我有一个视图,其中DataGrid
。 一个ViewModel作为DataContext
我可以在后台对象中访问DataTable
。 背景对象必须与DataTable
一起使用并保持更新。 该用户也被允许对该DataTable
进行更改。WPF DataGrid多线程崩溃
如果我创建了DataTable
的副本,它会停止崩溃,但用户明显不会处理数据。
如果我将访问权限留给用户打开,程序肯定会崩溃。
这里是一个简短的程序,这将崩溃:
app.cs
public partial class App : Application
{
public App()
{
SomeBackgroundThing background = new SomeBackgroundThing();
MainWindowViewModel viewmodel = new MainWindowViewModel(background);
MainWindowView view = new MainWindowView(viewmodel);
view.Show();
}
}
主要XAML
<Window x:Class="NullPointerDataGrid.MainWindowView"
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
Title="MainWindow" Height="350" Width="525">
<Grid>
<DataGrid Name="datagrid" ItemsSource="{Binding Path=table, UpdateSourceTrigger=PropertyChanged, Mode=TwoWay}"/>
</Grid>
</Window>
和程序代码:
using System;
using System.Collections.Generic;
using System.Linq;
using System.Windows;
using System.Windows.Controls;
using System.Windows.Documents;
using System.Windows.Media;
using System.Data;
using System.Diagnostics;
using System.Timers;
using System.ComponentModel;
namespace NullPointerDataGrid
{
public partial class MainWindowView : Window
{
public MainWindowView(MainWindowViewModel model)
{
DataContext = model;
InitializeComponent();
datagrid.Loaded += new RoutedEventHandler(ScrollToBottom);
datagrid.AutoGeneratedColumns += new EventHandler(StarSizeLastRow);
}
void ScrollToBottom(object sender, RoutedEventArgs e)
{
Debug.WriteLine("TableGrid_ScrollToBottom");
if (datagrid.Items.Count > 0)
{
var border = VisualTreeHelper.GetChild(datagrid, 0) as Decorator;
if (border != null)
{
var scroll = border.Child as ScrollViewer;
if (scroll != null) scroll.ScrollToEnd();
}
}
}
void StarSizeLastRow(object sender, EventArgs e)
{
Debug.WriteLine("TableGrid_StarSizeLastColumn");
try
{
datagrid.Columns[datagrid.Columns.Count - 1].Width = new DataGridLength(1, DataGridLengthUnitType.Star);
}
catch { }
}
}
public class MainWindowViewModel : INotifyPropertyChanged
{
public event PropertyChangedEventHandler PropertyChanged;
private SomeBackgroundThing thing;
public DataTable table
{
get
{
lock (thing.table)
{
//DataTable wpfcopy = thing.table.Copy();
return thing.table;
};
}
set
{
Debug.Write("This never happens");
}
}
public MainWindowViewModel(SomeBackgroundThing thing)
{
this.thing = thing;
thing.Changed += new EventHandler(thing_Changed);
}
void thing_Changed(object sender, EventArgs e)
{
if (PropertyChanged != null)
{
PropertyChanged(this, new PropertyChangedEventArgs("table"));
}
}
}
public class SomeBackgroundThing : IDisposable
{
public DataTable table;
private DataTable tablecopy;
private System.Timers.Timer timer, slowrowchanger;
public event EventHandler Changed = new EventHandler((o, e) => { ;});
protected void CallChanged(object sender, EventArgs e)
{
Changed(sender, e);
}
public SomeBackgroundThing()
{
CreateTable();
UpdateB(this, null);
tablecopy = table.Copy();
InitAndStartTimer(1);
}
#region timer
private void UpdateA()
{
Boolean haschanged = false;
DataTable newcopy = table.Copy(); ;
if (newcopy.Rows.Count != tablecopy.Rows.Count)
{
Debug.WriteLine("Different ammount of rows");
haschanged = true;
}
else if (newcopy.Columns.Count != tablecopy.Columns.Count)
{
Debug.WriteLine("Different ammount of columns");
haschanged = true;
}
else
{
for (int i = 0; i < newcopy.Rows.Count; i++)
{
for (int j = 0; j < newcopy.Columns.Count; j++)
{
if (newcopy.Rows[i][j].ToString() != tablecopy.Rows[i][j].ToString())
{
Debug.WriteLine(String.Format(
"Element [{0}/{1}]: {2} is different from {3}",
i, j, newcopy.Rows[i][j], tablecopy.Rows[i][j]
));
haschanged = true;
}
if (haschanged) break;
}
if (haschanged) break;
}
}
if (haschanged)
{
tablecopy = newcopy;
}
}
private void InitAndStartTimer(int interval)
{
timer = new System.Timers.Timer();
timer.Interval = interval;
timer.AutoReset = true;
timer.Elapsed += new ElapsedEventHandler((s, e) =>
{
UpdateA();
});
timer.Enabled = true;
slowrowchanger = new System.Timers.Timer();
slowrowchanger.Interval = 3000;
slowrowchanger.AutoReset = true;
slowrowchanger.Elapsed += new ElapsedEventHandler((s, e) =>
{
UpdateB(null, null);
});
slowrowchanger.Enabled = true;
}
public void Dispose()
{
timer.Enabled = false;
slowrowchanger.Enabled = false;
timer.Dispose();
slowrowchanger.Dispose();
}
#endregion
#region editlastrow
void UpdateB(object sender, EventArgs e)
{
Random rnd = new Random();
List<String> cells = new List<string>{
"The SAME",
rnd.Next(0,100).ToString(),
rnd.ToString(),
rnd.NextDouble().ToString()};
lock (table)
{
OverwriteOrAppendLastRow(ref table, cells);
table.AcceptChanges();
}
CallChanged(this, null);
}
private void OverwriteOrAppendLastRow(ref DataTable table, List<string> newrow)
{
if (table.Rows.Count == 0) CreteEmptyRow(ref table);
if (newrow[0].ToString() != table.Rows[table.Rows.Count - 1][0].ToString())
{
Debug.WriteLine(String.Format("Creating row because '{0}' is different from '{1}'", newrow[0], table.Rows[table.Rows.Count - 1][0]));
CreteEmptyRow(ref table);
}
OverwriteLastRow(ref table, newrow);
}
private void OverwriteLastRow(ref DataTable table, List<string> newrow)
{
for (int i = 0; i < newrow.Count() && i < table.Columns.Count; i++)
{
table.Rows[table.Rows.Count - 1][i] = newrow[i];
}
}
private void CreteEmptyRow(ref DataTable table)
{
table.Rows.Add(new String[table.Columns.Count]);
}
#endregion
private void CreateTable()
{
table = new DataTable();
table.Columns.Add("FirstCell", typeof(String));
table.Columns.Add("BananaCell", typeof(String));
table.Columns.Add("CherryCell", typeof(String));
table.Columns.Add("Blue", typeof(String));
Random rnd = new Random();
for (int i = 0; i < 145; i++)
{
table.Rows.Add(new String[]{
rnd.Next().ToString(),
rnd.Next(0,i+1).ToString(),
rnd.ToString(),
rnd.NextDouble().ToString()});
}
}
}
}
哪有我停止这个多人ead崩溃了?
编辑:
我不知道是否有多于一个原因造成的代码崩溃。但我尽我所能收集了一些关于崩溃原因的信息:
App.g.cs中的Nullpointer异常 - 自动生成的部分。调试器不会进入它 - 所以我不能说任何关于它崩溃的线。
这是异常详细信息,对德国人抱歉。
System.NullReferenceException wurde nicht behandelt.
Message=Der Objektverweis wurde nicht auf eine Objektinstanz festgelegt.
Source=PresentationFramework
InnerException:
Stacktrace只显示“Externer Code”,因此没有要跟踪的堆栈。我的代码可以处理它...不知何故,我需要封装WPF所以它不会崩溃,一种方法是复制DataTable - 但后来我放弃了写回来的能力该表格自其setter不被调用时,已编辑的东西。
编辑#2:
我重建这个例子来说明错误我已经在另一个程序,我只是发现了什么崩溃实际上是与滚动条相关。如果我将显示数据的数量更改为较低的数字,以便没有滚动条,则代码不会崩溃。
你有免疫吗?如果是这样,请编辑您的问题,并添加exeption消息和stacktrace。 – GameScripting 2012-07-27 17:49:25
哪条线会崩溃? – Paparazzi 2012-07-27 19:48:32
通过设计后台线程无法访问UI对象。我怀疑它试图更新UI时崩溃了。 UI不会每次检查正确的线程,因此您可能需要进行一些更新以使您相信这不是问题。但它确实很快,而且不好。不是肯定地说这是问题,但我可以告诉我有类似的症状类似的问题。我所做的就是让UI RO在后台处理副本,然后将UI绑定到回调中的处理副本并制作UI RW。 – Paparazzi 2012-07-28 20:47:34