1.创建DataEntity实体类
package database;
public class DataEntity {
private Integer id;
private String data_one;
private Integer data_two;
private String data_three;
public Integer getId() {
return id;
}
public void setId(Integer id) {
this.id = id;
}
public String getData_one() {
return data_one;
}
public void setData_one(String data_one) {
this.data_one = data_one;
}
public Integer getData_two() {
return data_two;
}
public void setData_two(Integer data_two) {
this.data_two = data_two;
}
public String getData_three() {
return data_three;
}
public void setData_three(String data_three) {
this.data_three = data_three;
}
}
2.创建DataBaseHelper类
package database;
import android.content.Context;
import android.database.sqlite.SQLiteDatabase;
import android.database.sqlite.SQLiteOpenHelper;
public class DataBaseHelper extends SQLiteOpenHelper {
public final static String CREATE_TABLE_SQL="create table if not exists test_data (id integer primary key autoincrement,data_one text,data_two integer,data_three text)";
public DataBaseHelper(Context context, String name, int version) {
super(context, name, null, version);
}
@Override
public void onCreate(SQLiteDatabase db) {
//db.execSQL("drop table test_data");
db.execSQL(CREATE_TABLE_SQL);
}
@Override
public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
}
}
该类需要继承SQLiteOpenHelper才行。
3.创建DataBaseService服务
package database;
import android.content.ContentValues;
import android.content.Context;
import android.database.Cursor;
import android.database.sqlite.SQLiteDatabase;
import java.text.SimpleDateFormat;
import java.util.ArrayList;
import java.util.Date;
import java.util.List;
public class DataBaseService {
private DataBaseHelper dbHelper;
private static DataBaseService instance = null;
public DataBaseService(Context context) {
this.dbHelper = new DataBaseHelper(context,"data.db",1);//数据库名称
}
public synchronized static DataBaseService getInstance(Context ctx) {
if (null == instance) {
instance = new DataBaseService(ctx);
}
return instance;
}
/**
* 新增数据
* @param data
*/
public void saveData(String data) {
SQLiteDatabase db = dbHelper.getWritableDatabase();
try {
db.beginTransaction();
ContentValues values = new ContentValues();
values.put("data_one", data);
values.put("data_two", 0);
SimpleDateFormat df = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss");
String date = df.format(new Date());
values.put("data_three", date);
db.insert("test_data", null, values);
db.setTransactionSuccessful();
}finally {
db.endTransaction();
}
}
/**
* 根据ID查询
* @param id
* @return
*/
public DataEntity findData(Integer id) {
DataEntity entity = null;
SQLiteDatabase db = dbHelper.getReadableDatabase();
Cursor cursor = db.query("test_data",null,
"id=?", new String[] {
id.toString() }, null, null,
null, "1");
try {
if (cursor.moveToFirst()) {
entity = filterEntity(cursor, entity);
return entity;
}
return null;
} finally {
cursor.close();
}
}
/**
* 查询list
* @param data_two
* @return
*/
public List<DataEntity> findDataList(String data_two, String limit) {
SQLiteDatabase db = dbHelper.getReadableDatabase();
Cursor cursor = db.query("test_data",null,
"data_two=?", new String[]{
data_two}, null, null,
null, limit);
ArrayList<DataEntity> list = new ArrayList<>();
try {
while (cursor.moveToNext()) {
DataEntity entity = new DataEntity();
entity = filterDataEntity(cursor, entity);
list.add(entity);
}
} finally {
cursor.close();
}
return list;
}
/**
* 封装实体类
* @param cursor
* @param entity
* @return
*/
private DataEntity filterDataEntity(Cursor cursor, DataEntity entity){
Integer id = cursor.getInt(cursor.getColumnIndex("id"));
entity.setId(id);
String data_one = cursor.getString(cursor.getColumnIndex("data_one"));
entity.setData_one(data_one);
Integer data_two = cursor.getInt(cursor.getColumnIndex("data_two"));
entity.setData_two(data_two);
String data_three = cursor.getString(cursor.getColumnIndex("data_three"));
entity.setData_three(data_three);
return entity;
}
/**
* 根据data_two查询数量
* @param data_two
* @return
*/
public int countDataByData_two(String data_two) {
SQLiteDatabase db = dbHelper.getReadableDatabase();
Cursor cursor = db.query("test_data",null,"data_two=?",
new String[]{
data_two}, null, null,null);
return cursor.getCount();
}
/**
* 查询所有数量
* @return
*/
public int countAllData() {
SQLiteDatabase db = dbHelper.getReadableDatabase();
Cursor cursor = db.query("test_data",null,null,
null,null, null,null);
return cursor.getCount();
}
/**
* 根据ID删除数据
* @param ids
* @return
*/
public int deleteWeightDataByIds(List<Integer> ids) {
SQLiteDatabase db = dbHelper.getWritableDatabase();
try {
db.beginTransaction();
for (int i = 0; i < ids.size(); i++) {
db.delete("test_data", "id=?", new String[]{
String.valueOf(sids.get(i))});
}
db.setTransactionSuccessful();
return 0;
}finally {
db.endTransaction();
}
}
public void updateData_twoByIds(String data_two, List<Integer> ids) {
SQLiteDatabase db = dbHelper.getWritableDatabase();
try {
db.beginTransaction();
for (Integer id : ids) {
ContentValues value = new ContentValues();
value.put("data_two", data_two);
db.update("test_data", value, "id=?", new String[] {
String.valueOf(id) });
}
db.setTransactionSuccessful();
}finally {
db.endTransaction();
}
}
public Cursor findTables(){
SQLiteDatabase db = dbHelper.getReadableDatabase();
Cursor cursor = db.rawQuery("select name from sqlite_master where type='table';", null);
/*while(cursor.moveToNext()){
//遍历出表名
String name = cursor.getString(0);
}*/
return cursor;
}
}
4.调用
DataBaseService service = new DataBaseService(MainActivity.this);
service.saveData(str);
5.问题说明
5.1.Cursor的方法
c.move(int offset); //以当前位置为参考,移动到指定行
c.moveToFirst(); //移动到第一行
c.moveToLast(); //移动到最后一行
c.moveToPosition(int position); //移动到指定行
c.moveToPrevious(); //移动到前一行
c.moveToNext(); //移动到下一行
c.isFirst(); //是否指向第一条
c.isLast(); //是否指向最后一条
c.isBeforeFirst(); //是否指向第一条之前
c.isAfterLast(); //是否指向最后一条之后
c.isNull(int columnIndex); //指定列是否为空(列基数为0)
c.isClosed(); //游标是否已关闭
c.getCount(); //总数据项数
c.getPosition(); //返回当前游标所指向的行数
c.getColumnIndex(String columnName);//返回某列名对应的列索引值
c.getString(int columnIndex); //返回当前行指定列的值
5.2.主键自增
第二步DataBaseHelper中sql：
create table if not exists test_data (id integer primary key autoincrement,data_one text,data_two integer,data_three text
其中id integer primary key autoincrement为自增，目前sqlite只支持integer类型的自增。
5.3.使用事务
使用事务防止断电事务未提交
public void saveData(String data) {
SQLiteDatabase db = dbHelper.getWritableDatabase();//使用读写操作才需要事务
try {
db.beginTransaction();//开启事务
db.setTransactionSuccessful();//设置事务成功完成
}finally {
db.endTransaction();//事务完成，进行提交
}
}
5.4.判断表是否存在，不存在进行创建
5.4.1.方式1：
第二步DataBaseHelper中sql：
create table if not exists test_data (id integer primary key autoincrement,data_one text,data_two integer,data_three text
其中if not exists进行判断。
5.4.2.方式2：
或者
String sql = "select count(*) as c from sqlite_master where type ='table' and name ='" + dbName + "';";
Cursor cursor = db.rawQuery(sql, null);
if (cursor.moveToNext()) {
int count = cursor.getInt(0); //如果count>0则存在，否则不存在
}
5.5. 关于程序卸载问题
只有当软件彻底卸载的时候，默认的数据库会自动被删除，如果想将数据库测地保存在系统中，需要在保存数据的时候，设置数据库数据保存的位置。