运行时异常错误搞不明白啊

我在写一个计算器可是在监听器上出问题了
public class JiSuanQi {
 TextField text1;
public void jisuanqi() {
TextField text1=new TextField("0");
text1.setEnabled(false);
button1.addActionListener(new NumberListener());
button2.addActionListener(new NumberListener());
}
class NumberListener implements ActionListener{
public void actionPerformed( ActionEvent e){
String s=e.getActionCommand();
text1.setText(s);
}
}
报的异常看不懂
Exception in thread "AWT-EventQueue-0" java.lang.NullPointerException
at xinshou.JiSuanQi$NumberListener.actionPerformed(JiSuanQi.java:63)
at java.awt.Button.processActionEvent(Button.java:392)
at java.awt.Button.processEvent(Button.java:360)
at java.awt.Component.dispatchEventImpl(Component.java:4583)
at java.awt.Component.dispatchEvent(Component.java:4413)
at java.awt.EventQueue.dispatchEvent(EventQueue.java:599)
at java.awt.EventDispatchThread.pumpOneEventForFilters(EventDispatchThread.java:269)
at java.awt.EventDispatchThread.pumpEventsForFilter(EventDispatchThread.java:184)
at java.awt.EventDispatchThread.pumpEventsForHierarchy(EventDispatchThread.java:174)
at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:169)
at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:161)
at java.awt.EventDispatchThread.run(EventDispatchThread.java:122)
不过确定是
text1.setText(s); 这里出问题了
如果我放在外面定义监听类text1又一直错误
我想知道到底什么问题异常类