0 .Thanks

官方文檔

Android系統下載管理DownloadManager功能介紹及使用示例

1 .概述

DowanloadManger：系統的服務，系統開放給第三方應用使用的類，用于管理下載。
DownloadManager.Query：用來查詢下載信息
DownloadManager.Request：用來請求一個下載

2 .DownloadManager.Request

• addRequestHeader(String header, String value)

Add an HTTP header to be included with the download request.
添加一個Http的頭到下載的請求。

• allowScanningByMediaScanner()

If the file to be downloaded is to be scanned by MediaScanner, this method should be called before enqueue(Request) is called.
可以理解為，允許媒體的掃描。需要在任務開始前調用。

• setAllowedNetworkTypes(int flags)
  Restrict the types of networks over which this download may proceed.
  限制什么類型的網絡可以下載：
  • DownloadManager.Request.NETWORK_MOBILE-Wifi或者移動網絡可以下載
  • DownloadManager.Request.NETWORK_WIFI-只允許Wifi的環境下，下載。

• setAllowedOverMetered(boolean allow)計量網絡下載？不懂。默認允許。

• setAllowedOverRoaming(boolean allowed)允許漫游網絡？默認運行。

• setDescription(CharSequence description)
  Set a description of this download, to be displayed in notifications (if enabled)
  設置下載的描述，會顯示在通知欄，如果允許的話。

• setDestinationInExternalFilesDir(Context context, String dirType, String subPath)
  Set the local destination for the downloaded file to a path within the application's external files directory (as returned by getExternalFilesDir(String).
  設置文件的存放目錄。這個方法設置的是，應用程序內能訪問的。其可以用的路徑：context.getExternalFilesDir(String).

• setDestinationInExternalPublicDir(String dirType, String subPath)
  Set the local destination for the downloaded file to a path within the public external storage directory (as returned by getExternalStoragePublicDirectory(String)).
  設置文件的存放目錄。這個方法設置的是，程序的外部存儲。其可以用的路徑：Environment.getExternalFilesDir(String).
  或者，可以自定義。

• setDestinationUri(Uri uri)
  Set the local destination for the downloaded file.
  設置下載地址。為uri.

• setMimeType(String mimeType)
  Set the MIME content type of this download.
  設置下載類型：MIME 參考手冊
  apk的Mime:application/vnd.android

• setNotificationVisibility(int visibility)
  Control whether a system notification is posted by the download manager while this download is running or when it is completed.
  設置通知欄是否顯示和顯示的規則：

  • VISIBILITY_HIDDEN ：不顯示在通知欄
  • VISIBILITY_VISIBLE ：顯示在通知欄，下載完成后，消失。
  • VISIBILITY_VISIBLE_NOTIFY_COMPLETED ：顯示在通知欄，下載完成后，也顯示。
  • VISIBILITY_VISIBLE_NOTIFY_ONLY_COMPLETION ：顯示在通知欄，只是完成后顯示。下載的時候，不顯示。

• setRequiresCharging(boolean requiresCharging)需要插入才下載？不懂

• setRequiresDeviceIdle(boolean requiresDeviceIdle)空閑的時候才下載？

• setTitle(CharSequence title)
  設置下載題目，顯示在通知欄，如果可以的話。

• setVisibleInDownloadsUi(boolean isVisible)
  Set whether this download should be displayed in the system's Downloads UI.
  設置下載的地址URI是否能在通知欄上可見。

3 .DownloadManager.Query

查詢任務。

• setFilterById(long... ids)
  Include only the downloads with the given IDs.
  根據下載的ID返回任務：DownloadManager.Query

• setFilterByStatus(int flags)
  include only downloads with status matching any the given status flags.
  根據Flags去過濾返回：DownloadManager.Query

查詢可以通過：

private void queryDownloadStatus() {
        DownloadManager.Query query = new DownloadManager.Query();
        final DownloadManager downloadManager= (DownloadManager) 
                  this.getSystemService(Context.DOWNLOAD_SERVICE);
        query.setFilterById(TaskID);
        Cursor c = downloadManager.query(query);
        if(c.moveToFirst()) {
            int status = c.getInt(c.getColumnIndex(DownloadManager.COLUMN_STATUS));
            switch(status) {
                case DownloadManager.STATUS_PAUSED:
                case DownloadManager.STATUS_PENDING:
                case DownloadManager.STATUS_RUNNING:
                case DownloadManager.STATUS_SUCCESSFUL:
            }
       }
}

去查詢任務的狀態。

下載的監聽：

 /**
     * 得到下載的狀態
     * @param context       上下文
     * @param downloadId    ID
     * @return  0 : 已經下載的量(bytes) , 1 : 總的大小， 2 ： 下載的狀態
     */
    public static int[] getBytesAndStatus(Context context, long downloadId) {
        int[] bytesAndStatus = new int[] { -1, -1, -1 };
        DownloadManager.Query query = new DownloadManager.Query()
                                      .setFilterById(downloadId);
        DownloadManager downloadManager = (DownloadManager)   
                  context.getSystemService(Context.DOWNLOAD_SERVICE);
        Cursor c = null;
        try {
            c = downloadManager.query(query);
            if (c != null && c.moveToFirst()) {
                bytesAndStatus[0] = c.getInt(c.getColumnIndexOrThrow(DownloadManager
                                .COLUMN_BYTES_DOWNLOADED_SO_FAR));
                bytesAndStatus[1] = c.getInt(c.getColumnIndexOrThrow(DownloadManager
                                .COLUMN_TOTAL_SIZE_BYTES));
                bytesAndStatus[2] = c.getInt(c.getColumnIndex(DownloadManager
                                .COLUMN_STATUS));
            }
        } finally {
            if (c != null) {
                c.close();
            }
        }
        return bytesAndStatus;
    }