当第一个为空时，java netbeans禁用另一个jFormattedTextField

Question

I'm using jFormattedTextField because it can be easily formatted as I want rather than jTextField. I allow only number as input.

Case:

I have two jFormattedTextfield forms, let's say they are txtA and txtB, txtB is disabled.

When txtA is empty, txtB always be disabled. Otherwise, when txtA isn't empty, txtB will be enabled.

If I delete all input in txtA, txtB should be disabled.

I put the code in KeyReleased event. Here is the piece of code:

private void txtAKeyReleased(java.awt.event.KeyEvent evt) {                                 
        if(!(txtA.getText().equals(""))){
            int as = txtA.getText().length(); 
            if(as > 0){
                txtB.setEnabled(true);
            }
            else{
                txtB.setEnabled(false); 
            }
        }
        else {
            txtB.setText(null); 
            txtB.setEnabled(false); 
        }
    } 

At a glance, it works. But, it doesn't work perfectly.

When I typed something in txtA, txtB is enabled.

Problem 1: But, if I delete all inputs in txtA, txtB still enable.

Problem 2: txtA should detect only number as input then txtB is enabled. But, when I typed letter or space in txtA, txtB still enable.

Surprisingly, when I tried it in JTextField, it works perfectly (txtB disabled when txtA is empty).

What should I do to fix this?

Answer 1

I put the code in KeyReleased event.

Don't use a KeyListener.

Instead you should be using a DocumentListener . It will fire an event whenever a change is made to the Document. Read the section from the Swing tutorial on How to Write a Document Listener for more information and examples.