在下面的代码示例中,我想从我的 BackgroundThread更改TextBox 的前景文本的颜色,但它得到了错误:
此线程无法访问此对象,因为它位于另一个线程中。
我必须在下面的代码中进行哪些更改,以便后台工作线程可以更改 TextBox 中的前景色?
回答:
谢谢安迪,这只是一个小小的疏忽,为了后代,这里是更正的代码:
using System.Windows;
using System.ComponentModel;
using System.Threading;
using System.Windows.Media;
namespace TestBackgroundWorker7338
{
public partial class Window1 : Window
{
private BackgroundWorker _worker;
int _percentageFinished = 0;
public Window1()
{
InitializeComponent();
ButtonCancel.IsEnabled = false;
}
private void Button_Start(object sender, RoutedEventArgs e)
{
_worker = new BackgroundWorker();
_worker.WorkerReportsProgress = true;
_worker.WorkerSupportsCancellation = true;
_worker.DoWork += (s, args) =>
{
BackgroundWorker worker = s as BackgroundWorker;
int numberOfTasks = 300;
for (int i = 1; i <= numberOfTasks; i++)
{
if (worker.CancellationPending)
{
args.Cancel = true;
return;
}
Thread.Sleep(10);
float percentageDone = (i / (float)numberOfTasks) * 100f;
worker.ReportProgress((int)percentageDone);
}
};
_worker.ProgressChanged += (s,args) =>
{
_percentageFinished = args.ProgressPercentage;
ProgressBar.Value = _percentageFinished;
Message.Text = _percentageFinished + "% finished";
if (_percentageFinished < 500)
{
Message.Text = "stopped at " + _percentageFinished + "%";
}
else
{
Message.Text = "finished";
}
if (_percentageFinished >= 70)
{
InputBox.Foreground = new SolidColorBrush(Colors.Red);
}
else if (_percentageFinished >= 40)
{
InputBox.Foreground = new SolidColorBrush(Colors.Orange);
}
else if (_percentageFinished >= 10)
{
InputBox.Foreground = new SolidColorBrush(Colors.Brown);
}
else
{
InputBox.Foreground = new SolidColorBrush(Colors.Black);
}
};
_worker.RunWorkerCompleted += (s,args) =>
{
ButtonStart.IsEnabled = true;
ButtonCancel.IsEnabled = false;
ProgressBar.Value = 0;
};
_worker.RunWorkerAsync();
ButtonStart.IsEnabled = false;
ButtonCancel.IsEnabled = true;
}
private void Button_Cancel(object sender, RoutedEventArgs e)
{
_worker.CancelAsync();
}
}
}