Why Doesn't My JFormattedTextField Clear Properly After an Invalid Sudoku Entry?

JFormattedTextField Not Clearing Properly

In a Java Sudoku solver program, the JFormattedTextField component used to display individual cells in the Sudoku grid is not properly clearing its contents when an invalid value is entered.

Understanding the Issue

The code provided in the question shows that when an invalid value is entered into a SudokuTextBox (which extends JFormattedTextField), the text box clears but then displays the previous valid value when the user tabs forward. This behavior is not expected.

Cause

The root cause of the issue is not explicitly stated in the question, but it is likely related to the use of a MaskFormatter with JFormattedTextField. MaskFormatters are designed to restrict the input format to specific patterns, such as a single integer in this case.

Possible Resolution

While the provided solution focuses on using a custom JDigit component, it may not fully address the original issue with JFormattedTextField. To resolve the issue specifically with JFormattedTextField, try disabling the MaskFormatter after setting an invalid value in the text box. This should allow the text box to clear properly.

Here's an example of how to do it:

if(sudoku.isValid(row, col, value)) {
    sudoku.set(row, col, value);
 }
 else {
    sudoku.set(row, col, 0);
    // Disable the MaskFormatter to allow the text box to clear
    tb.getFormatter().setMaskFactory(null);
    tb.setText(null);
 }

By disabling the MaskFormatter, you give JFormattedTextField more flexibility in accepting input, allowing it to clear the text box as intended. However, this solution may have other implications or limitations for your specific implementation, so testing and consideration are necessary.

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