我的程序有一个国家和州组合框，无论您选择什么，它都只会从州组合框中获得第一个值

Question

所以我为我的作业创建了一个程序，它创建了一个包含学生数据的顺序文件。我制作了一个国家和州的组合框，根据国家的不同会有相应的州，但是在顺序文件（这是一个 .dat 文件）中，无论我选择什么州，在顺序文件中，州总是第一个 one.For 示例如果选择澳大利亚和塔斯马尼亚州，顺序文件中的州将是新南威尔士州。这是我的代码提前致谢

public assignment1st() 
{
    super("create student file");

    try{
        output=new DataOutputStream(new FileOutputStream("studentRec.dat"));

    }
      catch ( IOException e )  {
           System.err.println( "File won't open properly/n" +
             e.toString( ) );
           System.exit( 1 );
    }

    initialize();

    //*******HERE STARTS THE COUNTRY/STATE COMBOBOX BUILD**************************************
    String[] countries = {"-CHOOSE","Australia","Belgium","Brazil","Canada","Georgia","Greece",
        "India","Lithuania","Macedonia"};
    comboBox_1 = new JComboBox<Object>(countries);
    comboBox_1.addActionListener(this);
    comboBox_1.setBounds(278, 142, 92, 20);
    frame.getContentPane().add(comboBox_1);


    //  Create sub combo box with multiple models
    //State Combobox

    comboBox_2 = new JComboBox<String>();
    comboBox_2.addItem("-CHOOSE-");
    comboBox_2.setBounds(452, 142, 109, 20);
    frame.getContentPane().add(comboBox_2);
    comboBox_2.setPrototypeDisplayValue("XXXXXXXXXX");

    String[] Australia = { "New South Wales", "Tasmania", "Queensland" ,"Victoria"};
    states.put(countries[1], Australia);

    String[] Belgium = { "Louxembourg", "Hainaut", "Flemish" };
    states.put(countries[2], Belgium);

    String[] Brazil = { "Amazonas", "Mato Grosso" };
    states.put(countries[3], Brazil);

    String[] Canada = { "Vancouver", "Quebec" };
    states.put(countries[4], Canada);

    String[] Georgia = {"Tbilisi", "S.Ossetia" };
    states.put(countries[5], Georgia);

    String[] Greece = { "Pelloponisos", "Chalchidikis", "Thesprotias" };
    states.put(countries[6], Greece);

    String[] India = {  "Jalpur", "Kolkata", "New Delhi" };
    states.put(countries[7], India);

    String[] Lithuania = { "Akmene", "Kretinga", "Varena" };
    states.put(countries[8],Lithuania);

    String[] Macedonia = {  "Bitola", "Struga", "Veles" };
    states.put(countries[9], Macedonia);


}

导入数据的代码

   if ( studentID > 0 )  {



                //PLACE FOR COMBOBOXEZ


                String sex=(String) comboBox.getSelectedItem();
                output.writeUTF(sex);

                String country=(String) comboBox_1.getSelectedItem();
                output.writeUTF(country);


                String state=(String) comboBox_2.getSelectedItem();
                output.writeUTF(state);



                String month=(String) comboBox_3.getSelectedItem();
                output.writeUTF(month);

                String day=(String) comboBox_4.getSelectedItem();
                output.writeUTF(day);

                String year=(String) comboBox_5.getSelectedItem();
                output.writeUTF(year);


                output.writeInt(maths);
                output.writeInt(buisness);
                output.writeInt(programming);
                output.writeInt(accounting);
                output.writeInt(art);
                output.writeInt(music);

最后是针对国家/地区组合框执行的操作

public void actionPerformed( ActionEvent e )  { 

    //*************FOR STATE AND COUNTRY COMBOBOXEZ*********************
    String country = (String)comboBox_1.getSelectedItem();
        Object o = states.get( country );

        if (o == null)
        {
            comboBox_2.setModel( new DefaultComboBoxModel<String>() );
        }
        else
        {
            comboBox_2.setModel( new DefaultComboBoxModel<String>( (String[])o ) );
        }
       //**********DONE WITH THE STATE AND COUNTRY COMBOBOXEZ**********

Answer 1

这是因为你的这部分代码:

if (o == null)
{
    comboBoxstate.setModel( new DefaultComboBoxModel<String>() );
}
else
{
    comboBoxstate.setModel( new DefaultComboBoxModel<String>( (String[])o ) );
}

在此之前：

if (e.getSource()==btnEnter){
    addRecord( ) ;
}

因此，您的组合框会先重新排列，然后再添加记录。

如果将第二部分放在第一部分之前，效果会很好。就是这样。

但是，我建议您检查是哪个组件导致了该操作，然后执行您想要执行的操作，否则对某些组件的操作可能会导致您希望其他组件执行的操作。如果需要，可以尝试 e.getActionCommand()

我的程序有一个国家和州组合框，无论您选择什么，它都只会从州组合框中获得第一个值

My program has a Country and State combobox, and from the state combobox it only gets the first value no matter what you choose

java

eclipse

swing

combobox

eclipse-mars