JTextField.getInputContext() returns null value

Question

In my Swing application, I use JTextField component to get Farsi text values.

I want to set locale for this component by using the following code:

txt_fname.getInputContext().selectInputMethod(new Locale("fa", "IR"));

But txt_fname.getInputContext() returns null and the code throws a NullPointerException.

How can I solve this problem?

Edited

the code is called in InternalJFrame constructor:

public DriversList() {
    initComponents();
    txt_fname.getInputContext().selectInputMethod(new Locale("fa", "IR"));        
}

Answer 1

This MCVE suggests the code you have not shown, is attempting to get the input context before the text field is first displayed.

Code

import java.awt.*;
import javax.swing.*;

class InputContextTest {

    public static void main(String[] args) {
        Runnable r = new Runnable() {

            @Override
            public void run() {
                JTextField tf = new JTextField(10);
                System.out.println(tf.getInputContext());
                JOptionPane.showMessageDialog(null, tf);
                System.out.println(tf.getInputContext());
            }
        };
        // Swing GUIs should be created and updated on the EDT
        // http://docs.oracle.com/javase/tutorial/uiswing/concurrency
        SwingUtilities.invokeLater(r);
    }
}

Output

null
sun.awt.im.InputMethodContext@1fa5e5e
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