Question

我在我的jframe上以编程方式创建了输入字段。现在我想创建一个保存按钮，将所有结果保存到数据库。我是JAVA的初学者，因此不熟悉。我有一个结果的实体对象，以及一个保存到数据库的控制器。这不是问题，但我的问题是编写事件处理程序。

private void jComboBoxSurveyFocusLost(java.awt.event.FocusEvent evt) {                                          
    // TODO add your handling code here:
    EntityManagerFactory emf = Persistence.createEntityManagerFactory("PTSchemePU");          
    EntityManager em = emf.createEntityManager();

    jPanelTests.setLayout(new GridLayout(0, 1));

    Query surveyQ = em.createNamedQuery("Survey.findBySurveyDescription");
    surveyQ.setParameter("surveyDescription", jComboBoxSurvey.getSelectedItem().toString());
    Survey survey = (Survey) surveyQ.getSingleResult();

    int testset_ID = survey.getTestset();

    Query testsetQ = em.createNamedQuery("TestsetV.findByTestSet");
    testsetQ.setParameter("testsetid", testset_ID);
    List<TestsetV> TestSetList = (List<TestsetV>)testsetQ.getResultList();
    totalTests = TestSetList.size();

    JPanel[] myPanel          = new JPanel[totalTests];
    JLabel[] myTestID         = new JLabel[totalTests];
    JTextField [] mytextfield = new JTextField[totalTests];
    JComboBox[] myCombo       = new JComboBox[totalTests];
    JCheckBox[] myNotReturn   = new JCheckBox[totalTests];
    JCheckBox[] myNotEval     = new JCheckBox[totalTests];
    JComboBox[] myReason      = new JComboBox[totalTests];
    JButton[] mySave          = new JButton[totalTests];

    jLabelTestcount.setText(Integer.toString(totalTests));
    jLabelToberesulted.setText(Integer.toString(totalTests));

    for (int tst=0; tst< TestSetList.size(); tst++) {
        myPanel[tst]     = new JPanel();
        myTestID[tst]    = new JLabel();
        mytextfield[tst] = new JTextField();
        myNotReturn[tst] = new JCheckBox("Not Returned");
        myNotEval[tst]   = new JCheckBox("Not Evaluated");
        myReason[tst]    = new JComboBox();
        mySave[tst]      = new JButton("Save");

        Query qR = em.createNamedQuery("Lookups.findByLookupType");
        qR.setParameter("lookupType","REAS");
        java.util.List<Lookups> reasonList = (java.util.List<Lookups>)qR.getResultList();

        for (int i = 0 ; i < reasonList.size(); i++) {
            Lookups lu = reasonList.get(i);
            myReason[tst].addItem(lu.getLookupDescription());
        }

        myPanel[tst].setLayout(new SpringLayout());
        int rows =1;
        int cols = 5;

        myPanel[tst].setSize(10, 10);
           myPanel[tst].setBorder(javax.swing.BorderFactory.createBevelBorder(javax.swing.border.BevelBorder.RAISED));
        myPanel[tst].setVisible(true);
        jPanelTests.add(myPanel[tst]);
        mytextfield[tst].setSize(10, 10);
        myNotReturn[tst].setName("No Return");
        myNotEval[tst].setName("Not Evauated");

        JLabel testName = new JLabel(TestSetList.get(tst).getTestDesctiption());
        myPanel[tst].add(new JLabel(Integer.toString(TestSetList.get(tst).getTestsId())));

        myPanel[tst].add(testName);

      switch (TestSetList.get(tst).getTestSetup()){
        case "TEXT" : {     
          myPanel[tst].add(mytextfield[tst]); 

          break;
        }
        case "COMB" : {
            Query q = em.createNamedQuery("Lookups.findByLookupType");
            q.setParameter("lookupType",TestSetList.get(tst).getLookup() );
            java.util.List<Lookups> lookupList = (java.util.List<Lookups>)q.getResultList();

            for (int i = 0 ; i < lookupList.size(); i++) {
                Lookups lu = lookupList.get(i);

                cb.addItem(lu.getLookupCode());
            }

            myPanel[tst].add(cb);

         break;
        } 

        case "SPIN" : {
             myPanel[tst].add(sp);

            break;
        }
    } // end switch

      myPanel[tst].add(myNotReturn[tst]);
      myPanel[tst].add(myNotEval[tst]);
      myPanel[tst].add(myReason[tst]); 
      myPanel[tst].add(mySave[tst]);

      SpringUtilities.makeCompactGrid(myPanel[tst], 1, myPanel[tst].getComponentCount(),6,6,6,6);  
    }
    pack();
    jPanelTests.setVisible(true);         
}

然后，当面板失去焦点时，我创建了一个事件handeler

myPanel[tst].addFocusListener(new FocusListener() {


               @Override
               public void focusGained(FocusEvent e) {
                   throw new UnsupportedOperationException("Not supported yet."); //To change body of generated methods, choose Tools | Templates.
               }

               @Override
               public void focusLost(FocusEvent e) {
                     myResults[tst].setResultValue(mytextfield[tst].getText());

               }
           });

但是现在我得到一个错误（本地变量从内部类重新引用，必须是有效的最终结果）myResults[tst].setResultValue(mytextfield[tst].getText());

如何引用jTextField / JComboBox / jSpinner中输入的值

谢谢

Answer 1

你的计数器变量tst不是final（意味着没有使用final关键字），也不是有效的final（意思是它被修改），因此，它不能从内部类中引用 - 在你的情况下是一个FocusListener的实例。

你修改它时不能将tst标记为final - 但是你可以在循环体中创建一个新变量。

请注意，有效的最终概念是Java8的新概念，在早期版本中，您必须是显式的，并将最终关键字添加到从内部类访问的所有局部变量。

研究以下示例：

public class TestFinalVariables {
    public static void main(String[] args) {
        String effectivelyFinal = "aaa";
        for (int tst=0; tst< 10; ++tst) {
            final int j = tst;  //explicit final not necessary here
            new Runnable() {
                @Override
                public void run() {
                    System.out.println(effectivelyFinal);
                    System.out.println(j);
                    //System.out.println(tst); Won't compile

                }
            }.run();
        }
    }
}

JAVA：用于动态创建按钮的EventHandler

1 个答案: