这篇博客介绍了在Android 8.0中，谷歌新增的FileSystemProvider类如何用于文件管理，特别是在重命名和移动文件时如何利用MediaStore进行操作。示例代码展示了如何根据文件类型创建DirectoryUri，并使用ContentResolver更新文件路径。
谷歌在android8.0开始，新增加了
sprdroido_pdk/frameworks/base/core/java/com/android/internal/content/FileSystemProvider.java
比如在修改文件重命名时，可以实现新增的文件夹URi:
final Uri externalUri = newVisibleFile.isDirectory()
? MediaStore.Files.getDirectoryUri("external")
: MediaStore.Files.getContentUri("external");
public static void moveInMediaStore(Context context,File oldVisibleFile,File newVisibleFile) {
// visibleFolders are null if we're moving a document in external thumb drive or SD card.
//
// They should be all null or not null at the same time. File#renameTo() doesn't work across
// volumes so an exception will be thrown before calling this method.
if (oldVisibleFile != null && newVisibleFile != null) {
final ContentResolver resolver = context.getContentResolver();
final Uri externalUri = newVisibleFile.isDirectory()
? MediaStore.Files.getDirectoryUri("external")
: MediaStore.Files.getContentUri("external");
String newPath = newVisibleFile.getAbsolutePath();
String oldPath = oldVisibleFile.getAbsolutePath();
Log.d(TAG," moveInMediaStore: oldPath="+oldPath+ " newPath="+newPath);
Log.d(TAG," moveInMediaStore: externalUri="+externalUri);
ContentValues values = new ContentValues();
values.put(MediaStore.Files.FileColumns.DATA, newPath);
// Logic borrowed from MtpDatabase.
// note - we are relying on a special case in MediaProvider.update() to update
// the paths for all children in the case where this is a directory.
resolver.update(externalUri,
values,
"_data LIKE ? AND lower(_data)=lower(?)",
new String[] { oldPath, oldPath });
}
}
/*
* Copyright (C) 2017 The Android Open Source Project
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package com.android.internal.content;
import android.annotation.CallSuper;
import android.annotation.Nullable;
import android.content.ContentResolver;
import android.content.ContentValues;
import android.content.Intent;
import android.content.res.AssetFileDescriptor;
import android.database.Cursor;
import android.database.MatrixCursor;
import android.database.MatrixCursor.RowBuilder;
import android.graphics.Point;
import android.net.Uri;
import android.os.CancellationSignal;
import android.os.FileObserver;
import android.os.FileUtils;
import android.os.Handler;
import android.os.ParcelFileDescriptor;
import android.provider.DocumentsContract;
import android.provider.DocumentsContract.Document;
import android.provider.DocumentsProvider;
import android.provider.MediaStore;
import android.text.TextUtils;
import android.util.ArrayMap;
import android.util.Log;
import android.webkit.MimeTypeMap;
import com.android.internal.annotations.GuardedBy;
import java.io.File;
import java.io.FileNotFoundException;
import java.io.IOException;
import java.util.LinkedList;
import java.util.List;
import java.util.Set;
/**
* A helper class for {@link android.provider.DocumentsProvider} to perform file operations on local
* files.
*/
public abstract class FileSystemProvider extends DocumentsProvider {
private static final String TAG = "FileSystemProvider";
private static final boolean LOG_INOTIFY = false;
private String[] mDefaultProjection;
@GuardedBy("mObservers")
private final ArrayMap
mObservers = new ArrayMap<>();
private Handler mHandler;
protected abstract File getFileForDocId(String docId, boolean visible)
throws FileNotFoundException;
protected abstract String getDocIdForFile(File file) throws FileNotFoundException;
protected abstract Uri buildNotificationUri(String docId);
@Override
public boolean onCreate() {
throw new UnsupportedOperationException(
"Subclass should override this and call onCreate(defaultDocumentProjection)");
}
@CallSuper
protected void onCreate(String[] defaultProjection) {
mHandler = new Handler();
mDefaultProjection = defaultProjection;
}
@Override
public boolean isChildDocument(String parentDocId, String docId) {
try {
final File parent = getFileForDocId(parentDocId).getCanonicalFile();
final File doc = getFileForDocId(docId).getCanonicalFile();
return FileUtils.contains(parent, doc);
} catch (IOException e) {
throw new IllegalArgumentException(
"Failed to determine if " + docId + " is child of " + parentDocId + ": " + e);
}
}
protected final List
findDocumentPath(File parent, File doc)
throws FileNotFoundException {
if (!doc.exists()) {
throw new FileNotFoundException(doc + " is not found.");
}
if (!FileUtils.contains(parent, doc)) {
throw new FileNotFoundException(doc + " is not found under " + parent);
}
LinkedList
path = new LinkedList<>();
while (doc != null && FileUtils.contains(parent, doc)) {
path.addFirst(getDocIdForFile(doc));
doc = doc.getParentFile();
}
return path;
}
@Override
public String createDocument(String docId, String mimeType, String displayName)
throws FileNotFoundException {
displayName = FileUtils.buildValidFatFilename(displayName);
final File parent = getFileForDocId(docId);
if (!parent.isDirectory()) {
throw new IllegalArgumentException("Parent document isn't a directory");
}
final File file = FileUtils.buildUniqueFile(parent, mimeType, displayName);
final String childId;
if (Document.MIME_TYPE_DIR.equals(mimeType)) {
if (!file.mkdir()) {
throw new IllegalStateException("Failed to mkdir " + file);
}
childId = getDocIdForFile(file);
addFolderToMediaStore(getFileForDocId(childId, true));
} else {
try {
if (!file.createNewFile()) {
throw new IllegalStateException("Failed to touch " + file);
}
childId = getDocIdForFile(file);
} catch (IOException e) {
throw new IllegalStateException("Failed to touch " + file + ": " + e);
}
}
return childId;
}
private void addFolderToMediaStore(@Nullable File visibleFolder) {
// visibleFolder is null if we're adding a folder to external thumb drive or SD card.
if (visibleFolder != null) {
assert (visibleFolder.isDirectory());
final ContentResolver resolver = getContext().getContentResolver();
final Uri uri = MediaStore.Files.getDirectoryUri("external");
ContentValues values = new ContentValues();
values.put(MediaStore.Files.FileColumns.DATA, visibleFolder.getAbsolutePath());
resolver.insert(uri, values);
}
}
@Override
public String renameDocument(String docId, String displayName) throws FileNotFoundException {
// Since this provider treats renames as generating a completely new
// docId, we're okay with letting the MIME type change.
displayName = FileUtils.buildValidFatFilename(displayName);
final File before = getFileForDocId(docId);
final File after = FileUtils.buildUniqueFile(before.getParentFile(), displayName);
final File visibleFileBefore = getFileForDocId(docId, true);
if (!before.renameTo(after)) {
throw new IllegalStateException("Failed to rename to " + after);
}
final String afterDocId = getDocIdForFile(after);
moveInMediaStore(visibleFileBefore, getFileForDocId(afterDocId, true));
if (!TextUtils.equals(docId, afterDocId)) {
return afterDocId;
} else {
return null;
}
}
@Override
public String moveDocument(String sourceDocumentId, String sourceParentDocumentId,
String targetParentDocumentId)
throws FileNotFoundException {
final File before = getFileForDocId(sourceDocumentId);
final File after = new File(getFileForDocId(targetParentDocumentId), before.getName());
final File visibleFileBefore = getFileForDocId(sourceDocumentId, true);
if (after.exists()) {
throw new IllegalStateException("Already exists " + after);
}
if (!before.renameTo(after)) {
throw new IllegalStateException("Failed to move to " + after);
}
final String docId = getDocIdForFile(after);
moveInMediaStore(visibleFileBefore, getFileForDocId(docId, true));
return docId;
}
private void moveInMediaStore(@Nullable File oldVisibleFile, @Nullable File newVisibleFile) {
// visibleFolders are null if we're moving a document in external thumb drive or SD card.
//
// They should be all null or not null at the same time. File#renameTo() doesn't work across
// volumes so an exception will be thrown before calling this method.
if (oldVisibleFile != null && newVisibleFile != null) {
final ContentResolver resolver = getContext().getContentResolver();
final Uri externalUri = newVisibleFile.isDirectory()
? MediaStore.Files.getDirectoryUri("external")
: MediaStore.Files.getContentUri("external");
ContentValues values = new ContentValues();
values.put(MediaStore.Files.FileColumns.DATA, newVisibleFile.getAbsolutePath());
// Logic borrowed from MtpDatabase.
// note - we are relying on a special case in MediaProvider.update() to update
// the paths for all children in the case where this is a directory.
final String path = oldVisibleFile.getAbsolutePath();
resolver.update(externalUri,
values,
"_data LIKE ? AND lower(_data)=lower(?)",
new String[] { path, path });
}
}
@Override
public void deleteDocument(String docId) throws FileNotFoundException {
final File file = getFileForDocId(docId);
final File visibleFile = getFileForDocId(docId, true);
final boolean isDirectory = file.isDirectory();
if (isDirectory) {
FileUtils.deleteContents(file);
}
if (!file.delete()) {
throw new IllegalStateException("Failed to delete " + file);
}
removeFromMediaStore(visibleFile, isDirectory);
}
private void removeFromMediaStore(@Nullable File visibleFile, boolean isFolder)
throws FileNotFoundException {
// visibleFolder is null if we're removing a document from external thumb drive or SD card.
if (visibleFile != null) {
final ContentResolver resolver = getContext().getContentResolver();
final Uri externalUri = MediaStore.Files.getContentUri("external");
// Remove media store entries for any files inside this directory, using
// path prefix match. Logic borrowed from MtpDatabase.
if (isFolder) {
final String path = visibleFile.getAbsolutePath() + "/";
resolver.delete(externalUri,
"_data LIKE ?1 AND lower(substr(_data,1,?2))=lower(?3)",
new String[] { path + "%", Integer.toString(path.length()), path });
}
// Remove media store entry for this exact file.
final String path = visibleFile.getAbsolutePath();
resolver.delete(externalUri,
"_data LIKE ?1 AND lower(_data)=lower(?2)",
new String[] { path, path });
}
}
@Override
public Cursor queryDocument(String documentId, String[] projection)
throws FileNotFoundException {
final MatrixCursor result = new MatrixCursor(resolveProjection(projection));
includeFile(result, documentId, null);
return result;
}
@Override
public Cursor queryChildDocuments(
String parentDocumentId, String[] projection, String sortOrder)
throws FileNotFoundException {
final File parent = getFileForDocId(parentDocumentId);
final MatrixCursor result = new DirectoryCursor(
resolveProjection(projection), parentDocumentId, parent);
for (File file : parent.listFiles()) {
includeFile(result, null, file);
}
return result;
}
/**
* Searches documents under the given folder.
*
* To avoid runtime explosion only returns the at most 23 items.
*
* @param folder the root folder where recursive search begins
* @param query the search condition used to match file names
* @param projection projection of the returned cursor
* @param exclusion absolute file paths to exclude from result
* @return cursor containing search result
* @throws FileNotFoundException when root folder doesn't exist or search fails
*/
protected final Cursor querySearchDocuments(
File folder, String query, String[] projection, Set
exclusion)
throws FileNotFoundException {
query = query.toLowerCase();
final MatrixCursor result = new MatrixCursor(resolveProjection(projection));
final LinkedList
pending = new LinkedList<>();
pending.add(folder);
while (!pending.isEmpty() && result.getCount() < 24) {
final File file = pending.removeFirst();
if (file.isDirectory()) {
for (File child : file.listFiles()) {
pending.add(child);
}
}
if (file.getName().toLowerCase().contains(query)
&& !exclusion.contains(file.getAbsolutePath())) {
includeFile(result, null, file);
}
}
return result;
}
@Override
public String getDocumentType(String documentId) throws FileNotFoundException {
final File file = getFileForDocId(documentId);
return getTypeForFile(file);
}
@Override
public ParcelFileDescriptor openDocument(
String documentId, String mode, CancellationSignal signal)
throws FileNotFoundException {
final File file = getFileForDocId(documentId);
final File visibleFile = getFileForDocId(documentId, true);
final int pfdMode = ParcelFileDescriptor.parseMode(mode);
if (pfdMode == ParcelFileDescriptor.MODE_READ_ONLY || visibleFile == null) {
return ParcelFileDescriptor.open(file, pfdMode);
} else {
try {
// When finished writing, kick off media scanner
return ParcelFileDescriptor.open(
file, pfdMode, mHandler, (IOException e) -> scanFile(visibleFile));
} catch (IOException e) {
throw new FileNotFoundException("Failed to open for writing: " + e);
}
}
}
private void scanFile(File visibleFile) {
final Intent intent = new Intent(Intent.ACTION_MEDIA_SCANNER_SCAN_FILE);
intent.setData(Uri.fromFile(visibleFile));
getContext().sendBroadcast(intent);
}
@Override
public AssetFileDescriptor openDocumentThumbnail(
String documentId, Point sizeHint, CancellationSignal signal)
throws FileNotFoundException {
final File file = getFileForDocId(documentId);
return DocumentsContract.openImageThumbnail(file);
}
protected RowBuilder includeFile(MatrixCursor result, String docId, File file)
throws FileNotFoundException {
if (docId == null) {
docId = getDocIdForFile(file);
} else {
file = getFileForDocId(docId);
}
int flags = 0;
if (file.canWrite()) {
if (file.isDirectory()) {
flags |= Document.FLAG_DIR_SUPPORTS_CREATE;
flags |= Document.FLAG_SUPPORTS_DELETE;
flags |= Document.FLAG_SUPPORTS_RENAME;
flags |= Document.FLAG_SUPPORTS_MOVE;
} else {
flags |= Document.FLAG_SUPPORTS_WRITE;
flags |= Document.FLAG_SUPPORTS_DELETE;
flags |= Document.FLAG_SUPPORTS_RENAME;
flags |= Document.FLAG_SUPPORTS_MOVE;
}
}
final String mimeType = getTypeForFile(file);
final String displayName = file.getName();
if (mimeType.startsWith("image/")) {
flags |= Document.FLAG_SUPPORTS_THUMBNAIL;
}
final RowBuilder row = result.newRow();
row.add(Document.COLUMN_DOCUMENT_ID, docId);
row.add(Document.COLUMN_DISPLAY_NAME, displayName);
row.add(Document.COLUMN_SIZE, file.length());
row.add(Document.COLUMN_MIME_TYPE, mimeType);
row.add(Document.COLUMN_FLAGS, flags);
// Only publish dates reasonably after epoch
long lastModified = file.lastModified();
if (lastModified > 31536000000L) {
row.add(Document.COLUMN_LAST_MODIFIED, lastModified);
}
// Return the row builder just in case any subclass want to add more stuff to it.
return row;
}
private static String getTypeForFile(File file) {
if (file.isDirectory()) {
return Document.MIME_TYPE_DIR;
} else {
return getTypeForName(file.getName());
}
}
private static String getTypeForName(String name) {
final int lastDot = name.lastIndexOf('.');
if (lastDot >= 0) {
final String extension = name.substring(lastDot + 1).toLowerCase();
final String mime = MimeTypeMap.getSingleton().getMimeTypeFromExtension(extension);
if (mime != null) {
return mime;
}
}
return "application/octet-stream";
}
protected final File getFileForDocId(String docId) throws FileNotFoundException {
return getFileForDocId(docId, false);
}
private String[] resolveProjection(String[] projection) {
return projection == null ? mDefaultProjection : projection;
}
private void startObserving(File file, Uri notifyUri) {
synchronized (mObservers) {
DirectoryObserver observer = mObservers.get(file);
if (observer == null) {
observer = new DirectoryObserver(
file, getContext().getContentResolver(), notifyUri);
observer.startWatching();
mObservers.put(file, observer);
}
observer.mRefCount++;
if (LOG_INOTIFY) Log.d(TAG, "after start: " + observer);
}
}
private void stopObserving(File file) {
synchronized (mObservers) {
DirectoryObserver observer = mObservers.get(file);
if (observer == null) return;
observer.mRefCount--;
if (observer.mRefCount == 0) {
mObservers.remove(file);
observer.stopWatching();
}
if (LOG_INOTIFY) Log.d(TAG, "after stop: " + observer);
}
}
private static class DirectoryObserver extends FileObserver {
private static final int NOTIFY_EVENTS = ATTRIB | CLOSE_WRITE | MOVED_FROM | MOVED_TO
| CREATE | DELETE | DELETE_SELF | MOVE_SELF;
private final File mFile;
private final ContentResolver mResolver;
private final Uri mNotifyUri;
private int mRefCount = 0;
public DirectoryObserver(File file, ContentResolver resolver, Uri notifyUri) {
super(file.getAbsolutePath(), NOTIFY_EVENTS);
mFile = file;
mResolver = resolver;
mNotifyUri = notifyUri;
}
@Override
public void onEvent(int event, String path) {
if ((event & NOTIFY_EVENTS) != 0) {
if (LOG_INOTIFY) Log.d(TAG, "onEvent() " + event + " at " + path);
mResolver.notifyChange(mNotifyUri, null, false);
}
}
@Override
public String toString() {
return "DirectoryObserver{file=" + mFile.getAbsolutePath() + ", ref=" + mRefCount + "}";
}
}
private class DirectoryCursor extends MatrixCursor {
private final File mFile;
public DirectoryCursor(String[] columnNames, String docId, File file) {
super(columnNames);
final Uri notifyUri = buildNotificationUri(docId);
setNotificationUri(getContext().getContentResolver(), notifyUri);
mFile = file;
startObserving(mFile, notifyUri);
}
@Override
public void close() {
super.close();
stopObserving(mFile);
}
}
}
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