我想在完全加载完成后将渐进式流式传输的mp3文件移动到SD卡中。有没有实现这一目标的办法。
我发现 MediaPlayer
在渐进式流式传输时会完全下载整个文件,然后我们可以跳转到文件的任何部分。我希望将完全流式传输的文件移动到外部存储器中,以便未来回放不浪费数据和电池。
我想在完全加载完成后将渐进式流式传输的mp3文件移动到SD卡中。有没有实现这一目标的办法。
我发现 MediaPlayer
在渐进式流式传输时会完全下载整个文件,然后我们可以跳转到文件的任何部分。我希望将完全流式传输的文件移动到外部存储器中,以便未来回放不浪费数据和电池。
这个想法是创建一个代理,让媒体播放器可以从中读取数据,而不是直接从网络读取数据。
我使用了danikula/AndroidVideoCache,它非常简单易用。我用它来处理音频而不是视频,但其原理是一样的。
对原帖的评论指出了正确的方向,但我认为稍微详细地解释一下可能会更有帮助...
我所做的是使用Apache HTTP库构建一个轻量级代理服务器。应该有很多例子可以获得这部分的基础知识。为MediaPlayer提供适当的本地主机URL,以便它打开到您的代理的套接字。当MediaPlayer发出请求时,使用代理发送一个等效请求到实际的媒体主机。您将在代理的packetReceived方法中收到byte[]数据,我使用它来构建一个HttpGet并使用AndroidHttpClient将其发送出去。
您将收到HttpResponse,并且可以使用其中的HttpEntity来访问流式传输的字节数据。我正在使用一个ReadableByteChannel,如下所示:
HttpEntityWrapper entity = (HttpEntityWrapper)response.getEntity();
ReadableByteChannel src = Channels.newChannel(entity.getContent());
当您读取数据时,您可以随意处理它(例如将其缓存到SD卡上的文件中)。要将正确的内容传递给MediaPlayer,请从客户端Socket获取SocketChannel,首先直接将响应头写入该通道,然后继续写实体的字节数据。我在while循环中使用NIO ByteBuffer(client是Socket,buffer是ByteBuffer)。
int read, written;
SocketChannel dst = client.getChannel();
while (dst.isConnected() &&
dst.isOpen() &&
src.isOpen() &&
(read = src.read(buffer)) >= 0) {
try {
buffer.flip();
// This is one point where you can access the stream data.
// Just remember to reset the buffer position before trying
// to write to the destination.
if (buffer.hasRemaining()) {
written = dst.write(buffer);
// If the player isn't reading, wait a bit.
if (written == 0) Thread.sleep(15);
buffer.compact();
}
}
catch (IOException ex) {
// handle error
}
}
在将响应传递给播放器之前,您可能需要更改响应中的主机标头,以便它看起来像是您的代理发送的。但我正在处理一个专有的MediaPlayer实现,所以行为可能会有所不同。希望这能帮到您。
虽然已经很晚了,但我发现大多数人仍然需要一个解决方案。我的解决方案基于 JakeWharton's DiskLruCache。
AsyncTask 用于读取文件或从网络下载并缓存它
Callback 用于从缓存中获取 InputStram/FileDescriptor
步骤1:
import android.content.Context;
import android.os.AsyncTask;
import org.apache.commons.io.IOUtils;
import java.io.FileInputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;
import java.net.HttpURLConnection;
import java.net.URL;
// you can use FileDescriptor as
// extends AsyncTask<String, Void, FileDescriptor>
public class AudioStreamWorkerTask extends AsyncTask<String, Void, FileInputStream> {
private OnCacheCallback callback = null;
private Context context = null;
public AudioStreamWorkerTask(Context context, OnCacheCallback callback) {
this.context = context;
this.callback = callback;
}
@Override
protected FileInputStream doInBackground(String... params) {
String data = params[0];
// Application class where i did open DiskLruCache
DiskLruCache cache = MyApplication.getDiskCache(context);
if (cache == null)
return null;
String key = hashKeyForDisk(data);
final int DISK_CACHE_INDEX = 0;
long currentMaxSize = cache.getMaxSize();
float percentageSize = Math.round((cache.size() * 100.0f) / currentMaxSize);
if (percentageSize >= 90) // cache size reaches 90%
cache.setMaxSize(currentMaxSize + (10 * 1024 * 1024)); // increase size to 10MB
try {
DiskLruCache.Snapshot snapshot = cache.get(key);
if (snapshot == null) {
Log.i(getTag(), "Snapshot is not available downloading...");
DiskLruCache.Editor editor = cache.edit(key);
if (editor != null) {
if (downloadUrlToStream(data, editor.newOutputStream(DISK_CACHE_INDEX)))
editor.commit();
else
editor.abort();
}
snapshot = cache.get(key);
} else
Log.i(getTag(), "Snapshot found sending");
if (snapshot != null)
return (FileInputStream) snapshot.getInputStream(DISK_CACHE_INDEX);
} catch (IOException e) {
e.printStackTrace();
}
Log.i(getTag(), "File stream is null");
return null;
}
@Override
protected void onPostExecute(FileInputStream fileInputStream) {
super.onPostExecute(fileInputStream);
if (callback != null) {
if (fileInputStream != null)
callback.onSuccess(fileInputStream);
else
callback.onError();
}
callback = null;
context = null;
}
public boolean downloadUrlToStream(String urlString, OutputStream outputStream) {
HttpURLConnection urlConnection = null;
try {
final URL url = new URL(urlString);
urlConnection = (HttpURLConnection) url.openConnection();
InputStream stream = urlConnection.getInputStream();
// you can use BufferedInputStream and BufferOuInputStream
IOUtils.copy(stream, outputStream);
IOUtils.closeQuietly(outputStream);
IOUtils.closeQuietly(stream);
Log.i(getTag(), "Stream closed all done");
return true;
} catch (final IOException e) {
e.printStackTrace();
} finally {
if (urlConnection != null)
IOUtils.close(urlConnection);
}
return false;
}
private String getTag() {
return getClass().getSimpleName();
}
private String hashKeyForDisk(String key) {
String cacheKey;
try {
final MessageDigest mDigest = MessageDigest.getInstance("MD5");
mDigest.update(key.getBytes());
cacheKey = bytesToHexString(mDigest.digest());
} catch (NoSuchAlgorithmException e) {
cacheKey = String.valueOf(key.hashCode());
}
return cacheKey;
}
private String bytesToHexString(byte[] bytes) {
// https://dev59.com/HXRC5IYBdhLWcg3wVvct
StringBuilder sb = new StringBuilder();
for (byte aByte : bytes) {
String hex = Integer.toHexString(0xFF & aByte);
if (hex.length() == 1)
sb.append('0');
sb.append(hex);
}
return sb.toString();
}
}
public interface OnCacheCallback {
void onSuccess(FileInputStream stream);
void onError();
}
示例
final String path = "http://www.example.com/test.mp3";
new AudioStreamWorkerTask (TestActivity.this, new OnCacheCallback() {
@Override
public void onSuccess(FileInputStream fileInputStream) {
Log.i(getClass().getSimpleName() + ".MediaPlayer", "now playing...");
if (fileInputStream != null) {
// reset media player here if necessary
mediaPlayer = new MediaPlayer();
try {
mediaPlayer.setDataSource(fileInputStream.getFD());
mediaPlayer.prepare();
mediaPlayer.setVolume(1f, 1f);
mediaPlayer.setLooping(false);
mediaPlayer.start();
fileInputStream.close();
} catch (IOException | IllegalStateException e) {
e.printStackTrace();
}
} else {
Log.e(getClass().getSimpleName() + ".MediaPlayer", "fileDescriptor is not valid");
}
}
@Override
public void onError() {
Log.e(getClass().getSimpleName() + ".MediaPlayer", "Can't play audio file");
}
}).execute(path);
注意:
这是针对音频文件缓存的测试样例,虽然经过测试但还比较粗糙,如果您发现任何问题请通知我:)
// Application class where i did open DiskLruCache
是什么意思? - Naz141