加载表单时的进度条

Question

I have created a lot of UserControls which have heavy background images. I placed them on a form. Everything works nice after form's loading has finished. Problem is - it takes 10 seconds before form appears on screen.

I searched through the internet and found a solution - showing a temporary form saying "Please wait...".

Now I am wondering is there a possibility to replace "Please wait" message with ProgressBar . Not marquee one. The one which would actually show form's loading progress.

I examined code and it turned out that heavy part is located in InitializeComponent . InitializeComponent is generated automatically so I should not edit manually, right? I tried to move InitializeComponent to separate thread. It turned out to be a bad idea because controls should not be created in different threads.

Answer 1

You should check out background worker.

BackgroundWorker

BackgroundWorker Tutorial

https://www.dotnetperls.com/progressbar

there are methods u can use for progress bar. I think it might help. Good luck.

Answer 2

As you have already experienced you cannot run the InitializeComponent method in another thread. But you can delay some initialization. If you are sure that the image loading is so slow (are they downloaded from a remote location?), then remove the image initialization from the designer (eg. by nullifying the Image properties) and load them only after the form is shown:

public Form1()
{
    InitializeComponent();
}

private async void Form1_Load(object sender, EventArgs e)
{
    progressBar1.Visible = true;
    progressBar1.Value = 0;
    await LoadImages();
    progressBar1.Visible = false;
}

// Just represents a simple source-target mapping so you can associate the loaded images with their targets
// Here I use a path-control mapping just for the case of the example
private ICollection<KeyValuePair<string, Control>> GetImageMapping()
{
    var basePath = Path.Combine(Environment.GetFolderPath(Environment.SpecialFolder.CommonPictures), "Sample Pictures");
    var mapping = new Dictionary<string, Control>
    {
        [Path.Combine(basePath, "Tulips.jpg")] = this, // form1
        [Path.Combine(basePath, "Chrysanthemum.jpg")] = button1,
        // etc, eg. myUserControl1...
    };

    return mapping;
}

private async Task LoadImages()
{
    var mapping = GetImageMapping();
    progressBar1.Maximum = mapping.Count;
    foreach (var item in mapping)
    {
        var image = await LoadImage(item.Key);
        item.Value.BackgroundImage = image;
        progressBar1.Value++;
    }
}

private async Task<Image> LoadImage(string imagePath)
{
    // This makes 1s delay for each image to imitate slow loading. You do NOT need this line actually.
    await Task.Delay(1000);

    // Only this part will be executed in another thread:
    return await Task.Run<Image>(() =>
    {
        // or download it, load from a stream, resource, whatever...
        var result = Image.FromFile(imagePath);
        return result;
    });
}

Please note that the form can be closed before the loading progress finishes so you might need some extra checks, too.