如何在进程等待完成时显示加载控件？

Question

我决定使用这个第三方组件在我的 windows 窗体中制作一个简单的加载控件。

http://www.codeproject.com/Articles/14841/How-to-write-a-loading-circle-animation-in-NET

当在单个请求（每次一个）中打开和关闭将属性“Active”更改为 true 或 false 时，这可以正常工作。问题是当一个进程正在等待服务时，我假装在进程开始之前激活 loadingControl 并在我“认为”该进程必须完成时关闭。当我这样做时，图像加载显示为静态图像。 （没有动画）。

对于这个问题，我很抱歉，我是 C# 新手。但我认为我需要使用 Threads 或类似的东西。

所以我的一般代码是这样的：

using [libraries here]...;
namespace [namespace here]
{
    Public partial class Form1 : Form
    {
        public Form1()
        {
            InitializeComponent();
            this.loadingCircle1.Visible = false;
        }

        private void button1_Click(object sender, EventArgs e)
        {
            Thread t = new Thread(new ThreadStart(showLoading));
            this.loadingCircle1.Visible = true;
            t.Start();

            //Import an Excel

            t.Abort();
        }

        public void showLoading()
        {
            loadingCircle1.Active = true;
            loadingCircle1.RotationSpeed = 10;
        }
    }
}

但始终加载显示为没有动画的静态图像。

Answer 1

您创建一个线程，它只是设置两个属性然后结束。 t.Abort 可能什么都不做，因为到那时线程已经退出了。更糟糕的是，您在 UI 线程上导入 excel 文件，这会阻止任何动画并冻结整个 UI。

你应该这样做：

备注：当然，如果您的表单是响应式的，您必须禁用/启用控件，并准备好在加载期间关闭表单时会发生什么情况。

1.使用线程

如果您真的想显式使用线程，请这样做：

public partial class Form1 : Form
{
    public Form1()
    {            
        InitializeComponent();
    }

    private Thread workerThread = null;

    private void btnImport_Click(object sender, EventArgs e)
    {
        // start the animation (I used a progress bar, start your circle here)
        progressBar1.Visible = true;
        progressBar1.Style = ProgressBarStyle.Marquee;

        // start the job and the timer, which polls the thread
        btnImport.Enabled = false;
        workerThread = new Thread(LoadExcel);
        workerThread.Start();
        timer1.Interval = 100;
        timer1.Start();
    }

    private void LoadExcel()
    {
        // some work takes 5 sec
        Thread.Sleep(5000);
    }

    private void timer1_Tick(object sender, EventArgs e)
    {
        if (workerThread == null)
        {
            timer1.Stop();
            return;
        }

        // still works: exiting
        if (workerThread.IsAlive)
            return;

        // finished
        btnImport.Enabled = true;
        timer1.Stop();
        progressBar1.Visible = false;
        workerThread = null;
    }
}

2。后台工作者

BackgroundWorker 可以在完成时抛出一个事件：

public partial class Form1 : Form
{
    public Form1()
    {
        InitializeComponent();
        backgroundWorker1.DoWork += BackgroundWorker1_DoWork;
        backgroundWorker1.RunWorkerCompleted += BackgroundWorker1_RunWorkerCompleted;
    }


    private void btnImport_Click(object sender, EventArgs e)
    {
        // start the animation
        progressBar1.Visible = true;
        progressBar1.Style = ProgressBarStyle.Marquee;

        // start the job
        btnImport.Enabled = false;
        backgroundWorker1.RunWorkerAsync();
    }

    private void BackgroundWorker1_DoWork(object sender, DoWorkEventArgs e)
    {
        LoadExcel();
    }

    private void BackgroundWorker1_RunWorkerCompleted(object sender, RunWorkerCompletedEventArgs e)
    {
        btnImport.Enabled = true;
        progressBar1.Visible = false;
    }

    private void LoadExcel()
    {
        // some work takes 5 sec
        Thread.Sleep(5000);
    }
}

3.使用异步等待

这是最简单的一个。

public partial class Form1 : Form
{
    public Form1()
    {
        InitializeComponent();
    }

    private async void btnImport_Click(object sender, EventArgs e)
    {
        // start the waiting animation
        progressBar1.Visible = true;
        progressBar1.Style = ProgressBarStyle.Marquee;

        // simply start and await the loading task
        btnImport.Enabled = false;
        await Task.Run(() => LoadExcel());

        // re-enable things
        btnImport.Enabled = true;
        progressBar1.Visible = false;
    }

    private void LoadExcel()
    {
        // some work takes 5 sec
        Thread.Sleep(5000);
    }
}

Answer 2

我建议使用 async/await（对于 C# 5.0）：

private void button1_Click(object sender, EventArgs e){
    ImportAsync();
}

private async Task ImportAsync(){
    // UI-thread
    showLoading();
    this.loadingCircle1.Visible = true;

    // wait until task will be finished
    await Task.Run(() => {
        // different non-blocking thread for all the hard work, but without UI-stuff
        // import an Excel
    });

    // going back to UI-thread
    this.loadingCircle1.Visible = false;
}