android4.4上sd卡的读写权限

1. /* 
2.  * Copyright (C) 2014 NextApp, Inc. 
3.  *  
4.  * Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except in compliance with the License. 
5.  * You may obtain a copy of the License at 
6.  *  
7.  * http://www.apache.org/licenses/LICENSE-2.0 
8.  *  
9.  * Unless required by applicable law or agreed to in writing, software distributed under the License is distributed on an "AS IS" 
10.  * BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the License for the specific language 
11.  * governing permissions and limitations under the License. 
12.  */  
13.   
14. package nextapp.mediafile;  
15.   
16. import java.io.File;  
17. import java.io.IOException;  
18. import java.io.OutputStream;  
19.   
20. import android.content.ContentResolver;  
21. import android.content.ContentValues;  
22. import android.net.Uri;  
23. import android.provider.MediaStore;  
24.   
25. /** 
26.  * Wrapper for manipulating files via the Android Media Content Provider. As of Android 4.4 KitKat, applications can no longer write 
27.  * to the "secondary storage" of a device. Write operations using the java.io.File API will thus fail. This class restores access to 
28.  * those write operations by way of the Media Content Provider. 
29.  *  
30.  * Note that this class relies on the internal operational characteristics of the media content provider API, and as such is not 
31.  * 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 
32.  * access, so all bets are off. 
33.  *  
34.  * If you're forced to use this class, it's because Google/AOSP made a very poor API decision in Android 4.4 KitKat. 
35.  * Read more at https://plus.google.com/+TodLiebeck/posts/gjnmuaDM8sn 
36.  * 
37.  * Your application must declare the permission "android.permission.WRITE_EXTERNAL_STORAGE". 
38.  */  
39. public class MediaFile {  
40.   
41.     private final File file;  
42.     private final ContentResolver contentResolver;  
43.     private final Uri filesUri;  
44.     private final Uri imagesUri;  
45.   
46.     public MediaFile(ContentResolver contentResolver, File file) {  
47.         this.file = file;  
48.         this.contentResolver = contentResolver;  
49.         filesUri = MediaStore.Files.getContentUri("external");  
50.         imagesUri = MediaStore.Images.Media.EXTERNAL_CONTENT_URI;  
51.     }  
52.   
53.     /** 
54.      * Deletes the file. Returns true if the file has been successfully deleted or otherwise does not exist. This operation is not 
55.      * recursive. 
56.      */  
57.     public boolean delete()  
58.             throws IOException {  
59.         if (!file.exists()) {  
60.             return true;  
61.         }  
62.   
63.         boolean directory = file.isDirectory();  
64.         if (directory) {  
65.             // Verify directory does not contain any files/directories within it.  
66.             String[] files = file.list();  
67.             if (files != null && files.length > 0) {  
68.                 return false;  
69.             }  
70.         }  
71.   
72.         String where = MediaStore.MediaColumns.DATA + "=?";  
73.         String[] selectionArgs = new String[] { file.getAbsolutePath() };  
74.   
75.         // Delete the entry from the media database. This will actually delete media files (images, audio, and video).  
76.         contentResolver.delete(filesUri, where, selectionArgs);  
77.   
78.         if (file.exists()) {  
79.             // If the file is not a media file, create a new entry suggesting that this location is an image, even  
80.             // though it is not.  
81.             ContentValues values = new ContentValues();  
82.             values.put(MediaStore.Files.FileColumns.DATA, file.getAbsolutePath());  
83.             contentResolver.insert(imagesUri, values);  
84.   
85.             // Delete the created entry, such that content provider will delete the file.  
86.             contentResolver.delete(filesUri, where, selectionArgs);  
87.         }  
88.   
89.         return !file.exists();  
90.     }  
91.   
92.     public File getFile() {  
93.         return file;  
94.     }  
95.   
96.     /** 
97.      * Creates a new directory. Returns true if the directory was successfully created or exists. 
98.      */  
99.     public boolean mkdir()  
100.             throws IOException {  
101.         if (file.exists()) {  
102.             return file.isDirectory();  
103.         }  
104.   
105.         ContentValues values;  
106.         Uri uri;  
107.   
108.         // Create a media database entry for the directory. This step will not actually cause the directory to be created.  
109.         values = new ContentValues();  
110.         values.put(MediaStore.Files.FileColumns.DATA, file.getAbsolutePath());  
111.         contentResolver.insert(filesUri, values);  
112.   
113.         // Create an entry for a temporary image file within the created directory.  
114.         // This step actually causes the creation of the directory.  
115.         values = new ContentValues();  
116.         values.put(MediaStore.Files.FileColumns.DATA, file.getAbsolutePath() + "/temp.jpg");  
117.         uri = contentResolver.insert(imagesUri, values);  
118.   
119.         // Delete the temporary entry.  
120.         contentResolver.delete(uri, null, null);  
121.   
122.         return file.exists();  
123.     }  
124.   
125.     /** 
126.      * Returns an OutputStream to write to the file. The file will be truncated immediately. 
127.      */  
128.     public OutputStream write()  
129.             throws IOException {  
130.         if (file.exists() && file.isDirectory()) {  
131.             throw new IOException("File exists and is a directory.");  
132.         }  
133.   
134.         // Delete any existing entry from the media database.  
135.         // This may also delete the file (for media types), but that is irrelevant as it will be truncated momentarily in any case.  
136.         String where = MediaStore.MediaColumns.DATA + "=?";  
137.         String[] selectionArgs = new String[] { file.getAbsolutePath() };  
138.         contentResolver.delete(filesUri, where, selectionArgs);  
139.   
140.         ContentValues values = new ContentValues();  
141.         values.put(MediaStore.Files.FileColumns.DATA, file.getAbsolutePath());  
142.         Uri uri = contentResolver.insert(filesUri, values);  
143.   
144.         if (uri == null) {  
145.             // Should not occur.  
146.             throw new IOException("Internal error.");  
147.         }  
148.   
149.         return contentResolver.openOutputStream(uri);  
150.     }  
151. }  

/*
 * 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);
    }
}