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>
笔记
为什么使用 FileProvider
- 从 Android 7.0 开始，我们无法与其他应用程序共享 FileUri。
- 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。
Provblem 使用“DownloadManager.getUriForDownloadedFile(long id)”
- 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。
- 因为从 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（但它在 Android 7.1 中已修复请参阅此处的 Android 提交）。
- 参考 Android 源代码DownloadManager.java & Downloads.java
- 因此，始终使用列“DownloadManager.COLUMN_LOCAL_URI”来获取 Uri。
参考
- https://developer.android.com/reference/android/app/DownloadManager.html
- https://developer.android.com/reference/android/support/v4/content/FileProvider.html