Background Worker loading screen in Winforms

问题

I have a Form where one can Sign In and it could take a while till the data gets loaded into the Form. So I wanted to create a seperate Form (loadScreen.cs) with a Progress Bar when the Form is loading. I tried this in the loadScreen.cs Form:

 private void Form1_Load(object sender, EventArgs e)
 {
   worker = new BackgroundWorker();
   worker.WorkerReportsProgress = true;
   worker.WorkerSupportsCancellation = true;

   worker.DoWork += new DoWorkEventHandler(worker_DoWork);
   worker.ProgressChanged +=
          new ProgressChangedEventHandler(worker_ProgressChanged);
   worker.RunWorkerCompleted +=
         new RunWorkerCompletedEventHandler(worker_RunWorkerCompleted);
 }



 void worker_DoWork(object sender, DoWorkEventArgs e)
 {
   int percentFinished = (int)e.Argument;
   while (!worker.CancellationPending && percentFinished < 100)
 {
   percentFinished++;
   worker.ReportProgress(percentFinished);
   System.Threading.Thread.Sleep(50);
 }
 e.Result = percentFinished;
 }


 void worker_ProgressChanged(object sender, ProgressChangedEventArgs e)
 {
   progressBar1.Value = e.ProgressPercentage;
 }


 void worker_RunWorkerCompleted(object sender, RunWorkerCompletedEventArgs e)
 {
  this.Close();
  }

I've read that the worker_DoWork method should have the code which takes longer to load. I don't know how to handle this since my button is in Form1. When it's clicked then I go to another class with

  private void signIn_Click(object sender, EventArgs e)
    {
        var logIn = new LogIn(this);
        logIn.checkUserInput(this);
    }

and there I execute the operations which load certain things. How to connect everything? I need help!

回答1:

I'm actually in the process of creating a general-purpose dialogue for this sort of thing. It's not going to be ready in time to be of use to you but I would suggest that you go along similar lines. Create your "Loading" dialogue so that it accepts a delegate and invokes it in the DoWork event handler. The main form can then contain a method that does the work and you can pass a delegate for that method to the dialogue. I'll post a very basic example.

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

    private DataTable table;

    private void button1_Click(object sender, EventArgs e)
    {
        var work = new Action(GetData);

        using (var f2 = new Form2(work))
        {
            f2.ShowDialog();
            this.dataGridView1.DataSource = this.table;
        }
    }

    private void GetData()
    {
        this.table = new DataTable();

        using (var adapter = new SqlDataAdapter("SELECT * FROM MyTable", "connectionstring here"))
        {
            adapter.Fill(table);
        }
    }
}


public partial class Form2 : Form
{
    private Action work;

    public Form2(Action work)
    {
        InitializeComponent();

        this.work = work;
    }

    private void Form2_Load(object sender, EventArgs e)
    {
        this.backgroundWorker1.RunWorkerAsync();
    }

    private void backgroundWorker1_DoWork(object sender, DoWorkEventArgs e)
    {
        this.work();
    }

    private void backgroundWorker1_RunWorkerCompleted(object sender, RunWorkerCompletedEventArgs e)
    {
        this.DialogResult = DialogResult.OK;
    }
}

Note that there's no real way to measure progress when using a data adapter so you could only really display a marquee progress bar in this case.

来源：https://stackoverflow.com/questions/29094016/background-worker-loading-screen-in-winforms

标签

winforms

backgroundworker