Android DownloadManager API - 下载后打开文件？

Question

通过 DownloadManager API 成功下载后，我面临打开下载文件的问题。在我的代码中:

Uri uri=Uri.parse("http://www.nasa.gov/images/content/206402main_jsc2007e113280_hires.jpg");

Environment
    .getExternalStoragePublicDirectory(Environment.DIRECTORY_DOWNLOADS)
    .mkdirs();

lastDownload = mgr.enqueue(new DownloadManager.Request(uri)
    .setAllowedNetworkTypes(DownloadManager.Request.NETWORK_WIFI |
                            DownloadManager.Request.NETWORK_MOBILE)
    .setAllowedOverRoaming(false)
    .setTitle("app update")
    .setDescription("New version 1.1")
    .setShowRunningNotification(true)
    .setDestinationInExternalPublicDir(Environment.DIRECTORY_DOWNLOADS, "a.apk"));

Cursor c=mgr.query(new DownloadManager.Query().setFilterById(lastDownload));

if(c.getInt(c.getColumnIndex(DownloadManager.COLUMN_STATUS)) == 8) {
    try {
        mgr.openDownloadedFile(c.getLong(c.getColumnIndex(DownloadManager.COLUMN_ID)));
    } catch (NumberFormatException e) {
        // TODO Auto-generated catch block
        e.printStackTrace();
        Log.d("MGR", "Error");
    } catch (FileNotFoundException e) {
        // TODO Auto-generated catch block
        e.printStackTrace();
        Log.d("MGR", "Error");
    }
}

问题是何时触发 if(c.getInt(c.getColumnIndex(DownloadManager.COLUMN_STATUS))==8)。我得到了状态 -1 和一个异常(exception)。有没有更好的方法，如何使用 DownloadManager API 打开下载的文件？在我的示例中，我正在下载一个大图像，在实际情况下，我将下载一个 APK 文件，并且我需要在 udpate 之后立即显示一个安装对话框。

编辑:我发现 status=8 是在成功下载之后。您可能有不同的“检查成功下载”方法

谢谢

Answer 1

问题

Android DownloadManager API - 下载后打开文件？

解决方案

/**
 * Used to download the file from url.
 * <p/>
 * 1. Download the file using Download Manager.
 *
 * @param url      Url.
 * @param fileName File Name.
 */
public void downloadFile(final Activity activity, final String url, final String fileName) {
    try {
        if (url != null && !url.isEmpty()) {
            Uri uri = Uri.parse(url);
            activity.registerReceiver(attachmentDownloadCompleteReceive, new IntentFilter(
                    DownloadManager.ACTION_DOWNLOAD_COMPLETE));

            DownloadManager.Request request = new DownloadManager.Request(uri);
            request.setMimeType(getMimeType(uri.toString()));
            request.setTitle(fileName);
            request.setDescription("Downloading attachment..");
            request.allowScanningByMediaScanner();
            request.setNotificationVisibility(DownloadManager.Request.VISIBILITY_VISIBLE_NOTIFY_COMPLETED);
            request.setDestinationInExternalPublicDir(Environment.DIRECTORY_DOWNLOADS, fileName);
            DownloadManager dm = (DownloadManager) activity.getSystemService(Context.DOWNLOAD_SERVICE);
            dm.enqueue(request);
        }
    } catch (IllegalStateException e) {
        Toast.makeText(activity, "Please insert an SD card to download file", Toast.LENGTH_SHORT).show();
    }
}

/**
 * Used to get MimeType from url.
 *
 * @param url Url.
 * @return Mime Type for the given url.
 */
private String getMimeType(String url) {
    String type = null;
    String extension = MimeTypeMap.getFileExtensionFromUrl(url);
    if (extension != null) {
        MimeTypeMap mime = MimeTypeMap.getSingleton();
        type = mime.getMimeTypeFromExtension(extension);
    }
    return type;
}

/**
 * Attachment download complete receiver.
 * <p/>
 * 1. Receiver gets called once attachment download completed.
 * 2. Open the downloaded file.
 */
BroadcastReceiver attachmentDownloadCompleteReceive = new BroadcastReceiver() {
    @Override
    public void onReceive(Context context, Intent intent) {
        String action = intent.getAction();
        if (DownloadManager.ACTION_DOWNLOAD_COMPLETE.equals(action)) {
            long downloadId = intent.getLongExtra(
                    DownloadManager.EXTRA_DOWNLOAD_ID, 0);
            openDownloadedAttachment(context, downloadId);
        }
    }
};

/**
 * Used to open the downloaded attachment.
 *
 * @param context    Content.
 * @param downloadId Id of the downloaded file to open.
 */
private void openDownloadedAttachment(final Context context, final long downloadId) {
    DownloadManager downloadManager = (DownloadManager) context.getSystemService(Context.DOWNLOAD_SERVICE);
    DownloadManager.Query query = new DownloadManager.Query();
    query.setFilterById(downloadId);
    Cursor cursor = downloadManager.query(query);
    if (cursor.moveToFirst()) {
        int downloadStatus = cursor.getInt(cursor.getColumnIndex(DownloadManager.COLUMN_STATUS));
        String downloadLocalUri = cursor.getString(cursor.getColumnIndex(DownloadManager.COLUMN_LOCAL_URI));
        String downloadMimeType = cursor.getString(cursor.getColumnIndex(DownloadManager.COLUMN_MEDIA_TYPE));
        if ((downloadStatus == DownloadManager.STATUS_SUCCESSFUL) && downloadLocalUri != null) {
            openDownloadedAttachment(context, Uri.parse(downloadLocalUri), downloadMimeType);
        }
    }
    cursor.close();
}

/**
 * Used to open the downloaded attachment.
 * <p/>
 * 1. Fire intent to open download file using external application.
 *
 * 2. Note:
 * 2.a. We can't share fileUri directly to other application (because we will get FileUriExposedException from Android7.0).
 * 2.b. Hence we can only share content uri with other application.
 * 2.c. We must have declared FileProvider in manifest.
 * 2.c. Refer - https://developer.android.com/reference/android/support/v4/content/FileProvider.html
 *
 * @param context            Context.
 * @param attachmentUri      Uri of the downloaded attachment to be opened.
 * @param attachmentMimeType MimeType of the downloaded attachment.
 */
private void openDownloadedAttachment(final Context context, Uri attachmentUri, final String attachmentMimeType) {
    if(attachmentUri!=null) {
        // Get Content Uri.
        if (ContentResolver.SCHEME_FILE.equals(attachmentUri.getScheme())) {
            // FileUri - Convert it to contentUri.
            File file = new File(attachmentUri.getPath());
            attachmentUri = FileProvider.getUriForFile(activity, "com.freshdesk.helpdesk.provider", file);;
        }

        Intent openAttachmentIntent = new Intent(Intent.ACTION_VIEW);
        openAttachmentIntent.setDataAndType(attachmentUri, attachmentMimeType);
        openAttachmentIntent.setFlags(Intent.FLAG_GRANT_READ_URI_PERMISSION);
        try {
            context.startActivity(openAttachmentIntent);
        } catch (ActivityNotFoundException e) {
            Toast.makeText(context, context.getString(R.string.unable_to_open_file), Toast.LENGTH_LONG).show();
        }
    }
}

初始化 FileProvider 详细信息

在 AndroidManifest 中清除 FileProvider

<provider
    android:name="android.support.v4.content.FileProvider"
    android:authorities="com.freshdesk.helpdesk.provider"
    android:exported="false"
    android:grantUriPermissions="true">
    <meta-data
        android:name="android.support.FILE_PROVIDER_PATHS"
        android:resource="@xml/file_path"/>
</provider>

添加以下文件“res -> xml -> file_path.xml”

<?xml version="1.0" encoding="utf-8"?>
<paths xmlns:android="http://schemas.android.com/apk/res/android">
    <external-path name="attachment_file" path="."/>
</paths>

注意

为什么使用 FileProvider

1. 从 Android 7.0 开始，我们无法与其他应用程序共享 FileUri。
2. 使用“DownloadManager.COLUMN_LOCAL_URI”我们将只获得 FileUri，因此我们需要将其转换为 ContentUri 并与其他应用程序共享。

使用“DownloadManager.getUriForDownloadedFile(long id)”的问题

1. 不要使用“DownloadManager.getUriForDownloadedFile(long id)” - 从 downloadId 获取 Uri 以使用外部应用程序打开文件。
2. 由于从 Android 6.0 和 7.0 开始，“getUriForDownloadedFile”方法返回本地 uri(只能由我们的应用程序访问)，我们无法与其他应用程序共享该 Uri，因为他们无法访问该 uri(但它已修复在 Android 7.1 see Android Commit Here 中)。
3. 引用Android源码DownloadManager.java & Downloads.java
4. 因此始终使用“DownloadManager.COLUMN_LOCAL_URI”列来获取 Uri。

引用

1. https://developer.android.com/reference/android/app/DownloadManager.html
2. https://developer.android.com/reference/android/support/v4/content/FileProvider.html