Blackberry: validate modal Dialog input, do not allow to Save/Ok - blackberry

Question

Hello fellow Blackberry developers,
please advise me how to validate data entered by user into two BasicEditField's (the myName should be longre than 2 characters; the myFloat should be > 10.0) and:
Mark the BasicEditField containing wrong data red
Prevent user from clicking the "Save" (or "OK") button
Anything else if above actions are not possible with Blackberry?
Below is my very simple test case. It is a complete code src\mypackage\MyApp.java and will run instantly if you paste it into JDE or Eclipse:
package mypackage;
import net.rim.device.api.system.*;
import net.rim.device.api.ui.*;
import net.rim.device.api.ui.component.*;
import net.rim.device.api.ui.container.*;
import net.rim.device.api.ui.decor.*;
public class MyApp extends UiApplication {
public static void main(String args[]) {
MyApp myApp = new MyEdit();
myApp.enterEventDispatcher();
}
public MyApp() {
pushScreen(new MyScreen());
}
}
class MyScreen extends MainScreen {
MenuItem myItem = new MenuItem("Show my dialog", 0, 0) {
public void run() {
String[] buttons = { "Save", "Cancel" };
Dialog dialog = new Dialog("My dialog", buttons, null, 0, Bitmap.getPredefinedBitmap(Bitmap.INFORMATION));
EditField myNameField = new EditField("Name (must be > 2 chars): ", "",
TextField.DEFAULT_MAXCHARS, EditField.NO_NEWLINE);
dialog.add(myNameField);
BasicEditField myFloatField = new BasicEditField("Number: (must be > 10.0)", "",
5, EditField.FILTER_REAL_NUMERIC | EditField.EDITABLE);
dialog.add(myFloatField);
if (dialog.doModal() == 0) {
String myName = myNameField.getText();
float myFloat = 0.0f;
try {
myFloat = Float.parseFloat(myFloatField.getText());
} catch (NumberFormatException e) {
}
Status.show("Name: " + myName + ", Number: " + myFloat);
}
}
};
public MyScreen() {
setTitle(new LabelField("How to validate input?"));
addMenuItem(myItem);
}
}
Before asking this question, I have looked at TextFilter and Field.isDataValid() but I'm still unsure how to validate user input in Blackberry (vs. I have a pretty clear picture on how to validate user input in a web script with a web form - with jQuery/PHP/Perl/whatever)
Thank you!
Alex

Answer 1

You can track field changes by setting a FieldChangeListener on your edit fields (use setChangeListener() method). On each change (a letter added or removed) the listener is notified, so you can get the latest edit field text and validate it according to any rules.
Mark the BasicEditField containing wrong data red
If validation fails you can change some color variable (a private memeber for the MyScreen) and request edit field invalidation (use Field.invalidate()) so the frameworks repaints it using the color you've just set.
Prevent user from clicking the "Save" (or "OK") button
With Dialog you can not do this. So instead you need to create a custom popup screen by extending the net.rim.device.api.ui.container.PopupScreen. In this screen class you will have your buttons as screen members, so you'll be able to access them from an edit field change listener. If validation fails you can disable a button with Field.setEnabled(boolean value).