1. 断点续下载:
思路:
1. 断点续下载不需要服务端提供特殊接口,客户端自己实现就可以,http 协议本身支持续下载
2. get 方式下载
3. 开始下载的文件位置传参:统一的 “Range” 字段,http 协议自带
4. 需要客户端创建数据库,记录断点下载信息
代码:
/**
* 文件下载任务
*/
public class DownloadTask extends AsyncTask<String, Integer, Integer> {
private final String TAG = DownloadTask.this.getClass().getSimpleName();
public static final int TYPE_SUCCESS = 0;
public static final int TYPE_FAILED = 1;
public static final int TYPE_PAUSED = 2;
public static final int TYPE_CANCELED = 3;
private Context mContext;
private DownloadFileBean mDownloadBean;
private DownloadListener mDownloadListener;
private boolean isCanceled = false;
private boolean isPaused = false;
private int mLastProgress;
public DownloadTask(Context context, DownloadFileBean downloadBean) {
try {
this.mContext = context;
this.mDownloadBean = downloadBean.clone();
} catch (CloneNotSupportedException e) {
e.printStackTrace();
}
}
@Override
protected Integer doInBackground(String... strings) {
Log.d(TAG, "doInBackground:");
if (mDownloadBean == null) {
Log.d(TAG, "doInBackground:Error: Download bean null!");
return TYPE_FAILED;
}
Log.d(TAG, "doInBackground: mDownloadBean=" + mDownloadBean);
InputStream is = null;
RandomAccessFile savedFile = null;
File file;
long downloadLength = 0; //记录已经下载的文件长度
//文件下载地址
String downloadUrl = mDownloadBean.getUrl();
String filePath = mDownloadBean.getPath();
file = new File(filePath);
if (file.exists()) {
//如果文件存在的话,得到文件的大小
downloadLength = file.length();
}
//得到下载内容的大小
long contentLength = getContentLengthOk(downloadUrl);
Log.d(TAG, "doInBackground: contentLength=" + contentLength +
" downloadLength=" + downloadLength);
if (contentLength == 0) {
return TYPE_FAILED;
} else if (contentLength == downloadLength) {
//已下载字节和文件总字节相等,说明已经下载完成了
Log.d(TAG, "doInBackground: Already exists!");
return TYPE_SUCCESS;
}
OkHttpClient client = new OkHttpClient();
/**
* HTTP请求是有一个Header的,里面有个Range属性是定义下载区域的,它接收的值是一个区间范围,
* 比如:Range:bytes=0-10000。这样我们就可以按照一定的规则,将一个大文件拆分为若干很小的部分,
* 然后分批次的下载,每个小块下载完成之后,再合并到文件中;这样即使下载中断了,重新下载时,
* 也可以通过文件的字节长度来判断下载的起始点,然后重启断点续传的过程,直到最后完成下载过程。
*/
Request request = new Request.Builder()
.addHeader("RANGE", "bytes=" + downloadLength + "-" + contentLength)
.url(downloadUrl)
.build();
try {
Response response = client.newCall(request).execute();
client.newCall(request).enqueue(new Callback() {
@Override
public void onFailure(Call call, IOException e) {
}
@Override
public void onResponse(Call call, Response response) throws IOException {
}
});
if (response != null) {
Log.d(TAG, "doInBackground: Get stream form response!");
is = response.body().byteStream();
savedFile = new RandomAccessFile(file, "rw");
savedFile.seek(downloadLength);//跳过已经下载的字节
byte[] b = new byte[1024];
int total = 0;
int len;
Log.d(TAG, "doInBackground: Start read file stream!");
while ((len = is.read(b)) != -1) {
if (isCanceled) {
return TYPE_CANCELED;
} else if (isPaused) {
return TYPE_PAUSED;
} else {
total += len;
savedFile.write(b, 0, len);
//计算已经下载的百分比
int progress = (int) ((total + downloadLength) * 100 / contentLength);
//注意:在doInBackground()中是不可以进行UI操作的,如果需要更新UI,比如说反馈当前任务的执行进度,
//可以调用publishProgress()方法完成。
publishProgress(progress);
}
}
response.close();
return TYPE_SUCCESS;
}
} catch (IOException e) {
Log.d(TAG, "doInBackground:IOException: " + e.getMessage());
e.printStackTrace();
} finally {
try {
if (is != null) {
is.close();
}
if (savedFile != null) {
savedFile.close();
}
if (isCanceled && file != null) {
file.delete();
}
} catch (Exception e) {
e.printStackTrace();
}
}
return TYPE_FAILED;
}
/**
* 得到下载内容的完整大小
*/
private long getContentLengthOk(String downloadUrl) {
Log.d(TAG, "getContentLengthOk:");
OkHttpClient client = new OkHttpClient();
Request request = new Request.Builder().url(downloadUrl).build();
try {
Response response = client.newCall(request).execute();
if (response != null && response.isSuccessful()) {
long contentLength = response.body().contentLength();
Log.d(TAG, "getContentLengthOk: contentLength=" + contentLength);
response.body().close();
return contentLength;
}
} catch (IOException e) {
e.printStackTrace();
}
return 0;
}
/**
* 当在后台任务中调用了publishProgress(Progress...)方法之后,onProgressUpdate()方法
* 就会很快被调用,该方法中携带的参数就是在后台任务中传递过来的。在这个方法中可以对UI进行操作,利用参数中的数值就可以
* 对界面进行相应的更新。
*
* @param values
*/
@Override
protected void onProgressUpdate(Integer... values) {
int progress = values[0];
if (progress > mLastProgress) {
if (mDownloadListener != null) mDownloadListener.onProgress(progress);
mLastProgress = progress;
}
}
/**
* 当后台任务执行完毕并通过Return语句进行返回时,这个方法就很快被调用。返回的数据会作为参数
* 传递到此方法中,可以利用返回的数据来进行一些UI操作。
*
* @param status
*/
@Override
protected void onPostExecute(Integer status) {
switch (status) {
case TYPE_SUCCESS:
if (mDownloadListener != null) mDownloadListener.onSuccess();
break;
case TYPE_FAILED:
if (mDownloadListener != null) mDownloadListener.onFailed();
break;
case TYPE_PAUSED:
if (mDownloadListener != null) mDownloadListener.onPaused();
break;
case TYPE_CANCELED:
if (mDownloadListener != null) mDownloadListener.onCanceled();
break;
default:
break;
}
}
public void pauseDownload() {
isPaused = true;
}
public void cancelDownload() {
isCanceled = true;
}
public void setDownloadListener(DownloadListener downloadListener) {
this.mDownloadListener = downloadListener;
}
}
/**
* 文件下载任务回调接口
*/
public interface DownloadListener {
/**
* 通知当前的下载进度
*/
void onProgress(int progress);
/**
* 通知下载成功
*/
void onSuccess();
/**
* 通知下载失败
*/
void onFailed();
/**
* 通知下载暂停
*/
void onPaused();
/**
* 通知下载取消事件
*/
void onCanceled();
}
参考:
使用 HttpUrlConnection 原生接口封装 request 实现:https://blog.csdn.net/SEU_Calvin/article/details/53749776
使用 OkHttp 封装 request 实现:https://juejin.cn/post/6844903854115389447
2. 文件分片上传:
思路:
1. 文件分片上传,需要服务端给出特殊接口,实现文件分片接收和整体拼接的操作;
2. 端上从文件指定位置读取并写入传输流就可以;
3. 需要客户端创建数据库,记录断点上传信息
代码:
/**
* 分片文件,上传,这部分是通用的
*/
public class PartFileBody extends FileBody {
/**
* 分片写入的开始位置,字节偏移量
*/
private final long mOffset;
/**
* 分片写入的长度,最后一次分片大小不定,前面的分片都是固定的
*/
private final long mLength;
/**
* 文件流输出计数
*/
private long mCount;
public PartFileBody(File file, long offset, long length) {
super(file);
this.mOffset = offset;
this.mLength = length;
this.mCount = 0;
}
@Override
public long getContentLength() {
return mLength;
}
@Override
public void writeTo(OutputStream out) throws IOException {
RandomAccessFile raf = new RandomAccessFile(mFile, "r");
raf.seek(mOffset);
try {
byte[] buffer = new byte[4096];
int length;
while ((length = raf.read(buffer)) != -1) {
if ((mCount + length) > mLength) {
length = (int) (mLength - mCount);
}
out.write(buffer, 0, length);
mCount += length;
if (mCount == mLength) {
break;
}
}
} catch (Exception e) {
e.printStackTrace();
} finally {
raf.close();
}
}
}
/**
* 上传请求,这部分是自定义的服务端接口协议,关键字段都一样,具体传输方式可自定义
*/
public synchronized void uploadFile(Context ctx, UploadFileBean uploadBean, String filePath, long contentOffset, long contentLength, RequestListener listener) {
String url = url;
File file = new File(filePath);
Log.d(TAG, "VFU:" + "uploadFile: " + file .getAbsolutePath());
MultipartBody body = new MultipartBody();
body.addPart("content", new PartFileBody(file , contentOffset, contentLength));
Request request = new Request
.Builder()
.url(url)
.urlParam("size", uploadBean.getSize())
.urlParam("sid", uploadBean.getSid())
.urlParam("range_start", uploadBean.getRange_start())
.urlParam("range_end", uploadBean.getRange_end())
.post(body)
.build();
Log.d(TAG, "VFU:" + "uploadFile:");
//TODO 发起请求
}
3. 总结
理论上讲,上传和下载,都可以分片传,同步传输一个文件的不同分片来提高效率。但实际使用中,上传文件一般会分片上传,是否同步看业务需要,而文件下载只需要做断点续传就可以并不需要分片;
可以参考:断点续传和分片传输的区别