Xamarin.forms滑块作为音频播放器栏

Question

I would like to use slider control of xamarin.forms as an audio player bar. I have a dependency service to play the recording and get the total duration and current position. How will have to set it to my slider?

Her is my code:

Button btnPlay = new Button
{
    Text = "Play/Pause",
    Command = new Command(() =>
                    {
                        DependencyService.Get<IAudio>().PlayMp3File();
                    })
};
Button btnStop = new Button { Text = "Stop" };
TimeSpan timeSpan = DependencyService.Get<IAudio>().GetInfo();
Label lblDuration = new Label { Text = String.Format("{0:hh\\:mm\\:ss}", timeSpan) };

var slider = new Slider {
    Minimum = 0,
    Maximum = timeSpan.TotalHours,
};
var label = new Label {
    Text = "Slider value is 0",
    FontSize = 25,
    HorizontalOptions = LayoutOptions.Start,
};
slider.ValueChanged += 
    (sender, e) => 
    {
        label.Text = String.Format("Slider value is {0:hh\\:mm\\:ss}", TimeSpan.FromMilliseconds(e.NewValue));
        DependencyService.Get<IAudio>().SeekTo(Convert.ToInt32(e.NewValue));

    };
MainPage = new ContentPage
{
    Content = new StackLayout {
        Children = {
            btnPlay,
            btnStop,
            slider,
            lblDuration,
            label
        }
    },  
    Padding = new Thickness (10, Device.OnPlatform (20, 0, 0), 10, 5)
};

I am setting total duration in a label. How will I have to program on change slider to set label to current position . And how will my slider value will be incremented based on file played?

Edit

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

namespace AudioTest
{
    public interface IAudio
    {
        Task PlayMp3File();
       // bool PlayWavFile(string fileName);

        Task SeekTo(int msec);
        TimeSpan GetInfo();

        void Stop();
        double CurrentPosition();

        bool Isplaying();
    }
}

Audioservice.cs

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;

using Android.App;
using Android.Content;
using Android.OS;
using Android.Runtime;
using Android.Views;
using Android.Widget;
using AudioTest.Droid;
using Xamarin.Forms;
using Android.Media;
using System.Threading.Tasks;


[assembly: Dependency(typeof(AudioService))]

namespace AudioTest.Droid
{

    public class AudioService : IAudio
    {
        public AudioService() { }

        MediaPlayer player = null;

        public async Task StartPlayerAsync()
        {
            try
            {
                if (player == null)
                {
                    player = new MediaPlayer();
                    player = MediaPlayer.Create(global::Android.App.Application.Context, Resource.Raw.test);
                    player.Start();
                }
                else
                {
                    if (player.IsPlaying == true)
                    {
                        player.Pause();
                    }
                    else
                    {
                        player.Start();
                    }
                }
            }
            catch (Exception ex)
            {
                Console.Out.WriteLine(ex.StackTrace);
            }
        }

        public void StopPlayer()
        {
            if ((player != null))
            {
                if (player.IsPlaying)
                {
                    player.Stop();
                }
                player.Release();
                player = null;
            }
        }

        public async Task PlayMp3File()
        {
            await StartPlayerAsync();
        }

        public void Stop()
        {
            this.StopPlayer();
        }

        public async Task SeekTo( int s)
        {
            await seekTo(s);
        }

        public double CurrentPosition()
        {
            if ((player != null))
            {
                return player.CurrentPosition;
            }
            else
            { return 0; }
        }

        private async Task seekTo(int mseconds)
        {
            if (player == null)
            {
                player = new MediaPlayer();
                player = MediaPlayer.Create(global::Android.App.Application.Context, Resource.Raw.test);

            }

            player.SeekTo(mseconds);
            player.Start();
        }



        public TimeSpan GetInfo()
        {
            int arr;
            if (player == null)
            {
                player = new MediaPlayer();
                player = MediaPlayer.Create(global::Android.App.Application.Context, Resource.Raw.test);

            }
            arr = player.Duration;

            return TimeSpan.FromMilliseconds(arr);
        }


       public bool Isplaying()
        {
            if (player == null)
            {
                return false;


            }
            else { 
            return player.IsPlaying;
                }

        }
    }
}

Answer 1

Before I answer the question, let me ask you one of my own: do you really want the slider to track hours? I would expect a media slider to track seconds or tenths of seconds; hours is a very coarse step.

Assuming that you are the author of the IAudio interface and its implementation, my recommendation would be for the IAudio interface to expose and fire an event (for example: PositionChanged ) that includes the current position whenever the playback position changes. The implementation of the IAudio interface is beyond the scope of this question, but I would expect that you'd subscribe to an event or register a callback with whatever media stack you're using, and that would in turn fire the PositionChanged event.

NOTE: I'm also assuming you really meant seconds; if you really DID mean hours, change the below position to Hours.

public class PositionChangedEventArgs : EventArgs
{
    public PositionChangedEventArgs(int seconds)
    {
        Seconds = seconds;
    }

    public int Seconds { get; set; }
}

public interface IAudio
{
    ...
    event EventHandler<PositionChangedEventArgs> PositionChanged;
}

Then, in the event handler for PositionChanged, you would update the position of the slider:

// note that we're caching our reference to IAudio;
// I don't know whether it's a singleton or not
var audioService = DependencyService.Get<IAudio>(); 
TimeSpan timeSpan = audioService.GetInfo();
Label lblDuration = new Label { Text = String.Format("{0:hh\\:mm\\:ss}", timeSpan) };

var slider = new Slider {
    Minimum = 0,
    Maximum = timeSpan.TotalSeconds,
};
audioService.PositionChanged += (s, e) => {
    slider.Value = e.Position;
    label.Text = String.Format("Slider value is {0}", e.Position);
}