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This page contains an archived post to the Java Answers Forum made prior to February 25, 2002.
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Message:
Set a new document model
Posted by Kishori Sharan on February 08, 2002 at 10:24 AM
You need to create a text field class inheriting from JTextField and then override createDefaultModel method. In that method you need to return an object which extends PlainDocument and override the insertString method. I have included an example. Compile and run TextTest.java and it will demonstrate what you want. In example I have set maximum chars to 5.
Thanks
Kishori
/////////////// TextTest.java file
import javax.swing.* ;
import javax.swing.text.* ; public class TextTest extends JFrame {
MyJTextField t1 = new MyJTextField ( 20 ) ;
public TextTest ( ) {
// set the maximum chars to 5
t1.setMaxCharacters ( 5 ) ;
this.getContentPane().add ( t1, "North" ) ;
}
public static void main ( String[] args ) {
TextTest t = new TextTest ( ) ;
t.setBounds ( 50, 50, 300, 300 ) ;
t.show() ;
} }
class MyJTextField extends JTextField {
private int maxChars = 50 ; // By default set the max chars to 50
public MyJTextField (int cols) {
super(cols);
}
public void setMaxCharacters ( int maxChars ) {
if ( maxChars < 0 ) {
this.maxChars = 0 ;
}
else {
this.maxChars = maxChars ;
}
}
protected Document createDefaultModel() {
return new PlainDocument ( ) {
public void insertString(int offs, String str, AttributeSet a)
throws BadLocationException { if (str == null) {
return;
}
// Get the length of the text in JTextField
int len = 0 ;
if ( MyJTextField.this.getText() == null ) {
len = 0 ;
}
else {
len = MyJTextField.this.getText().length() ;
}
if ( len + str.length() > MyJTextField.this.maxChars ) {
// Total chars will be more than max allowed. So, just return
return ;
}
else {
// Update the text field
super.insertString(offs, str, a);
}
}
} ;
}
}
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