Android数据库缓存
简单的数据库缓存实现，有不足的地方请指出~使用示例：
CacheHelper.init(this).setJson("url", "json");
CacheHelper.init(this).getJson("url", new Handler(){
@Override
public void handleMessage(Message msg) {
String json = (String) msg.obj;
}
});
CacheHelper.init(this).clear();import android.content.ContentValues;
import android.content.Context;
import android.database.Cursor;
import android.database.sqlite.SQLiteDatabase;
import android.database.sqlite.SQLiteOpenHelper;
import android.os.Handler;
import android.os.Message;
/**
* 缓存数据库
* @author lu
*
*/
public class CacheHelper extends SQLiteOpenHelper {
private static final String tableName = "JSONCACHE";
private static final String URL = "URL";
private static final String JSON = "JSON";
private static final String DATE = "DATE";
public CacheHelper(Context context) {
super(context, "cache.db", null, 1);
}
@Override
public void onCreate(SQLiteDatabase db) {
//建表jsoncache，字段：请求地址url、缓存数据json、时间date
db.execSQL("CREATE TABLE "+tableName+" (ID INTEGER PRIMARY KEY AUTOINCREMENT, "+URL+" TEXT NOT NULL, "+JSON+" TEXT NOT NULL, "+DATE+" INTEGER NOT NULL )");
}
@Override
public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
}
private static CacheHelper helper = null;
public static CacheHelper init(Context context){
if (helper==null) {
helper = new CacheHelper(context);
}
return helper;
}
/**储存缓存json*/
public void setJson(final String url0,final String json){
new Thread(){
public void run() {
String url = urlEncode(url0);
ContentValues cv = new ContentValues();
cv.put(URL, url);
cv.put(JSON, json);
cv.put(DATE, System.currentTimeMillis());
helper.getReadableDatabase().delete(tableName, URL+"=?", new String[]{url});
helper.getReadableDatabase().insert(tableName, null, cv);
}
}.start();
}
/**获取缓存json，以handler的obj返回（懒得写监听器了）*/
public void getJson(final String url0,final Handler handler){
new Thread(){
public void run() {
String url = urlEncode(url0);
String result = null;
Cursor c =
helper.getReadableDatabase().query(tableName,
null,
URL+"=?",
new String[]{url},
null,
null,
null);
if (c.moveToNext()) {
result = c.getString(c.getColumnIndex(JSON));
}
Message msg = Message.obtain();
msg.obj = result;
handler.sendMessage(msg);
}
}.start();
}
/**缓存需要定时清空*/
public void clear(){
new Thread(){
public void run() {
helper.getReadableDatabase().delete(tableName, "ID>?", new String[]{"0"});
}
}.start();
}
/**url需要去掉token*/
private String urlEncode(String url){
String result = url.replaceAll("accessToken.*?\\&", "");
if (result.contains("accessToken")) {//如果还没去掉，说明是在尾部
result = result.replaceAll("\\&accessToken.*?$", "");
}
return result;
}
}
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