Android中利用ContentResolver获取本地音乐和相片

在Android中，例如图库和音乐播放器，它们能够扫描我们的系统，获取到本地的相片跟音乐，这一点是如何做到的呢？

当我们往手机上放图片或者音乐的时候，会在手机内存中某个位置上的某个database中存放图片或者音乐的信息，而我们的应用程序是能够通过ContentResolver去读取到这些数据的。

下面可以先看一下database在哪，如下：

然后在data/data/下面呢，有很多provider提供的数据库，而我们的音乐或者图片就是在一个叫做Media的库下：

external是智能手机中内置的SD卡，而internal则是机身的内存。

这两个database里面的结构是一样的，我们把external给拉到本地电脑上，如下红色框框显示的，左边就是从手机SD卡拉到电脑，右边是从电脑推到手机SD卡上。

接下来可以利用SQLiteSpy之类的工具打开我们的数据库，可以看到Images 和 Audio 相关的表和视图：

比如图片，我们可以查看images这张表，其结构如下：

音乐，可以查看audio的视图，如下：

既然知道了这些表的数据结构，那么如何在我们的应用程序中去获取到这些数据呢？答案，当然就是利用ContentResolver了。

具体看代码，下面我写的一个MusicLoader，是为了获取本地音乐，其中利用了一些过滤条件，只拿出我想要的音乐。

[java] view plaincopy

1. package com.example.nature;  
2.   
3. import java.util.ArrayList;  
4. import java.util.List;  
5.   
6. import android.content.ContentResolver;  
7. import android.content.ContentUris;  
8. import android.database.Cursor;  
9. import android.net.Uri;  
10. import android.os.Parcel;  
11. import android.os.Parcelable;  
12. import android.provider.MediaStore.Audio.Media;  
13. import android.util.Log;  
14.   
15. public class MusicLoader {  
16.       
17.     private static final String TAG = "com.example.nature.MusicLoader";  
18.       
19.     private static List<MusicInfo> musicList = new ArrayList<MusicInfo>();  
20.       
21.     private static MusicLoader musicLoader;  
22.       
23.     private static ContentResolver contentResolver;  
24.     //Uri，指向external的database   
25.     private Uri contentUri = Media.EXTERNAL_CONTENT_URI;      
26.     //projection：选择的列; where：过滤条件; sortOrder：排序。  
27.     private String[] projection = {  
28.             Media._ID,  
29.             Media.DISPLAY_NAME,  
30.             Media.DATA,  
31.             Media.ALBUM,  
32.             Media.ARTIST,  
33.             Media.DURATION,           
34.             Media.SIZE  
35.     };  
36.     private String where =  "mime_type in ('audio/mpeg','audio/x-ms-wma') and bucket_display_name <> 'audio' and is_music > 0 " ;  
37.     private String sortOrder = Media.DATA;  
38.       
39.     public static MusicLoader instance(ContentResolver pContentResolver){  
40.         if(musicLoader == null){  
41.             contentResolver = pContentResolver;  
42.             musicLoader = new MusicLoader();              
43.         }  
44.         return musicLoader;  
45.     }  
46.       
47.     private MusicLoader(){                                                                                                             //利用ContentResolver的query函数来查询数据，然后将得到的结果放到MusicInfo对象中，最后放到数组中  
48.         Cursor cursor = contentResolver.query(contentUri, projection, where, null, sortOrder);  
49.         if(cursor == null){  
50.             Log.v(TAG,"Line(37  )   Music Loader cursor == null.");  
51.         }else if(!cursor.moveToFirst()){  
52.             Log.v(TAG,"Line(39  )   Music Loader cursor.moveToFirst() returns false.");  
53.         }else{            
54.             int displayNameCol = cursor.getColumnIndex(Media.DISPLAY_NAME);  
55.             int albumCol = cursor.getColumnIndex(Media.ALBUM);  
56.             int idCol = cursor.getColumnIndex(Media._ID);  
57.             int durationCol = cursor.getColumnIndex(Media.DURATION);  
58.             int sizeCol = cursor.getColumnIndex(Media.SIZE);  
59.             int artistCol = cursor.getColumnIndex(Media.ARTIST);  
60.             int urlCol = cursor.getColumnIndex(Media.DATA);           
61.             do{  
62.                 String title = cursor.getString(displayNameCol);  
63.                 String album = cursor.getString(albumCol);  
64.                 long id = cursor.getLong(idCol);                  
65.                 int duration = cursor.getInt(durationCol);  
66.                 long size = cursor.getLong(sizeCol);  
67.                 String artist = cursor.getString(artistCol);  
68.                 String url = cursor.getString(urlCol);  
69.                   
70.                 MusicInfo musicInfo = new MusicInfo(id, title);  
71.                 musicInfo.setAlbum(album);  
72.                 musicInfo.setDuration(duration);  
73.                 musicInfo.setSize(size);  
74.                 musicInfo.setArtist(artist);  
75.                 musicInfo.setUrl(url);  
76.                 musicList.add(musicInfo);  
77.                   
78.             }while(cursor.moveToNext());  
79.         }  
80.     }  
81.       
82.     public List<MusicInfo> getMusicList(){  
83.         return musicList;  
84.     }  
85.       
86.     public Uri getMusicUriById(long id){  
87.         Uri uri = ContentUris.withAppendedId(contentUri, id);  
88.         return uri;  
89.     }     
90.         //下面是自定义的一个MusicInfo子类，实现了Parcelable，为的是可以将整个MusicInfo的ArrayList在Activity和Service中传送，=_=!!,但其实不用  
91.     static class MusicInfo implements Parcelable{                                         
92.         private long id;  
93.         private String title;  
94.         private String album;  
95.         private int duration;  
96.         private long size;  
97.         private String artist;        
98.         private String url;       
99.           
100.         public MusicInfo(){  
101.               
102.         }  
103.           
104.         public MusicInfo(long pId, String pTitle){  
105.             id = pId;  
106.             title = pTitle;  
107.         }  
108.           
109.         public String getArtist() {  
110.             return artist;  
111.         }  
112.   
113.         public void setArtist(String artist) {  
114.             this.artist = artist;  
115.         }  
116.   
117.         public long getSize() {  
118.             return size;  
119.         }  
120.   
121.         public void setSize(long size) {  
122.             this.size = size;  
123.         }         
124.   
125.         public long getId() {  
126.             return id;  
127.         }  
128.   
129.         public void setId(long id) {  
130.             this.id = id;  
131.         }  
132.   
133.         public String getTitle() {  
134.             return title;  
135.         }  
136.   
137.         public void setTitle(String title) {  
138.             this.title = title;  
139.         }  
140.   
141.         public String getAlbum() {  
142.             return album;  
143.         }  
144.   
145.         public void setAlbum(String album) {  
146.             this.album = album;  
147.         }  
148.   
149.         public int getDuration() {  
150.             return duration;  
151.         }  
152.   
153.         public void setDuration(int duration) {  
154.             this.duration = duration;  
155.         }     
156.   
157.         public String getUrl() {  
158.             return url;  
159.         }  
160.   
161.         public void setUrl(String url) {  
162.             this.url = url;  
163.         }  
164.   
165.         @Override  
166.         public int describeContents() {  
167.             return 0;  
168.         }  
169.   
170.         @Override  
171.         public void writeToParcel(Parcel dest, int flags) {  
172.             dest.writeLong(id);  
173.             dest.writeString(title);  
174.             dest.writeString(album);  
175.             dest.writeString(artist);  
176.             dest.writeString(url);  
177.             dest.writeInt(duration);  
178.             dest.writeLong(size);  
179.         }  
180.           
181.         public static final Parcelable.Creator<MusicInfo>   
182.             CREATOR = new Creator<MusicLoader.MusicInfo>() {  
183.               
184.             @Override  
185.             public MusicInfo[] newArray(int size) {  
186.                 return new MusicInfo[size];  
187.             }  
188.               
189.             @Override  
190.             public MusicInfo createFromParcel(Parcel source) {  
191.                 MusicInfo musicInfo = new MusicInfo();  
192.                 musicInfo.setId(source.readLong());  
193.                 musicInfo.setTitle(source.readString());  
194.                 musicInfo.setAlbum(source.readString());  
195.                 musicInfo.setArtist(source.readString());  
196.                 musicInfo.setUrl(source.readString());  
197.                 musicInfo.setDuration(source.readInt());  
198.                 musicInfo.setSize(source.readLong());  
199.                 return musicInfo;  
200.             }  
201.         };  
202.     }  
203. }  

[java] view plain copy

 

1. package com.example.nature;  
2.   
3. import java.util.ArrayList;  
4. import java.util.List;  
5.   
6. import android.content.ContentResolver;  
7. import android.content.ContentUris;  
8. import android.database.Cursor;  
9. import android.net.Uri;  
10. import android.os.Parcel;  
11. import android.os.Parcelable;  
12. import android.provider.MediaStore.Audio.Media;  
13. import android.util.Log;  
14.   
15. public class MusicLoader {  
16.       
17.     private static final String TAG = "com.example.nature.MusicLoader";  
18.       
19.     private static List<MusicInfo> musicList = new ArrayList<MusicInfo>();  
20.       
21.     private static MusicLoader musicLoader;  
22.       
23.     private static ContentResolver contentResolver;  
24.     //Uri，指向external的database  
25.     private Uri contentUri = Media.EXTERNAL_CONTENT_URI;      
26.     //projection：选择的列; where：过滤条件; sortOrder：排序。  
27.     private String[] projection = {  
28.             Media._ID,  
29.             Media.DISPLAY_NAME,  
30.             Media.DATA,  
31.             Media.ALBUM,  
32.             Media.ARTIST,  
33.             Media.DURATION,           
34.             Media.SIZE  
35.     };  
36.     private String where =  "mime_type in ('audio/mpeg','audio/x-ms-wma') and bucket_display_name <> 'audio' and is_music > 0 " ;  
37.     private String sortOrder = Media.DATA;  
38.       
39.     public static MusicLoader instance(ContentResolver pContentResolver){  
40.         if(musicLoader == null){  
41.             contentResolver = pContentResolver;  
42.             musicLoader = new MusicLoader();              
43.         }  
44.         return musicLoader;  
45.     }  
46.       
47.     private MusicLoader(){                                                                                                             //利用ContentResolver的query函数来查询数据，然后将得到的结果放到MusicInfo对象中，最后放到数组中  
48.         Cursor cursor = contentResolver.query(contentUri, projection, where, null, sortOrder);  
49.         if(cursor == null){  
50.             Log.v(TAG,"Line(37  )   Music Loader cursor == null.");  
51.         }else if(!cursor.moveToFirst()){  
52.             Log.v(TAG,"Line(39  )   Music Loader cursor.moveToFirst() returns false.");  
53.         }else{            
54.             int displayNameCol = cursor.getColumnIndex(Media.DISPLAY_NAME);  
55.             int albumCol = cursor.getColumnIndex(Media.ALBUM);  
56.             int idCol = cursor.getColumnIndex(Media._ID);  
57.             int durationCol = cursor.getColumnIndex(Media.DURATION);  
58.             int sizeCol = cursor.getColumnIndex(Media.SIZE);  
59.             int artistCol = cursor.getColumnIndex(Media.ARTIST);  
60.             int urlCol = cursor.getColumnIndex(Media.DATA);           
61.             do{  
62.                 String title = cursor.getString(displayNameCol);  
63.                 String album = cursor.getString(albumCol);  
64.                 long id = cursor.getLong(idCol);                  
65.                 int duration = cursor.getInt(durationCol);  
66.                 long size = cursor.getLong(sizeCol);  
67.                 String artist = cursor.getString(artistCol);  
68.                 String url = cursor.getString(urlCol);  
69.                   
70.                 MusicInfo musicInfo = new MusicInfo(id, title);  
71.                 musicInfo.setAlbum(album);  
72.                 musicInfo.setDuration(duration);  
73.                 musicInfo.setSize(size);  
74.                 musicInfo.setArtist(artist);  
75.                 musicInfo.setUrl(url);  
76.                 musicList.add(musicInfo);  
77.                   
78.             }while(cursor.moveToNext());  
79.         }  
80.     }  
81.       
82.     public List<MusicInfo> getMusicList(){  
83.         return musicList;  
84.     }  
85.       
86.     public Uri getMusicUriById(long id){  
87.         Uri uri = ContentUris.withAppendedId(contentUri, id);  
88.         return uri;  
89.     }     
90.         //下面是自定义的一个MusicInfo子类，实现了Parcelable，为的是可以将整个MusicInfo的ArrayList在Activity和Service中传送，=_=!!,但其实不用  
91.     static class MusicInfo implements Parcelable{                                         
92.         private long id;  
93.         private String title;  
94.         private String album;  
95.         private int duration;  
96.         private long size;  
97.         private String artist;        
98.         private String url;       
99.           
100.         public MusicInfo(){  
101.               
102.         }  
103.           
104.         public MusicInfo(long pId, String pTitle){  
105.             id = pId;  
106.             title = pTitle;  
107.         }  
108.           
109.         public String getArtist() {  
110.             return artist;  
111.         }  
112.   
113.         public void setArtist(String artist) {  
114.             this.artist = artist;  
115.         }  
116.   
117.         public long getSize() {  
118.             return size;  
119.         }  
120.   
121.         public void setSize(long size) {  
122.             this.size = size;  
123.         }         
124.   
125.         public long getId() {  
126.             return id;  
127.         }  
128.   
129.         public void setId(long id) {  
130.             this.id = id;  
131.         }  
132.   
133.         public String getTitle() {  
134.             return title;  
135.         }  
136.   
137.         public void setTitle(String title) {  
138.             this.title = title;  
139.         }  
140.   
141.         public String getAlbum() {  
142.             return album;  
143.         }  
144.   
145.         public void setAlbum(String album) {  
146.             this.album = album;  
147.         }  
148.   
149.         public int getDuration() {  
150.             return duration;  
151.         }  
152.   
153.         public void setDuration(int duration) {  
154.             this.duration = duration;  
155.         }     
156.   
157.         public String getUrl() {  
158.             return url;  
159.         }  
160.   
161.         public void setUrl(String url) {  
162.             this.url = url;  
163.         }  
164.   
165.         @Override  
166.         public int describeContents() {  
167.             return 0;  
168.         }  
169.   
170.         @Override  
171.         public void writeToParcel(Parcel dest, int flags) {  
172.             dest.writeLong(id);  
173.             dest.writeString(title);  
174.             dest.writeString(album);  
175.             dest.writeString(artist);  
176.             dest.writeString(url);  
177.             dest.writeInt(duration);  
178.             dest.writeLong(size);  
179.         }  
180.           
181.         public static final Parcelable.Creator<MusicInfo>   
182.             CREATOR = new Creator<MusicLoader.MusicInfo>() {  
183.               
184.             @Override  
185.             public MusicInfo[] newArray(int size) {  
186.                 return new MusicInfo[size];  
187.             }  
188.               
189.             @Override  
190.             public MusicInfo createFromParcel(Parcel source) {  
191.                 MusicInfo musicInfo = new MusicInfo();  
192.                 musicInfo.setId(source.readLong());  
193.                 musicInfo.setTitle(source.readString());  
194.                 musicInfo.setAlbum(source.readString());  
195.                 musicInfo.setArtist(source.readString());  
196.                 musicInfo.setUrl(source.readString());  
197.                 musicInfo.setDuration(source.readInt());  
198.                 musicInfo.setSize(source.readLong());  
199.                 return musicInfo;  
200.             }  
201.         };  
202.     }  
203. }  

最后，我们就可以在我们的手机上看到我们音乐了，不过数据库中有些是乱码的，我还不知道怎么解决。。。

图片的获取也是相类似的，放上代码，具体的自行琢磨：

[java] view plaincopy

1. package com.example.hmgallery;  
2.   
3. import java.util.ArrayList;  
4. import java.util.List;  
5.   
6. import android.content.ContentResolver;  
7. import android.database.Cursor;  
8. import android.provider.MediaStore.Images.Media;  
9. import android.provider.MediaStore.Images.Thumbnails;  
10. import android.util.SparseArray;  
11.   
12. public class Images{  
13.   
14.     public static final String IMAGE_PATH = "IMAGE_PATH";  
15.     public static final String IMAGE_ID = "IMAGE_ID";  
16.     public static final String IMAGE_POSITION = "IMAGE_POSITION";  
17.     public static final String IMAGE_COUNTS = "IMAGE_COUNTS";     
18.       
19.     private static List<ImageItem> imageItems = new ArrayList<ImageItem>();  
20.       
21.     private static SparseArray<ImageItem> tempArray;  
22.       
23.     public static void loadImages(ContentResolver contentResolver){  
24.         tempArray = new SparseArray<ImageItem>();  
25.         String[] projection = {Media._ID,Media.DATA,Media.ORIENTATION};  
26.         String where =  Media.BUCKET_DISPLAY_NAME + " = 'Camera'";  
27.         String sortOrder = Media._ID + " desc";  
28.         StringBuilder inImageIds = new StringBuilder(Thumbnails.IMAGE_ID);  
29.         inImageIds.append(" in ( ");  
30.         Cursor cursor = contentResolver.query(Media.EXTERNAL_CONTENT_URI, projection, where, null, sortOrder);        
31.         if(cursor.moveToFirst()){  
32.             do {  
33.                 int imageId = cursor.getInt(cursor.getColumnIndex(Media._ID));  
34.                 String imagePath = cursor.getString(cursor.getColumnIndex(Media.DATA));  
35.                 int orientation = cursor.getInt(cursor.getColumnIndex(Media.ORIENTATION));  
36.                 ImageItem imageItem = new ImageItem(imageId,imagePath,orientation);               
37.                 imageItems.add(imageItem);  
38.                 tempArray.put(imageId, imageItem);  
39.                 inImageIds.append(imageId).append(",");  
40.             }while(cursor.moveToNext());  
41.         }         
42.           
43.         inImageIds.deleteCharAt(inImageIds.length() - 1);  
44.         inImageIds.append(" ) ");   
45.           
46.         String[] thumbnailProjection = {Thumbnails.DATA,Thumbnails.IMAGE_ID};  
47.         cursor = contentResolver.query(Thumbnails.EXTERNAL_CONTENT_URI, thumbnailProjection, inImageIds.toString(), null, null);  
48.         if(cursor.moveToFirst()){  
49.             do {                  
50.                 int imageId = cursor.getInt(cursor.getColumnIndex(Thumbnails.IMAGE_ID));  
51.                 String thumnbailPath = cursor.getString(cursor.getColumnIndex(Media.DATA));               
52.                 ImageItem imageItem = tempArray.get(imageId);  
53.                 if(imageItem != null){  
54.                     imageItem.setThumbnailPath(thumnbailPath);  
55.                 }  
56.             }while(cursor.moveToNext());  
57.         }         
58.         tempArray = null;  
59.     }  
60.       
61.     public static ImageItem[] getImageItems(){  
62.         return imageItems.toArray(new ImageItem[]{});  
63.     }     
64. }  

[java] view plain copy

 

1. package com.example.hmgallery;  
2.   
3. import java.util.ArrayList;  
4. import java.util.List;  
5.   
6. import android.content.ContentResolver;  
7. import android.database.Cursor;  
8. import android.provider.MediaStore.Images.Media;  
9. import android.provider.MediaStore.Images.Thumbnails;  
10. import android.util.SparseArray;  
11.   
12. public class Images{  
13.   
14.     public static final String IMAGE_PATH = "IMAGE_PATH";  
15.     public static final String IMAGE_ID = "IMAGE_ID";  
16.     public static final String IMAGE_POSITION = "IMAGE_POSITION";  
17.     public static final String IMAGE_COUNTS = "IMAGE_COUNTS";     
18.       
19.     private static List<ImageItem> imageItems = new ArrayList<ImageItem>();  
20.       
21.     private static SparseArray<ImageItem> tempArray;  
22.       
23.     public static void loadImages(ContentResolver contentResolver){  
24.         tempArray = new SparseArray<ImageItem>();  
25.         String[] projection = {Media._ID,Media.DATA,Media.ORIENTATION};  
26.         String where =  Media.BUCKET_DISPLAY_NAME + " = 'Camera'";  
27.         String sortOrder = Media._ID + " desc";  
28.         StringBuilder inImageIds = new StringBuilder(Thumbnails.IMAGE_ID);  
29.         inImageIds.append(" in ( ");  
30.         Cursor cursor = contentResolver.query(Media.EXTERNAL_CONTENT_URI, projection, where, null, sortOrder);        
31.         if(cursor.moveToFirst()){  
32.             do {  
33.                 int imageId = cursor.getInt(cursor.getColumnIndex(Media._ID));  
34.                 String imagePath = cursor.getString(cursor.getColumnIndex(Media.DATA));  
35.                 int orientation = cursor.getInt(cursor.getColumnIndex(Media.ORIENTATION));  
36.                 ImageItem imageItem = new ImageItem(imageId,imagePath,orientation);               
37.                 imageItems.add(imageItem);  
38.                 tempArray.put(imageId, imageItem);  
39.                 inImageIds.append(imageId).append(",");  
40.             }while(cursor.moveToNext());  
41.         }         
42.           
43.         inImageIds.deleteCharAt(inImageIds.length() - 1);  
44.         inImageIds.append(" ) ");   
45.           
46.         String[] thumbnailProjection = {Thumbnails.DATA,Thumbnails.IMAGE_ID};  
47.         cursor = contentResolver.query(Thumbnails.EXTERNAL_CONTENT_URI, thumbnailProjection, inImageIds.toString(), null, null);  
48.         if(cursor.moveToFirst()){  
49.             do {                  
50.                 int imageId = cursor.getInt(cursor.getColumnIndex(Thumbnails.IMAGE_ID));  
51.                 String thumnbailPath = cursor.getString(cursor.getColumnIndex(Media.DATA));               
52.                 ImageItem imageItem = tempArray.get(imageId);  
53.                 if(imageItem != null){  
54.                     imageItem.setThumbnailPath(thumnbailPath);  
55.                 }  
56.             }while(cursor.moveToNext());  
57.         }         
58.         tempArray = null;  
59.     }  
60.       
61.     public static ImageItem[] getImageItems(){  
62.         return imageItems.toArray(new ImageItem[]{});  
63.     }     
64. }