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窗口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

当打开和关闭在单个请求中将属性"Active"更改为 true 或 false 时，这工作正常（每次一个）。问题是当一个进程正在等待被服务时，我假装在进程开始之前激活 loadControl，并在我"认为"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。（无动画）。

我很抱歉这个问题，我是 C# 的新手。 但我认为我需要使用线程或类似的东西。

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

创建一个线程，该线程仅设置两个属性，然后结束。t.Abort可能什么都不做，因为到那时线程已经退出。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。

这是你应该如何做到的：

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

1. 使用线程

如果你真的想显式使用线程，可以这样做：

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可以在完成后引发事件：

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;
}