【Android开发】使用OkHttp3下载文件（支持直接下载 / 支持断点续传）

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使用OkHttp3下载文件

1.直接下载版本：

        String filesDirPath = getFilesDir().getPath();        OkHttpClient okHttpClient = new OkHttpClient();Request request = new Request.Builder().get().url(URL).build();Call call = okHttpClient.newCall(request);call.enqueue(new Callback() {@Overridepublic void onFailure(@NotNull Call call, @NotNull IOException e) {//}@Overridepublic void onResponse(@NotNull Call call, @NotNull Response response) throws IOException {// Log.d(TAG, "onResponse.");InputStream inputStream = Objects.requireNonNull(response.body()).byteStream();File target = new File(filesDirPath, FILE_NAME);FileOutputStream fileOutputStream = new FileOutputStream(target);try {byte[] buffer = new byte[2048];int len;while ((len = inputStream.read(buffer)) != -1) {fileOutputStream.write(buffer, 0, len);// Log.d(TAG, "read: " + len);}fileOutputStream.flush();} catch (IOException e) {e.printStackTrace();}}});

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2.断点续传版本

    final Call call = mOkhttpClient.newCall(request);range =dst.length();File dst = new File(downloadTo, PACKAGE_FILE_NAME);Callback callback = new Callback() {@Overridepublic void onFailure(@NotNull Call call, @NotNull IOException e) {}@Overridepublic void onResponse(@NotNull Call call, @NotNull Response response) throws IOException {long hasDownload = dst.length();ResponseBody responseBody = response.body();try (InputStream inputStream = responseBody.byteStream();RandomAccessFile accessFile = new RandomAccessFile(dst, "rw")) {// 移动文件指针到断点续传的位置accessFile.seek(hasDownload);byte[] buffer = new byte[2048];int len;while (!stopDownload && -1 != (len = inputStream.read(buffer))) {accessFile.write(buffer, 0, len);hasDownload += len;}if (stopDownload) {LogUtil.i("Download paused.");return;}} catch (IOException e) {LogUtil.e("Download error. " + e.getMessage());return;}}};String rangeStr = String.format(Locale.CHINESE, "bytes=%d-", range);final Request request = new Request.Builder().url(url).header("Range", rangeStr).build();call.enqueue(callback);

总结

其实就是在下载前判断文件是否存在，是否已下载完成。一定要在本地记录该文件的配套元信息（Size，Url，MD5），用于判别。

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