retrofit：文件断点下载

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学习于：http://blog.csdn.net/sk719887916/article/details/51988507

所谓断点下载就是从暂停的地方重新开始下载：
下载过程中，点击暂停按钮时，会记录一个断点（就是已经下载的文件大小），恢复下载时通过添加请求头实现从断点位置继续下载。range:"bytes=" + length + "-"；length表示断点位置，初始时length = 0，然后下载的数据拼接到第一次下载的文件的后面组成一个文件。

API

public interface ApiService {

    /*断点下载接口*/
    @Streaming/*大文件需要加入这个判断，防止下载过程中写入到内存中*/
    @GET
    Flowable<ResponseBody> download(@Header("RANGE") String start, @Url String url);

}

下载

//暂停下载
    public void cancel(View view) {
        mSubscribe.dispose();
    }
//开始下载
    public void load(View view) {
        mFile = DownLoadManager.getFutureStudioIconFile();
        if (mFile != null) {
            length = mFile.length();
        }

        Log.d(TAG, "请求下载的初始位置：" + length);

        mSubscribe = RetrofitClient.getInstance(getApplication()).getApiService()
                .download("bytes=" + length + "-", url)
                .subscribeOn(Schedulers.io())
                .observeOn(Schedulers.io())
                .map(new Function<ResponseBody, Boolean>() {
                    @Override
                    public Boolean apply(@NonNull ResponseBody responseBody) throws Exception {
                        return DownLoadManager.writeFile(getApplication(), responseBody, mProgressBar);
                    }
                })
                .observeOn(AndroidSchedulers.mainThread())
                .subscribe(new Consumer<Boolean>() {
                    @Override
                    public void accept(@NonNull Boolean aBoolean) throws Exception {

                    }
                });
    }

文件写入的工具类

public class DownLoadManager {

    private static final String TAG = "DownLoadManager";
    private static String APK_CONTENTTYPE = "application/vnd.android.package-archive";
    private static String PNG_CONTENTTYPE = "image/png";
    private static String JPG_CONTENTTYPE = "image/jpg";
    private static String MP4_CONTENTTYPE = "video/mp4";
    private static String fileSuffix = "";
    private static File sFutureStudioIconFile;
    private static long sFileSize;
    private static String fileName = "whstywh";
    public static String getFileName() {
        return fileName;
    }
    public static File getFutureStudioIconFile() {
        return sFutureStudioIconFile;
    }
   public static boolean writeFile(Context context, ResponseBody body, ProgressBar progressBar) {

        Log.d(TAG, "contentType:>>>>" + body.contentType().toString());
        String type = body.contentType().toString();
        if (type.equals(APK_CONTENTTYPE)) {
            fileSuffix = ".apk";
        } else if (type.equals(PNG_CONTENTTYPE)) {
            fileSuffix = ".png";
        } else if (type.equals(JPG_CONTENTTYPE)) {
            fileSuffix = ".jpg";
        } else if (type.equals(MP4_CONTENTTYPE)) {
            fileSuffix = ".mp4";
        }

        String sPath = Environment.getExternalStorageDirectory() + File.separator + fileName + fileSuffix;
        Log.d(TAG, "path:>>>>" + sPath);
        try {
            // todo change the file location/name according to your needs
            sFutureStudioIconFile = new File(sPath);
            InputStream inputStream = null;
            OutputStream outputStream = null;

            try {
                byte[] fileReader = new byte[4096];
                //需要下载的文件总长度
                if (sFileSize == 0) {
                    sFileSize = body.contentLength();
                }
                //已经下载的文件长度
                long fileSizeDownloaded = sFutureStudioIconFile.length();
                inputStream = body.byteStream();
                outputStream = new FileOutputStream(sFutureStudioIconFile, true);
                progressBar.setMax((int) sFileSize);
                while (true) {
                    int read = inputStream.read(fileReader);
                    if (read == -1) {
                        break;
                    }
                    outputStream.write(fileReader, 0, read);
                    fileSizeDownloaded += read;
                    progressBar.setProgress((int) fileSizeDownloaded);
                    Log.d(TAG, "file download: " + fileSizeDownloaded + " of " + sFileSize);
                }
                outputStream.flush()

                return true;
            } catch (IOException e) {
                return false;
            } finally {
                if (inputStream != null) {
                    inputStream.close();
                }

                if (outputStream != null) {
                    outputStream.close();
                }
            }
        } catch (IOException e) {
            return false;
        }
    }
}

对于retrofit的学习才刚刚开始！
retrofit ：入门
retrofit ：Json数据缓存
retrofit ：文件断点下载