Android视频/音频缓存框架AndroidVideoCache怎么用

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具体内容如下

对于视频/音频软件，音乐软件，视频软件，都有缓存这个功能，那如何实现边下边播功能：

• 如何实现这个边下边播功能？

• 文件是否支持同时读写？（Mediaplayer 播放文件，从网络上下载文件）

• 播放与下载进度如何协调?

• 已缓存的文件需及时清理
  

经过一番折腾，我 find 了 ： [ AndroidVideoCache ],这个库是 danikula 大神写，看完源码后收益匪浅。实现流媒体边下边播原理利用socket 开启一个本机的代理服务器

结合自身需求，修改了该库，使用okhttp进行网络请求：
AndroidVideoCache （改成 okhttp 缓存）

package com.danikula.videocache;import android.text.TextUtils;import java.io.BufferedInputStream;import java.io.IOException;import java.io.InputStream;import java.io.InterruptedIOException;import java.util.Map;import java.util.concurrent.TimeUnit;import com.danikula.videocache.file.MyLog;import okhttp3.Call;import okhttp3.OkHttpClient;import okhttp3.Request;import okhttp3.Response;import static com.danikula.videocache.ProxyCacheUtils.DEFAULT_BUFFER_SIZE;import static com.danikula.videocache.ProxyCacheUtils.LOG_TAG;import static java.net.HttpURLConnection.HTTP_OK;import static java.net.HttpURLConnection.HTTP_PARTIAL;/** * {@link Source} that uses http resource as source for {@link ProxyCache}. * * @author Alexey Danilov (danikula@gmail.com). *  * 从URL 获取数据 */public class HttpUrlSource implements Source {  private static final int MAX_REDIRECTS = 5;  public final String url;  private static OkHttpClient okHttpClient = new OkHttpClient();  private Call requestCall = null;  private InputStream inputStream;  private volatile int length = Integer.MIN_VALUE;  private volatile String mime;  private Map headers;  public HttpUrlSource(String url) {    this(url, ProxyCacheUtils.getSupposablyMime(url));  }  public HttpUrlSource(String url, Map headers) {    this(url, ProxyCacheUtils.getSupposablyMime(url));    this.headers = headers;  }  public HttpUrlSource(String url, String mime) {    this.url = Preconditions.checkNotNull(url);    this.mime = mime;  }  public HttpUrlSource(HttpUrlSource source) {    this.url = source.url;    this.mime = source.mime;    this.length = source.length;  }  @Override  public synchronized int length() throws ProxyCacheException {    if (length == Integer.MIN_VALUE) {      fetchContentInfo();    }    return length;  }  @Override  public void open(int offset) throws ProxyCacheException {    try {      Response response = openConnection(offset, -1);      mime = response.header("Content-Type");      inputStream = new BufferedInputStream(response.body().byteStream(), DEFAULT_BUFFER_SIZE);      length = readSourceAvailableBytes(response, offset, response.code());    } catch (IOException e) {      throw new ProxyCacheException("Error opening okHttpClient for " + url + " with offset " + offset, e);    }  }  private int readSourceAvailableBytes(Response response, int offset, int responseCode) throws IOException {    int contentLength = Integer.valueOf(response.header("Content-Length", "-1"));    return responseCode == HTTP_OK ? contentLength        : responseCode == HTTP_PARTIAL ? contentLength + offset : length;  }  @Override  public void close() throws ProxyCacheException {    if (okHttpClient != null && inputStream != null && requestCall != null) {      try {        inputStream.close();        requestCall.cancel();      } catch (IOException e) {        e.printStackTrace();      }    }  }  @Override  public int read(byte[] buffer) throws ProxyCacheException {    if (inputStream == null) {      throw new ProxyCacheException("Error reading data from " + url + ": okHttpClient is absent!");    }    try {      return inputStream.read(buffer, 0, buffer.length);    } catch (InterruptedIOException e) {      throw new InterruptedProxyCacheException("Reading source " + url + " is interrupted", e);    } catch (IOException e) {      throw new ProxyCacheException("Error reading data from " + url, e);    }  }  private void fetchContentInfo() throws ProxyCacheException {    MyLog.d(LOG_TAG, "Read content info from " + url);    Response response = null;    InputStream inputStream = null;    try {      response = openConnection(0, 20000);      length = Integer.valueOf(response.header("Content-Length", "-1"));      mime = response.header("Content-Type");      inputStream = response.body().byteStream();      MyLog.i(LOG_TAG, "Content info for `" + url + "`: mime: " + mime + ", content-length: " + length);    } catch (IOException e) {      MyLog.e(LOG_TAG, "Error fetching info from " + url, e);    } finally {      ProxyCacheUtils.close(inputStream);      if (response != null) {        requestCall.cancel();      }    }  }  private Response openConnection(int offset, int timeout) throws IOException, ProxyCacheException {    boolean redirected;    int redirectCount = 0;    String url = this.url;    Request request = null;    //do {      MyLog.d(LOG_TAG, "Open okHttpClient " + (offset > 0 ? " with offset " + offset : "") + " to " + url);//      okHttpClient = (HttpURLConnection) new URL(url).openConnection();      Request.Builder builder = new Request.Builder();      builder.url(url);      //flac      if(headers != null) {        //设置请求头        for (Map.Entry entry : headers.entrySet()) {          MyLog.i(LOG_TAG, "请求头信息 key:" + entry.getKey() +" Value" + entry.getValue());//          okHttpClient.setRequestProperty(entry.getKey(), entry.getValue());          builder.addHeader(entry.getKey(), entry.getValue());        }      }      if (offset > 0) {        builder.addHeader("Range", "bytes=" + offset + "-");      }      request = builder.build();      requestCall = okHttpClient.newCall(request);      /*if (redirected) {        url = okHttpClient.getHeaderField("Location");        redirectCount++;        okHttpClient.disconnect();      }      if (redirectCount > MAX_REDIRECTS) {        throw new ProxyCacheException("Too many redirects: " + redirectCount);      }*/    //} while (redirected);    return requestCall.execute();  }  public synchronized String getMime() throws ProxyCacheException {    if (TextUtils.isEmpty(mime)) {      fetchContentInfo();    }    return mime;  }  public String getUrl() {    return url;  }  @Override  public String toString() {    return "HttpUrlSource{url='" + url + "}";  }}

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