BeatLyrics/BeatLyrics.Tool/Utils/LoadingWrap.cs

using BeatLyrics.Tool.Properties;
using System;
using System.Drawing;
using System.Threading;
using System.Threading.Tasks;
using System.Windows.Forms;

namespace BeatLyrics.Tool.Utils
{
    public static class LoadingWrap
    {
        private static readonly Image LoadingImage = Resources.loading;

        public static IDisposable ShowLoading(this Form control, string text, int delayMs = 500, int fadingMs = 500)
        {
            if (false == control.InvokeRequired)
                throw new InvalidOperationException("需要从非界面线程调用此方法");

            Form form = null;

            void CreateControl()
            {
                form = new Form
                {
                    FormBorderStyle = FormBorderStyle.None
                    ,
                    Width = 320
                    ,
                    Height = 64
                    ,
                    StartPosition = FormStartPosition.CenterParent
                    ,
                    ShowInTaskbar = false
                    ,
                    Opacity = 0
                };

                var panel = new Panel { BorderStyle = BorderStyle.FixedSingle, Dock = DockStyle.Fill, };
                form.Controls.Add(panel);

                var size = Math.Min(form.Width, form.Height);

                panel.Controls.Add(new Label
                {
                    Text = text,
                    Dock = DockStyle.Fill,
                    TextAlign = ContentAlignment.MiddleLeft,
                });

                panel.Controls.Add(new PictureBox
                {
                    Dock = DockStyle.Left
                    ,
                    Height = size
                    ,
                    Width = size
                    ,
                    SizeMode = PictureBoxSizeMode.Zoom
                    ,
                    Image = LoadingImage
                });

                panel.Controls.Add(new Panel { Height = 20, Dock = DockStyle.Top });
                panel.Controls.Add(new Panel { Height = 20, Dock = DockStyle.Bottom });
            }

            const int stepMs = 100;

            var closed = false;
            var step = 1d / ((double)fadingMs / stepMs);

            void ShowInvisibleForm()
            {
                control.Invoke(new Action(() => form.ShowDialog(control)));
            }

            void DelayAndFadeIn()
            {
                Thread.Sleep(delayMs);
                if (closed)
                    return;

                var alpha = 0d;
                while (false == closed && alpha < 1)
                {
                    alpha += step;
                    if (alpha > 1)
                        alpha = 1;

                    var localVar = alpha;
                    control.Invoke(new Action(() => form.Opacity = localVar));

                    Thread.Sleep(stepMs);
                }
            }

            void FadeOutAndClose()
            {
                closed = true;

                var alpha = 0d;
                control.Invoke(new Action(() => alpha = form.Opacity));

                while (alpha > 0)
                {
                    alpha -= step;
                    if (alpha < 0)
                        alpha = 0;
                    control.Invoke(new Action(() => form.Opacity = alpha));
                    Thread.Sleep(stepMs);
                }

                control.Invoke(new Action(() => form.Close()));
            }

            control.Invoke(new Action(CreateControl));
            Task.Factory.StartNew(ShowInvisibleForm);
            Task.Factory.StartNew(DelayAndFadeIn);
            return new Disposable(FadeOutAndClose);
        }

        private class Disposable : IDisposable
        {
            private readonly Action _action;

            public Disposable(Action action)
            {
                _action = action;
            }

            public void Dispose()
            {
                _action();
            }
        }
    }
}