问题描述
我正在使用sqlite数据库开发Windows Phone应用程序。我能够显示数据库并删除要删除的特定行。但是问题是我选择了该行并单击删除后，该行不会消失那个时候。我必须租用该页面才能看到它已被删除。
下面是我使用click_delete事件的类的代码
I am developing an windows phone app using sqlite database.I am able to show out the database and delete the particular row I want to delete.But the problem is after I select the row and click delete the row does not vanishes at that time.I have to renter that page to see that it is deleted.Below here is the code of the class where I use the click_delete event
public partial class History : PhoneApplicationPage
{
ObservableCollection<historyTableSQlite> DB_HistoryList = new ObservableCollection<historyTableSQlite>();
DbHelper Db_helper = new DbHelper();
//public static int Selected_HistoryId;
//int Selected_HistoryId;
public static int Selected_HistoryId {get; set;}
// string dbPath = Path.Combine(Windows.Storage.ApplicationData.Current.LocalFolder.Path, "db.sqlite");
public History()
{
InitializeComponent();
}
protected override void OnNavigatedTo(NavigationEventArgs e)
{
Db_helper.AddInfo();
ReadHistoryList_Loaded();
// Selected_HistoryId = int.Parse(NavigationContext.QueryString["SelectedHistoryID"]);
}
public void ReadHistoryList_Loaded()
{
ReadAllContactsList dbhistory = new ReadAllContactsList();
DB_HistoryList = dbhistory.GetAllHistory();//Get all DB contacts
ListData.ItemsSource = DB_HistoryList.OrderByDescending(i => i.Id).ToList();
//Latest contact ID can Display first
}
public void ListData_SelectionChanged(object sender, SelectionChangedEventArgs e)
{
if (ListData.SelectedIndex != -1)
{
historyTableSQlite listitem = ListData.SelectedItem as historyTableSQlite;
History.Selected_HistoryId = listitem.Id;
}
}
private void Delete_Click(object sender, EventArgs e)
{
Db_helper.DeleteContact(History.Selected_HistoryId);
NavigationService.Navigate(new Uri("/History.xaml", UriKind.Relative));
}
private void DeleteAll_Click(object sender, EventArgs e)
{
DbHelper Db_helper = new DbHelper();
Db_helper.DeleteAllContact();//delete all DB contacts
DB_HistoryList.Clear();//Clear collections
ListData.ItemsSource = DB_HistoryList;
}
}
}
下面是具有所有主要功能的类
below is the class with all main functions
public class DbHelper
{
SQLiteConnection dbConn;
public async Task<bool> onCreate(string DB_PATH)
{
try
{
if (!CheckFileExists(DB_PATH).Result)
{
using (dbConn = new SQLiteConnection(DB_PATH))
{
dbConn.CreateTable<historyTableSQlite>();
}
}
return true;
}
catch
{
return false;
}
}
private async Task<bool> CheckFileExists(string fileName)
{
try
{
var store = await Windows.Storage.ApplicationData.Current.LocalFolder.GetFileAsync(fileName);
return true;
}
catch
{
return false;
}
}
//retrieve all list from the database
public ObservableCollection<historyTableSQlite> ReadHistory()
{
using (var dbConn = new SQLiteConnection(App.DB_PATH))
{
List<historyTableSQlite> myCollection = dbConn.Table<historyTableSQlite>().ToList<historyTableSQlite>();
ObservableCollection<historyTableSQlite> HistoryList = new ObservableCollection<historyTableSQlite>(myCollection);
return HistoryList;
}
}
// Insert the new info in the histrorytablesqlite table.
public void Insert(historyTableSQlite newcontact)
{
using (var dbConn = new SQLiteConnection(App.DB_PATH))
{
dbConn.RunInTransaction(() =>
{
dbConn.Insert(newcontact);
});
}
}
public void AddInfo()
{
DbHelper Db_helper = new DbHelper();
Db_helper.Insert((new historyTableSQlite
{
Date = DateTime.Now.ToShortDateString(),
Time = DateTime.Now.ToShortTimeString(),
Zone = Checkin.Zone_st,
Floor = Checkin.Floor_st,
latitude = Checkin.Latitud_do,
longtitude = Checkin.Longtitude_do
}));
}
// Delete specific contact
public void DeleteContact(int Id)
{
using (var dbConn = new SQLiteConnection(App.DB_PATH))
{
var existingvalue = dbConn.Query<historyTableSQlite>("select * from historyTableSQlite where Id =" + Id).FirstOrDefault();
if (existingvalue != null)
{
dbConn.RunInTransaction(() =>
{
dbConn.Delete(existingvalue);
});
}
}
}
//Delete all contactlist or delete Contacts table
public void DeleteAllContact()
{
using (var dbConn = new SQLiteConnection(App.DB_PATH))
{
//dbConn.RunInTransaction(() =>
// {
dbConn.DropTable<historyTableSQlite>();
dbConn.CreateTable<historyTableSQlite>();
dbConn.Dispose();
dbConn.Close();
//});
}
}
下面是带有所有表的类
public class historyTableSQlite : INotifyPropertyChanged
{
[SQLite.PrimaryKey, SQLite.AutoIncrement]
public int Id
{
get;
set;
}
private int idValue;
private string dateValue = string.Empty;
public string Date
{
get { return this.dateValue; }
set
{
if (value != this.dateValue)
{
this.dateValue = value;
NotifyPropertyChanged("Date");
}
}
}
private string timeValue = string.Empty;
public string Time
{
get { return this.timeValue; }
set
{
if (value != this.timeValue)
{
this.timeValue = value;
NotifyPropertyChanged("Time");
}
}
}
private string floorValue = string.Empty;
public string Floor
{
get { return this.floorValue; }
set
{
if (value != this.floorValue)
{
this.floorValue = value;
NotifyPropertyChanged("Floor");
}
}
}
public string zoneValue;
public string Zone
{
get { return this.zoneValue; }
set
{
if (value != this.zoneValue)
{
this.zoneValue = value;
NotifyPropertyChanged("Zone");
}
}
}
private double latValue;
public double latitude
{
get { return latValue; }
set
{
if (value != this.latValue)
{
this.latValue = value;
NotifyPropertyChanged("Latitude");
}
}
}
private double lonValue;
public double longtitude
{
get { return this.lonValue; }
set
{
if (value != this.lonValue)
{
this.lonValue = value;
NotifyPropertyChanged("Longitude");
}
}
}
// public string isMarkPoint { get; set; }
public historyTableSQlite()
{
}
public historyTableSQlite(string date, string time, string floor, string zone, double lat, double lng)
{
Date = date;
Time = time;
Floor = floor;
Zone = zone;
latitude = lat;
longtitude = lng;
}
public event PropertyChangedEventHandler PropertyChanged;
private void NotifyPropertyChanged(String info)
{
if (PropertyChanged != null)
{
PropertyChanged(this, new PropertyChangedEventArgs(info));
}
}
}
推荐答案
如果从 ObservableCollection 中删除该项目，它将通知ListBox更新其容器。
If you delete the item from your ObservableCollection, it will notify the ListBox to update its container.
在您的代码中
// this is correct
ObservableCollection<historyTableSQlite> DB_HistoryList = new ObservableCollection<historyTableSQlite>();
但是您的问题是您没有实际上没有将您的 ListBox 链接到它。
But your problem is that you don't actually link your ListBox to it.
在代码中，您将创建一个副本（以及您要尝试执行的最糟糕的副本），然后设置 ListBox ItemsSource。见下文（您有这个）
In your code you create a copy (and the worst kind of copy given what you're trying to do) and you set the ListBox ItemsSource to it. See below (you have this)
ListData.ItemsSource = DB_HistoryList.OrderByDescending(i => i.Id).ToList();
因此，基本上，您的ListBox不是 ObservableCollection ，但这是一个 List 结构。
So basically, your ListBox is not an ObservableCollection but it's a List structure.
删除并插入到列表中不会更新ListBox的UI。
Deleting and Inserting into the List will not update the ListBox's UI.
摆脱此列表，找到另一种排序 ObservableCollection 的方法。
Get rid of this List, find another way to sort your ObservableCollection.
那么您基本上可以做到这一点
Then you can basically do this
ListData.ItemsSource = DB_HistoryList; // set the listbox to the actual obs collection
DB_HistoryList.RemoveAt(i); // remove the item at index i
DB_HistoryList.RemoveItem(object); // remove the object that matches
这篇关于删除一行后，它不会从屏幕上消失的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持！