在網上找了很多資料，但是都存在一定的bug，問題解決后，特寫出問題解決方案，

1.使用安卓自帶的downloadmanage下載，（推薦，下載后的檔案可在手機最近的目錄查看）

final DownloadManager dManager = (DownloadManager) getSystemService(Context.DOWNLOAD_SERVICE);
Uri uri = Uri.parse(UrlUtils.BASE_URL+"/media/"+list_show.get(position).get("file_path")+"/"+list_show.get(position).get("file_show"));
DownloadManager.Request request = new DownloadManager.Request(uri);
// 設定下載路徑和檔案名 request.setDestinationInExternalPublicDir(Environment.DIRECTORY_DOWNLOADS, list_show.get(position).get("file_show").toString());
            request.setDescription(list_show.get(position).get("file_show")+"下載中");           request.setNotificationVisibility(DownloadManager.Request.VISIBILITY_VISIBLE_NOTIFY_COMPLETED);
//apk的type型別，下載apk時可以打開
//request.setMimeType("application/vnd.android.package-archive");
// 設定為可被媒體掃描器找到
request.allowScanningByMediaScanner();
// 設定為可見和可管理
request.setVisibleInDownloadsUi(true);
// 獲取此次下載的ID
final long refernece = dManager.enqueue(request);

效果圖：

2.使用okhttp下載檔案，（暫未解決問題：在手機上找不到檔案位置，歡迎大佬給出解決方案）

因為之前的后端局限性，我發的是post請求的下載檔案方式，

代碼改了后，效果圖沒截，

progressDialog = new ProgressDialog(FileActivity.this);
canReturn=false;
progressDialog.setProgressStyle(ProgressDialog.STYLE_HORIZONTAL);
progressDialog.setTitle("正在下載");
progressDialog.setMessage("請稍后...");
progressDialog.setProgress(0);
progressDialog.setMax(100);
progressDialog.setCancelable(false);
progressDialog.show();


MyApplication myApplication= (MyApplication) getApplication().getApplicationContext();
            String accessKey = AccessKeyUtils.getAccessKey(myApplication.getMenuApplication(), 54);
            String json="{\"businessJson\":{\"file_type\": \""+list_show.get(position).get("file_type")+"\",\"file_path\": \""+list_show.get(position).get("file_path")+"\",\"file_name\": \""+list_show.get(position).get("file_name")+"\"},\"controlJson\":{\"menuId\":54,\"opt\":\"c\",\"accessKey\":\""+accessKey+"\",\"token\":\""+myApplication.getToken()+"\",\"opt_desc\":\"下載檔案\"}}";
            RequestBody body = RequestBody.create(JSON, json);
            Request request = new Request.Builder()
                    .url(UrlUtils.BASE_URL+"/app/hsdj/xxjymgr/views/downloadFile")
                    .post(body)
                    .build();
            OkHttpClient client = new OkHttpClient();
            okhttp3.Call task=client.newCall(request);
            task.enqueue(new Callback() {
                @Override
                public void onFailure(okhttp3.Call call, IOException e) {
                    Looper.prepare();
                    progressDialog.dismiss();
                    Toast.makeText(myApplication, "檔案獲取失敗！", Toast.LENGTH_SHORT).show();
                    Looper.loop();
                }

                @Override
                public void onResponse(okhttp3.Call call, Response response) throws IOException {
                    Looper.prepare();
                    final long startTime = System.currentTimeMillis();
                    InputStream is = null;
                    byte[] buf = new byte[2048];
                    int len = 0;
                    FileOutputStream fos = null;
                    // 儲存下載檔案的目錄
                    ContextWrapper cw = new ContextWrapper(getApplicationContext());
//                    java.io.File directory = cw.getExternalFilesDir(Environment.DIRECTORY_DOWNLOADS);
                    java.io.File directory = Environment.getExternalStoragePublicDirectory(Environment.DIRECTORY_DOWNLOADS);
                    try {
                        is = response.body().byteStream();
                        long total = response.body().contentLength();
                        java.io.File file = new java.io.File(directory,list_show.get(position).get("file_show").toString());
                        fos = new FileOutputStream(file);
                        long sum = 0;
                        while ((len = is.read(buf)) != -1) {
                            fos.write(buf, 0, len);
                            sum += len;
                            progress = (int) (sum * 1.0f / total * 100);
                            progressDialog.setProgress(progress);
                        }
                        fos.flush();
                        // 下載完成
//                    listener.onDownloadSuccess();
                        Log.i("DOWNLOAD","download success");
                        Log.i("DOWNLOAD","totalTime="+ (System.currentTimeMillis() - startTime));
                    } catch (Exception e) {
                        e.printStackTrace();
//                    listener.onDownloadFailed();
                        Log.i("DOWNLOAD","download failed");
                    } finally {
                        try {
                            if (is != null)
                                is.close();
                        } catch (IOException e) {
                        }
                        try {
                            if (fos != null)
                                fos.close();
                        } catch (IOException e) {
                        }
                    }
                    progressDialog.dismiss();
                    Toast.makeText(myApplication, "檔案下載成功！", Toast.LENGTH_SHORT).show();
                    Looper.loop();
                }
            });

參考：（如果是apk的更新建議參考以下）

使用Android系統提供的DownloadManager來下載檔案， - 黑暗中的一盞明燈 - 博客園 (cnblogs.com)