Java JTextfield只给我空数据
我做了一个Mainmenu JFrame，它可以生成4个不同的新框架代表每个菜单。 Mainmenu框架工作正常。 但我发现它无法从新的框架文本框中获取文本。 这里是错误报告和源代码。 请让我知道如何解决它。
import java.awt.BorderLayout;
import java.awt.GridLayout;
import java.awt.TextField;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.awt.event.WindowEvent;
import java.awt.event.WindowListener;
import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.JTextArea;
import javax.swing.WindowConstants;
import javax.swing.JTable;
public class PhoneBook extends JFrame implements ActionListener
{
private String[] colName;
JPanel panel_main;
JPanel panel_phbook;
JPanel panel_numb;
JPanel panel_grp;
JButton btn_main_phb;
JButton btn_main_name;
JButton btn_main_numb;
JButton btn_main_grp;
JTextArea ta_name_serch;
TextField tf_name_input;
JButton btn_name_search;
JButton btn_name_cancel;
JButton btn_name_modify;
JButton btn_name_del;
JButton btn_name_send;
JTextArea ta_numb_serch;
TextField tf_numb_input;
JButton btn_numb_search;
JButton btn_numb_cancel;
JButton btn_numb_modify;
JButton btn_numb_del;
JButton btn_numb_send;
JButton btn_grp_search;
JButton btn_grp_cancel;
JButton btn_grp_modify;
JButton btn_grp_del;
JButton btn_grp_send;
private JTable table;
public static void main(String[] args)
{
PhoneBook frame = new PhoneBook();
}
public PhoneBook()
{
colName = new String[3];
panel_main = new JPanel();
panel_main.setLayout(new GridLayout());
btn_main_phb = new JButton("phonbook");
btn_main_name = new JButton("name");
btn_main_numb = new JButton("number");
btn_main_grp = new JButton("grp");
btn_main_phb.addActionListener(this);
btn_main_name.addActionListener(this);
btn_main_numb.addActionListener(this);
btn_main_grp.addActionListener(this);
panel_main.add(btn_main_phb);
panel_main.add(btn_main_name);
panel_main.add(btn_main_numb);
panel_main.add(btn_main_grp);
// table = new JTable();
// table.setColumnSelectionAllowed(true);
// panel_main.add(table);
// table.set
panel_phbook = new JPanel();
panel_phbook.setLayout(new GridLayout());
// panel_phbook.add(btn_main_phb);
// panel_phbook.add(btn_main_name);
// panel_phbook.add(btn_main_numb);
// panel_phbook.add(btn_main_grp);
btn_name_search = new JButton("Serch");
btn_name_cancel = new JButton("Serch Cancel");
btn_name_modify = new JButton("Modi");
btn_name_del = new JButton("del");
btn_name_send = new JButton("sms send");
TextField tf_name_input = new TextField();
panel_phbook.add(tf_name_input);
panel_phbook.add(btn_name_search);
btn_name_search.addActionListener(this);
//
panel_numb = new JPanel();
panel_grp = new JPanel();
//getContentPane().setLayout(BorderLayout());
getContentPane().setLayout(new BorderLayout());
setLocation(500, 400);
getContentPane().add(panel_main);
setSize(650,150);
setDefaultCloseOperation(EXIT_ON_CLOSE);
setVisible(true);
}
@Override public void actionPerformed(ActionEvent e) {
// TODO Auto-generated method stub
if(e.getSource().equals(btn_main_phb))
{
JFrame frame2 = new JFrame();
frame2.getContentPane().add(panel_phbook);
frame2.setLocation(400, 300);
frame2.setSize(500,400);
setDefaultCloseOperation(EXIT_ON_CLOSE);
frame2.setVisible(true);
}
else if(e.getSource().equals(btn_main_name))
{
}
else if(e.getSource().equals(btn_main_numb))
{
}
else if(e.getSource().equals(btn_main_grp))
{
}
else if(e.getSource().equals(btn_name_search))//this is the problem
{
System.out.println(tf_name_input.getText());
}
}
异常在线程“AWT-EventQueue-0”java.lang.NullPointerException在PhoneBook.actionPerformed（PhoneBook.java:166）在javax.swing.AbstractButton.fireActionPerformed（未知源）在javax.swing.AbstractButton $ Handler.actionPerformed（未知Source）at javax.swing.DefaultButtonModel.fireActionPerformed（Unknown Source）at javax.swing.DefaultButtonModel.setPressed（Unknown Source）at javax.swing.plaf.basic.BasicButtonListener.mouseReleased（Unknown Source）at java.awt.Component.processMouseEvent （Unknown Source）at java.awt.Component.processEvent（Unknown Source）at java.awt.Component.dispatchEventImpl（Unknown）（位于java.awt.Component.processEvent（Unknown Source））java.awt.Component.processEvent（Unknown Source）在javax.swing.JComponent.processMouseEvent（Unknown Source） Source）在java.awt.LightweightDispatcher.processMouseEvent（Unknown Source）上的java.awt.LightweightDispatcher.retargetMouseEvent（Unknown Source）java.awt.Component.dispatchEventImpl（Unknown Source）在java.awt.Component.dispatchEvent（Unknown Source）在java.awt.Lightwe 在java.awt.Window.dispatchEventImpl（Unknown Source）上的java.awt.Container.dispatchEventImpl（Unknown Source）处的java.awt.Component.dispatchEvent（Unknown Source）处的java.awt.EventQueue处的ightDispatcher.dispatchEvent（Unknown Source）。 java.awt.EventQueue上的dispatchEventImpl（Unknown Source）java.awt.EventQueue上的$ 200（Unknown Source）java.awt.EventQueue上的$ 3.run（Unknown Source）java.security.AccessController上的$ 3.run（Unknown Source） java.security.ProtectionDomain上的.doPrivileged（Native方法）java.security.ProtectionDomain上的$ 1.doIntersectionPrivilege（Unknown Source）java.awt.EventQueue上的$ 1.doIntersectionPrivilege（Unknown Source）java.awt上的$ 4.run（Unknown Source）。在java.security.ProtectionDomain上的java.security.AccessController.doPrivileged（Native方法）处的EventQueue $ 4.run（未知源）在java.awt上的java.awt.EventQueue.dispatchEvent（Unknown Source）上的$ 1.doIntersectionPrivilege（Unknown Source）。 java.awt.EventDispatchThread的EventDispatchThread.pumpOneEventForFilters（Unknown Source） 在java.awt.EventDispatchThread.pumpEventsForHierarchy（Unknown Source）上的java.util.PeaseEventsForFilter（Unknown Source）在java.awt.EventDispatchThread.pumpEvents（Unknown Source）在java.awt.EventDispatchThread.pumpEvents（Unknown Source）
你遇到这个问题的原因是因为你创建了一个新的局部变量，其名称与你的一个类成员变量相同：
TextField tf_name_input = new TextField();
代替：
tf_name_input = new TextField();
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