问题描述
我有一个 JFrame
,包含一些文本字段(10)和一个TextArea。我想验证所有文本字段并查看它们是否为空,并检查是否在其中一个文本字段中输入了10位数的联系人号码。检查文本字段后,我想启用一个提交按钮,用于将所有这些数据提交到我的数据库。
I have a JFrame
consisting of some text fields (10) and a TextArea. I want to validate all the text fields and see if they are not empty and also check if a 10 digit contact no is entered in one of the text field. After checking the text fields, I want to enable a submit button which is used to submit all this dat to my database.
我使用以下代码添加文本区域条件但它不起作用,给出错误: - 线程AWT-EventQueue-0java.lang中的异常。 NullPointerException
I used following code with adding the text area condition but it is not working,gives the error:- Exception in thread "AWT-EventQueue-0" java.lang.NullPointerException
这是我使用的代码,但它不起作用: -
Here is the code i used but it is not working:-
public class DataEntered1 implements DocumentListener
{
private JButton button;
List<JTextField> txtfields=new ArrayList<JTextField>();
JTextArea ta;
public DataEntered1(JButton dbadd)
{
this.button=dbadd;
}
public void addTextField(JTextField txtfield)
{
txtfields.add(txtfield);
txtfield.getDocument().addDocumentListener(this);
}
public void addTextArea(JTextArea ta)
{
this.ta=ta;
ta.getDocument().addDocumentListener(this);
}
public boolean isDataEntered()
{
for(JTextField txtfield:txtfields)
{
if(txtfield.getText().length()==0)
return false;
}
return true;
}
public boolean isData()
{
if(ta.getText().trim().length()==0)
{
return false;
}
return true;
}
public void insertUpdate(DocumentEvent e) {
checkdata();
}
public void removeUpdate(DocumentEvent e) {
checkdata();
}
public void changedUpdate(DocumentEvent e) {
checkdata();
}
public void checkdata(){
Boolean d1=isDataEntered();
Boolean d2=isData();
if(d1&&d2)
button.setEnabled(true);
}
}
推荐答案
这是一个通用类,它将在一组文本字段中添加/删除文本时启用/禁用按钮。
Here is a general purpose class that will enable/disable a button as text is added/removed from a group of text fields.
它添加了一个DocumentListener到每个文本字段的Documenent。只有当文本输入到每个文档时,该按钮才会启用:
It adds a DocumentListener to the Documenent of each text field. The button will then ben enable only when text has been entered into each Document:
import java.awt.*;
import java.awt.event.*;
import java.util.List;
import java.util.ArrayList;
import javax.swing.*;
import javax.swing.event.*;
public class DataEntered implements DocumentListener
{
private JButton button;
private List<JTextField> textFields = new ArrayList<JTextField>();
public DataEntered(JButton button)
{
this.button = button;
}
public void addTextField(JTextField textField)
{
textFields.add( textField );
textField.getDocument().addDocumentListener( this );
}
public boolean isDataEntered()
{
for (JTextField textField : textFields)
{
if (textField.getText().trim().length() == 0)
return false;
}
return true;
}
@Override
public void insertUpdate(DocumentEvent e)
{
checkData();
}
@Override
public void removeUpdate(DocumentEvent e)
{
checkData();
}
@Override
public void changedUpdate(DocumentEvent e) {}
private void checkData()
{
button.setEnabled( isDataEntered() );
}
private static void createAndShowUI()
{
JButton submit = new JButton( "Submit" );
submit.setEnabled( false );
JTextField textField1 = new JTextField(10);
JTextField textField2 = new JTextField(10);
DataEntered de = new DataEntered( submit );
de.addTextField( textField1 );
de.addTextField( textField2 );
JFrame frame = new JFrame("SSCCE");
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
frame.add(textField1, BorderLayout.WEST);
frame.add(textField2, BorderLayout.EAST);
frame.add(submit, BorderLayout.SOUTH);
frame.pack();
frame.setLocationByPlatform( true );
frame.setVisible( true );
}
public static void main(String[] args)
{
EventQueue.invokeLater(new Runnable()
{
public void run()
{
createAndShowUI();
}
});
}
}
您需要自定义isDataEntered()方法以添加检查这个额外的要求。
You would need to customize the isDataEntered() method to add a check for this additional requirement.
这篇关于验证文本字段并联系无文本字段的文章就介绍到这了,希望我们推荐的答案对大家有所帮助,也希望大家多多支持!