Uwp——NaiveMediaPlayer2

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       经过上次的惨痛教训，好吧，尽管这样我也不想直接加一个AreTransportControlsEnabled="True"让这个播放器更美的。
       经过一番思考，我非常快的实现了滑块修改音量的功能，没有数据绑定，也没有反人类的按音量之后才能修改音量了，这些智障问题就不提了，不提了。

I 实现通过Url播放网络上的歌曲

       第一次做的时候就了解过了，修改source为对应的url就可以了，在第一次的基础上新添了一个按钮
代码如下：

 private void Play2_Click(object sender, RoutedEventArgs e)
        {
            mediaElement.Source = new Uri("http://www.neu.edu.cn/indexsource/neusong.mp3", UriKind.Absolute);
        }

       同理，当药下载某个页面的MP3文件时，只要输入url或者修改代码中的uri就可以实现，如果再要实现用户手动实现的功能就需要添加TextBox输入文字再传到Uri里……

II 实现下载歌曲保存到本地再播放

       核心问题就是怎么把网上的mp3资源（此处）下载到本地，一是资源获取，二是存储地址。通过查资料我知道这里要用到httpclient（下载小型文件）
[HttpClient官方文档]（https://docs.microsoft.com/en-us/windows/uwp/networking/httpclient）
参考代码：

//Create an HTTP client object
Windows.Web.Http.HttpClient httpClient = new Windows.Web.Http.HttpClient();

//Add a user-agent header to the GET request. 
var headers = httpClient.DefaultRequestHeaders;

//The safe way to add a header value is to use the TryParseAdd method and verify the return value is true,
//especially if the header value is coming from user input.
string header = "ie";
if (!headers.UserAgent.TryParseAdd(header))
{
    throw new Exception("Invalid header value: " + header);
}

header = "Mozilla/5.0 (compatible; MSIE 10.0; Windows NT 6.2; WOW64; Trident/6.0)";
if (!headers.UserAgent.TryParseAdd(header))
{
    throw new Exception("Invalid header value: " + header);
}

Uri requestUri = new Uri("http://www.contoso.com");

//Send the GET request asynchronously and retrieve the response as a string.
Windows.Web.Http.HttpResponseMessage httpResponse = new Windows.Web.Http.HttpResponseMessage();
string httpResponseBody = "";

try
{
    //Send the GET request
    httpResponse = await httpClient.GetAsync(requestUri);
    httpResponse.EnsureSuccessStatusCode();
    httpResponseBody = await httpResponse.Content.ReadAsStringAsync();
}
catch (Exception ex)
{
    httpResponseBody = "Error: " + ex.HResult.ToString("X") + " Message: " + ex.Message;
}

我的代码：

private async void Download_Click(object sender, RoutedEventArgs e)
        {
            Windows.Web.Http.HttpClient httpClient = new Windows.Web.Http.HttpClient();
            var buffer = await httpClient.GetBufferAsync(new Uri("http://www.neu.edu.cn/indexsource/neusong.mp3"));
            if (buffer == null) return;
            //创建本地资源
            FileSavePicker fileSavePicker = new FileSavePicker();
            fileSavePicker.SuggestedStartLocation = Windows.Storage.Pickers.PickerLocationId.MusicLibrary;
            fileSavePicker.FileTypeChoices.Add("校歌", new List<string>() { ".mp3" });
            var storageFile = await fileSavePicker.PickSaveFileAsync();
            if (storageFile == null) return;
            //写入本地资源
            CachedFileManager.DeferUpdates(storageFile);
            await FileIO.WriteBufferAsync(storageFile, buffer);
            await CachedFileManager.CompleteUpdatesAsync(storageFile);
            MessageDialog msg = new MessageDialog("Welcome!");//.....
            //写入MediaElement
            var stream = await storageFile.OpenAsync(FileAccessMode.Read);
            mediaElement.SetSource(stream, "");
        }

同时还要注意

image.png

StorageFolder testFolder = await StorageFolder.GetFolderFromPathAsync(@"C:\test");
StorageFile sourceFile = await testFolder.GetFileAsync("TestImage.jpg");
StorageFile destinationFile = await KnownFolders.CameraRoll.CreateFileAsync("MyTestImage.jpg");
using (var sourceStream = (await sourceFile.OpenReadAsync()).GetInputStreamAt(0))
{
    using (var destinationStream = (await destinationFile.OpenAsync(FileAccessMode.ReadWrite)).GetOutputStreamAt(0))
    {
        await RandomAccessStream.CopyAndCloseAsync(sourceStream, destinationStream);
    }
}

       找资料是个技术活，运气好就成了，运气不好就沉了哎。最近有点忙，还要写很多别的作业和项目，就不再多写了吧。