静态 JComboBox 不在 GUI 中显示

Question

我需要从多个类中访问 goToTop 和 discCrop 方法，因为我需要使用同一个 plantList JComboBox 实例，所以我尝试将其设为静态。但是当我运行下面的代码时，JComboBox 不会显示在 GUI 中。如果我把静电去掉，它就会完美显示。

import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.util.ArrayList;

import javax.swing.JComboBox;
import javax.swing.JLabel;
import javax.swing.JPanel;

import org.jdesktop.swingx.autocomplete.AutoCompleteDecorator;

public class PlantList extends JPanel {

private static final long serialVersionUID = 1L;

static DBio getData = new DBio();
MinorMethods extMethod = new MinorMethods();

static ArrayList<String> plantIDs = new ArrayList<String>(getData.dataSetString("SELECT plantID FROM variety ORDER BY plantID"));
static Object[] plantsObject = plantIDs.toArray();
static JComboBox plantList = new JComboBox(plantsObject);

String oldID = "";

ActionListener comboListener = new ActionListener() {

    @Override
    public void actionPerformed(ActionEvent e) {
        if (oldID == "") {
            oldID = plantList.getSelectedItem().toString();
            Launcher.repaintData(oldID);
            MinorMethods.setCurrentID(oldID);
        } else {
            String newID = plantList.getSelectedItem().toString();
            if (newID != oldID) {
                oldID = newID;
                Launcher.repaintData(oldID);
                MinorMethods.setCurrentID(oldID);
            }
        }
    }
};

public PlantList() {
    setLayout(null);
    AutoCompleteDecorator.decorate(plantList);
    plantList.addActionListener(comboListener);

    JLabel lbl = new JLabel("Choose Plant:");

    lbl.setBounds(1, 1, 84, 9);
    plantList.setBounds(1, 17, 140, 22);

    add(lbl);
    add(plantList);
}

public void addNewPlant() {
    plantList.insertItemAt(MinorMethods.getCurrentID(), 0);
    goToTop();
}

public static void goToTop() {
    plantList.setSelectedIndex(0);
}

public static void discCrop() {
    int currentIndex = plantList.getSelectedIndex();
    plantList.removeItemAt(currentIndex);
    goToTop();
}

}

Answer 1

问题是您的 ComboBox 是静态的，并且您将其添加到非静态构造函数中的 JPanel 中，这不会产生任何问题并将 UI 组件添加到 JFrame 或任何父组件。事情是您用于 JCombobox 的数据或模型在某些情况下也需要是静态的，以便显示。