Android在Sqlite3中的应用及多线程使用数据库的建议
作者：互联网
1、首先先建立一个DatabaseHelper类，继承自SQLiteOpenHelper，用于建立数据库，并可更新数据库例如我新建了两张表
public class DatabaseHelper extends SQLiteOpenHelper {
private static DatabaseHelper _databaseHelper;
private static final String TAG = DatabaseHelper.class.getSimpleName();
public synchronized static DatabaseHelper getInstance(Context context)
{
if(_databaseHelper==null)
{
_databaseHelper = new DatabaseHelper(context,"cgjlb",null,2);
}
return _databaseHelper;
}
public synchronized static void destoryInstance(){
if(_databaseHelper!=null){
_databaseHelper=null;
}
}
public DatabaseHelper(@Nullable Context context, @Nullable String name, @Nullable SQLiteDatabase.CursorFactory factory, int version) {
super(context, name, factory, version);
}
@Override
public void onCreate(SQLiteDatabase sqLiteDatabase) {
//主表记录
String sql = "create table t_share(_id integer primary key autoincrement,sharenum text,sharename text,shareprice real,sharelastprice real,addtime text,uptime text,bl real)";
sqLiteDatabase.execSQL(sql);
//记录历史表
sql = "create table t_sharehis(_id integer primary key autoincrement,shareid integer, shareprice real,uptime text)";
sqLiteDatabase.execSQL(sql);
}
@Override
public void onUpgrade(SQLiteDatabase sqLiteDatabase, int i, int i1) {
Log.d(TAG, "onUpgrade: upddatabase");
sqLiteDatabase.execSQL("drop table t_share");
sqLiteDatabase.execSQL("drop table t_sharehis");
onCreate(sqLiteDatabase);
}
}
2、编写数据库具体操作类、增删改查我都写了
public class ShareDbService {
SQLiteDatabase db = null;
DatabaseHelper databaseHelper;
private static final String TAG = ShareDbService.class.getSimpleName();
public ShareDbService(Context context) {
databaseHelper = DatabaseHelper.getInstance(context);
db = databaseHelper.getWritableDatabase();
}
public void addShareInfo(ShareBean shareBean)
{
int Id = getShareId(shareBean.getShareNum());
if(Id==-1) {
ContentValues values = new ContentValues();
values.put("sharenum", shareBean.getShareNum());
values.put("sharename", shareBean.getShareName());
values.put("shareprice", shareBean.getSharePrice());
values.put("sharelastprice", shareBean.getShareLastPrice());
values.put("uptime", shareBean.getUptime());
values.put("addtime",shareBean.getAddtime());
double shareprice = shareBean.getSharePrice();
double sharelastprice = shareBean.getShareLastPrice();
double bl = (sharelastprice-shareprice)/shareprice*100;
values.put("bl", new DecimalFormat("0.00").format(bl));
db = databaseHelper.getWritableDatabase();
db.insert("t_share", null, values);
ShareHisBean shareHisBean = new ShareHisBean();
shareHisBean.setShareId(getShareId(shareBean.getShareNum()));
shareHisBean.setSharePrice(shareBean.getSharePrice());
shareHisBean.setUpTime(shareBean.getUptime());
addShareHis(shareHisBean);
db.close();
}
}
private void addShareHis(ShareHisBean shareHisBean){
ContentValues values = new ContentValues();
values.put("shareid", shareHisBean.getShareId());
values.put("shareprice", shareHisBean.getSharePrice());
values.put("uptime", shareHisBean.getUptime());
db = databaseHelper.getWritableDatabase();
db.insert("t_sharehis", null, values);
db.close();
}
public void refreshShare(ShareHisBean shareHisBean,double sharePrice){
try {
//更新信息主表
db = databaseHelper.getWritableDatabase();
ContentValues values = new ContentValues();
values.put("uptime", shareHisBean.getUptime());
values.put("sharelastprice", shareHisBean.getSharePrice());
String[] args = {String.valueOf(shareHisBean.getShareId())};
double sharelastprice = shareHisBean.getSharePrice();
double bl = (sharelastprice - sharePrice) / sharePrice * 100;
values.put("bl", bl);
db.update("t_share", values, "_Id=?", new String[]{String.valueOf(shareHisBean.getShareId())});
//添加记录
values = new ContentValues();
values.put("shareid", shareHisBean.getShareId());
values.put("shareprice", shareHisBean.getSharePrice());
values.put("uptime", shareHisBean.getUptime());
db.insert("t_sharehis", null, values);
}catch(Exception ex){
ex.printStackTrace();
}
finally {
db.close();
}
}
public void delShare(String Id){
db = databaseHelper.getWritableDatabase();
db.delete("t_share","_Id=?",new String[]{Id});
db.delete("t_sharehis","shareid=?",new String[]{Id});
db.close();
}
private int getShareId(String shareNum) {
db = databaseHelper.getReadableDatabase();
String sql = "select _Id from t_share where sharenum='" + shareNum + "'";
int Id = -1;
Cursor cursor = db.rawQuery(sql, null);
if (cursor != null) {
while (cursor.moveToNext()){
Id = cursor.getInt(0);
}
}
cursor.close();
db.close();
return Id;
}
public List<ShareBean> getShareList(){
db = databaseHelper.getReadableDatabase();
List<ShareBean> shareBeans = new ArrayList<>();
String sql = "select _id,sharenum,sharename,shareprice,sharelastprice,uptime,addtime,bl from t_share order by _Id desc";
Cursor cursor = db.rawQuery(sql, null);
if (cursor != null) {
while (cursor.moveToNext()){
ShareBean shareBean = new ShareBean();
shareBean.set_Id(cursor.getInt(0));
shareBean.setShareNum(cursor.getString(1));
shareBean.setShareName(cursor.getString(2));
shareBean.setSharePrice(cursor.getDouble(3));
shareBean.setShareLastPrice(cursor.getDouble(4));
shareBean.setUptime(cursor.getString(5));
shareBean.setAddtime(cursor.getString(6));
shareBean.setBl(cursor.getDouble(7));
shareBeans.add(shareBean);
}
}
cursor.close();
db.close();
return shareBeans;
}
public List<ShareHisBean> getShareListHis(int ShareId){
db = databaseHelper.getReadableDatabase();
List<ShareHisBean> shareHisBeans = new ArrayList<>();
String sql = "select _id,shareid,shareprice,uptime from t_sharehis where shareid='"+String.valueOf(ShareId)+"' order by _id desc";
Cursor cursor = db.rawQuery(sql, null);
if (cursor != null) {
while (cursor.moveToNext()){
ShareHisBean shareHisBean = new ShareHisBean();
shareHisBean.set_Id(cursor.getInt(0));
shareHisBean.setShareId(cursor.getInt(1));
shareHisBean.setSharePrice(cursor.getDouble(2));
shareHisBean.setUpTime(cursor.getString(3));
shareHisBeans.add(shareHisBean);
}
}
cursor.close();
db.close();
return shareHisBeans;
}
public ShareBean getShareInfo(int ShareId) {
db = databaseHelper.getReadableDatabase();
ShareBean shareBean = new ShareBean();
//_id integer primary key autoincrement,sharenum text,sharename text,shareprice real,sharelastprice real,addtime text,uptime text,bl real
String sql = "select _id,sharenum,sharename,shareprice,sharelastprice,addtime,uptime,bl from t_share where _Id='"+String.valueOf(ShareId)+"'";
Cursor cursor = db.rawQuery(sql, null);
if (cursor != null) {
if (cursor.moveToNext()){
shareBean.set_Id(cursor.getInt(0));
shareBean.setShareNum(cursor.getString(1));
shareBean.setShareName(cursor.getString(2));
shareBean.setSharePrice(cursor.getDouble(3));
shareBean.setShareLastPrice(cursor.getDouble(4));
shareBean.setAddtime(cursor.getString(5));
shareBean.setUptime(cursor.getString(6));
shareBean.setBl(cursor.getDouble(7));
}
}
cursor.close();
db.close();
return shareBean;
}
}
3、实际中的应用，就举一个例子吧，数据库操作不用开新线程，直接在主线程里弄就行
ShareDbService shareDbService = new ShareDbService(getContext()); shareDbService.delShare(String.valueOf(shareBean.get_Id()));
4、需要注意的是SQLite不支持多线程，最好是能批量修改，否则很麻烦，如果一定要多线程 ，比如循环请求网络更新数据库时，可以使用CountDownLatch，先将数据弄在一个集合里，等子线程全部执行完成后，再更新数据库。此方法具体应用如下
先声明一个变量
CountDownLatch latch;
实际应用代码
//设置多线程 个数，一共用多少个线程一定要写清楚，后面是要减的。
latch = new CountDownLatch(count);
for (int i = 0; i < count; i++) {
new Thread(()-> {
try {
//网络请求等操作
} catch (Exception e) {
e.printStackTrace();
} finally {
//这里会自动减1操作，一定要写。
latch.countDown();
}
}).start();
};
try {
latch.await();
//最后执行主程序，比如更新数据库
Toast.makeText(getContext(), "刷新成功", Toast.LENGTH_SHORT).show();
} catch (InterruptedException e) {
e.printStackTrace();
}
标签：shareHisBean,shareBean,db,cursor,values,Sqlite3,Android,多线程,String 来源： https://www.cnblogs.com/youyuan1980/p/16185784.html