I tried to use reverseBystack, reverseBylink and remove.. but I don't know why when i use these functions, it has error like this.
Exception in thread "main" java.lang.NullPointerException
at LinkedQueue$Node.access$200(LinkedQueue.java:44)
at LinkedQueue.reverseBylink(LinkedQueue.java:185)
at LinkedQueue.main(LinkedQueue.java:238)
void reverseByStack() - This method reverses the order of the items in the linked list (first
becomes last and last becomes first) using a stack data strucenter code hereture`
• void reverseByLinks() - This method also reverses the order of the items in the linked list.
It should not create a new list or use a stack. It should only reverse the order of the nodes by
modifying the next values for each node in the list.
• int remove(Item item) - This method scans the queue for occurrences of item and removes
them from the queue. It returns the number of items deleted from the queue.
these are what i want to make.
enter code here public class LinkedQueue<Item> implements Iterable<Item> {
private int N; // number of elements on queue
private Node first; // beginning of queue
private Node last; // end of queue
// helper linked list class
private class Node {
private Item item;
private Node next;
}
public LinkedQueue() {
first = null;
last = null;
N = 0;
assert check();
}
public boolean isEmpty() {
return first == null;
}
public int size() {
return N;
}
public Item peek() {
if (isEmpty()) throw new NoSuchElementException("Queue
underflow");
return first.item;
}
public void enqueue(Item item) {
Node oldlast = last;
last = new Node();
last.item = item;
last.next = null;
if (isEmpty()) first = last;
else oldlast.next = last;
N++;
assert check();
}
public Item dequeue() {
if (isEmpty()) throw new NoSuchElementException("Queue
underflow");
Item item = first.item;
first = first.next;
N--;
if (isEmpty()) last = null; // to avoid loitering
assert check();
return item;
}
public String toString() {
StringBuilder s = new StringBuilder();
for (Item item : this)
s.append(item + " ");
return s.toString();
}
private boolean check() {
if (N == 0) {
if (first != null) return false;
if (last != null) return false;
}
else if (N == 1) {
if (first == null || last == null) return false;
if (first != last) return false;
if (first.next != null) return false;
}
else {
if (first == last) return false;
if (first.next == null) return false;
if (last.next != null) return false;
// check internal consistency of instance variable N
int numberOfNodes = 0;
for (Node x = first; x != null; x = x.next) {
numberOfNodes++;
}
if (numberOfNodes != N) return false;
// check internal consistency of instance variable last
Node lastNode = first;
while (lastNode.next != null) {
lastNode = lastNode.next;
}
if (last != lastNode) return false;
}
return true;
}
void reverseBystack(){
Stack<Item> s = new Stack<>();
Item item;
while (s.isEmpty() != true){
item = dequeue();
s.push(item);
}
while(s.isEmpty() != true){
item = s.pop();
enqueue(item);
}
}
void reverseBylink() {
Node prev = null;
Node current = this.first;
Node next = null;
while (current != null) {
next = current.next;
current.next = prev;
prev = current;
current = next;
}
prev.next = current.next;
}
int remove(Item item){
Node cur = first;
Node prev = last;
while(cur != null) {
if(cur.item.equals(item))
System.out.println(cur.item);
}
cur = cur.next;
prev = cur.next;
return 0;
}
public Iterator<Item> iterator() {
return new ListIterator();
}
private class ListIterator implements Iterator<Item> {
private Node current = first;
public boolean hasNext() { return current != null;
}
public void remove() { throw new
UnsupportedOperationException(); }
public Item next() {
if (!hasNext()) throw new NoSuchElementException();
Item item = current.item;
current = current.next;
return item;
}
}
/**
* Unit tests the <tt>LinkedQueue</tt> data type.
*/
public static void main(String[] args) {
LinkedQueue<String> q = new LinkedQueue<String>();
while (!StdIn.isEmpty()) {
String item = StdIn.readString();
if (!item.equals("-")) q.reverseBylink();
else if (!q.isEmpty()) StdOut.print(q.dequeue() + " ");
}
StdOut.println("(" + q.size() + " left on queue)");
}
}
I have an app in which i mainly have a webview. i am having a problem. i have made the back button to goto previous webpage of webview it works fine and when it has no previous pages it quits with a MessageBox(Popup). The problem is when i navigate another page and press back it recursively triggers back button event and shows the MessageBox
Windows.UI.Core.SystemNavigationManager.GetForCurrentView().BackRequested += (s, e) =>
{
e.Handled = true;
if (Web_view.CanGoBack)
{
Web_view.GoBack();
e.Handled = true;
}
else
{
quit();
e.Handled = true;
}
};
The above is code of my main page
private async void quit()
{
MessageDialog msg = new MessageDialog("Do you really want to quit?", "Quit");
msg.Commands.Add(new UICommand("Yes") { Id = 0 });
msg.Commands.Add(new UICommand("No") { Id = 1 });
var ans = await msg.ShowAsync();
if(ans.Id.Equals(0))
{
//System.Diagnostics.Debug.WriteLine("Exit");
App.Current.Exit();
}
}
this is the code of quit function.
I am navigating to another page from this using code
private void about_Click(object sender, RoutedEventArgs e)
{
Frame.Navigate(typeof(BlankPage1));
}
And the backRequested code of blanckPage1 is
SystemNavigationManager.GetForCurrentView().BackRequested += (s,e)=>
{
e.Handled = true;
// Windows.UI.Core.SystemNavigationManager.GetForCurrentView().BackRequested -= BlankPage1_BackRequested;
//System.Diagnostics.Debug.WriteLine("BackRequested");
if (Frame.CanGoBack)
{
e.Handled = true;
Frame.GoBack();
}
else
{
e.Handled = true;
}
};
To make it more clear for example when i open the app the webview navigates to www.example.com then following the links there i will get to some other page(for example www.example.com/link/firstlink). then i will navigate my frame to blankpage1 and from there i will press back. then insted of coming back to previous page (www.example.com/link/firstlink) it comes to beginning page (www.example.com) and shows the quit popup how can i fix this?
Thank you for all your replay.
Your problem is that you are still keeping the event handler: In your code when navigating back from BlankPage1, both .BackRequested handlers are called. You would need to deregister from .BackRequested on MainPage when leaving it, for example like this:
MainPage:
protected override void OnNavigatedTo(NavigationEventArgs e) {
SystemNavigationManager.GetForCurrentView().BackRequested += OnBackRequested;
}
protected override void OnNavigatedFrom(NavigationEventArgs e) {
SystemNavigationManager.GetForCurrentView().BackRequested -= OnBackRequested;
}
private void OnBackRequested(object sender, BackRequestedEventArgs e) {
// Your code to navigate back
if (Web_view.CanGoBack)
{
Web_view.GoBack();
e.Handled = true;
}
else
{
quit();
e.Handled = true;
}
}
And the same on BlankPage1... Though it would be far easier to register to BackRequested in your App.xaml.cs where you would handle your (Window.Current.Content as Frame) for the whole app, something like this. To make it "nice" code also with an interface:
INavigationPage:
public interface INavigationPage {
// When overriding the method returns true or false if the Page handled back request
bool HandleBackRequested();
}
App.xaml.cs:
// ... Code before
protected override void OnLaunched(LaunchActivatedEventArgs e) {
SystemNavigationManager.GetForCurrentView().BackRequested += OnBackRequested;
}
private void OnBackRequested(object sender, BackRequestedEventArgs e) {
Frame frame = Window.Current.Content as Frame;
if (frame == null) return;
INavigationPage page = frame.Content as INavigationPage;
if (page == null) return;
// Ask if the page handles the back request
if (page.HandleBackRequested()) {
e.Handled = true;
// If not, go back in frame
} else if (frame.CanGoBack) {
e.Handled = true;
frame.GoBack();
}
}
// ... Code after
MainPage.xaml.cs:
... class MainPage : Page, INavigationPage {
// ... Code before
// Implement the interface handling the backRequest here if possible
public bool HandleBackRequested() {
if (Web_view.CanGoBack) {
Web_view.GoBack();
return true;
}
return false;
}
// ... Code after
}
Then the BlankPage does not require any code and no subscribing to .BackRequested.
I am trying to draw a list of all contacts saved in device. Everything is fine but when I select all contacts, I get only those contacts which are drawn on the screen. In other words, list drawing only those contacts which are visible on screen. To get the remaining contacts I have to scroll the list.
Here is my code:
public class CheckboxListField extends VerticalFieldManager implements ListFieldCallback, FieldChangeListener {
private static Vector selectedContacts ;
private ChecklistData[] mListData = new ChecklistData[] {};
private ListField mListField;
private static Vector mContacts;
private ContactList contactList;
private Enumeration allContacts;
private SendEmail sendEmail;
private boolean isChecked=false;
private BlackBerryContact contactItem;
private VerticalFieldManager _mainVFM = new VerticalFieldManager();
private int i;
private int j=0;
private String emails="";
private ButtonField _inviteButton;
private HorizontalFieldManager selectAllHFM;
private CustomButtonField selectAllButton;
private Bitmap _uncheckBmp;
private Bitmap _checkBmp;
private LabelField selectAllLabel;
private CheckboxField selectAllCheckBox;
private VerticalFieldManager contactListVFM;
private boolean listItemChecked=false;
private StringBuffer rowString;
private boolean getCBoxStatus;
// A class to hold the Strings in the CheckBox and it's checkbox state
// (checked or unchecked).
private class ChecklistData {
private String _stringVal;
private boolean _checked;
private String _telNumber;
ChecklistData(String stringVal, boolean checked) {
_stringVal = stringVal;
_checked = checked;
//_telNumber = telNumber;
}
// Get/set methods.
private String getStringVal() {
return _stringVal;
}
private boolean isChecked() {
return _checked;
}
// Toggle the checked status.
public void toggleChecked() {
_checked = !_checked;
}
}
public CheckboxListField() {
_mainVFM.add(createContactList(isChecked));
add(_mainVFM);
}
public VerticalFieldManager createContactList(boolean checked){
isChecked = checked;
selectedContacts = new Vector();
//INVITE BUTTON
contactListVFM = new VerticalFieldManager();
_inviteButton=new ButtonField("Invite Friend");
_inviteButton.setChangeListener(this);
_inviteButton.setMargin(2,0,10,0);
//SELECT ALL CHECKBOX
selectAllHFM = new HorizontalFieldManager();
_uncheckBmp = Bitmap.getBitmapResource("Uncheck.png");
_checkBmp = Bitmap.getBitmapResource("checked.png");
selectAllButton = new CustomButtonField(29, "", _uncheckBmp, _checkBmp, ButtonField.CONSUME_CLICK);
selectAllButton.setChangeListener(this);
selectAllButton.setMargin(5,5,5,5);
selectAllCheckBox = new CheckboxField("Select All", isChecked){
protected boolean navigationClick(int status,
int time) {
selectedContacts = new Vector();
emails = "";
boolean getCBoxStatus = selectAllCheckBox.getChecked();
if(listItemChecked == false){
if(_mainVFM.getFieldCount()!= 0){
_mainVFM.deleteAll();
_mainVFM.add(createContactList(getCBoxStatus));
}
}
return true;
}
};
selectAllCheckBox.setChangeListener(this);
selectAllLabel = new LabelField("Select All");
selectAllLabel.setMargin(5,5,5,5);
selectAllHFM.add(selectAllCheckBox);
//selectAllHFM.add(selectAllLabel);
// toggle list field item on navigation click
mListField = new ListField() {
protected boolean navigationClick(int status,
int time) {
toggleItem();
return true;
};
};
// set two line row height
//mListField.setRowHeight(getFont().getHeight() * 2);
mListField.setCallback(this);
//contactListVFM.add(new NullField(NullField.FOCUSABLE));
contactListVFM.add(_inviteButton);
contactListVFM.add(selectAllHFM);
contactListVFM.add(new SeparatorField());
contactListVFM.add(mListField);
//LOAD CONTACTS
// load contacts in separate thread
loadContacts.run();
return contactListVFM;
}
protected Runnable loadContacts = new Runnable() {
public void run() {
reloadContactList();
// fill list field control in UI event thread
UiApplication.getUiApplication().invokeLater(
fillList);
}
};
protected Runnable fillList = new Runnable() {
public void run() {
int size = mContacts.size();
mListData = new ChecklistData[size];
for (int i =0; i < mContacts.size() ; i++) {
contactItem = (BlackBerryContact) mContacts
.elementAt(i);
String displayName = getDisplayName(contactItem);
// String telContact = getContact(item);
mListData[i] = new ChecklistData(
displayName, isChecked);
mListField.invalidate(i);
System.out.println(">>>>>>>>>"+mListData[i]);
}
mListField.setSize(size);
//invalidate();
}
};
protected void toggleItem() {
listItemChecked = true ;
selectAllCheckBox.setChecked(false);
listItemChecked =false ;
// Get the index of the selected row.
int index = mListField.getSelectedIndex();
System.out.println("..............."+index);
if (index != -1) {
// Get the ChecklistData for this row.
ChecklistData data = mListData[index];
// Toggle its status.
data.toggleChecked();
mListField.invalidate(index);
}
}
private boolean reloadContactList() {
try {
contactList = (ContactList) PIM
.getInstance()
.openPIMList(PIM.CONTACT_LIST,
PIM.READ_ONLY);
allContacts = contactList.items();
mContacts = enumToVector(allContacts);
mListField.setSize(mContacts.size());
System.out.println(",,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,>>>>>>>>>>"+mListField.getSize());
return true;
} catch (PIMException e) {
return false;
}
}
// Convert the list of contacts from an Enumeration to a Vector
private Vector enumToVector(Enumeration contactEnum) {
Vector v = new Vector();
if (contactEnum == null)
return v;
while (contactEnum.hasMoreElements()){
Contact contact = (Contact) allContacts.nextElement();
if(contactList.isSupportedField(Contact.EMAIL)&& (contact.countValues(Contact.EMAIL) > 0)) {
String emailID=contact.getString(Contact.EMAIL, 0);
if(emailID.length() !=0 && emailID != null ){
v.addElement(contact);
}
}
}
return v;
}
public void drawListRow(ListField list,
Graphics graphics, int index, int y, int w) {
rowString = new StringBuffer();
Object obj = this.get(list, index);
if (list.getSelectedIndex() != index) {
graphics.setBackgroundColor(index % 2 == 0 ||index==0 ? Color.WHITE
: Color.LIGHTGRAY);
graphics.clear();
//list.setFocus();
}
BlackBerryContact contact = (BlackBerryContact) mContacts
.elementAt(index);
String email= contact.getString(Contact.EMAIL, 0);
int vecIndex = selectedContacts.indexOf(email);
if (obj != null) {
ChecklistData currentRow = (ChecklistData) obj;
if (currentRow.isChecked()) {
if(vecIndex == -1){
selectedContacts.addElement(email);
}
rowString
.append(Characters.BALLOT_BOX_WITH_CHECK);
} else {
selectedContacts.removeElement(email);
rowString.append(Characters.BALLOT_BOX);
}
// Append a couple spaces and the row's text.
rowString.append(Characters.SPACE);
rowString.append(Characters.SPACE);
rowString.append(currentRow.getStringVal());
// Draw the text.
}
graphics.drawText(rowString.toString(), 0, y,
0, w);
}
public static String getDisplayName(Contact contact) {
if (contact == null) {
return null;
}
String displayName = null;
// First, see if there is a meaningful name set for the contact.
if (contact.countValues(Contact.NAME) > 0) {
final String[] name = contact.getStringArray(
Contact.NAME, 0);
final String firstName = name[Contact.NAME_GIVEN];
final String lastName = name[Contact.NAME_FAMILY];
if (firstName != null && lastName != null) {
displayName = firstName + " " + lastName;
} else if (firstName != null) {
displayName = firstName;
} else if (lastName != null) {
displayName = lastName;
}
if (displayName != null) {
final String namePrefix = name[Contact.NAME_PREFIX];
if (namePrefix != null) {
displayName = namePrefix + " "
+ displayName;
}
return displayName;
}
}
return displayName;
}
// Returns the object at the specified index.
public Object get(ListField list, int index) {
Object result = null;
if (mListData.length > index) {
result = mListData[index];
}
System.out.println(",,,,,,,,,,,,,,,,,,,,,,,"+mListData.length);
return result;
}
// Returns the first occurrence of the given String,
// beginning the search at index, and testing for
// equality using the equals method.
public int indexOfList(ListField list, String p, int s) {
return -1;
}
// Returns the screen width so the list uses the entire screen width.
public int getPreferredWidth(ListField list) {
return Graphics.getScreenWidth();
// return Display.getWidth();
}
public void fieldChanged(Field field, int context) {
if(field==_inviteButton){
for(int n=0 ; n<selectedContacts.size() ; n++){
emails= emails + selectedContacts.elementAt(n)+",";
}
//}
String mailBody =": "+Jxa.loginUserName+" invited you on NaijaPings app. Please download NaijaPings Android app from here "+"http://appworld.blackberry.com/webstore/content/77264/?lang=en" ;
sendEmail=new SendEmail(mailBody);
sendEmail.Email(emails,Constant.emailSubject);
emails ="" ;
selectedContacts.removeAllElements();
}else if(field == selectAllCheckBox){
selectedContacts = new Vector();
emails = "";
getCBoxStatus = selectAllCheckBox.getChecked();
//selectedContacts.removeAllElements();
if(listItemChecked == false){
if(_mainVFM.getFieldCount()!= 0){
_mainVFM.deleteAll();
_mainVFM.add(createContactList(getCBoxStatus));
}
}
}
}
}
Here ,in drawListRow() , get() method is called only that many times that is number of contacts are visible on the screen. For remaining contact to add, I have to scroll the list.
In drawListRow() method I am adding those contacts into selectedContacts vector and than using those vector to get contact to send a mail. Contacts will be added only when particular list item will be drawn.
So, how I can get all selected contact without scrolling the list?
This is similar to the problem you had in one of your other recent questions. The problem is that drawListRow() is a callback designed to let you draw the rows that need drawing. It's not meant to do anything else, like assembling a list of contacts to email.
The BlackBerry OS tries to be efficient, so it will only ask you to drawListRow() for the rows that are actually visible to the user (on screen). Anything more would be wasteful.
So, if you want to assemble a list of all selected rows, you should do it somewhere else, not in drawListRow().
It looks to me like you can build a list of all currently selected rows by using this code, wherever you want:
public Vector getSelectedContacts() {
selectedContacts.removeAllElements();
for (int i = 0; i < mListData.length; i++) {
Object obj = mListData[i];
if (obj != null) {
BlackBerryContact contact = (BlackBerryContact) mContacts.elementAt(i);
String email = contact.getString(Contact.EMAIL, 0);
int vecIndex = selectedContacts.indexOf(email);
ChecklistData currentRow = (ChecklistData) obj;
if (currentRow.isChecked()) {
if(vecIndex == -1){
selectedContacts.addElement(email);
}
} else {
// this line is probably not actually needed, since we
// call removeAllElements() at the start of this method
selectedContacts.removeElement(email);
}
}
}
return selectedContacts;
}
I have added a BasicEditField to a GridFieldManager. When I test it, it allows input values like 11.11.11. How can I make my BasicEditField accept only correct double numbers, like 101.1 or 123.123. That is, allow only one decimal point.
gfm = new GridFieldManager(1, 2, 0);
gfm.add(new LabelField(" Enter value : "));
bef = new BasicEditField(BasicEditField.NO_NEWLINE|BasicEditField.FILTER_REAL_NUMERIC);
bef.setFilter(TextFilter.get(NumericTextFilter.REAL_NUMERIC));
bef.setFilter(TextFilter.get(TextFilter.REAL_NUMERIC));
bef.setText("1");
bef.setMaxSize(8);
gfm.add(bef);
add(gfm);
i had tried everything that i can. but the problem is yet in my app. can anyone give me a proper way to design a input field tha accepts decimal numbers?
Please add all the objects into the mainScreen with add(field);.
and then trying to get value of that fields.
now in your code put
String s = bef.getText();
Dialog.alert(s);
after
add(gfm);
and
To accept number like 1.1111.
then add
BasicEditField.FILTER_REAL_NUMERIC
in BasicEditFieldConstructor.
Now i think you got your solution.
finally i got the solution for a forum(forgot to copy the link)..
here it is...
inside my class i put the variables...
private int maxIntDigits = -1;
private int maxFractDigits = -1;
private String old;
i had added a BasicEditField, bef..
bef = new BasicEditField("","1");
bef.setMaxSize(8);
bef.setChangeListener(this);
add(bef);
And then in its fieldChanged().
public void fieldChanged(Field field, int context)
{
if(field==bef)
{
String str = bef.getText();
if(str.equals(""))
{
old = "";
//return;
}
if(str.indexOf('.') == str.lastIndexOf('.'))
{
if(str.indexOf('-') >= 0)
{
bef.setText(old);
}
if(validateIntPart(str) && validateFractPart(str))
{
old = str;
//return;
}
else
{
bef.setText(old);
}
}
else
{
bef.setText(old);
//return;
}
}
}
and then two functions in it...
private boolean validateIntPart(String str) {
if(maxIntDigits == -1) {
return true; //no limit has been set
}
int p = str.indexOf('.');
if(p == -1) {
p = str.length();
}
int digits = str.substring(0, p).length();
if(digits > maxIntDigits) {
return false;
} else {
return true;
}
}
private boolean validateFractPart(String str) {
if(maxFractDigits == -1) {
return true; //no limit has been set
}
int p = str.indexOf('.');
if(p == -1) {
return true; //if no '.' found then the fract part can't be too big
}
int digits = str.substring(p + 1, str.length()).length();
if(digits > maxFractDigits) {
return false;
} else {
return true;
}
}
I have a single button which I want to use as Start/Stop button. How can I make the buttonfield work as toggle button?
Please help.
Just change button label on fieldChange or navigationClick or touchEvent, don't forget to save toggle state in class member:
class ToggleButtonField extends ButtonField {
int mToggleState = -1;
String[] mLabels = {};
public ToggleButtonField(String[] labels) {
super(CONSUME_CLICK);
if(labels != null && labels.length > 0)
{
mLabels = labels;
mToggleState = 0;
updateLabel();
}
}
private void updateLabel() {
setLabel(mLabels[mToggleState]);
}
protected void fieldChangeNotify(int context) {
mToggleState = getNextToggleState(mToggleState);
updateLabel();
super.fieldChangeNotify(context);
}
private int getNextToggleState(int state) {
int result = mToggleState+1;
if(result >= mLabels.length)
result = 0;
return result;
}
}