Question

我想更改系统的音量。我使用以下代码：

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Windows.Forms;
using System.Runtime.InteropServices;

namespace shaped_form
{
    class VolumeChange
    {
        private const int APPCOMMAND_VOLUME_MUTE = 0x80000;
        private const int APPCOMMAND_VOLUME_UP = 0xA0000;
        private const int APPCOMMAND_VOLUME_DOWN = 0x90000;
        private const int WM_APPCOMMAND = 0x319;
        [DllImport("user32.dll")]
        public static extern IntPtr SendMessageW(IntPtr hWnd, int Msg, IntPtr wParam, IntPtr lParam);
        private void btnMute_Click(object sender, EventArgs e)
        {
            SendMessageW(**this.Handle * *, WM_APPCOMMAND, **this.Handle * *, (IntPtr)APPCOMMAND_VOLUME_MUTE);
        }

        private void btnDecVol_Click(object sender, EventArgs e)
        {
            SendMessageW(**this.Handle * *, WM_APPCOMMAND, **this.Handle * *, (IntPtr)APPCOMMAND_VOLUME_DOWN);
        }

        private void btnIncVol_Click(object sender, EventArgs e)
        {
            SendMessageW(**this.Handle * *, WM_APPCOMMAND, **this.Handle * *, (IntPtr)APPCOMMAND_VOLUME_UP);
        }
    }
}

但我在突出显示的地方收到错误"shaped_form.VolumeChange does not contain a definition for Handle"。

我从一些互联网资源中获取此代码。

Answer 1

您收到错误是因为this.Handle未在普通类中定义，例如您所拥有的VolumeChange类。它来自system.windows.forms form类。

需要，因为SendMessageW方法需要窗口句柄

由于您没有在新课程中定义它，因此无法使用它。

尝试在VolumeChange的构造函数中传递有效的窗口句柄，并使用它来调用SendMessageW

public class VolumeChange
{
  private const int APPCOMMAND_VOLUME_MUTE = 0x80000;
  private const int APPCOMMAND_VOLUME_UP = 0xA0000;
  private const int APPCOMMAND_VOLUME_DOWN = 0x90000;
  private const int WM_APPCOMMAND = 0x319;

  private IntPtr windowHandle;


  public VolumeChange(IntPtr hwnd)
  {
     windowHandle = hwnd;
  }

  [DllImport("user32.dll")]
  public static extern IntPtr SendMessageW(IntPtr hWnd, int Msg, IntPtr wParam, IntPtr    lParam);
  private void btnMute_Click(object sender, EventArgs e)
  {
    SendMessageW(windowHandle, WM_APPCOMMAND, windowHandle,(IntPtr)APPCOMMAND_VOLUME_MUTE);
  }

  private void btnDecVol_Click(object sender, EventArgs e)
  {
    SendMessageW(windowHandle, WM_APPCOMMAND, windowHandle,(IntPtr)APPCOMMAND_VOLUME_DOWN);
  }

  private void btnIncVol_Click(object sender, EventArgs e)
  {
    SendMessageW(windowHandle, WM_APPCOMMAND,windowHandle,(IntPtr)APPCOMMAND_VOLUME_UP);
  }
}

如果在构造函数中传递窗口句柄不是一个选项，（例如，如果你想让VolumeChange静态）

查看GetActiveWindow (MSDN)

Answer 2

要扩展Timothy的答案，您应该将类VolumeChange提取到自己的类，并从表单按钮单击中使用它。这样，如果你想改变其他表格或类的音量，你也可以这样做。

基本上，您最终会得到两个类，即Form类和实用程序类VolumeChanger。通过表单的Handle属性创建VolumeChanger实例时，可以检索所需的句柄。

public class VolumeChanger
{
    private const int APPCOMMAND_VOLUME_MUTE = 0x80000;
    private const int APPCOMMAND_VOLUME_UP = 0xA0000;
    private const int APPCOMMAND_VOLUME_DOWN = 0x90000;
    private const int WM_APPCOMMAND = 0x319;

    public VolumeChange(IntPtr hwnd)
    {
        Handle = hwnd;
    }

    public IntPtr Handle { get; private set; }

    [DllImport("user32.dll")]
    public static extern IntPtr SendMessageW(IntPtr hWnd, int Msg, IntPtr wParam, IntPtr lParam);

    public void Mute() {
        SendMessageW(Handle, WM_APPCOMMAND, Handle, (IntPtr)APPCOMMAND_VOLUME_MUTE);
    }

    public void IncreaseVolume() {
        SendMessageW(Handle, WM_APPCOMMAND, Handle, (IntPtr)APPCOMMAND_VOLUME_UP);
    }

    public void DecreaseVolume() {
        SendMessageW(Handle, WM_APPCOMMAND, Handle, (IntPtr)APPCOMMAND_VOLUME_DOWN);
    }
}

public class Form1 : Form {

    private VolumeChanger _volume;
    public Form1() {
        InitializeComponent();
        _volume = new VolumeChanger(Handle);
    }

    private void btnMute_Click(object sender, EventArgs e)
    {
        _volume.Mute();
    }

    private void btnDecVol_Click(object sender, EventArgs e)
    {
        _volume.DecreaseVolume();
    }

    private void btnIncVol_Click(object sender, EventArgs e)
    {
        _volume.IncreaseVolume();
    }
}

如何以编程方式更改系统卷

2 个答案: