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<>Android数据存储之Sqlite数据库存储
<>1.继承SQLiteOpenHelper
创建一个用于管理数据库创建和版本管理的助手类。
package com.androidlearning.datastore_88; import android.content.Context;
import android.database.sqlite.SQLiteDatabase; import android.database.sqlite.
SQLiteOpenHelper; import android.util.Log; import androidx.annotation.Nullable;
/** * 实现数据库帮助抽象类 * @author 刘昌兴 * @date 2022/3/11 15:02 */ public class
SQLiteHelper extends SQLiteOpenHelper { public SQLiteHelper(@Nullable Context
context,int version) { super(context, "school.db", null, version); } /** *
1.数据库文件创建时调用（1次） * 2.在此方法中进行建表和初始化数据 * @author 刘昌兴 * @date 2022/3/11 15:13 *
@param db */ @Override public void onCreate(SQLiteDatabase db) { Log.i("TAG",
"SQLiteHelper onCreate"); //创建数据库 String sql="create table student(_id integer
primary key autoincrement,name varchar,age Integer,grade varchar)"; db.execSQL(
sql); //初始化数据 db.execSQL("insert into student(name,age,grade)
values('周华健',18,'三年一班')"); db.execSQL("insert into student(name,age,grade)
values('黄建国',20,'三年一班')"); db.execSQL("insert into student(name,age,grade)
values('王维',25,'三年二班')"); db.execSQL("insert into student(name,age,grade)
values('何淑华',23,'三年三班')"); } /** * 更新数据库 * @author 刘昌兴 * @date 2022/3/11 15:39
* @param db * @param oldVersion * @param newVersion * @return */ @Override
public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) { Log.i
("TAG","SQLiteHelper onUpgrade"); } }
<>2.获得连接后实现增删改查及事物
具体见代码
package com.androidlearning.datastore_88; import androidx.appcompat.app.
AppCompatActivity; import android.content.ContentValues; import android.database
.Cursor; import android.database.sqlite.SQLiteDatabase; import android.os.Bundle
; import android.util.Log; import android.view.View; import android.widget.Toast
; public class DatabaseStore extends AppCompatActivity { @Override protected
void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState);
setContentView(R.layout.activity_database_store); } /* * 创建库 */ public void
testCreateDB(View v) { //创建SQLiteHelper对象 SQLiteHelper sqLiteHelper=new
SQLiteHelper(this,1); //获得连接 SQLiteDatabase sqLiteDatabase=sqLiteHelper.
getWritableDatabase(); Toast.makeText(this,"创建数据库成功",Toast.LENGTH_SHORT).show();
} /* * 更新库 */ public void testUpdateDB(View v) { //创建SQLiteHelper对象 SQLiteHelper
sqLiteHelper=new SQLiteHelper(this,2); //获得连接 SQLiteDatabase sqLiteDatabase=
sqLiteHelper.getWritableDatabase(); Toast.makeText(this,"更新数据库成功",Toast.
LENGTH_SHORT).show(); } /* * 添加记录 */ public void testInsert(View v) {
//创建SQLiteHelper对象 SQLiteHelper sqLiteHelper=new SQLiteHelper(this,2); //获得连接
SQLiteDatabase sqLiteDatabase=sqLiteHelper.getWritableDatabase(); //插入数据
//创建字段-数值对象 ContentValues contentValues=new ContentValues(); contentValues.put(
"name","王宇飞"); contentValues.put("age",29); contentValues.put("grade","三年一班");
long id = sqLiteDatabase.insert("student", null, contentValues); //关闭连接
sqLiteDatabase.close(); //提示 Toast.makeText(this,"学生id："+id,Toast.LENGTH_SHORT).
show(); } /* * 更新 */ public void testUpdate(View v) { //创建SQLiteHelper对象
SQLiteHelper sqLiteHelper=new SQLiteHelper(this,2); //获得连接 SQLiteDatabase
sqLiteDatabase=sqLiteHelper.getWritableDatabase(); //更新数据 ContentValues
contentValues=new ContentValues(); contentValues.put("age",30); contentValues.
put("grade","三年二班"); int updateRow = sqLiteDatabase.update("student",
contentValues, "_id=?", new String[]{"5"}); //关闭连接 sqLiteDatabase.close(); //提示
Toast.makeText(this,"更新"+updateRow+"行数据",Toast.LENGTH_SHORT).show(); } /* * 删除
*/ public void testDelete(View v) { //创建SQLiteHelper对象 SQLiteHelper sqLiteHelper
=new SQLiteHelper(this,2); //获得连接 SQLiteDatabase sqLiteDatabase=sqLiteHelper.
getWritableDatabase(); //删除数据 int deleteRow = sqLiteDatabase.delete("student",
"_id=2",null); //关闭连接 sqLiteDatabase.close(); //提示 Toast.makeText(this,"删除"+
deleteRow+"行数据",Toast.LENGTH_SHORT).show(); } /* * 查询 */ public void testQuery(
View v) { //创建SQLiteHelper对象 SQLiteHelper sqLiteHelper=new SQLiteHelper(this,2);
//获得连接 SQLiteDatabase sqLiteDatabase=sqLiteHelper.getWritableDatabase(); //查询
// Cursor studentCursor = sqLiteDatabase.query("student", null, null, null,
null, null, null); //条件查询 Cursor studentCursor = sqLiteDatabase.query("student",
null, "_id=?", new String[]{"3"}, null, null, null); int sum=studentCursor.
getCount(); Toast.makeText(this,"共有"+sum+"条数据",Toast.LENGTH_SHORT).show(); while
(studentCursor.moveToNext()){ int id=studentCursor.getInt(0); String name=
studentCursor.getString(1); int age=studentCursor.getInt(2); String grade=
studentCursor.getString(studentCursor.getColumnIndex("grade")); Log.i("students"
,id+"-"+name+"-"+age+"-"+grade); } //关闭游标 studentCursor.close(); //关闭连接
sqLiteDatabase.close(); } /* * 测试事务处理 */ public void testTransaction(View v) {
//创建SQLiteHelper对象 SQLiteHelper sqLiteHelper=new SQLiteHelper(this,2); //获得连接
SQLiteDatabase sqLiteDatabase=sqLiteHelper.getWritableDatabase(); try{ //开启事务
sqLiteDatabase.beginTransaction(); //更新第一条数据 ContentValues contentValues=new
ContentValues(); contentValues.put("age",25); int updateRow1 = sqLiteDatabase.
update("student", contentValues, "_id=?", new String[]{"4"}); Log.i(
"transaction","updateRow1："+updateRow1); if(true) throw new RuntimeException(
"出异常了！！！"); //更新第二条数据 contentValues=new ContentValues(); contentValues.put("age"
,25); int updateRow2 = sqLiteDatabase.update("student", contentValues, "_id=?",
new String[]{"5"}); Log.i("transaction","updateRow2："+updateRow2); //完成提交事物
sqLiteDatabase.setTransactionSuccessful(); }finally { //结束事物 sqLiteDatabase.
endTransaction(); //关闭连接 sqLiteDatabase.close(); } } }