如何在加载栏存在时防止程序无响应

Question

我正在创建一个程序，它可以在启动时从文件中读取大量数据。

我尝试了一个进度条来显示加载进度，希望它能停止无响应，但它在中途冻结并更新屏幕上的标签以解决问题。

//This will be 'private void Form1_Shown(object sender, EventArgs e)'
private void loadingBarToolStripMenuItem_Click(object sender, EventArgs e)
{
    progressBar1.Show();
    for (int i = 0; i < 100; i++)
    {
        progressBar1.Value = i;
        System.Threading.Thread.Sleep(50);
        //StartRespondingAgain();
    }
    progressBar1.Hide();
}

Answer 1

这个问题不是加载栏，而是你在 GUI 线程上运行了长时间的操作。

应该调用事件，完成它们的工作并尽快返回。只能同时运行一段代码，并且当此事件运行时，不能执行其他事件 - 甚至不能执行更改的绘制。

您需要添加某种形式的多任务处理。此操作不会受益于大量线程/任务（例如每个文件一个），但至少可以将长时间运行的循环移至单独的任务中。 BackgroundWorkers、Threads 和 Async/Await 只是 3 种方法。我个人认为 BackgroundWorker 很好——但有点过时了——学习多任务处理，尤其是多线程处理的“训练轮”。我什至得到了一些示例代码：

#region Primenumbers
private void btnPrimStart_Click(object sender, EventArgs e)
{
    if (!bgwPrim.IsBusy)
    {
        //Prepare ProgressBar and Textbox
        int temp = (int)nudPrim.Value;
        pgbPrim.Maximum = temp;
        tbPrim.Text = "";

        //Start processing
        bgwPrim.RunWorkerAsync(temp);
    }
}

private void btnPrimCancel_Click(object sender, EventArgs e)
{
    if (bgwPrim.IsBusy)
    {
        bgwPrim.CancelAsync();
    }
}

private void bgwPrim_DoWork(object sender, DoWorkEventArgs e)
{
    int highestToCheck = (int)e.Argument;
    //Get a reference to the BackgroundWorker running this code
    //for Progress Updates and Cancelation checking
    BackgroundWorker thisWorker = (BackgroundWorker)sender;

    //Create the list that stores the results and is returned by DoWork
    List<int> Primes = new List<int>();


    //Check all uneven numbers between 1 and whatever the user choose as upper limit
    for(int PrimeCandidate=1; PrimeCandidate < highestToCheck; PrimeCandidate+=2)
    {
        //Report progress
        thisWorker.ReportProgress(PrimeCandidate);
        bool isNoPrime = false;

        //Check if the Cancelation was requested during the last loop
        if (thisWorker.CancellationPending)
        {
            //Tell the Backgroundworker you are canceling and exit the for-loop
            e.Cancel = true;
            break;
        }

        //Determin if this is a Prime Number
        for (int j = 3; j < PrimeCandidate && !isNoPrime; j += 2)
        {
            if (PrimeCandidate % j == 0)
                isNoPrime = true;
        }

        if (!isNoPrime)
            Primes.Add(PrimeCandidate);
    }

    //Tell the progress bar you are finished
    thisWorker.ReportProgress(highestToCheck);

    //Save Return Value
    e.Result = Primes.ToArray();
}

private void bgwPrim_ProgressChanged(object sender, ProgressChangedEventArgs e)
{
    pgbPrim.Value = e.ProgressPercentage;
}

private void bgwPrim_RunWorkerCompleted(object sender, RunWorkerCompletedEventArgs e)
{
    pgbPrim.Value = pgbPrim.Maximum;
    this.Refresh();

    if (!e.Cancelled && e.Error == null)
    {
        //Show the Result
        int[] Primes = (int[])e.Result;

        StringBuilder sbOutput = new StringBuilder();

        foreach (int Prim in Primes)
        {
            sbOutput.Append(Prim.ToString() + Environment.NewLine);
        }

        tbPrim.Text = sbOutput.ToString();
    }
    else 
    {
        tbPrim.Text = "Operation canceled by user or Exception";
    }
}
#endregion

但那是你可以挑选毒药的地方。