WPF中使用Free解决访问非UI线程创建的对象抛出的Thread异常

本文链接：https://blog.youkuaiyun.com/mybloglucis009/article/details/8796399

本文介绍了一个WPF应用程序如何使用多线程技术在后台加载图像并安全地更新UI的过程。通过分离图像加载和UI更新操作，可以避免UI冻结，实现更流畅的用户体验。

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using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Windows;
using System.Windows.Controls;
using System.Windows.Data;
using System.Windows.Documents;
using System.Windows.Input;
using System.Windows.Media;
using System.Windows.Media.Imaging;
using System.Windows.Navigation;
using System.Windows.Shapes;
using System.Threading;
using System.Windows.Threading;
namespace WpfMultiThread
{
    /// <summary>
    /// MainWindow.xaml 的交互逻辑
    /// </summary>
    public partial class MainWindow : Window
    {
        class WasImage
        {
            public BitmapSource bmp = null;

        }
        public MainWindow()
        {
            InitializeComponent();
        }
        private double BoodWidth = 0;
        private void Window_Loaded(object sender, RoutedEventArgs e)
        {
            BoodWidth = m_rectBood.Width;
        }
        private double counter = 1;
        private delegate void NormalDelegate();
        private WasImage Cal()
        {
            WasImage wasImg = new WasImage();
            wasImg.bmp = new BitmapImage(new Uri(System.Environment.CurrentDirectory + "\\zz.jpg"));
            wasImg.bmp.Freeze();//如果没有此步则在UI线程中调用会失败
            return wasImg;

        }
        private void UpdateUI()
        {
            m_rectBood.Width = counter * BoodWidth;
            //m_tblCounter.Text = counter.ToString();
        }

        private void m_btnStart_Click(object sender, RoutedEventArgs e)
        {
            //异步任务封装在一个delegate中, 此delegate将运行在后台线程 
            Func<WasImage> asyncAction = this.Cal;

            //在UI线程中得到异步任务的返回值，并更新UI
            //必须在UI线程中执行 
            Action<IAsyncResult> resultHandler = delegate(IAsyncResult asyncResult)
            {
                    WasImage wasImage = asyncAction.EndInvoke(asyncResult);
                            m_imgtest.Source = wasImage.bmp;
            };

            //异步任务执行完毕后的callback, 此callback运行在后台线程上. 
            //此callback会异步调用resultHandler来处理异步任务的返回值.
            AsyncCallback asyncActionCallback = delegate(IAsyncResult asyncResult)
            {
                this.Dispatcher.BeginInvoke(DispatcherPriority.Background, resultHandler, asyncResult);
            };

            //在UI线程中开始异步任务, 
            //asyncAction(后台线程), asyncActionCallback(后台线程)和resultHandler(UI线程)
            //将被依次执行
            asyncAction.BeginInvoke(asyncActionCallback, null);

            //NormalDelegate calDele = new NormalDelegate(Cal);
            //calDele.BeginInvoke(null, null);   
        }

        private void m_btnInvoke_Click(object sender, RoutedEventArgs e)
        {
            //m_imgtest.Source = (this.Tag as WasImage).bmp;
        }

    }
}