Question

C＃2008 SP1

我正在使用以下代码录制，播放和停止保存录制内容。一切正常。但是，我想添加一个回调，当回放结束时将会触发。

我使用winmm.dll库进行P / Invoke。

非常感谢您的任何建议。

public partial class SoundTest : Form
    {
        const uint SND_ASYNC = 0x0001;
        const uint SND_FILENAME = 0x00020000;
        const uint SND_NODEFAULT = 0x0002;

        [DllImport("winmm.dll")]
        private static extern int mciSendString(string lpstrCommand, string lpstrReturnString, 
                                                int returnLength, int hwndCallBack);

        [DllImport("winmm.dll")]
        private static extern bool PlaySound(string pszsound, UIntPtr hmod, uint fdwSound);

        public SoundTest()
        {
            InitializeComponent();
        }

        private void Form1_Load(object sender, EventArgs e)
        {
            // Disable stop button
            this.btnSaveStop.Enabled = false;
        }

        private void btnRecord_Click(object sender, EventArgs e)
        {
            // Disable play and record button
            this.btnRecord.Enabled = false;
            this.btnPlay.Enabled = false;
            // Enable stop button
            this.btnSaveStop.Enabled = true;

            // Record from microphone
            mciSendString("Open new Type waveaudio Alias recsound", "", 0, 0);
            mciSendString("record recsound", "", 0, 0);     
        }

        private void btnSaveStop_Click(object sender, EventArgs e)
        {
            // Enable play and record
            this.btnRecord.Enabled = true;
            this.btnPlay.Enabled = true;
            // Disable Stop button
            this.btnSaveStop.Enabled = false;
            mciSendString("save recsound c:\\record.wav", "", 0, 0);
            mciSendString("close recsound ", "", 0, 0);
        }

        private void btnPlay_Click(object sender, EventArgs e)
        {
            //// Diable record button while playing back
            //this.btnRecord.Enabled = false;
            PlaySound("c:\\record.wav", UIntPtr.Zero, SND_ASYNC | SND_FILENAME | SND_NODEFAULT);   
        }
    }

Answer 1

据我所知，你能够做到这一点的唯一方法就是在你调用PlaySound API函数并传递一个回调函数后立即调用它。 SND_SYNC参数而不是SND_ASYNC。

private void btnPlay_Click(object sender, EventArgs e)
{
    //// Disable record button while playing back
    //this.btnRecord.Enabled = false;
    PlaySound("c:\\record.wav", UIntPtr.Zero, SND_SYNC | SND_FILENAME | SND_NODEFAULT);   

    //write your callback code here
}

Answer 2

来自MCI的'回调'实际上是一个Windows消息。如果您将表单的句柄作为hwndcallback传递并覆盖WndProc，则可以处理该消息。

有关WndProc here以及64位友好dllimport规范here的更多信息。

C＃创建回调播放完成

2 个答案: