多线程更新UI的常用方法

Posted 2020-07-25

     开发Winform或者WPF相关GUI程序中，遇到执行耗时程序片段，并且需要在ui界面上实时展示状态信息的问题时，为了防止界面出现假死状态，会用到多线程技术，异步跨线程访问ui界面元素；下面总结下Winform和WPF中常用的几种异步跨线程访问ui界面的技术。

Winform中常用技术

 1、采用BackgroundWorker控件

public partial class Form1 : Form
    {
        private BackgroundWorker worker;
        public Form1()
        {
            InitializeComponent();
            worker = new BackgroundWorker();
            worker.WorkerReportsProgress = true;// To report progress from the background worker we need to set this property
            worker.DoWork += worker_DoWork;// This event will be raised on the worker thread when the worker starts
            worker.ProgressChanged += worker_ProgressChanged;// This event will be raised when we call ReportProgress
        }

        private void worker_ProgressChanged(object sender, ProgressChangedEventArgs e)
        {
            progressBar1.Value = e.ProgressPercentage;
            lblPercent.Text = string.Format("{0}%", e.ProgressPercentage);
            if (e.ProgressPercentage == 100)
            {
                MessageBox.Show("数据处理完毕！");
            }
        }

        private void worker_DoWork(object sender, DoWorkEventArgs e)
        {
            for (int i = 1; i <= 100; i++)
            {
                // Report progress to ‘UI‘ thread
                worker.ReportProgress(i);
                Thread.Sleep(100);
            }
        }

        private void btnCompute_Click(object sender, EventArgs e)
        {
            //Start the background worker
            worker.RunWorkerAsync();
        }
    }

2、采用Timer控件

public partial class Form1 : Form
    {
        private Timer timer;
        private int current;
        public Form1()
        {
            InitializeComponent();
            timer = new Timer();
            timer.Interval = 500;
            timer.Tick += timer_Tick;
        }

        private void timer_Tick(object sender, EventArgs e)
        {
            progressBar1.Value = current;
            lblPercent.Text = string.Format("{0}%", current);
            if (current == 100)
            {
                timer.Stop();
                MessageBox.Show("数据处理完毕！");
            }
        }

        private void btnCompute_Click(object sender, EventArgs e)
        {
            Thread thread = new Thread(new ThreadStart(doWork));
            thread.Start();
            timer.Start();
        }

        private void doWork()
        {
            for (int i = 1; i <= 100; i++)
            {
                current = i;
                Thread.Sleep(100);
            }
        }
    }

3、采用委托的方式

public partial class Form1 : Form
    {
        private delegate void UpdateProgress(int percent);
        public Form1()
        {
            InitializeComponent();
        }

        private void btnCompute_Click(object sender, EventArgs e)
        {
            Thread thread = new Thread(new ThreadStart(doWork));
            thread.Start();
        }

        private void doWork()
        {
            for (int i = 1; i <= 100; i++)
            {
                //progressBar1.BeginInvoke((Action)(() => { progressBar1.Value = i; }));
                //lblPercent.BeginInvoke((Action)(() => { lblPercent.Text = string.Format("{0}%", i); }));
                //if (i == 100)
                //{
                //    MessageBox.Show("数据处理完毕！");
                //}
                update(i);
                Thread.Sleep(100);
            }
        }

        private void update(int percent)
        {
            if (InvokeRequired)
            {
                this.Invoke(new UpdateProgress(update), percent);
            }
            else
            {
                progressBar1.Value = percent;
                lblPercent.Text = string.Format("{0}%", percent);
                if (percent == 100)
                {
                    MessageBox.Show("数据处理完毕！");
                }
            }
        }
    }

WPF中常用技术

     WPF中引入了Dispatcher，常用来解决非ui线程中更新ui控件状态的问题。

/// <summary>
    /// MainWindow.xaml 的交互逻辑
    /// </summary>
    public partial class MainWindow : Window
    {
        private delegate void UpdateProgress(int percent);
        public MainWindow()
        {
            InitializeComponent();
        }

        private void BtnCompute_OnClick(object sender, RoutedEventArgs e)
        {
            Task task = new Task(DoWork);
            task.Start();
        }

        private void DoWork()
        {
            for (int i = 1; i <= 100; i++)
            {
                //Dispatcher.BeginInvoke((Action)(() =>
                //{
                //    progressBar1.Value = i;
                //    lblPercent.Content = string.Format("{0}%", i);
                //    if (i == 100)
                //    {
                //        MessageBox.Show("数据处理完毕！");
                //    }
                //}));
                Dispatcher.BeginInvoke(new UpdateProgress(Update), i);
                Thread.Sleep(100);
            }
        }

        private void Update(int percent)
        {
            progressBar1.Value = percent;
            lblPercent.Content = string.Format("{0}%", percent);
            if (percent == 100)
            {
                MessageBox.Show("数据处理完毕！");
            }
        }
    }