稳扎稳打Silverlight(18) - 2.0视频之详解MediaElement, 开发一个简易版的全功能播放器

<UserControl x:Class="Silverlight20.Video.VideoPlayer"
        xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"    
        xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml">
        <StackPanel HorizontalAlignment="Left">
        
                <!--
                Source - 需要播放的媒体地址
                Stretch - 拉伸值 [System.Windows.Media.Stretch 枚举]。参见：本Demo的Shape/Shape.xaml
                AutoPlay - 是否自动播放媒体
                -->
                <MediaElement x:Name="mediaElement"
                                Width="400" Height="200"
                                Source="http://download.microsoft.com/download/2/0/5/205d8c39-3d55-4032-8195-7b0e6eda4cb6/WinVideo-SL-InstallExperience.wmv"    
                                Stretch="Fill"    
                                AutoPlay="False">
                </MediaElement>

<Button x:Name="play" Content="播放" Margin="5" Click="play_Click" />
                <Button x:Name="pause" Content="暂停" Margin="5" Click="pause_Click" />
                <Button x:Name="stop" Content="停止" Margin="5" Click="stop_Click" />
                <Button x:Name="mute" Content="静音" Margin="5" Click="mute_Click" />

<Slider x:Name="playSlider" Minimum="0" Maximum="1" Margin="5" ToolTipService.ToolTip="播放进度" ValueChanged="playSlider_ValueChanged" />
                <Slider x:Name="volumeSlider" Minimum="0" Maximum="1" Margin="5" ToolTipService.ToolTip="音量大小" ValueChanged="volumeSlider_ValueChanged" />
                <Slider x:Name="balanceSlider" Minimum="-1" Maximum="1" Margin="5" ToolTipService.ToolTip="音量平衡" ValueChanged="balanceSlider_ValueChanged" />

<TextBlock x:Name="lblPlayTime" Margin="5" />
                <TextBlock x:Name="lblVolume" Margin="5" />
                <TextBlock x:Name="lblBalance" Margin="5" />

<TextBlock x:Name="lblDownloadProgress" Margin="5" />
                <TextBlock x:Name="lblBufferingProgress" Margin="5" />
                <TextBlock x:Name="lblDroppedFramesPerSecond" Margin="5" />
                <TextBlock x:Name="lblState" Margin="5" />

<TextBlock x:Name="lblWidth" Margin="5" />
                <TextBlock x:Name="lblHeight" Margin="5" />
                <TextBlock x:Name="lblTotalTime" Margin="5" />
                <TextBlock x:Name="lblBufferingTime" Margin="5" />

</StackPanel>
</UserControl>

VideoPlayer.xaml.cs

using System;
using System.Collections.Generic;
using System.Linq;
using System.Net;
using System.Windows;
using System.Windows.Controls;
using System.Windows.Documents;
using System.Windows.Input;
using System.Windows.Media;
using System.Windows.Media.Animation;
using System.Windows.Shapes;

using System.Windows.Threading;

namespace Silverlight20.Video
{
        public partial class VideoPlayer : UserControl
        {
                // 媒体的时长
                private TimeSpan _duration;

                private DispatcherTimer _timer = new DispatcherTimer();

                public VideoPlayer()
                {
                        InitializeComponent();

                        this.Loaded += new RoutedEventHandler(VideoPlayer_Loaded);

                        /*
                         * MediaOpened - 当媒体被成功地打开时所触发的事件
                         * MediaFailed - 当媒体未能被成功地打开时所触发的事件
                         * CurrentStateChanged - 播放状态（CurrentState）发生改变时所触发的事件
                         * DownloadProgressChanged - 下载进度（DownloadProgress）发生变化时所触发的事件（当下载增加量大于等于 0.05 或下载进度增加到 1 时会触发此事件）
                         * MediaEnded - 当媒体播放到末尾时所触发的事件
                         * BufferingProgressChanged - 缓冲进度（BufferingProgress）发生变化时所触发的事件（当缓冲增加量大于等于 0.05 或缓冲进度增加到 1 时会触发此事件）
                         */

                        mediaElement.MediaOpened += new RoutedEventHandler(mediaElement_MediaOpened);
                        mediaElement.CurrentStateChanged += new RoutedEventHandler(mediaElement_CurrentStateChanged);
                        mediaElement.DownloadProgressChanged += new RoutedEventHandler(mediaElement_DownloadProgressChanged);
                        mediaElement.MediaEnded += new RoutedEventHandler(mediaElement_MediaEnded);
                        mediaElement.BufferingProgressChanged += new RoutedEventHandler(mediaElement_BufferingProgressChanged);
                }

                void VideoPlayer_Loaded(object sender, RoutedEventArgs e)
                {
                        // 每 500 毫秒调用一次指定的方法
                        _timer.Interval = TimeSpan.FromMilliseconds(500);
                        _timer.Tick += new EventHandler(_timer_Tick);
                        _timer.Start();
                }

                void _timer_Tick(object sender, EventArgs e)
                {
                        // CurrentState - 播放状态 [System.Windows.Media.MediaElementState枚举]
                        // Position - 媒体的位置（单位：秒）
                        if (mediaElement.CurrentState == MediaElementState.Playing)
                        {
                                lblPlayTime.Text = string.Format(
                                        "{0}{1:00}:{2:00}:{3:00}",
                                        "播放进度：",
                                        mediaElement.Position.Hours,
                                        mediaElement.Position.Minutes,
                                        mediaElement.Position.Seconds);
                        }

                        // DroppedFramesPerSecond - 媒体每秒正在丢弃的帧数
                        lblDroppedFramesPerSecond.Text = "每秒正在丢弃的帧数：" + mediaElement.DroppedFramesPerSecond.ToString();
                }

                void mediaElement_BufferingProgressChanged(object sender, RoutedEventArgs e)
                {
                        // BufferingProgress - 缓冲进度（0 - 1 之间）
                        lblBufferingProgress.Text = string.Format(
                                "缓冲进度：{0:##%}",
                                mediaElement.BufferingProgress);
                }

                void mediaElement_MediaEnded(object sender, RoutedEventArgs e)
                {
                        mediaElement.Stop();
                }

                void mediaElement_DownloadProgressChanged(object sender, RoutedEventArgs e)
                {
                        // DownloadProgress - 下载进度（0 - 1 之间）
                        lblDownloadProgress.Text = string.Format(
                                "下载进度：{0:##%}",
                                mediaElement.DownloadProgress);
                }
                private void mediaElement_MediaOpened(object sender, RoutedEventArgs e)
                {
                        /*
                         * NaturalVideoWidth - 媒体文件的宽
                         * NaturalVideoHeight - 媒体文件的高
                         * HasTimeSpan - 是否可取得媒体文件的时长
                         * NaturalDuration - 媒体文件的时长
                         * Volume - 音量大小（0 - 1 之间）
                         * Balance - 音量平衡（-1 - 1 之间）
                         * BufferingTime - 需要缓冲的时间的长度
                         */

                        lblWidth.Text = "媒体文件的宽：" + mediaElement.NaturalVideoWidth.ToString();
                        lblHeight.Text = "媒体文件的高：" + mediaElement.NaturalVideoHeight.ToString();

                        _duration = mediaElement.NaturalDuration.HasTimeSpan ? mediaElement.NaturalDuration.TimeSpan : TimeSpan.FromMilliseconds(0);

                        lblTotalTime.Text = string.Format(
                                "{0}{1:00}:{2:00}:{3:00}", "时长：",
                                _duration.Hours,
                                _duration.Minutes,
                                _duration.Seconds);

                        mediaElement.Volume = 0.8;
                        volumeSlider.Value = 0.8;
                        lblVolume.Text = "音量大小：80%";

                        mediaElement.Balance = 0;
                        balanceSlider.Value = 0;
                        lblBalance.Text = "音量平衡：0%";

                        mediaElement.BufferingTime = TimeSpan.FromSeconds(30);
                        lblBufferingTime.Text = "缓冲长度：30秒";
                }

                private void mediaElement_CurrentStateChanged(object sender, RoutedEventArgs e)
                {
                        /*
                         * CurrentState - 播放状态 [System.Windows.Media.MediaElementState枚举]
                         *         MediaElementState.Closed - 无可用媒体
                         *         MediaElementState.Opening - 尝试打开媒体（此时Play(),Pause(),Stop()命令会被排进队列，等到媒体被成功打开后再依次执行）
                         *         MediaElementState.Buffering - 缓冲中
                         *         MediaElementState.Playing - 播放中
                         *         MediaElementState.Paused - 被暂停（显示当前帧）
                         *         MediaElementState.Stopped - 被停止（显示第一帧）
                         */

                        lblState.Text = "播放状态：" + mediaElement.CurrentState.ToString();
                }

                private void play_Click(object sender, RoutedEventArgs e)
                {
                        // Play() - 播放媒体（在当前 Position 处播放）
                        mediaElement.Play();
                }

                private void pause_Click(object sender, RoutedEventArgs e)
                {
                        // CanPause - 媒体是否可暂停
                        // Pause() - 暂停媒体的播放
                        if (mediaElement.CanPause)
                                mediaElement.Pause();
                }

                private void stop_Click(object sender, RoutedEventArgs e)
                {
                        // Stop() - 停止媒体的播放
                        mediaElement.Stop();
                }

                void mute_Click(object sender, RoutedEventArgs e)
                {
                        // IsMuted - 是否静音
                        if (mediaElement.IsMuted == true)
                        {
                                mute.Content = "静音";
                                mediaElement.IsMuted = false;
                        }
                        else
                        {
                                mute.Content = "有声";
                                mediaElement.IsMuted = true;
                        }
                }

                private void playSlider_ValueChanged(object sender, RoutedPropertyChangedEventArgs<double> e)
                {
                        // CanSeek - 是否可以通过设置 Position 来重新定位媒体
                        // Position - 媒体的位置（单位：秒）
                        if (mediaElement.CanSeek)
                        {
                                mediaElement.Pause();
                                mediaElement.Position = TimeSpan.FromSeconds(_duration.TotalSeconds * playSlider.Value);
                                mediaElement.Play();
                        }
                }

                private void volumeSlider_ValueChanged(object sender, RoutedPropertyChangedEventArgs<double> e)
                {
                        // Volume - 音量大小（0 - 1 之间）
                        mediaElement.Volume = volumeSlider.Value;
                        lblVolume.Text = string.Format(
                                "音量大小：{0:##%}",
                                volumeSlider.Value);
                }

                private void balanceSlider_ValueChanged(object sender, RoutedPropertyChangedEventArgs<double> e)
                {
                        // Balance - 音量平衡（-1 - 1 之间）
                        mediaElement.Balance = balanceSlider.Value;
                        lblBalance.Text = string.Format(
                                "音量平衡：{0:##%}",
                                balanceSlider.Value);
                }
        }
}

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