WPF BackgroundWorker 更新进度条

先看运行效果

 在WPF 中如果直接在UI线程更新进度条，会造成界面卡死，因此使用BackgroundWorker来进行更新，既简单又方便。

先看xaml

<Window
    x:Class="BackgroundWorker使用方法.MainWindow"
    xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
    xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
    xmlns:local="clr-namespace:BackgroundWorker使用方法"
    xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
    Title="MainWindow"
    Width="800"
    Height="450"
    mc:Ignorable="d">
    <Grid>
        <StackPanel VerticalAlignment="Center" Orientation="Vertical">
            <TextBlock
                x:Name="showText"
                HorizontalAlignment="Center"
                FontSize="30" />
            <Grid>
                <ProgressBar
                    x:Name="bar"
                    Height="30"
                    Background="Green" />
                <TextBlock
                    HorizontalAlignment="Center"
                    VerticalAlignment="Center"
                    FontSize="20"
                    Text="{Binding ElementName=bar, Path=Value}" />
            </Grid>
            <Grid Height="30" Margin="3">
                <Grid.ColumnDefinitions>
                    <ColumnDefinition Width="1*" />
                    <ColumnDefinition Width="1*" />
                </Grid.ColumnDefinitions>
                <Button
                    x:Name="start"
                    Grid.Column="0"
                    Margin="3,0"
                    Click="Start"
                    Content="启动" />
                <Button
                    x:Name="cancel"
                    IsEnabled="False"
                    Grid.Column="1"
                    Margin="3,0"
                    Click="Stop"
                    Content="取消" />
            </Grid>
        </StackPanel>
    </Grid>
</Window>

后台代码

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Linq;
using System.Text;
using System.Threading;
using System.Threading.Tasks;
using System.Windows;
using System.Windows.Controls;
using System.Windows.Data;
using System.Windows.Documents;
using System.Windows.Input;
using System.Windows.Media;
using System.Windows.Media.Imaging;
using System.Windows.Navigation;
using System.Windows.Shapes;

namespace BackgroundWorker使用方法
{
    /// <summary>
    /// 进度条参数
    /// </summary>
    public class BarState
    {
        private double _value;

        /// <summary>
        /// 进度条的颜色 也可以用渐变色来代替
        /// </summary>
        public Brush Color { get; set; }

        /// <summary>
        /// 提示文本
        /// </summary>
        public string ShowText { get; set; }

        /// <summary>
        /// 进度显示
        /// </summary>
        public double Value
        {
            get => _value;

            set
            {
                if (value != _value)
                {
                    OnValueChanged(this, new EventArgs());//触发事件
                    _value = value;
                }
            }
        }

        public BarState()
        {
            Color = new SolidColorBrush(Colors.Green);
            Color.Opacity = 0.0;
            ShowText = "还未启动";
            Value = 0;
        }

        /// <summary>
        /// 进度显示事件
        /// </summary>
        public event EventHandler ValueChanged;

        public void OnValueChanged(object sender, EventArgs e)
        {
            ValueChanged?.Invoke(this, e);
            Color.Opacity = Value / 100;
            if (Value <= 5)
            {
                ShowText = "启动中。。。";
            }
            else if (Value <= 75)
            {
                ShowText = "运行中。。。";
            }
            else if (Value <= 95)
            {
                ShowText = "即将完成。。。";
            }
            else
            {
                ShowText = "已完成！";
            }
        }
    }

    /// <summary>
    /// MainWindow.xaml 的交互逻辑
    /// </summary>
    public partial class MainWindow : Window
    {
        private BackgroundWorker _worker;

        private Brush barColor;

        public MainWindow()
        {
            InitializeComponent();
            barColor = new SolidColorBrush(Colors.Green);
            bar.Background = barColor;
            _worker = new BackgroundWorker();
            _worker.WorkerReportsProgress = true;//获取或设置一个值，该值指示能否报告进度更新
            _worker.WorkerSupportsCancellation = true;//获取或设置一个值，该值指示是否支持异步取消

            _worker.DoWork += DoSomething;//挂载要运行的方法
            _worker.ProgressChanged += ChangeValue;//挂载进度值改变的方法
            _worker.RunWorkerCompleted += Complete;//当方法完成时候
        }

        private void ChangeValue(object sender, ProgressChangedEventArgs e)
        {
            var state = e.UserState as BarState;
            bar.Value = state.Value;

            //bar.Background.Opacity = state.Value / 100;//此处不能直接更改背景颜色，因为是依赖属性,此处只做演示，实际应在xaml中用动画
            barColor.Opacity = bar.Value / 100;
            showText.Text = state.ShowText;
        }

        private void Complete(object sender, RunWorkerCompletedEventArgs e)
        {
            if (e.Error != null)//如果发生异常
            {
                MessageBox.Show(e.Error.Message);
                return;
            }
            if (e.Cancelled)//如果操作被取消
            {
                MessageBox.Show("操作被取消！");
                return;
            }

            if (MessageBox.Show(e.Result.ToString()) == MessageBoxResult.OK)
            {
                start.IsEnabled = true;
                cancel.IsEnabled = false;
            };
        }

        private void DoSomething(object sender, DoWorkEventArgs e)
        {
            var state = new BarState();//自定义属性
            for (int i = 0; i <= 100; i++)
            {
                Thread.Sleep(100);
                state.Value = i;
                _worker.ReportProgress(i, state);//报告进度
                if (_worker.CancellationPending)//如果检查到取消操作，退出运行
                {
                    e.Cancel = true;//通知RunWorkerCompletedEventArgs操作已取消
                    break;
                }
            };
            e.Result = "运行完成";//运行完成后传递参数给RunWorkerCompleted事件
        }

        private void Start(object sender, RoutedEventArgs e)
        {
            start.IsEnabled = false;
            cancel.IsEnabled = true;
            _worker.RunWorkerAsync();//运行
        }

        private void Stop(object sender, RoutedEventArgs e)
        {
            _worker.CancelAsync();//取消运行
            start.IsEnabled = true;
            cancel.IsEnabled = false;
        }
    }
}