelectedItem();
            String urlString = frame2.makeURL(a, y, m, d);
            frame2.openURL(urlString);
            frame2.setVisible(true);
        }
    }
});

frame2 中的代码:

public void openURL(String urlString) {
    try {
        // Open connection
        URL u = new URL(urlString);
        URLConnection connection = u.openConnection();

        // check to make sure the page exists
        HttpURLConnection httpConnection = (HttpURLConnection) connection;
        int code = httpConnection.getResponseCode();
        String message = httpConnection.getResponseMessage();
        System.out.println(code + " " + message);
        if (code != HttpURLConnection.HTTP_OK)
            return;

        // Read server response
        InputStream instream = connection.getInputStream();
        Scanner in = new Scanner(instream);
        //use comma to separate values
        in.useDelimiter(",");

        /* 
         * Store Weather Data in ArrayList
         */
        // display server response to console
        WeatherData data = new WeatherData();
        ArrayList<String> weatherData = data.getWeatherData();
        while (in.hasNext()) {
            String input = in.next();
            weatherData.add(input);
        }

        int averageTemperature = data.calculateAverageTemperature(weatherData);
        Container contentPane = this.getContentPane();

        //add Label at the Top
        JPanel centerPanel = new JPanel(new GridLayout(5, 2));
        contentPane.add(graphImage, BorderLayout.CENTER);

        JLabel temper = new JLabel("Average Temperature: ");
        JTextField tempField= new JTextField(String.valueOf(averageTemperature));
        tempField.setEditable(false);

        centerPanel.add(temper);
        centerPanel.add(tempField);
        contentPane.add(centerPanel, BorderLayout.SOUTH);
    }
    catch (IOException i) {
        System.out.println("Can't display page " + urlString);
    }
}

private JPanel centerPanel;

public String makeURL(String a, String y, String m, String d) {
    String urlString = "http://www.wunderground.com/history/airport/"+a+"/"+y+"/"+m+"/"+d+"/DailyHistory.html?HideSpecis=%201&format=1";
    return urlString;
}

openURL() 方法似乎会导致以下错误:

Exception in thread "AWT-EventQueue-0" java.lang.NumberFormatException: For input string: "temperature history"
at sun.misc.FloatingDecimal.readJavaFormatString(FloatingDecimal.java:1250)
at java.lang.Double.parseDouble(Double.java:540)
at WeatherData.calculateAverageTemperature(WeatherDataTest2.java:171)
at WeatherGraphFrame.openURL(WeatherGUITest.java:227)
at WeatherGUIFrame$1.actionPerformed(WeatherGUITest.java:133)
at javax.swing.AbstractButton.fireActionPerformed(AbstractButton.java:2018)
at javax.swing.AbstractButton$Handler.actionPerformed(AbstractButton.java:2341)
at javax.swing.DefaultButtonModel.fireActionPerformed(DefaultButtonModel.java:402)
at javax.swing.DefaultButtonModel.setPressed(DefaultButtonModel.java:259)
at javax.swing.plaf.basic.BasicButtonListener.mouseReleased(BasicButtonListener.java:252)
at java.awt.Component.processMouseEvent(Component.java:6516)
at javax.swing.JComponent.processMouseEvent(JComponent.java:3320)
at java.awt.Component.processEvent(Component.java:6281)
at java.awt.Container.processEvent(Container.java:2229)
at java.awt.Component.dispatchEventImpl(Component.java:4872)
at java.awt.Container.dispatchEventImpl(Container.java:2287)
at java.awt.Component.dispatchEvent(Component.java:4698)
at java.awt.LightweightDispatcher.retargetMouseEvent(Container.java:4832)
at java.awt.LightweightDispatcher.processMouseEvent(Container.java:4492)
at java.awt.LightweightDispatcher.dispatchEvent(Container.java:4422)
at java.awt.Container.dispatchEventImpl(Container.java:2273)
at java.awt.Window.dispatchEventImpl(Window.java:2719)
at java.awt.Component.dispatchEvent(Component.java:4698)
at java.awt.EventQueue.dispatchEventImpl(EventQueue.java:735)
at java.awt.EventQueue.access$200(EventQueue.java:103)
at java.awt.EventQueue$3.run(EventQueue.java:694)
at java.awt.EventQueue$3.run(EventQueue.java:692)
at java.security.AccessController.doPrivileged(Native Method)
at java.security.ProtectionDomain$1.doIntersectionPrivilege(ProtectionDomain.java:76)
at java.security.ProtectionDomain$1.doIntersectionPrivilege(ProtectionDomain.java:87)
at java.awt.EventQueue$4.run(EventQueue.java:708)
at java.awt.EventQueue$4.run(EventQueue.java:706)
at java.security.AccessController.doPrivileged(Native Method)
at java.security.ProtectionDomain$1.doIntersectionPrivilege(ProtectionDomain.java:76)
at java.awt.EventQueue.dispatchEvent(EventQueue.java:705)
at java.awt.EventDispatchThread.pumpOneEventForFilters(EventDispatchThread.java:242)
at java.awt.EventDispatchThread.pumpEventsForFilter(EventDispatchThread.java:161)
at java.awt.EventDispatchThread.pumpEventsForHierarchy(EventDispatchThread.java:150)
at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:146)
at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:138)
at java.awt.EventDispatchThread.run(EventDispatchThread.java:91)

我希望您了解基本概念。如果您需要更多信息，请告诉我。

Answer 1

如以上评论所述，您正在读取来自 HTTP 请求的输入并期望一个或多个数值。相反，该请求返回一个文本字符串“temperature history”。我查看了该站点，认为您的方法存在缺陷。您提交的 URL 返回 HTML 页面。这些页面包含您要查找的天气历史记录 - 但它们还包含用于在浏览器中格式化此数据的 HTML。

众所周知，从 HTML 中提取数据是一种不好的做法。问题是您无法控制 HTML 的结构。该站点可以随时更改它。解决方案是调用一个纯 API(如果存在)。在这种情况下，该站点似乎确实支持 REST API。请参阅:http://www.wunderground.com/weather/api/有关如何执行此操作的详细信息。

因此我建议您更改代码以调用 REST API。因此，您的程序将以有保证的已知格式接收数据。看起来您可以选择接收 XML 或 JSON。