I am having a problem with navigating between a MainPage and a details Page.
On the main page the code looks like this:
private void MainPage_Loaded(object sender, RoutedEventArgs e)
{
State.Clear();
List<Level> lst = new List<Level>();
using (SqliteCommand selectCmd = Constants.conn.CreateCommand())
{
Constants.conn.Open();
selectCmd.Transaction = Constants.conn.BeginTransaction();
selectCmd.CommandText = " SELECT * FROM Levels";
using (SqliteDataReader reader = selectCmd.ExecuteReader())
{
while (reader.Read())
{
Level lev = new Level();
lev.ID = Convert.ToInt32(reader.GetValue(0));
lev.Name = reader.GetValue(1).ToString();
lev.levelScore = Convert.ToInt32(reader.GetValue(2));
lst.Add(lev);
}
}
selectCmd.Transaction.Connection.Close();
}
Constants.conn.Close();
levelList.ItemsSource = lst;
}
It sets the items on the page. I navigate on the detail page.
The problem comes when I navigate back to the MainPage... Although the State is Clear and the levelItems is 0 It renders The previous view of the page and when it tries to access the sqlConnection throwsan exception.
Related
I have a list picker which is displayed in my phone application page.I have created list picker in starting of class,and i am adding the list picker in the phoneApplicationPage_loaded() method.When the page is launched the first time, ,the scenario works perfectly and its navigates further to second page.When i navigate back to previous page(containing list picker),it shows Invalid Operation Exception occured stating "Element is already the child of another element."
I want to know how to handle these scenarios?
Code is below
namespace My.Design
{
public partial class myclass : PhoneApplicationPage
{
String[] values = null;
ListPicker picker = new ListPicker();
StackPanel sp;
StackPanel mainFrame;
String statementInfo = "";
public myclass()
{
InitializeComponent();
}
private void PhoneApplicationPage_Loaded(object sender, RoutedEventArgs e)
{
Debug.WriteLine("Phone Application Page Loaded_>>>>>>");
List<String> source = new List<String>();
displayUI();
}
public void displayUI()
{
Debug.WriteLine("About to display UI in miniStatement");
Debug.WriteLine("<-------------Data--------->");
Debug.WriteLine(statementInfo);
Debug.WriteLine("<-------------Data--------->");
int count = VisualTreeHelper.GetChildrenCount(this);
if (count > 0)
{
for (int i = 0; i < count; i++)
{
UIElement child = (UIElement)VisualTreeHelper.GetChild(this, i);
string childTypeName = child.GetType().ToString();
Debug.WriteLine("Elements in this Child" + childTypeName);
}
}
List<String> source = new List<String>();
String[] allParams = ItemString.Split('#');
source.Add("PleaseSelect");
for (int i = 0; i < allParams.Length; i++)
{
Debug.WriteLine("All Params Length" + allParams[i]);
if (!(allParams[i].Equals("") && (!allParams[i].Equals(null))))
{
if (values != null)
{
Debug.WriteLine("Values length" + values.Length);
values[values.Length] = allParams[i];
}
else
{
Debug.WriteLine("Allparams Length" + allParams[i]);
source.Add(allParams[i]);
}
}
}
//picker = new ListPicker();
this.picker.ItemsSource = source;
mainFrame = new StackPanel();
TextBlock box = new TextBlock();
box.Text = "> DEmoClass";
box.FontSize = 40;
mainFrame.Children.Add(box);
Canvas canvas = new Canvas();
StackPanel sp = new StackPanel();
TextBlock box1 = new TextBlock();
box1.Text = "Number";
box1.HorizontalAlignment = HorizontalAlignment.Center;
box1.FontSize = 40;
SolidColorBrush scb1 = new SolidColorBrush(Colors.Black);
box1.Foreground = scb1;
sp.Children.Add(box1);
picker.Width = 400;
picker.Height = 150;
sp.Children.Add(picker);
Canvas.SetTop(sp, 150);
canvas.Children.Add(sp);
mainFrame.Children.Add(canvas);
this.ContentPanel1.Children.Add(mainFrame);
}
protected override void OnNavigatingFrom(System.Windows.Navigation.NavigatingCancelEventArgs e)
{
/*
Debug.WriteLine("OnNavigatingFrom>>>.>>MainPage");
if (sp != null)
{
sp.Children.Remove(picker);
}*/
base.OnNavigatingFrom(e);
}
}
}
If you are not intending to update the listpicker after navigating back from the second page add the following line in your Loaded event handler
private void PhoneApplicationPage_Loaded(object sender, RoutedEventArgs e)
{
this.Loaded -= PhoneApplicationPage_Loaded;
Debug.WriteLine("Phone Application Page Loaded_>>>>>>");
List<String> source = new List<String>();
displayUI();
}
i don't know why you can not use that case when app resume from tombstoned.
error happened because when you back to your page , loaded event runs again.
by the way,
Application_Activated 's argument can tell you app resumes from tombstoned or not--.
if (e.IsApplicationInstancePreserved)
{
IsTombstoning = false;
}
else
{
IsTombstoning = true;
}
I'm curious why you're creating it in code and not leaving it in XAML? Also the error is coming from the fact that you're attempting to add it twice into a location that can probably only have a single content element. What's the higher level problem you're trying to solve?
Basically i am trying to pull the contacts from the phone and showing them in the Listpicker control for a feature in my app. I have two Listpickers, one for name of contacts list and the other showing the list of phonenumbers for the chosen contact.
Here is my code:
//Declarations
ContactsSearchEventArgs e1;
String SelectedName;
String SelectedNumber;
List<string> contacts = new List<string>();
List<string> phnum = new List<string>();
public AddressBook() // Constructor
{
InitializeComponent();
Contacts contacts = new Contacts();
contacts.SearchCompleted += new EventHandler<ContactsSearchEventArgs>(contacts_SearchCompleted);
contacts.SearchAsync(string.Empty,FilterKind.None,null);
}
void contacts_SearchCompleted(object sender, ContactsSearchEventArgs e)
{
e1 = e;
foreach (var result in e.Results)
{
if (result.PhoneNumbers.Count() != 0)
{
contacts.Add(result.DisplayName.ToString());
}
}
Namelist.ItemsSource = contacts;
}
private void Namelist_SelectionChanged(object sender, SelectionChangedEventArgs e)
{
SelectedName = (sender as ListPicker).SelectedItem.ToString();
phnum.Clear();
foreach (var result in e1.Results)
{
if (SelectedName == result.DisplayName)
{
phnum.Add(result.PhoneNumbers.FirstOrDefault().ToString());
}
}
Numbers.ItemsSource = phnum;
}
private void Numbers_SelectionChanged(object sender, SelectionChangedEventArgs e)
{
SelectedNumber = (sender as ListPicker).SelectedItem.ToString();
}
Am able to populate the Numberlist with phonenumbers for the chosen name at the Listpicker background, but the number is not showing up in the front. I think Numbers_SelectionChanged() event is called only one time when the page loads and am not seeing it triggerd when i change the contact list. Anyone has an idea of where am going wrong ?
If you change
List<string>
To
ObservableCollection<string>
this should work.
Also then you only need to set the ItemSource once, in Xaml or you constructor.
But you may run into another issue with the November 2011 Toolkit and ListPicker.
See more in thread.
private void Namelist_SelectionChanged(object sender, SelectionChangedEventArgs e)
{
SelectedName = (sender as ListPicker).SelectedItem.ToString();
phnum = new List<string>(); // Changed instead of phnum.Clear()
foreach (var result in e1.Results)
{
if (SelectedName == result.DisplayName)
{
phnum.Add(result.PhoneNumbers.FirstOrDefault().ToString());
}
}
Numbers.ItemsSource = phnum;
}
This works !!. While debugging i found its phnum.Clear() giving a problem. So i thought to create a new instance of phnum list for selected contact.
I have tried hundreds of times to find errors for this piece of codes.
It only works through WIFI, but When I switch off WIFI on my phone, and run the app again, this app just shut down automatically, which means it thrown an exception.
The app is simple, I used WebClint() to download HTML source and parsed it with HTML Agility Pack, then added them to a list, foreach the list to creat each news object.
I have tried catch the exception stacktrace and bind it to a texblock, It said some of ArgumentOutOfRange exception and Genericlist(int32 index)???
I have no idea about it, It was fine in wifi, but not in 3G network. Can anyone help?
public partial class MainPage : PhoneApplicationPage
{
string srcHTML;
HtmlNode UrlNode;
ObservableCollection<News> newsList = new ObservableCollection<News>();
List<HtmlNode> headlines;
HtmlDocument hd;
News n;
// Constructor
public MainPage()
{
InitializeComponent();
}
private void PhoneApplicationPage_Loaded(object sender, RoutedEventArgs e)
{
WebClient webClenet = new WebClient();
webClenet.Encoding = new HtmlAgilityPack.Gb2312Encoding();
webClenet.DownloadStringAsync(new Uri("http://www.6park.com/news/multi1.shtml", UriKind.RelativeOrAbsolute));
webClenet.DownloadStringCompleted += new DownloadStringCompletedEventHandler(webClenet_DownloadStringCompleted);
}
private void webClenet_DownloadStringCompleted(object sender, DownloadStringCompletedEventArgs e)
{
srcHTML = e.Result;
GetHeadlinePage(srcHTML);
}
private void GetHeadlinePage(string srcHTML)
{
hd = new HtmlDocument();
hd.LoadHtml(srcHTML);
try
{
UrlNode = hd.DocumentNode.ChildNodes[1].ChildNodes[3].ChildNodes[8].ChildNodes["tr"].ChildNodes["td"].ChildNodes["ul"];
headlines = UrlNode.Descendants("a").ToList();
foreach (var headline in headlines)
{
if (headline.Attributes["href"].Value.Contains("6park"))
{
n = new News();
n.NewsTitle = headline.InnerText;
n.NewsUrl = headline.Attributes["href"].Value;
n.NewsDetails = headline.NextSibling.InnerText.Replace("- ", "新闻来源：") + headline.NextSibling.NextSibling.InnerText + headline.NextSibling.NextSibling.NextSibling.InnerText;
newsList.Add(n);
}
}
}
catch (Exception ex)
{
//NewsSource.Text = ex.StackTrace + "\n" + ex.Message;
}
NewslistBox.ItemsSource = newsList;
//NewsHeadlineWebBrowser.NavigateToString(ConvertExtendedASCII(headNews));
}
}
I'd debug the value passed to GetHeadlinePage().
I'd suspect that the response is different based on the network or the request is timing out or you're getting some other error.
I'd assume that the call to LoadHtml() is failing as this isn't inside any exception handling/trapping and you've not validating the value passed to it.
I've recently upgraded my WP7 app to Mango and am having some problems with the camera. The code below used to work on 7.0, but on 7.1 the completed handler fires before the dialog is even shown, so I can't capture the result. After taking the photo, the phone displays "Resuming..." which it never used to do.
var dlg = new CameraCaptureTask();
dlg.Completed += (s, e) =>
{
if (e.TaskResult == TaskResult.OK) {
BitmapImage bmp = new BitmapImage();
bmp.SetSource(e.ChosenPhoto);
//var img = new Image();
//img.Source = bmp;
string caption = string.Empty;
var inputDialog = new InputPrompt()
{
Title = "Caption",
Message = "Enter caption/description for snapshot",
};
inputDialog.Completed += (ss, ee) =>
{
if (ee.PopUpResult == PopUpResult.Ok)
{
caption = ee.Result;
var snap = SnapshotBLL.AddSnapshot(recipeId, bmp, caption);
onComplete(null, new SnapshotEventArgs(snap));
}
};
inputDialog.Show();
}
};
dlg.Show();
The MSDN docs appear to show a variation of my code but I can no longer get the result of the camera capture task.
Assuming that your sample comes from a single method I wouldn't expect it to ahve worked pre Mango.
The CameraCaptureTask should be created and the callback assigned in the constructor of the page for it to work properly.
Something like:
public partial class MainPage : PhoneApplicationPage
{
private CameraCaptureTask cct = new CameraCaptureTask();
public MainPage()
{
InitializeComponent();
cct.Completed += new EventHandler<PhotoResult>(cct_Completed);
}
private void cct_Completed(object sender, PhotoResult e)
{
// Do whatever here
}
private void SomeEventHandler(object sender, RoutedEventArgs e)
{
cct.Show();
}
}
This works in both 7.0 & 7.1
I'm using this to make a web request and download some data:
public partial class MainPage : PhoneApplicationPage
{
public MainPage()
{
InitializeComponent();
var client = new WebClient();
client.DownloadStringCompleted += (s, e) => {
textBlock1.Text = e.Result;
};
client.DownloadStringAsync(new Uri("http://example.com"));
}
}
The text of textBlock1 never changes even though e.Result has the correct data. How do I update that from the callback?
Edit: If I add MessageBox.Show(e.Result); in the callback along with the textBlock1.Text assignment, both the messsage box and the text box show the correct data.
Edit Again: If I add a TextBox and set it's text right after the line textBlock1.Text line, they both show the correct text.
I think, it's a bug.
I also ran into some problems with updating the UI from different dispatchers. What I finally did was use the TextBlock's (or other UI Element) own dispatcher and that worked for me. I think the phone framework may be using different dispatchers between the app and UI Elements. Notice the change from dispatcher.BeginInvoke to textbox1.Dispatcher...
void MainPage_Loaded(object sender, RoutedEventArgs e)
{
var dispatcher = Deployment.Current.Dispatcher;
var client = new WebClient();
client.DownloadStringCompleted += (s, e) =>
{
var result = e.Result;
textBlock1.Dispatcher.BeginInvoke(
()=> textBlock1.Text = result
);
};
client.DownloadStringAsync(new Uri("http://example.com"));
}
From browsing through the WP7 forums, a bunch of people were reporting that this was related to a video card driver issue. I've updated my ATI Radeon HD 3400 drivers to the latest version and it appears to work now.
client.DownloadStringAsync is expecting a Uri like this:
client.DownloadStringAsync(new Uri("http://example.com"));
also, shouldn't you update your TextBlock through a Dispatcher.BeginInvoke like this:
client.DownloadStringCompleted += (s, e) =>
{
if (null == e.Error)
Dispatcher.BeginInvoke(() => UpdateStatus(e.Result));
else
Dispatcher.BeginInvoke(() => UpdateStatus("Operation failed: " + e.Error.Message));
};
public partial class MainPage : PhoneApplicationPage
{
public MainPage()
{
InitializeComponent();
Loaded += MainPage_Loaded;
}
void MainPage_Loaded(object sender, RoutedEventArgs e)
{
var dispatcher = Deployment.Current.Dispatcher;
var client = new WebClient();
client.DownloadStringCompleted += (s, e) =>
{
var result = e.Result;
dispatcher.BeginInvoke(
()=> textBlock1.Text = result
);
};
client.DownloadStringAsync(new Uri("http://example.com"));
}
}
I want to comment but can't yet. Yes, I have a very similar issue. In my case it's my viewmodel that is updating a DownloadStatus property, then when the download is completed I do some more work and continue updating this property.
The view stops updating once the ViewModel code hits the OpenReadCompleted method. I've stepped carefully through the code. PropertyChanged fires, and the view even comes back and retrieves the new property value, but never shows the change.
I was sure it was a bug, but then I created a brand new project to reproduce the issue, and it works fine!
Here's a snippet of my non-reproducing code. The UI textblock bound to "DownloadStatus" happily updates properly all the way through. But the same paradigm doesn't work in my main project. Infuriating!
public void BeginDownload(bool doWorkAfterDownload)
{
DownloadStatus = "Starting ...";
_doExtraWork = doWorkAfterDownload;
var webClient = new WebClient();
string auth = "Basic " + Convert.ToBase64String(System.Text.Encoding.UTF8.GetBytes("test:password"));
webClient.Headers["Authorization"] = auth;
webClient.DownloadProgressChanged += new DownloadProgressChangedEventHandler(webClient_DownloadProgressChanged);
webClient.OpenReadCompleted += new OpenReadCompletedEventHandler(webClient_OpenReadCompleted);
webClient.OpenReadAsync(new Uri("http://www.ben.geek.nz/samsung1.jpg"));
}
void webClient_OpenReadCompleted(object sender, OpenReadCompletedEventArgs e)
{
if (e.Error != null)
{
DownloadStatus = e.Error.Message;
return;
}
DownloadStatus = "Completed. Idle.";
if(_doExtraWork)
{
Thread t = new Thread(DoWork);
t.Start(e.Result);
}
}
void DoWork(object param)
{
InvokeDownloadCompleted(new EventArgs());
// just do some updating
for (int i = 1; i <= 10; i++)
{
DownloadStatus = string.Format("Doing work {0}/10", i);
Thread.Sleep(500);
}
DownloadStatus = "Completed extra work. Idle.";
InvokeExtraWorkCompleted(new EventArgs());
}