MeidaStreamTrack是媒體流的一部分

  //它的兩種狀態(tài)分別是工作狀態(tài)和結(jié)束狀態(tài)
  public enum State { LIVE, ENDED }

  // 構(gòu)造方法，在創(chuàng)建MediaStream的時(shí)候，需要傳入一個(gè)nativeTrack
  final long nativeTrack;

  public MediaStreamTrack(long nativeTrack) {
    this.nativeTrack = nativeTrack;
  }

  //這里面的方法和native層的方法是一一對(duì)應(yīng)的
  //獲取Id  
  public String id() {
    return nativeId(nativeTrack);
  }
  
  //獲取類別
  public String kind() {
    return nativeKind(nativeTrack);
  }

  //獲取是否被mute 
  public boolean enabled() {
    return nativeEnabled(nativeTrack);
  }

  //mute或者取消
  public boolean setEnabled(boolean enable) {
    return nativeSetEnabled(nativeTrack, enable);
  }

  //獲取當(dāng)前的狀態(tài)
  public State state() {
    return nativeState(nativeTrack);
  }

  //釋放掉
  public void dispose() {
    free(nativeTrack);
  }

  private static native String nativeId(long nativeTrack);

  private static native String nativeKind(long nativeTrack);

  private static native boolean nativeEnabled(long nativeTrack);

  private static native boolean nativeSetEnabled(long nativeTrack, boolean enabled);

  private static native State nativeState(long nativeTrack);

  private static native void free(long nativeTrack);