基于DownloadManager的简单下载器编写小结

DownloadManager downloadManager = (DownloadManager)context.getSystemService(Context.DOWNLOAD_SERVICE);
构建下载请求

DownloadManager.Request request = new DownloadManager.Request(Uri.parse("目标文件下载地址"));
//设置目标文件夹，如果你想在系统的storage目录下载一个testDownload/test/test.apk
request.setDestinationInExternalPublicDir("testDownload", "test/test.apk");
//设置下载所需的网络环境,设置了移动网络和WiFi环境下均能下载 request.setAllowedNetworkTypes(DownloadManager.Request.NETWORK_MOBILE | DownloadManager.Request.NETWORK_WIFI);
//通知栏设置
//显示在通知栏
request.setNotificationVisibility(DownloadManager.Request.VISIBILITY_VISIBLE);

//设置文件类型为apk类型，当downloadManager调用openFile时会唤起相应的程序
request.setMimeType("application/cn.trinea.download.file");
 //开始下载,得到一个唯一的downloadId，大有用处
long downloadId = downloadManager.enqueue(request);

private int[] getBytesAndStatus(long downloadId) {

    //构建一个数组，存放已下载文件大小、总大小、下载状态
    int[] bytesAndStatus = new int[]{
        -1, -1, 0
    };
    //通过构建下载请求时获得的downloadId进行文件查询
    DownloadManager.Query query = new DownloadManager.Query().setFilterById(downloadId);
    Cursor cursor = null;
    try {
      cursor = downloadManager.query(query);
      if (cursor != null && cursor.moveToFirst()) {
        //已经下载文件大小
        bytesAndStatus[0] = cursor.getInt(cursor.getColumnIndexOrThrow(DownloadManager.COLUMN_BYTES_DOWNLOADED_SO_FAR));
        //下载文件的总大小
        bytesAndStatus[1] = cursor.getInt(cursor.getColumnIndexOrThrow(DownloadManager.COLUMN_TOTAL_SIZE_BYTES));
        //下载状态
        bytesAndStatus[2] = cursor.getInt(cursor.getColumnIndex(DownloadManager.COLUMN_STATUS));
      }
    } finally {
      if (cursor != null) {
        cursor.close();
      }
    }
    return bytesAndStatus;
  }

private BroadcastReceiver downloadCompleteReceiver;
downloadCompleteReceiver = new BroadcastReceiver() {
      @Override
      public void onReceive(Context context, Intent intent) {
        //文件下载成功时
         DownloadManager.Query query = new DownloadManager.Query();
        //通过下载的id查找
        query.setFilterById(downloadId);
        Cursor c = downloadManager.query(query);
        if (c.moveToFirst()) {
            int status = c.getInt(c.getColumnIndex(DownloadManager.COLUMN_STATUS));
            switch (status) {
              //下载完成
              case DownloadManager.STATUS_SUCCESSFUL:

                 break;

               }

         }
      }
    };
//注册，这里只能拦截文件下载成功的广播，并不能进行进度监听，在适当的地方取消订阅广播
context.registerReceiver(downloadCompleteReceiver,
        new IntentFilter(DownloadManager.ACTION_DOWNLOAD_COMPLETE));

/**
 * 由于DownloadManager自身没有提供实时进度的api，所以通过以下定时器获取已下载的文件大小
 */
  private void updateProgress() {
        //每隔0.5秒刷新一次进度，在适当的地方记得注销 timeDisposable
        Disposable timeDisposable = Observable.interval(500, TimeUnit.MILLISECONDS).subscribeOn(Schedulers.io())
        .observeOn(AndroidSchedulers.mainThread()).subscribe(new DataConsumer<Long>() {
          @Override
          public void acceptData(@io.reactivex.annotations.NonNull Long aLong) {

            int [ ] bytesAndStatus = getBytesAndStatus(downloadId);
            //todo 在这里进行回调即可
          }
        });

  }

 DownloadHelper.Builder builder = new DownloadHelper.Builder(this).title("下载通知")
          .description("正在下载新版本V1.2.0")
          .downloadUrl("http://download.sj.qq.com/upload/connAssitantDownload/upload/MobileAssistant_1.apk")
          .fileSaveName("MobileAssistant_1.apk").fileSavePath("testDownload")
          .notifyVisible(true)
          .fileType(DownloadHelper.FileType.APK).apkInstallHint(true).onProgressListener(new DownloadHelper.OnDownloadProgressListener() {
            @Override
            public void onProgress(int downloadedSize, int totalSize) {

              int progress =(int)((downloadedSize*1.0f/totalSize)*100);
              Logger.d("progress=%d",progress);
               //进度回调

            }

            @Override
            public void onSuccess(Uri fileUri) {
             //文件下载成功回调的Uri
 

            }

            @Override
            public void onFail() {
             //文件下载失败
  

            }

            @Override
            public void fileAlreadyExits(File file) { 
            //当你想重复下载同样的文件时，本地检测是否存在同样的文件，进行回调
             
            }
          });
      DownloadHelper downloadHelper = builder.build();
      //开始下载
      downloadHelper.start();
      //移除下载任务
      downloadHelper.deleteDownloadFile();