为什么我不能从单独的对象播放 MP3 文件？

Question

WIP MP3 播放器

注释的代码不起作用，但下面当前未注释的代码起作用。我可以打开对话框 window，但在选择 mp3 文件后，它无法播放。未注释的代码确实播放了 mp3 文件。

“Öffnen der Datei”区域出现问题。

MainWindow.xaml.cs

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
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;
using Microsoft.Win32;

namespace Music_Player
{
    /// <summary>
    /// Interaktionslogik für MainWindow.xaml
    /// </summary>
    public partial class MainWindow : Window
    {
        public MainWindow()
        {
            InitializeComponent();
        }

        public MediaPlayer mp = new MediaPlayer();

        #region Öffnen der Datei
        private void menuOffnen_Click(object sender, RoutedEventArgs e)
        {
            mp.Pause();
            OpenFileDialog dlg = new OpenFileDialog();
            dlg.DefaultExt = ".mp3";
            dlg.Filter = "MP3 files (*.mp3)|*.mp3|M4A files (*.m4a)|*.m4a|All files (*.*)|*.*";
            if (dlg.ShowDialog() == true)
            {
                mp.Open(new Uri(dlg.FileName));
                labelsong.Content = dlg.SafeFileName;
            }
            //Offnen o = new Offnen();
            //o.OffnenDerDatei();
            mp.Play();
        }
        #endregion

        #region ActionButtons
        private void button_play_Click(object sender, RoutedEventArgs e)
        {
            mp.Play();
        }

        private void button_pause_Click(object sender, RoutedEventArgs e)
        {
            mp.Pause();
        }

        private void button_stop_Click(object sender, RoutedEventArgs e)
        {
            mp.Stop();
        }
        #endregion

        private void slider_volume_ValueChanged(object sender, RoutedPropertyChangedEventArgs<double> e)
        {
            slidervolume.Maximum = 100;
            slidervolume.Minimum = 0;


        }


        #region Beenden
        private void menuBeenden_Click(object sender, RoutedEventArgs e)
        {
            Application.Current.Shutdown();
        }
        #endregion
    }
}

Offnen.cs

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using Microsoft.Win32;
using System.Windows.Media;

namespace Music_Player
{
    class Offnen : MainWindow
    {
        public void OffnenDerDatei()
        {
            MediaPlayer mp = new MediaPlayer();
            OpenFileDialog dlg = new OpenFileDialog();
            dlg.DefaultExt = ".mp3";
            dlg.Filter = "MP3 files (*.mp3)|*.mp3|M4A files (*.m4a)|*.m4a|All files (*.*)|*.*";
            if (dlg.ShowDialog() == true)
            {
                mp.Open(new Uri(dlg.FileName));
                labelsong.Content = dlg.SafeFileName;
            }
        }
    }
}

Answer 1

您在 Offnen.cs 文件中编写的代码未对该文件执行任何操作，因为变量 "mp" 是对象 o (Offnen) 的本地变量。也许您正在寻找这样的东西：

MainWindow.xaml.cs

#region Öffnen der Datei
private void menuOffnen_Click(object sender, RoutedEventArgs e)
{
    mp.Pause();
    Offnen o = new Offnen();
    o.OffnenDerDatei(mp);
    mp.Play();
}
#endregion

Offnen.cs

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using Microsoft.Win32;
using System.Windows.Media;

namespace Music_Player
{
    class Offnen : MainWindow
    {
        public void OffnenDerDatei(MediaPlayer mPlayer)
        {
            OpenFileDialog dlg = new OpenFileDialog();
            dlg.DefaultExt = ".mp3";
            dlg.Filter = "MP3 files (*.mp3)|*.mp3|M4A files (*.m4a)|*.m4a|All files (*.*)|*.*";
            if (dlg.ShowDialog() == true)
            {
                mPlayer.Open(new Uri(dlg.FileName));
                //labelsong.Content = dlg.SafeFileName; // fyi this variable looks to be undeclared
            }
        }
    }
}

我看到您从 MainWindow 继承了 Offnen，但我认为您可能假设继承意味着它将继承该对象。这不是真的，class 继承只是继承结构，所以所有属于 MainWindow 的变量（例如 mp 和 labelsong）将不属于您在 MainWindow 中创建的 Offnen 实例。

这可能超出了问题的范围，但我建议您考虑将 OffnenDerDatei 设为属于 MainWindow 的函数。否则，就像你现在拥有的那样，Offnen 从 MainWindow 继承是没有意义的。

为什么我不能从单独的对象播放 MP3 文件？

Why can't I play an MP3 file from a separate object?

c#

wpf

class

openfiledialog

WIP MP3 播放器