数据库Dao层编增删改查写，数据库事务，数据库升级

 1 package com.example.databasedemo;
 2 
 3 import android.content.Context;
 4 import android.database.sqlite.SQLiteDatabase;
 5 import android.database.sqlite.SQLiteOpenHelper;
 6 import android.util.Log;
 7 
 8 import androidx.annotation.Nullable;
 9 
10 public class DataBaseHelper extends SQLiteOpenHelper {
11 
12     private static final String TGA ="DatabaseHelper";
13 
14     public DataBaseHelper(@Nullable Context context) {
15         super(context, Constants.DATABASE_NAME, null, Constants.VRESION_CODE);
16     }
17 
18     @Override
19     public void onCreate(SQLiteDatabase db) {
20         //创建时回调
21         Log.d(TGA,"创建数据库。。。");
22         //创建字段
23         //sql creat table table_name(
24         String sql="create table "+Constants.TABLE_NAME+"(_id integer,name varchar,age integer,salary integer)";
25         db.execSQL(sql);
26     }
27 
28     @Override
29     public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
30         //升级时回调
31         Log.d(TGA,"升级数据库。。。");
32 
33         String sql;
34         //db.execSQL(sql);
35 
36         switch (oldVersion)
37         {
38             case 1:
39 
40                 sql="alert table "+Constants.TABLE_NAME+" add address varchar";
41                 db.execSQL(sql);
42                 break;
43 
44             case 2:
45                 sql="alert table "+Constants.TABLE_NAME+" add phone integer ,address varchar";
46                 db.execSQL(sql);
47                 break;
48 
49 
50         }
51 
52     }
53 }

 1 package com.example.databasedemo;
 2 
 3 import android.content.Context;
 4 import android.database.Cursor;
 5 import android.database.sqlite.SQLiteDatabase;
 6 import android.util.Log;
 7 
 8 import java.security.AccessControlContext;
 9 
10 public class Dao {
11 
12     private static final String TAG="Dao";
13     private final DataBaseHelper mHelper;
14 
15     public Dao(AccessControlContext context){
16 
17          mHelper =new DataBaseHelper(context);
18     }
19 
20     public void  insert(){
21         SQLiteDatabase db= mHelper.getWritableDatabase();
22         String sql ="insert into "+Constants.TABLE_NAME +" (_id ,name ,age,salary,phone,address) values (?,?,?,?,?,?)";
23         db.execSQL(sql,new Object[]{1,"BillGates",60,1,110,"USA"});
24         db.close();
25     }
26 
27     public void delete(){
28         SQLiteDatabase db= mHelper.getWritableDatabase();
29         String sql ="delete  from  "+Constants.TABLE_NAME +" where age = 60";
30         db.execSQL(sql);
31         db.close();
32     }
33 
34     public void update(){
35         SQLiteDatabase db= mHelper.getWritableDatabase();
36         String sql ="update  from  "+Constants.TABLE_NAME +" set salary= 2 where age = 60";
37         db.execSQL(sql);
38         db.close();
39     }
40 
41     public void query(){
42 
43         SQLiteDatabase db= mHelper.getWritableDatabase();
44         String sql ="select  form  "+Constants.TABLE_NAME +" ";
45         Cursor cursor =db.rawQuery(sql,null);
46 
47         while (cursor.moveToNext()){
48             int index=cursor.getColumnIndex("name");
49             String name =cursor.getColumnName(index);
50             Log.d(TAG,"name=="+name);
51         }
52         cursor.close();
53         db.execSQL(sql);
54         db.close();
55     }
56 }