Question

我正在尝试创建一个组合框，根据我的数据库填充内部项目。目前数据库包含5条记录，分别是test1，test2，test3，test4，test5。我制作了一个循环，用于填充每条记录。

private void selectschoolActionPerformed(java.awt.event.ActionEvent evt) {                                             
    ResultSet rs = null;
    selectschool.setVisible(true);
    try{
      rs = DAO.getAllSchool();
      ArrayList allSchoolName = new ArrayList();
      int count = 0;
      while(rs.next()){
          allSchoolName.add(rs.getString("SchoolName"));
      count++;

      }
      Object ob[] = new Object[count];
      for (int i = 0; i < count; i++){
            ob[i] = allSchoolName.get(i);
            selectschool.addItem(ob[i]);
      }
  }catch (Exception e){
      System.out.println("Exception: " + e);
  }
CreateTimeTable ctt = new CreateTimeTable();
    ctt.setVisible(true);
    String sch = selectschool.getSelectedItem().toString();
    ctt.jTextArea1.setText(sch);

我已经在for循环中进行了测试，它循环了适当的时间来填充数组，所有的记录都不会少。但是当我下拉组合框时，在GUI中，它是空的。但是，当我单击并按住鼠标时，将其拖到下面的空白字段，它将选择test1并仅测试1.我怎样才能显示其余的值？我测试了它，ob []保存了需要输入组合框的正确记录。我认为它可能是choosechool.addItem（），它不能正常工作。非常感谢，谢谢。

（DAO.getAllSchool（）;只从sql中检索数据库记录）

Answer 1

您需要创建JComboBox并为其添加ActionListener。不创建ActionPerformed，并在其中设置JComboBox。

试试这样：

// fill with values from ResultSet rs (however you obtain it)
ArrayList<String> schools = new ArrayList<String>();
while(rs.next())
  schools.add(rs.getString("SchoolName"));

// create the JComboBox
final JComboBox<String> selectSchool = new JComboBox<String>(schools.toArray(new String[]{}));
// add an actionlistener
selectSchool.addActionListener(new ActionListener() {
  public void actionPerformed(ActionEvent e) {
    // do something with e.g. printing the selection
    String school = (String) selectSchool.getSelectedItem();
    System.out.println("You selected " + school);
  }
});

编辑：或者在一个完整的，非常简单但有效的例子中：

package sto;

import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.util.ArrayList;
import javax.swing.JComboBox;
import javax.swing.JFrame;

public class Main {

    public static void main(String[] args) {
        // create school list (in your example here would be the ResultSet)
        ArrayList<String> schools = new ArrayList<String>();
        schools.add("School 1");
        schools.add("School 2");
        schools.add("School 3");
        schools.add("School 4");

        // create the JComboBox
        final JComboBox<String> selectSchool = new JComboBox<String>(schools.toArray(new String[]{}));
        // add an actionlistener
        selectSchool.addActionListener(new ActionListener() {
            public void actionPerformed(ActionEvent e) {
                // do something with e.g. printing the selection
                String school = (String) selectSchool.getSelectedItem();
                System.out.println("You selected " + school);
            } 
        });

        // create a JFrame and add the JComboBox
        JFrame frame = new JFrame();
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        frame.add(selectSchool);
        frame.pack();
        frame.setVisible(true);
    }
}

在jcombobox中制作物品是可见的

1 个答案: