android实现服务器图片本地缓存

情况：在做ostocy-jshop开源系统的时候，需要做一个关于android如何进行服务器图片本地缓存的功能。我使用了如下几个东西。

1,android 本地数据库SQLite

2,android下载网络图片

3,正则截取

4,Bitmap保存到本地

那就一个一个来说说吧

1,android 本地数据库SQLite：我要建立一个本地数据库，用来存放服务器返回的数据，缓存起来，下次就读取这个SQLite数据库了。

看代码先，然后解释

public class DBHelper extends SQLiteOpenHelper {//数据库名称public static final String DB_NAME="jshopmactive.db";//商品表名称public static final String GOODS_TM_NAME="goods_tm";//创建商品sqlprivate static final String CREATE_GOODS_TM="create table "+"goods_tm(_id integer primary key autoincrement,goodsCategoryTid text,goodsid text,goodsname text,memberprice text,pictureurl text)";private SQLiteDatabase db;public DBHelper(Context context) {super(context, DB_NAME, null, 3);// TODO Auto-generated constructor stub}@Overridepublic void onCreate(SQLiteDatabase db) {this.db=db;db.execSQL(CREATE_GOODS_TM);}public void createDB(){db=this.getWritableDatabase();db.execSQL(CREATE_GOODS_TM);}/** * 插入数据 * @param values * @param tablename */public void insert(String tablename,ContentValues values){SQLiteDatabase db=this.getWritableDatabase();db.insert(tablename, null, values);db.close();}/** * 查询数据 * @param tablename * @return */public Cursor query(String tablename){SQLiteDatabase db=this.getWritableDatabase();Cursor c=db.query(tablename, null, null, null, null, null, null);return c;}/** * 查询数据 * @param tablename * @return */public Cursor queryByParam(String tablename,String param){SQLiteDatabase db=this.getWritableDatabase();Cursor c=db.rawQuery("select * from "+tablename+" where goodsCategoryTid=?", new String[]{String.valueOf(param)}); return c;}/** * 删除数据 * @param talbename * @param id */public void delete(String talbename,String id){if(db==null){db=this.getWritableDatabase();db.delete(talbename, "_id=?", new String[]{String.valueOf(id)});}}/** * 删除所有数据 * @param tablename */public void deleteAll(String tablename){if(db==null){db=this.getWritableDatabase();db.delete(tablename, null, null);}}/** * 删除数据库表 * @param tablename */public void DropTable(String tablename){db=this.getWritableDatabase();db.execSQL("drop table "+tablename);}/** * 删除数据库 * @param tablename */public void DropDB(){db=this.getWritableDatabase();//db.execSQL("drop database jshopmactive");onUpgrade(db,3,4);}/** * 关闭数据库连接 */public void close(){if(db!=null){db.close();}}@Overridepublic void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {// TODO Auto-generated method stubdb.execSQL("DROP TABLE IF EXISTS "+TABLE_TM_NAME);db.execSQL("DROP TABLE IF EXISTS "+GOODS_CATEGORY_TM_NAME);db.execSQL("DROP TABLE IF EXISTS "+GOODS_TM_NAME);        onCreate(db);}}

这里主要就是在建立数据表，抽取了一部分代码。

2,android下载网络图片：我通过android访问基于http的服务器方法，获取一个有图片的信息。

看代码

public ArrayList<HashMap<String, Object>> getGoodsList(String goodsCategoryTid) throws IOException {requestjsonstr = this.queryGoodsListForJshop(goodsCategoryTid);if (Validate.StrNotNull(requestjsonstr)) {JSONArray ja = (JSONArray) JSONValue.parse(requestjsonstr);for (int i = 0; i < ja.size(); i++) {HashMap<String, Object> map = new HashMap<String, Object>();JSONObject jo = (JSONObject) (ja.get(i));map.put("pictureurl",getPictureurlImg(JshopActivityUtil.BASE_URL+ jo.get("pictureurl").toString()));map.put("goodsname", jo.get("goodsname").toString());map.put("memberprice", "￥" + jo.get("memberprice").toString());map.put("goodsid", jo.get("goodsid").toString());map.put("goodsCategoryTid", goodsCategoryTid);map.put("pictureurlpath", downloadpcurl);goodslists.add(map);}}return goodslists;}private Bitmap getPictureurlImg(String pictureurl) throws IOException {URL url = new URL(pictureurl);HttpURLConnection conn = (HttpURLConnection) url.openConnection();conn.setRequestMethod("GET");conn.setConnectTimeout(5 * 1000);InputStream in = conn.getInputStream();Bitmap bm = BitmapFactory.decodeStream(in);// 保存本地图片String fileName=savePicturetoDeviceAndReturnFixedUrl(pictureurl);saveOnlinePictureToCard(bm,fileName);in.close();return bm;}

3,正则截取

/** * 获取网络图片名称 *  * @param pictureurl * @return */private String savePicturetoDeviceAndReturnFixedUrl(String pictureurl) {String regstr = "(http:|https:)\\/\\/[\\S\\.:/]*\\/(\\S*)\\.(jpg|png|gif)";String postfix = "", filename = "", resultstr = "";Pattern patternForImg = Pattern.compile(regstr,Pattern.CASE_INSENSITIVE);Matcher matcher = patternForImg.matcher(pictureurl);if (matcher.find()) {filename = matcher.group(2);postfix = matcher.group(3);}return resultstr = filename + "." + postfix;}

4,Bitmap保存到本地

private void saveOnlinePictureToCard(Bitmap bm, String fileName)throws IOException {File dirFile = new File(JshopMParams.SAVEPCPATH);if (!dirFile.exists()) {dirFile.mkdir();}String onlineFilePath = JshopMParams.SAVEPCPATH +fileName;File myOnlineFile = new File(onlineFilePath);BufferedOutputStream bos = new BufferedOutputStream(new FileOutputStream(myOnlineFile));bm.compress(Bitmap.CompressFormat.JPEG, 100, bos);bos.flush();bos.close();this.downloadpcurl = onlineFilePath;}

详情请见https://github.com/sdywcd/ostocy-jshop开源项目

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