import android.content.Context;
import android.database.sqlite.SQLiteDatabase;
import android.database.sqlite.SQLiteOpenHelper;
public class DBHelper extends SQLiteOpenHelper {
 private static final String name="my";//數(shù)據(jù)庫(kù)名
 private static final int version=1;//版本號(hào)
 //重寫(xiě)構(gòu)造方法的時(shí)候選擇參數(shù)少的一項(xiàng)
 public DBHelper(Context context) {
  //1：上下文 2：數(shù)據(jù)庫(kù)名稱 3：游標(biāo)創(chuàng)建工廠 4：數(shù)據(jù)庫(kù)版本 版本只能是整數(shù) 1 2 3..
  super(context, name, null, version);
 }
 //數(shù)據(jù)庫(kù)的初始化 SQLiteDatabase數(shù)據(jù)庫(kù)操作對(duì)象
 //一般只在第一次運(yùn)行和版本更新的時(shí)候調(diào)用
 @Override
 public void onCreate(SQLiteDatabase db) {
  //創(chuàng)建數(shù)據(jù)庫(kù) 主鍵默認(rèn)自增
  db.execSQL("create table student(" +
    "_id integer not null primary key autoincrement," +
    "name varchar(20)," +
    "phone varchar(11)," +
    "gender varchar(2))");
  //添加一條測(cè)試數(shù)據(jù)
  db.execSQL("insert into student values(null,?,?,?)"
    ,new Object[]{"小黑","12345678901","男"});
 }
 /**
  * 在版本升級(jí)的時(shí)候調(diào)用
  * 修改version 為2 表示版本升級(jí) 就會(huì)調(diào)用這個(gè)方法
  * @param db 數(shù)據(jù)庫(kù)操作對(duì)象
  * @param oldVersion 舊版本號(hào)
  * @param newVersion 新版本號(hào)
  */
 @Override
 public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
 }
}

 　　　　//創(chuàng)建數(shù)據(jù)
  DBHelper helper =new DBHelper(this);
  //調(diào)用數(shù)據(jù)操作對(duì)象
  SQLiteDatabase dbWrite=helper.getWritableDatabase();
  SQLiteDatabase dbRead=helper.getReadableDatabase();

try {
   db.beginTransaction();//開(kāi)啟事務(wù)
   // db.update();
   // db.insert();
   db.setTransactionSuccessful(); //沒(méi)有設(shè)置事物成功 finally就會(huì)回滾
  } catch (Exception e) {
   e.printStackTrace();
  }finally {
   db.endTransaction();
  }

private void query() {
  StringBuffer sb=new StringBuffer("select * from student where 1=1");
  //參數(shù)集合
  List<String> params=new ArrayList<>();
  if(!TextUtils.isEmpty(id)){
   sb.append(" and _id=?");
   params.add(id);
  }
  if(!TextUtils.isEmpty(phone)){
   sb.append(" and phone=?");
   params.add(phone);
  }
  if(!TextUtils.isEmpty(name)){
   sb.append(" and name=?");
   params.add(name);
  }
  if(!TextUtils.isEmpty(gender)){
   sb.append(" and gender=?");
   params.add(gender);
  }
  SQLiteDatabase db=helper.getReadableDatabase();
  String [] projection=new String [params.size()];
  params.toArray(projection);
  //返回值 游標(biāo)
  Cursor cursor=db.rawQuery(sb.toString(),projection);
　　　　//判斷游標(biāo)是否為空，是否有一個(gè)值
  while(cursor!=null&&cursor.moveToNext()){
   // getColumnIndex獲取列的下標(biāo) cursor.getXXXX()獲取指定列的值
   String name=cursor.getString(cursor.getColumnIndex("name"));
   Integer id=cursor.getInt(cursor.getColumnIndex("_id"));
  }
 }

private void update() {
  StringBuffer sb=new StringBuffer("update student set ");
  List params=new ArrayList();
  if(!TextUtils.isEmpty(phone)){
   sb.append("phone=?,");
   params.add(phone);
  }
  if(!TextUtils.isEmpty(name)){
   sb.append("name=?,");
   params.add(name);
  }
  if(!TextUtils.isEmpty(gender)){
   sb.append("gender=?,");
   params.add(gender);
  }
  if (params.size()!=0){
   //更新操作拼接字符串末尾有一個(gè)","需要去除
   //刪除最后一位的“，”
   sb.setLength(sb.length()-1);
   sb.append(" where 1=1");
   //通過(guò)id指定 更新那行數(shù)據(jù)
   if(!TextUtils.isEmpty(id)){
    sb.append(" and _id=?");
    params.add(id);
   }else{
    Toast.makeText(this,"請(qǐng)?zhí)顚?xiě)id",Toast.LENGTH_SHORT).show();
    return;
   }
   SQLiteDatabase db=helper.getWritableDatabase();
   Object [] o=new Object[params.size()];
   params.toArray(o);//將數(shù)據(jù)存放到指定的數(shù)組中
   db.execSQL(sb.toString(),o);
  }
 }

ContentValues cv = new ContentValues();//實(shí)例化ContentValues
cv.put("name","123");//添加要更改的字段及內(nèi)容
String whereClause = "phone=?";//修改條件
String[] whereArgs = {"12312313213"};//修改條件的參數(shù)
db.update("student",cv,whereClause,whereArgs);//執(zhí)行修改

private void delete() {
  getAllText();
  //拼接sql語(yǔ)句
  StringBuffer sb=new StringBuffer("delete from student where 1=1");
  //保存參數(shù)的list
  List params=new ArrayList();
  //判斷條件 動(dòng)態(tài)拼接
  if(!TextUtils.isEmpty(id)){
   sb.append(" and _id=?");
   params.add(id);
  }
  if(!TextUtils.isEmpty(phone)){
   sb.append(" and phone=?");
   params.add(phone);
  }
  if(!TextUtils.isEmpty(name)){
   sb.append(" and name=?");
   params.add(name);
  }
  if(!TextUtils.isEmpty(gender)){
   sb.append(" and gender=?");
   params.add(gender);
  }
  SQLiteDatabase db=helper.getWritableDatabase();
  if (params.size()!=0){
   Object [] o=new Object[params.size()];
   params.toArray(o);//將數(shù)據(jù)存放到指定的數(shù)組中
   //執(zhí)行刪除
   db.execSQL(sb.toString(),o);
  }else{
   db.execSQL(sb.toString());
  }
  Toast.makeText(this,"刪除完成",Toast.LENGTH_SHORT).show();
 }

String whereClause = "name=?";//刪除的條件
String[] whereArgs = {"123"};//刪除的條件參數(shù)
db.delete("student",whereClause,whereArgs);//執(zhí)行刪除

private void insert() {//保存數(shù)據(jù)到object數(shù)組
  Object [] o=new Object[]{name,phone,gender};
  //獲取數(shù)據(jù)庫(kù)操作對(duì)象
  SQLiteDatabase db=helper.getWritableDatabase();
  //sql:sql語(yǔ)句 bingArgs:參數(shù)數(shù)組
  db.execSQL("insert into student values(null,?,?,?)",o);
  //關(guān)閉連接
  db.close();
  Toast.makeText(this,"增加成功",Toast.LENGTH_SHORT).show();
 }

ContentValues cv = new ContentValues();//實(shí)例化一個(gè)ContentValues用來(lái)裝載待插入的數(shù)據(jù)
cv.put("name","123"); 
db.insert("student",null,cv);//執(zhí)行插入操作