Blackberry: saving ListField content and dirty state management - blackberry

Question

I have prepared a simple test case to demonstrate my problem.
It is just 1 file which will run instantly when added to a new project.
I would like to have a MainScreen displaying an editable list of items:
and when leaving this screen, the user should be asked - if she wants to save the modified list to persistent storage, by presenting the standard Save/Discard/Cancel-dialog:
I have added setDirty(true) to my menu items and the standard dialog does come up okay.
My problem is: I don't know how to clear the dirty flag after saving - in my current code the Save/Discard/Cancel-dialog comes again and again, even if I just view the ListField, without editing it.
src\mypackage\MyList.java:
package mypackage;
import java.util.*;
import net.rim.device.api.collection.*;
import net.rim.device.api.collection.util.*;
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.*;
import net.rim.device.api.util.*;
public class MyList extends UiApplication implements FieldChangeListener {
MyScreen myScreen = new MyScreen();
public static void main(String args[]) {
MyList app = new MyList();
app.enterEventDispatcher();
}
public MyList() {
MainScreen titleScreen = new MainScreen();
titleScreen.setTitle("Click the button:");
ButtonField myButton = new ButtonField("Show the list", ButtonField.CONSUME_CLICK) ;
myButton.setChangeListener(this);
titleScreen.add(myButton);
pushScreen(titleScreen);
}
public void fieldChanged(Field field, int context) {
pushScreen(myScreen);
}
}
class MyScreen extends MainScreen {
ObjectListField myList = new ObjectListField();
static PersistentObject myStore;
static Vector myData;
static {
myStore = PersistentStore.getPersistentObject(0xb77f8e453754f37aL);
myData = (Vector) myStore.getContents();
if (myData == null) {
myData = new Vector();
myData.addElement("String 1");
myData.addElement("String 2");
myData.addElement("String 3");
myStore.setContents(myData);
}
}
public MyScreen() {
setTitle("Edit the list below:");
add(myList);
addMenuItem(addItem);
addMenuItem(editItem);
addMenuItem(removeItem);
}
// load data from persistent store into the ListField
private void loadData() {
// clear the ListField
myList.setSize(0);
// copy data from the Vector to the ListField
for (int i = myData.size() - 1; i >= 0; i--)
myList.insert(0, myData.elementAt(i));
}
// save data from the ListField into the persistent store
private void saveData() {
// clear the Vector
myData.removeAllElements();
// copy data from the ListField to the Vector
for (int i = myList.getSize() - 1; i >=0; i--)
myData.addElement(myList.get(myList, i));
synchronized(PersistentStore.getSynchObject()) {
myStore.commit();
}
}
protected void onUiEngineAttached(boolean attached) {
if (attached) {
loadData();
}
}
public void save() {
saveData();
// UPDATE: when I call setDirty(false); here, then
// the app starts displaying Save/Discard/Cancel dialog
// on its exit - so there must be a better way...
}
private final MenuItem addItem = new MenuItem("Add Item", 0, 0) {
public void run() {
String[] buttons = {"Add", "Cancel"};
Dialog myDialog = new Dialog("Add Item", buttons, null, 0, null);
EditField myEdit = new EditField("Item: ", "");
myDialog.add(myEdit);
if (myDialog.doModal() == 0) {
myList.insert(0, myEdit.getText());
setDirty(true);
}
}
};
private final MenuItem editItem = new MenuItem("Edit Item", 0, 0) {
public void run() {
String[] buttons = {"Save", "Cancel"};
Dialog myDialog = new Dialog("Edit Item", buttons, null, 0, null);
int index = myList.getSelectedIndex();
if (index == -1) {
return;
}
String selectedItem = (String) myList.get(myList, index);
EditField myEdit = new EditField("Item: ", selectedItem);
myDialog.add(myEdit);
if (myDialog.doModal() == 0) {
myList.set(index, myEdit.getText());
setDirty(true);
}
}
};
private final MenuItem removeItem = new MenuItem("Remove Item", 0, 0) {
public void run() {
String[] buttons = {"Delete", "Cancel"};
Dialog myDialog = new Dialog("Remove Item", buttons, null, 0, null);
int index = myList.getSelectedIndex();
if (index == -1) {
return;
}
String selectedItem = (String) myList.get(myList, index);
LabelField myLabel = new LabelField("Really delete " + selectedItem + "?");
myDialog.add(myLabel);
if (myDialog.doModal() == 0) {
myList.delete(index);
setDirty(true);
}
}
};
}
Please share your Blackberry 6 experience, advices in regard to persistent storage are also welcome.
In my real program I'm using KeywordFilterField for viewing a SortedReadableList, so from reading Blackberry docs I suppose, that I must always copy data between SortedReadableList and Vector - because the latter is persistable and the former is not?

Answer 1

setDirty(false) will clear the dirty flag if that is what you are after.