Android提取系统所有的缩略图
Android系统能够帮助我们实现把图片缩略到合适的尺寸:
提取图片和视频的所有缩略图可以直接访问：
android.provider.MediaStroe.Imamge.Thumbnails
android.provider.MediaStroe.Imamge.Thumbnails
这是两个系统提供的数据库，可以用来查询缩略图（contentprovider）。
想要知道这两个数据库是如何存储数据的，可以参见这篇博文：http://blog.csdn.net/java2009cgh/article/details/8364735。
我这里只上一下自己写的代码，用来提取android系统的所有缩略图：
首先建立一个类，声明要用到的一些类和变量
final String TAG = getClass().getSimpleName();
Context context;
ContentResolver cr;
// 缩略图列表
HashMap<String, String> thumbnailList = new HashMap<String, String>();
// 专辑列表
List<HashMap<String, String>> albumList = new ArrayList<HashMap<String, String>>();
HashMap<String, PhotoUpImageBucket> bucketList = new HashMap<String, PhotoUpImageBucket>();
private GetAlbumList getAlbumList;
/**
* 是否创建了图片集
*/
boolean hasBuildImagesBucketList = false;
private PhotoUpAlbumHelper() {
}
public static PhotoUpAlbumHelper getHelper() {
PhotoUpAlbumHelper instance = new PhotoUpAlbumHelper();
return instance;
}
/**
* 初始化
*
* @param context
*/
public void init(Context context) {
if (this.context == null) {
this.context = context;
cr = context.getContentResolver();
}
}
其中PhotoUpImageBucket是一个相册对象，如下：
package android.apps.bean;
import java.io.Serializable;
import java.util.List;
/**
* 一个目录下的相册对象
*/
@SuppressWarnings("serial")
public class PhotoUpImageBucket implements Serializable{
public int count = 0;
public String bucketName;
public List<PhotoUpImageItem> imageList;
public int getCount() {
return count;
}
public void setCount(int count) {
this.count = count;
}
public String getBucketName() {
return bucketName;
}
public void setBucketName(String bucketName) {
this.bucketName = bucketName;
}
public List<PhotoUpImageItem> getImageList() {
return imageList;
}
public void setImageList(List<PhotoUpImageItem> imageList) {
this.imageList = imageList;
}
}
相册对象中有一个PhotoUpImageItem类，是缩略图对象，其中的属性如下：
package android.apps.bean;
import java.io.Serializable;
@SuppressWarnings("serial")
public class PhotoUpImageItem implements Serializable {
//图片ID
private String imageId;
//原图路径
private String imagePath;
//是否被选择
private boolean isSelected = false;
public String getImageId() {
return imageId;
}
public void setImageId(String imageId) {
this.imageId = imageId;
}
public String getImagePath() {
return imagePath;
}
public void setImagePath(String imagePath) {
this.imagePath = imagePath;
}
public boolean isSelected() {
return isSelected;
}
public void setSelected(boolean isSelected) {
this.isSelected = isSelected;
}
}
随后
1.得到系统的缩略图：
/**
* 得到缩略图
*/
private void getThumbnail() {
String[] projection = { Thumbnails._ID, Thumbnails.IMAGE_ID,
Thumbnails.DATA };
Cursor cursor1 = Thumbnails.queryMiniThumbnails(cr,
Thumbnails.EXTERNAL_CONTENT_URI, Thumbnails.MINI_KIND,
projection);
getThumbnailColumnData(cursor1);
cursor1.close();
}
/**
* 从数据库中得到缩略图
*
* @param cur
*/
private void getThumbnailColumnData(Cursor cur) {
if (cur.moveToFirst()) {
int image_id;
String image_path;
int image_idColumn = cur.getColumnIndex(Thumbnails.IMAGE_ID);
int dataColumn = cur.getColumnIndex(Thumbnails.DATA);
do {
image_id = cur.getInt(image_idColumn);
image_path = cur.getString(dataColumn);
thumbnailList.put("" + image_id, image_path);
} while (cur.moveToNext());
}
}
2.得到缩略图对应的原图：
/**
* 得到原图-n
*/
void getAlbum() {
String[] projection = { Albums._ID, Albums.ALBUM, Albums.ALBUM_ART,
Albums.ALBUM_KEY, Albums.ARTIST, Albums.NUMBER_OF_SONGS };
Cursor cursor1 = cr.query(Albums.EXTERNAL_CONTENT_URI, projection,
null, null, Albums.ALBUM_ID + " desc");
getAlbumColumnData(cursor1);
cursor1.close();
}
/**
* 从本地数据库中得到原图
*
* @param cur
*/
private void getAlbumColumnData(Cursor cur) {
if (cur.moveToFirst()) {
int _id;
String album;
String albumArt;
String albumKey;
String artist;
int numOfSongs;
int _idColumn = cur.getColumnIndex(Albums._ID);
int albumColumn = cur.getColumnIndex(Albums.ALBUM);
int albumArtColumn = cur.getColumnIndex(Albums.ALBUM_ART);
int albumKeyColumn = cur.getColumnIndex(Albums.ALBUM_KEY);
int artistColumn = cur.getColumnIndex(Albums.ARTIST);
int numOfSongsColumn = cur.getColumnIndex(Albums.NUMBER_OF_SONGS);
do {
_id = cur.getInt(_idColumn);
album = cur.getString(albumColumn);
albumArt = cur.getString(albumArtColumn);
albumKey = cur.getString(albumKeyColumn);
artist = cur.getString(artistColumn);
numOfSongs = cur.getInt(numOfSongsColumn);
HashMap<String, String> hash = new HashMap<String, String>();
hash.put("_id", _id + "");
hash.put("album", album);
hash.put("albumArt", albumArt);
hash.put("albumKey", albumKey);
hash.put("artist", artist);
hash.put("numOfSongs", numOfSongs + "");
albumList.add(hash);
} while (cur.moveToNext());
}
}
3.最后编写一个方法来构建图片集合
public void buildImagesBucketList() {
// 构造缩略图索引
getThumbnail();
// 构造相册索引
String columns[] = new String[] { Media._ID, Media.BUCKET_ID,
Media.PICASA_ID, Media.DATA, Media.DISPLAY_NAME, Media.TITLE,
Media.SIZE, Media.BUCKET_DISPLAY_NAME };
// 得到一个游标
Cursor cur = cr.query(Media.EXTERNAL_CONTENT_URI, columns, null, null,
Media.DATE_MODIFIED + " desc");
if (cur.moveToFirst()) {
// 获取指定列的索引
int photoIDIndex = cur.getColumnIndexOrThrow(Media._ID);
int photoPathIndex = cur.getColumnIndexOrThrow(Media.DATA);
int bucketDisplayNameIndex = cur
.getColumnIndexOrThrow(Media.BUCKET_DISPLAY_NAME);
int bucketIdIndex = cur.getColumnIndexOrThrow(Media.BUCKET_ID);
/**
* Description:这里增加了一个判断：判断照片的名字是否合法，例如.jpg .png 图片名字是不合法的，直接过滤掉
*/
do {
if (cur.getString(photoPathIndex)
.substring(
cur.getString(photoPathIndex).lastIndexOf("/") + 1,
cur.getString(photoPathIndex).lastIndexOf("."))
.replaceAll(" ", "").length() <= 0) {
Log.d(TAG, "出现了异常图片的地址：cur.getString(photoPathIndex)="
+ cur.getString(photoPathIndex));
Log.d(TAG,
"出现了异常图片的地址：cur.getString(photoPathIndex).substring="
+ cur.getString(photoPathIndex).substring(
cur.getString(photoPathIndex)
.lastIndexOf("/") + 1,
cur.getString(photoPathIndex)
.lastIndexOf(".")));
} else {
String _id = cur.getString(photoIDIndex);
String path = cur.getString(photoPathIndex);
String bucketName = cur.getString(bucketDisplayNameIndex);
String bucketId = cur.getString(bucketIdIndex);
PhotoUpImageBucket bucket = bucketList.get(bucketId);
if (bucket == null) {
bucket = new PhotoUpImageBucket();
bucketList.put(bucketId, bucket);
bucket.imageList = new ArrayList<PhotoUpImageItem>();
bucket.bucketName = bucketName;
}
bucket.count++;
PhotoUpImageItem imageItem = new PhotoUpImageItem();
imageItem.setImageId(_id);
imageItem.setImagePath(path);
// imageItem.setThumbnailPath(thumbnailList.get(_id));
bucket.imageList.add(imageItem);
Log.i(TAG,
"PhotoUpAlbumHelper类中 的——》path="
+ thumbnailList.get(_id));
}
} while (cur.moveToNext());
}
cur.close();
hasBuildImagesBucketList = true;
}
4.得到图片集合：
/**
* 得到图片集
*
* @param refresh
* @return
*/
public List<PhotoUpImageBucket> getImagesBucketList(boolean refresh) {
if (refresh || (!refresh && !hasBuildImagesBucketList)) {
buildImagesBucketList();
}
List<PhotoUpImageBucket> tmpList = new ArrayList<PhotoUpImageBucket>();
Iterator<Entry<String, PhotoUpImageBucket>> itr = bucketList.entrySet()
.iterator();
while (itr.hasNext()) {
Map.Entry<String, PhotoUpImageBucket> entry = (Map.Entry<String, PhotoUpImageBucket>) itr
.next();
tmpList.add(entry.getValue());
}
return tmpList;
}
最后提供一个获取图片路径的方法：
/**
* 得到原始图像路径
*
* @param image_id
* @return
*/
String getOriginalImagePath(String image_id) {
String path = null;
Log.i(TAG, "--" + image_id);
String[] projection = { Media._ID, Media.DATA };
Cursor cursor = cr
.query(Media.EXTERNAL_CONTENT_URI, projection, Media._ID + "="
+ image_id, null, Media.DATE_MODIFIED + " desc");
if (cursor != null) {
cursor.moveToFirst();
path = cursor.getString(cursor.getColumnIndex(Media.DATA));
}
return path;
}
一般像这种获取图片的类都要使用异步的方式获取，在其中使用异步回调机制来获取图片集合。
有问题的可以随时问我。。。先写这么多