I cannot seem to get my buttons to change colour despite using the Dispatcher from a thread instantiated from the UI thread.
Here is my simple XAML:
<Window x:Class="GOL.MainWindow"
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
xmlns:local="clr-namespace:GOL"
mc:Ignorable="d"
Title="MainWindow">
<Grid Name="GOL">
<Grid.RowDefinitions>
<RowDefinition/>
<RowDefinition/>
<RowDefinition/>
<RowDefinition/>
<RowDefinition/>
<RowDefinition/>
<RowDefinition/>
<RowDefinition/>
<RowDefinition/>
<RowDefinition/>
<RowDefinition/>
<RowDefinition/>
<RowDefinition/>
<RowDefinition/>
<RowDefinition/>
<RowDefinition/>
<RowDefinition/>
<RowDefinition/>
<RowDefinition/>
<RowDefinition/>
<RowDefinition/>
<RowDefinition/>
<RowDefinition/>
<RowDefinition/>
<RowDefinition/>
<RowDefinition/>
<RowDefinition/>
<RowDefinition/>
<RowDefinition/>
<RowDefinition/>
<!--extra row for START button-->
<RowDefinition/>
</Grid.RowDefinitions>
<Grid.ColumnDefinitions>
<ColumnDefinition/>
<ColumnDefinition/>
<ColumnDefinition/>
<ColumnDefinition/>
<ColumnDefinition/>
<ColumnDefinition/>
<ColumnDefinition/>
<ColumnDefinition/>
<ColumnDefinition/>
<ColumnDefinition/>
<ColumnDefinition/>
<ColumnDefinition/>
<ColumnDefinition/>
<ColumnDefinition/>
<ColumnDefinition/>
<ColumnDefinition/>
<ColumnDefinition/>
<ColumnDefinition/>
<ColumnDefinition/>
<ColumnDefinition/>
<ColumnDefinition/>
<ColumnDefinition/>
<ColumnDefinition/>
<ColumnDefinition/>
<ColumnDefinition/>
<ColumnDefinition/>
<ColumnDefinition/>
<ColumnDefinition/>
<ColumnDefinition/>
<ColumnDefinition/>
</Grid.ColumnDefinitions>
</Grid>
Further, here is the logic:
using System;
using System.Threading;
using System.Windows;
using System.Windows.Controls;
using System.Windows.Media;
namespace GOL
{
public partial class MainWindow : Window
{
private const int LENGTH = 30;
private Thread gameThread;
public MainWindow()
{
gameThread = null;
InitializeComponent();
//Load the game grid:
Button cell;
for (int i = 0; i < LENGTH; i) {
for (int j = 0; j < LENGTH; j) {
cell = new Button();
cell.Background = Brushes.Black;
cell.Name = "cell_" ((LENGTH * i) j).ToString();
cell.Click = new RoutedEventHandler(Button_Click);
Grid.SetRow(cell, i);
Grid.SetColumn(cell, j);
//adds children in same order as in name
GOL.Children.Add(cell);
}
}
//finally add start button:
Button start = new Button();
start.Name = "start";
start.Content = "GO!";
start.Click = new RoutedEventHandler(Button_Start);
Grid.SetRow(start, (LENGTH 1));
Grid.SetColumn(start, (LENGTH/2));
GOL.Children.Add(start);
}
/**
* Changes state of cell
*/
private void Button_Click(object sender, RoutedEventArgs e)
{
Button cell = (Button)sender;
if (cell.Background.Equals(Brushes.Black))
cell.Background = Brushes.White;
else
cell.Background = Brushes.Black;
}
/**
*
*/
private void Button_Start(object sender, RoutedEventArgs e)
{
Button start = (Button)sender;
if (start.Content.Equals("GO!")) {
start.Content = "STOP";
gameThread = new Thread(game);
gameThread.Start();
}
else {
start.Content = "GO!";
try {
gameThread.Abort();
gameThread.Join();
} catch (ThreadAbortException){
;//Assumption: gameThread halted
}
}
}
private void game()
{
int neighbours = 0;
Button cell = null;
while (true)
{
//forAll <i, j> of the board:
for (int i = 0; (i < LENGTH); i)
{
for (int j = 0; (j < LENGTH); j)
{
//board is owned by UI thread
Dispatcher.Invoke(() => {
//reference cell (i, j)
cell = (Button)GOL.Children[(LENGTH * i) j];
});
//get neighbour count
neighbours = liveNeighbours(i, j);
//State transition w/r neighbour count:
switch (neighbours) {
case 0:
cell.Dispatcher.BeginInvoke((Action)(() =>
cell.Background = Brushes.Black
));
break;
case 1:
cell.Dispatcher.BeginInvoke((Action)(() =>
cell.Background = Brushes.Black
));
break;
case 2:
//no change
break;
case 3:
cell.Dispatcher.BeginInvoke((Action)(() =>
cell.Background = Brushes.White
));
break;
case 4:
cell.Dispatcher.BeginInvoke((Action)(() =>
cell.Background = Brushes.Black
));
break;
case 5:
cell.Dispatcher.BeginInvoke((Action)(() =>
cell.Background = Brushes.Black
));
break;
case 6:
cell.Dispatcher.BeginInvoke((Action)(() =>
cell.Background = Brushes.Black
));
break;
case 7:
cell.Dispatcher.BeginInvoke((Action)(() =>
cell.Background = Brushes.Black
));
break;
case 8:
cell.Dispatcher.BeginInvoke((Action)(() =>
cell.Background = Brushes.Black
));
break;
}
}
}
}
}
private int liveNeighbours(int x, int y)
{
int living = 0, location;
Button neighbour = null;
for (int Xoff = -1; (Xoff < 2); Xoff) {
for (int Yoff = -1; (Yoff < 2); Yoff) {
location = ((x Xoff) * LENGTH) y Yoff;
if ((Xoff == 0) && (Yoff == Xoff))
;//skip if self
else if ((location < 0) || (location > (Math.Pow(LENGTH, 2) - 1)))
;//skip if outside grid
else {
Dispatcher.Invoke(() => {
neighbour = (Button)GOL.Children[location];
if (neighbour.Background.Equals(Brushes.White))
living;//add to living iff white
});
}
}
}
return living;
}
}
}
Observe the method game() for the main procedure. Also, I refer to the buttons as cells except for the start button.
Now notice I always encapsulate any call to the grid GOL, or any child of it, in a Dispatch operation as was explained to me by other forums. However, it does not seem to have any effect on the UI.
Thanks for any help.
CodePudding user response：
You should take a second look at your switch cases.
Change the Brushes.Black in case 0: to Brushes.White and the dispatcher will update the UI without any problems.
CodePudding user response：
Your code gets stuck in a while loop. Since it is an endless loop, it cannot exit the loop and prevents you from doing any further action.
You can create a DispatcherTimer that works in the UI thread and create your Game function inside it.
DispatcherTimer dispatcherTimer = new DispatcherTimer();
You can avoid it getting stuck by deleting while(true) inside the game function. You can hook the game() function to the DispatcherTimer tick function you created.
private void Button_Start(object sender, RoutedEventArgs e)
{
Button start = (Button)sender;
if (start.Content.Equals("GO!"))
{
start.Content = "STOP";
dispatcherTimer.Start();
dispatcherTimer.Interval = TimeSpan.FromMilliseconds(1);
dispatcherTimer.Tick = DispatcherTimer_Tick;
dispatcherTimer.Start();
}
else
{
start.Content = "GO!";
try
{
dispatcherTimer.Stop();
}
catch (ThreadAbortException)
{
;//Assumption: gameThread halted
}
}
}
private void DispatcherTimer_Tick(object sender, EventArgs e)
{
game();
}
private void game()
{
int neighbours = 0;
Button cell = null;
//forAll <i, j> of the board:
for (int i = 0; (i < LENGTH); i)
{
for (int j = 0; (j < LENGTH); j)
{
//board is owned by UI thread
Dispatcher.Invoke(() => {
//reference cell (i, j)
cell = (Button)GOL.Children[(LENGTH * i) j];
});
//get neighbour count
neighbours = liveNeighbours(i, j);
//State transition w/r neighbour count:
switch (neighbours)
{
case 0:
cell.Dispatcher.BeginInvoke((Action)(() =>
cell.Background = Brushes.Black
));
break;
case 1:
cell.Dispatcher.BeginInvoke((Action)(() =>
cell.Background = Brushes.Black
));
break;
case 2:
//no change
break;
case 3:
cell.Dispatcher.BeginInvoke((Action)(() =>
cell.Background = Brushes.White
));
break;
case 4:
cell.Dispatcher.BeginInvoke((Action)(() =>
cell.Background = Brushes.Black
));
break;
case 5:
cell.Dispatcher.BeginInvoke((Action)(() =>
cell.Background = Brushes.Black
));
break;
case 6:
cell.Dispatcher.BeginInvoke((Action)(() =>
cell.Background = Brushes.Black
));
break;
case 7:
cell.Dispatcher.BeginInvoke((Action)(() =>
cell.Background = Brushes.Black
));
break;
case 8:
cell.Dispatcher.BeginInvoke((Action)(() =>
cell.Background = Brushes.Black
));
break;
}
}
}
}
When you add the following code to the ButtonClick event, the button colors will not be changed before the game starts.
if (!dispatcherTimer.IsEnabled) return;