文本框加入的事件出现问题

Question

一段用NetBeans生成的 有些没用的直接忽略就可以的 问题在前十来行的 e.consume(); 是这样的 本来是文本框加个事件不是数字不能输入 结果出现了 什么都能输入 而且退格左右移动光标都废了 是否数字判断也没问题 !
package cn.itcast_07;

import java.awt.event.KeyAdapter;
import java.awt.event.KeyEvent;

/**
*

• @author Hunter
  */
  public class NewJFrame extends javax.swing.JFrame {

  public NewJFrame() {
  initComponents();
  onlynum();
  init();
  }

  public void onlynum() {
  this.firstNumber.addKeyListener(new KeyAdapter() {

       @Override
       public void keyPressed(KeyEvent e) {
           char ch = e.getKeyChar();
           if (!(ch > '0' && ch < '9')) {
               e.consume();
           }
       }
   });
  this.secondNumber.addKeyListener(new KeyAdapter() {
  
      @Override
      public void keyPressed(KeyEvent e) {
          char ch = e.getKeyChar();
          if (!(ch > '0' && ch < '9')) {
              e.consume();
          }
      }
  });
  

  }

  private void init() {
  this.setTitle("模拟四呢运算");
  }

  private void initComponents() {

  jLabel1 = new javax.swing.JLabel();
  jLabel2 = new javax.swing.JLabel();
  jLabel3 = new javax.swing.JLabel();
  firstNumber = new javax.swing.JTextField();
  secondNumber = new javax.swing.JTextField();
  result = new javax.swing.JTextField();
  operator = new javax.swing.JComboBox();
  jButton1 = new javax.swing.JButton();
  
  setDefaultCloseOperation(javax.swing.WindowConstants.EXIT_ON_CLOSE);
  
  jLabel1.setText("第一个数");
  
  jLabel2.setText("第二个数");
  
  jLabel3.setText("结果");
  
  operator.setModel(new javax.swing.DefaultComboBoxModel(new String[] { "+", "-", "*", "/" }));
  
  jButton1.setText("计算");
  jButton1.addActionListener(new java.awt.event.ActionListener() {
      public void actionPerformed(java.awt.event.ActionEvent evt) {
          jButton1ActionPerformed(evt);
      }
  });
  
  javax.swing.GroupLayout layout = new javax.swing.GroupLayout(getContentPane());
  getContentPane().setLayout(layout);
  layout.setHorizontalGroup(
      layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
      .addGroup(layout.createSequentialGroup()
          .addGroup(layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
              .addGroup(layout.createSequentialGroup()
                  .addGap(25, 25, 25)
                  .addComponent(firstNumber)
                  .addGap(20, 20, 20))
              .addGroup(layout.createSequentialGroup()
                  .addGap(37, 37, 37)
                  .addComponent(jLabel1, javax.swing.GroupLayout.PREFERRED_SIZE, 78, javax.swing.GroupLayout.PREFERRED_SIZE)
                  .addPreferredGap(javax.swing.LayoutStyle.ComponentPlacement.RELATED, 26, Short.MAX_VALUE)))
          .addComponent(operator, javax.swing.GroupLayout.PREFERRED_SIZE, javax.swing.GroupLayout.DEFAULT_SIZE, javax.swing.GroupLayout.PREFERRED_SIZE)
          .addGap(18, 18, 18)
          .addGroup(layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
              .addGroup(layout.createSequentialGroup()
                  .addGap(0, 22, Short.MAX_VALUE)
                  .addComponent(jLabel2, javax.swing.GroupLayout.PREFERRED_SIZE, 57, javax.swing.GroupLayout.PREFERRED_SIZE)
                  .addGap(75, 75, 75)
                  .addComponent(jLabel3)
                  .addGap(62, 62, 62))
              .addGroup(layout.createSequentialGroup()
                  .addComponent(secondNumber, javax.swing.GroupLayout.PREFERRED_SIZE, 92, javax.swing.GroupLayout.PREFERRED_SIZE)
                  .addPreferredGap(javax.swing.LayoutStyle.ComponentPlacement.RELATED, javax.swing.GroupLayout.DEFAULT_SIZE, Short.MAX_VALUE)
                  .addGroup(layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING, false)
                      .addComponent(jButton1, javax.swing.GroupLayout.DEFAULT_SIZE, 79, Short.MAX_VALUE)
                      .addComponent(result))
                  .addGap(0, 0, Short.MAX_VALUE))))
  );
  layout.setVerticalGroup(
      layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
      .addGroup(layout.createSequentialGroup()
          .addGap(33, 33, 33)
          .addGroup(layout.createParallelGroup(javax.swing.GroupLayout.Alignment.BASELINE)
              .addComponent(jLabel1, javax.swing.GroupLayout.PREFERRED_SIZE, 28, javax.swing.GroupLayout.PREFERRED_SIZE)
              .addComponent(jLabel2)
              .addComponent(jLabel3))
          .addPreferredGap(javax.swing.LayoutStyle.ComponentPlacement.UNRELATED)
          .addGroup(layout.createParallelGroup(javax.swing.GroupLayout.Alignment.BASELINE)
              .addComponent(firstNumber, javax.swing.GroupLayout.PREFERRED_SIZE, javax.swing.GroupLayout.DEFAULT_SIZE, javax.swing.GroupLayout.PREFERRED_SIZE)
              .addComponent(secondNumber, javax.swing.GroupLayout.PREFERRED_SIZE, javax.swing.GroupLayout.DEFAULT_SIZE, javax.swing.GroupLayout.PREFERRED_SIZE)
              .addComponent(result, javax.swing.GroupLayout.PREFERRED_SIZE, javax.swing.GroupLayout.DEFAULT_SIZE, javax.swing.GroupLayout.PREFERRED_SIZE)
              .addComponent(operator, javax.swing.GroupLayout.PREFERRED_SIZE, javax.swing.GroupLayout.DEFAULT_SIZE, javax.swing.GroupLayout.PREFERRED_SIZE))
          .addPreferredGap(javax.swing.LayoutStyle.ComponentPlacement.RELATED, 28, Short.MAX_VALUE)
          .addComponent(jButton1)
          .addContainerGap())
  );
  
  pack();
  

  }// //GEN-END:initComponents

  private void jButton1ActionPerformed(java.awt.event.ActionEvent evt) {//GEN-FIRST:event_jButton1ActionPerformed
  //获取第一个操作数
  String firstNumberString = this.firstNumber.getText().trim();
  //获取第二个操作数
  String secondNumberString = this.secondNumber.getText().trim();
  //获取运算符
  String operatorString = this.operator.getSelectedItem().toString();

  ////第一个数转成int
  int firstNumber = Integer.parseInt(firstNumberString);
  //第二个数转成int
  int secondNumber = Integer.parseInt(secondNumberString);

  int resultNumber = 0;
  switch (operatorString) {
      case "+":
          resultNumber = firstNumber + secondNumber;
          break;
      case "-":
          resultNumber = firstNumber - secondNumber;
          break;
      case "*":
          resultNumber = firstNumber * secondNumber;
          break;
      case "/":
          resultNumber = firstNumber / secondNumber;
          break;
  }
  this.result.setText(String.valueOf(resultNumber));
  

  }//GEN-LAST:event_jButton1ActionPerformed

  /**

  • @param args the command line arguments
    */
    public static void main(String args[]) {

    try {
    for (javax.swing.UIManager.LookAndFeelInfo info : javax.swing.UIManager.getInstalledLookAndFeels()) {
    if ("Nimbus".equals(info.getName())) {
    javax.swing.UIManager.setLookAndFeel(info.getClassName());
    break;

        }
    }
    

    } catch (ClassNotFoundException ex) {
    java.util.logging.Logger.getLogger(NewJFrame.class
    .getName()).log(java.util.logging.Level.SEVERE, null, ex);
    } catch (InstantiationException ex) {
    java.util.logging.Logger.getLogger(NewJFrame.class
    .getName()).log(java.util.logging.Level.SEVERE, null, ex);
    } catch (IllegalAccessException ex) {
    java.util.logging.Logger.getLogger(NewJFrame.class
    .getName()).log(java.util.logging.Level.SEVERE, null, ex);
    } catch (javax.swing.UnsupportedLookAndFeelException ex) {
    java.util.logging.Logger.getLogger(NewJFrame.class
    .getName()).log(java.util.logging.Level.SEVERE, null, ex);
    }
    //

    /* Create and display the form */
    java.awt.EventQueue.invokeLater(new Runnable() {
    public void run() {
    new NewJFrame().setVisible(true);
    }
    });
    }

  // Variables declaration - do not modify//GEN-BEGIN:variables
  private javax.swing.JTextField firstNumber;
  private javax.swing.JButton jButton1;
  private javax.swing.JLabel jLabel1;
  private javax.swing.JLabel jLabel2;
  private javax.swing.JLabel jLabel3;
  private javax.swing.JComboBox operator;
  private javax.swing.JTextField result;
  private javax.swing.JTextField secondNumber;
  // End of variables declaration//GEN-END:variables
  }

图片说明

Answer 1

你的想法是正确的，通过判断按下的键是否是0-9的值在进行输入，但是你的逻辑是错误的，你的判断方法中先不说对不对，你的if是当输入的字符不是0-9时什么也不错继续进行，这样就跟你想的完全相反了，按我的理解当不是0-9时要做些什么处理的，而你用consume方法是没有意义的。
要不是你理解的consume有误，要不就是逻辑写反了。

其次，你这样判断是不正确的，这个KeyEvent只是在你按下的时候触发无法满足你的需求，即使你改了输入的Key值也无法阻止摁下的键输入到文本框中；

最后告诉你在文本框中Java是提供了Document接口来实现特定内容的输入的，比如数字，你可以参考我下面改写的你的方法，这样就只能输入正整数了，需要输入浮点数或者负数只要在for循环中更改条件即可。

public void onlynum() {
        this.firstNumber.setDocument(new PlainDocument() {
            @Override
            public void insertString(int offs, String str, AttributeSet a)
                    throws BadLocationException {
                // TODO Auto-generated method stub
                for (int i = 0; i < str.length(); i++) {
                    if (str.charAt(i) < '0' || str.charAt(i) > '9') {
                        return;
                    }
                }
                super.insertString(offs, str, a);
            }

        });
        this.secondNumber.setDocument(new PlainDocument() {
            @Override
            public void insertString(int offs, String str, AttributeSet a)
                    throws BadLocationException {
                // TODO Auto-generated method stub
                for (int i = 0; i < str.length(); i++) {
                    if (str.charAt(i) < '0' || str.charAt(i) > '9') {
                        return;
                    }
                }
                super.insertString(offs, str, a);
            }

        });
        this.firstNumber.addKeyListener(new KeyAdapter() {
            @Override
            public void keyPressed(KeyEvent e) {
                char ch = e.getKeyChar();
                if (!(ch > '0' && ch < '9')) {
                    e.consume();
                }
            }
        });
        this.secondNumber.addKeyListener(new KeyAdapter() {

            @Override
            public void keyPressed(KeyEvent e) {
                char ch = e.getKeyChar();
                if (!(ch > '0' && ch < '9')) {
                    e.consume();
                }
            }
        });
    }