Android 4.4无法写sdcard解决方案
/* * Copyright (C) 2014 NextApp, Inc. * * 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 nextapp.mediafile;import java.io.File;import java.io.IOException;import java.io.OutputStream;import android.content.ContentResolver;import android.content.ContentValues;import android.net.Uri;import android.provider.MediaStore;/** * Wrapper for manipulating files via the Android Media Content Provider. As of Android 4.4 KitKat, applications can no longer write * to the "secondary storage" of a device. Write operations using the java.io.File API will thus fail. This class restores access to * those write operations by way of the Media Content Provider. * * Note that this class relies on the internal operational characteristics of the media content provider API, and as such is not * guaranteed to be future-proof. Then again, we did all think the java.io.File API was going to be future-proof for media card * access, so all bets are off. * * If you're forced to use this class, it's because Google/AOSP made a very poor API decision in Android 4.4 KitKat. * Read more at https://plus.google.com/+TodLiebeck/posts/gjnmuaDM8sn * * Your application must declare the permission "android.permission.WRITE_EXTERNAL_STORAGE". */public class MediaFile { private final File file; private final ContentResolver contentResolver; private final Uri filesUri; private final Uri imagesUri; public MediaFile(ContentResolver contentResolver, File file) { this.file = file; this.contentResolver = contentResolver; filesUri = MediaStore.Files.getContentUri("external"); imagesUri = MediaStore.Images.Media.EXTERNAL_CONTENT_URI; } /** * Deletes the file. Returns true if the file has been successfully deleted or otherwise does not exist. This operation is not * recursive. */ public boolean delete() throws IOException { if (!file.exists()) { return true; } boolean directory = file.isDirectory(); if (directory) { // Verify directory does not contain any files/directories within it. String[] files = file.list(); if (files != null && files.length > 0) { return false; } } String where = MediaStore.MediaColumns.DATA + "=?"; String[] selectionArgs = new String[] { file.getAbsolutePath() }; // Delete the entry from the media database. This will actually delete media files (images, audio, and video). contentResolver.delete(filesUri, where, selectionArgs); if (file.exists()) { // If the file is not a media file, create a new entry suggesting that this location is an image, even // though it is not. ContentValues values = new ContentValues(); values.put(MediaStore.Files.FileColumns.DATA, file.getAbsolutePath()); contentResolver.insert(imagesUri, values); // Delete the created entry, such that content provider will delete the file. contentResolver.delete(filesUri, where, selectionArgs); } return !file.exists(); } public File getFile() { return file; } /** * Creates a new directory. Returns true if the directory was successfully created or exists. */ public boolean mkdir() throws IOException { if (file.exists()) { return file.isDirectory(); } ContentValues values; Uri uri; // Create a media database entry for the directory. This step will not actually cause the directory to be created. values = new ContentValues(); values.put(MediaStore.Files.FileColumns.DATA, file.getAbsolutePath()); contentResolver.insert(filesUri, values); // Create an entry for a temporary image file within the created directory. // This step actually causes the creation of the directory. values = new ContentValues(); values.put(MediaStore.Files.FileColumns.DATA, file.getAbsolutePath() + "/temp.jpg"); uri = contentResolver.insert(imagesUri, values); // Delete the temporary entry. contentResolver.delete(uri, null, null); return file.exists(); } /** * Returns an OutputStream to write to the file. The file will be truncated immediately. */ public OutputStream write() throws IOException { if (file.exists() && file.isDirectory()) { throw new IOException("File exists and is a directory."); } // Delete any existing entry from the media database. // This may also delete the file (for media types), but that is irrelevant as it will be truncated momentarily in any case. String where = MediaStore.MediaColumns.DATA + "=?"; String[] selectionArgs = new String[] { file.getAbsolutePath() }; contentResolver.delete(filesUri, where, selectionArgs); ContentValues values = new ContentValues(); values.put(MediaStore.Files.FileColumns.DATA, file.getAbsolutePath()); Uri uri = contentResolver.insert(filesUri, values); if (uri == null) { // Should not occur. throw new IOException("Internal error."); } return contentResolver.openOutputStream(uri); }}