package yuzhengzhong;import java.awt.BorderLayout;
import java.awt.Button;
import java.awt.Frame;
import java.awt.TextField;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.awt.event.WindowAdapter;
import java.awt.event.WindowEvent;import javax.swing.JOptionPane;public class CodeTest { public static void main(String[] args){
Frame frame=new Frame("余正忠的加解密软件");
final TextField textOne=new TextField();
final TextField textTwo=new TextField();
final TextField textThree=new TextField();
Button buttonOne=new Button("加密");
Button buttonTwo=new Button("解密");
frame.add(textOne,BorderLayout.NORTH);
frame.add(textTwo,BorderLayout.CENTER);
frame.add(textThree,BorderLayout.SOUTH);
frame.add(buttonOne,BorderLayout.WEST);
frame.add(buttonTwo,BorderLayout.EAST);
buttonOne.addActionListener(new ActionListener(){
public void actionPerformed(ActionEvent e){
String str;
String result = "";
str=textOne.getText();
if(str==null || str==""){
String ooo="请输入要加密的文档";
JOptionPane.showMessageDialog(null,ooo);
return;
}
for(int i=0;i<str.length();i++){
char c=str.charAt(i);
c=(char)(c+10);
result=result+c;
}
textTwo.setText(result);
}
});
frame.addWindowListener(new WindowAdapter(){
public void windowClosing(WindowEvent e){
System.exit(1);
}
});
frame.setSize(600,300);
frame.setVisible(true);
}
}
这里 if(str==null || str==""){
String ooo="请输入要加密的文档";
JOptionPane.showMessageDialog(null,ooo);
return;
}
判断文本框textOne的内容为空的话,就弹出对话框,然后退出按钮的事件处理,可是文本框为空,按下加密按钮,完全没反应,这是为啥?谢谢各位前辈的回答^ - ^
import java.awt.Button;
import java.awt.Frame;
import java.awt.TextField;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.awt.event.WindowAdapter;
import java.awt.event.WindowEvent;import javax.swing.JOptionPane;public class CodeTest { public static void main(String[] args){
Frame frame=new Frame("余正忠的加解密软件");
final TextField textOne=new TextField();
final TextField textTwo=new TextField();
final TextField textThree=new TextField();
Button buttonOne=new Button("加密");
Button buttonTwo=new Button("解密");
frame.add(textOne,BorderLayout.NORTH);
frame.add(textTwo,BorderLayout.CENTER);
frame.add(textThree,BorderLayout.SOUTH);
frame.add(buttonOne,BorderLayout.WEST);
frame.add(buttonTwo,BorderLayout.EAST);
buttonOne.addActionListener(new ActionListener(){
public void actionPerformed(ActionEvent e){
String str;
String result = "";
str=textOne.getText();
if(str==null || str==""){
String ooo="请输入要加密的文档";
JOptionPane.showMessageDialog(null,ooo);
return;
}
for(int i=0;i<str.length();i++){
char c=str.charAt(i);
c=(char)(c+10);
result=result+c;
}
textTwo.setText(result);
}
});
frame.addWindowListener(new WindowAdapter(){
public void windowClosing(WindowEvent e){
System.exit(1);
}
});
frame.setSize(600,300);
frame.setVisible(true);
}
}
这里 if(str==null || str==""){
String ooo="请输入要加密的文档";
JOptionPane.showMessageDialog(null,ooo);
return;
}
判断文本框textOne的内容为空的话,就弹出对话框,然后退出按钮的事件处理,可是文本框为空,按下加密按钮,完全没反应,这是为啥?谢谢各位前辈的回答^ - ^
if(str==null || str.length < 0)){
//
}
//
}
字符串为空白字符串的话可能呗通过!!