JTextField不读取用户输入的数据

Question

Here I am trying to make a Swing Java app, where I am getting a String from the JTextField t1 and comparing it whether it matches with any other string in a text file and then displaying the matched String in the JTextField t2 . However, the JTextField t1 doesn't even reads the input by the user(I have tried even displaying the input by the user) * Note:- *There is no problem with the 'main' or with the GUI of this program.

JButton b1;
JTextField t1,t2;

    public void actionPerformed(ActionEvent ae){try{
    String a=t1.getText();
    String search="";
    try{
        if(a.length()!=0){
           search=atomicnumber(a);
           t2.setText(a);}
        }catch(Exception x){System.out.println("Error");}

}catch (Exception x) {System.err.println("An Unexpected error encountered."+x);}
}
public static String atomicnumber(String a){try{
              boolean found=false;
              File atmno=new File("C:/Users/DELL/Periodic/text/AtomicNumber.txt");
              String e;
                  Scanner sc=new Scanner(atmno);
             while((e = sc.nextLine()) != null){
                  if (e.startsWith(a)){
                found=true;
                return e;//break;
                }
                  return("0");}}catch(IOException x){}
return("0");}
}

Answer 1

Create instance variable a and set this variable in the method actionPerformed and use this instance variable in another method atomicnumber .

You need to make the method atomicnumber as non-static to access it.

Answer 2

You make an instance variable. You need to make it 'visible'. Also where is your startsWith method? Make sure you are passing the correct parameters.

pseudo code

class SomeClass {
    var1 < THIS IS an instance method accessible to any method in that class

method1 {
    var2

}

method2 {
   something.doSomeMethodOn(var2) <<<<< THIS is NOT accessible
   something.doSomeMethodON(var1)<<< THIS IS!
}

Answer 3

In your actionperformed method you are creating a second String a variable in another scope : the scope of that function. So you are not initializing the value to static String a but to String a (function scope). In the atomicNumber() function you are referencing the static String a variable which is not initialized... Try following solution, change:

String a = t1.getText();

To

a = t1.getText();