之前开发的一个和第三方合作的apk，在之前公司的 Android 5.1 系统的手表上运行正常，今天在公司新开发的 Android 7.1系统的手表上运行的时候，使用 DownloadManager 下载之后，查询下载状态的时候，报了异常

java.lang.SecurityException: COLUMN_LOCAL_FILENAME is deprecated; use ContentResolver.openFileDescriptor() instead

异常详细信息如下：

03-17 15:59:43.288 31487-31487/com.netease.xtc.cloudmusic E/CloudMusicDownloadService: DownloadChangeObserver.onChange() throwable = java.lang.SecurityException: COLUMN_LOCAL_FILENAME is deprecated; use ContentResolver.openFileDescriptor() instead

                                                                                           at android.app.DownloadManager$CursorTranslator.getString(DownloadManager.java:1545)

                                                                                           at com.netease.xtc.cloudmusic.services.download.CloudMusicDownloadService.queryDownloadStatus(CloudMusicDownloadService.java:634)

                                                                                           at com.netease.xtc.cloudmusic.services.download.CloudMusicDownloadService.access$900(CloudMusicDownloadService.java:55)

                                                                                           at com.netease.xtc.cloudmusic.services.download.CloudMusicDownloadService$DownloadChangeObserver$3.call(CloudMusicDownloadService.java:590)

                                                                                           at com.netease.xtc.cloudmusic.services.download.CloudMusicDownloadService$DownloadChangeObserver$3.call(CloudMusicDownloadService.java:587)

                                                                                           at rx.Observable.unsafeSubscribe(Observable.java:8666)

                                                                                           at rx.internal.operators.OperatorSubscribeOn$1.call(OperatorSubscribeOn.java:94)

                                                                                           at rx.internal.schedulers.CachedThreadScheduler$EventLoopWorker$1.call(CachedThreadScheduler.java:220)

                                                                                           at rx.internal.schedulers.ScheduledAction.run(ScheduledAction.java:55)

                                                                                           at java.util.concurrent.Executors$RunnableAdapter.call(Executors.java:428)

                                                                                           at java.util.concurrent.FutureTask.run(FutureTask.java:237)

                                                                                           at java.util.concurrent.ScheduledThreadPoolExecutor$ScheduledFutureTask.run(ScheduledThreadPoolExecutor.java:272)

                                                                                           at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1133)

                                                                                           at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:607)

                                                                                           at java.lang.Thread.run(Thread.java:761)

跳转到报错的地方，如下图所示：

在运行下面两行代码的时候报错了。

  int fileNameIdx = c.getColumnIndex(DownloadManager.COLUMN_LOCAL_FILENAME);

  String fileName = c.getString(fileNameIdx);

而且 DownloadManager.COLUMN_LOCAL_FILENAME 已经是被废弃的常量了，点击查看源代码如下所示：

 /**

     * Path to the downloaded file on disk.

     * <p>

     * Note that apps may not have filesystem permissions to directly access

     * this path. Instead of trying to open this path directly, apps should use

     * {@link ContentResolver#openFileDescriptor(Uri, String)} to gain access.

     *

     * @deprecated apps should transition to using

     *             {@link ContentResolver#openFileDescriptor(Uri, String)}

     *             instead.

     */

    @Deprecated

    public final static String COLUMN_LOCAL_FILENAME = "local_filename";

Android 在 Android 7.0 或更高版本开发的应用在尝试访问DownloadManager.COLUMN_LOCAL_FILENAME 时会触发java.lang.SecurityException。

Android官方建议我们使用 ContentResolver#openFileDescriptor(Uri, String)来获取文件相关信息。源代码如下所示：

 /**

     * Open a raw file descriptor to access data under a URI.  This

     * is like {@link #openAssetFileDescriptor(Uri, String)}, but uses the

     * underlying {@link ContentProvider#openFile}

     * ContentProvider.openFile()} method, so will <em>not</em> work with

     * providers that return sub-sections of files.  If at all possible,

     * you should use {@link #openAssetFileDescriptor(Uri, String)}.  You

     * will receive a FileNotFoundException exception if the provider returns a

     * sub-section of a file.

     *

     * <h5>Accepts the following URI schemes:</h5>

     * <ul>

     * <li>content ({@link #SCHEME_CONTENT})</li>

     * <li>file ({@link #SCHEME_FILE})</li>

     * </ul>

     *

     * <p>See {@link #openAssetFileDescriptor(Uri, String)} for more information

     * on these schemes.

     * <p>

     * If opening with the exclusive "r" or "w" modes, the returned

     * ParcelFileDescriptor could be a pipe or socket pair to enable streaming

     * of data. Opening with the "rw" mode implies a file on disk that supports

     * seeking. If possible, always use an exclusive mode to give the underlying

     * {@link ContentProvider} the most flexibility.

     * <p>

     * If you are writing a file, and need to communicate an error to the

     * provider, use {@link ParcelFileDescriptor#closeWithError(String)}.

     *

     * @param uri The desired URI to open.

     * @param mode The file mode to use, as per {@link ContentProvider#openFile

     * ContentProvider.openFile}.

     * @return Returns a new ParcelFileDescriptor pointing to the file.  You

     * own this descriptor and are responsible for closing it when done.

     * @throws FileNotFoundException Throws FileNotFoundException if no

     * file exists under the URI or the mode is invalid.

     * @see #openAssetFileDescriptor(Uri, String)

     */

    public final @Nullable ParcelFileDescriptor openFileDescriptor(@NonNull Uri uri,

            @NonNull String mode) throws FileNotFoundException {

        return openFileDescriptor(uri, mode, null);

    }

查看Android 官方文档，关于Android 7.0 的权限管理更改，如下图所示：

参考链接为：

https://developer.android.google.cn/about/versions/nougat/android-7.0-changes.html#sharing-files

因此为了解决这个异常，我们有以下两个方法解决。

方法一、使用 ContentResolver#openFileDescriptor(Uri, String)来替代访问由 DownloadManager 公开的文件。

方法二、使用DownloadManager.COLUMN_LOCAL_URI查出文件Uri，然后使用Uri new一个File，再获取File的相关信息，如下所示：

int fileUriIdx = c.getColumnIndex(DownloadManager.COLUMN_LOCAL_URI);

String fileUri = c.getString(fileUriIdx);

String fileName = null;

if (Build.VERSION.SDK_INT > Build.VERSION_CODES.M) {

    if (fileUri != null) {

        fileName = Uri.parse(fileUri).getPath();

    }

} else {

    //Android 7.0以上的方式：请求获取写入权限，这一步报错

    //过时的方式：DownloadManager.COLUMN_LOCAL_FILENAME

    int fileNameIdx = c.getColumnIndex(DownloadManager.COLUMN_LOCAL_FILENAME);

    fileName = c.getString(fileNameIdx);

}

运行之后，不会报错，并且能够获取到正常的文件名。

参考链接

1. https://developer.android.google.cn/about/versions/nougat/android-7.0-changes.html#sharing-files

2. http://www.cnblogs.com/dazhao/p/6547811.html

3. http://www.jianshu.com/p/56b9fb319310

作者：欧阳鹏 欢迎转载，与人分享是进步的源泉！

转载请保留原文地址： http://blog.csdn.net/ouyang_peng/article/details/62891782