Sqlite数据库连接

项目包中有Constants/Dao/DatabseHelper三个类和一个MainActivity

Constants类中定义一些常量如数据库名 版本号 表名等。

Constants类

public class Constants {
    public  static final String DATABASE_NAME = "sakura.db";
    public static final int VERSION_CODE = 1;
    public static final String TABLE_NAME = "table1";
}

Dao层编写操作数据库的方法

import android.content.Context;
import android.database.Cursor;
import android.database.sqlite.SQLiteDatabase;
import android.util.Log;

//用于数据库的增删改查
public class Dao {
    private static final String TAG ="Dao" ;
    private final DatabaseHelper mHelper;

    public Dao(Context context){
        mHelper = new DatabaseHelper(context);
    }
    public  void  insert(String a,String b, String c, String d, String e){
        Log.d(TAG, "insert: ");
    SQLiteDatabase db =  mHelper.getWritableDatabase();
    String sql = "insert into "+Constants.TABLE_NAME+"(name,date,time,address,tiwen)values(?,?,?,?,?)";
    db.execSQL(sql,new Object[]{a,b,c,d,e});
    db.close();
    }
    public  void  delete(){
        SQLiteDatabase db =  mHelper.getWritableDatabase();
        String sql = " delete from " + Constants.TABLE_NAME + " where age = 60 ";
        db.execSQL(sql);
        db.close();
    }
    public  void  update(){
        SQLiteDatabase db =  mHelper.getWritableDatabase();
        String sql = " update " + Constants.TABLE_NAME + " set salary = 2";
        db.execSQL(sql);
        db.close();
    }
    public  void  query(){
        SQLiteDatabase db =  mHelper.getWritableDatabase();
        String sql = " select *from " + Constants.TABLE_NAME ;
        Cursor cursor = db.rawQuery(sql,null);
        while(cursor.moveToNext()){
           int index = cursor.getColumnIndex("name");
           String name = cursor.getString(index);
            Log.d(TAG, "name == "+name);
        }
        cursor.close();
        db.close();
    }
}
DatabaseHelper类编写数据库的创建和升级操作，DatabaseHelp类继承自SQLiteOpenHelper类，当Constants.version_code = 1时在活动中创建DatabaseHelper实例，通过对象的getWriteDatabase方法创建数据库

import android.content.Context;
import android.database.sqlite.SQLiteDatabase;
import android.database.sqlite.SQLiteOpenHelper;
import android.util.Log;
import android.widget.Switch;

import androidx.annotation.Nullable;

public class DatabaseHelper extends SQLiteOpenHelper {
    private static final String TAG ="DatabaseHelper" ;
    private DatabaseHelper mHelper;
//    context   上下文
//    name   数据库名称
//    factory   游标工厂
//        version  版本号

    public DatabaseHelper(@Nullable Context context) {
        super(context, Constants.DATABASE_NAME, null, Constants.VERSION_CODE);
    }

    @Override
    public void onCreate(SQLiteDatabase db) {

        Log.d(TAG, "创建数据库。。。。。");

        String sql = "create table "+Constants.TABLE_NAME+"(name varchar,date varchar,time varchar,address varchar,tiwen varchar)";
        db.execSQL(sql);

    }

    @Override
    public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
        Log.d(TAG, "升级数据库 。。。。。");
        String sql;

        switch (oldVersion){
            case 1:
                  sql = " alter table " + Constants.TABLE_NAME + " add  address varchar";
                  db.execSQL(sql);
                break;
            case 2:
                sql = " alter table " + Constants.TABLE_NAME + " add  tiwen varchar";
                db.execSQL(sql);
                break;
            case 3:
                break;
        }
    }
}
MainActivity中插入操作

new Thread(new Runnable() {
    @Override
    public void run() {
String str1;
str1 = name.getText().toString();

String str2;
str2 = date.getText().toString();

String str3;
str3 = time.getText().toString();

String str4;
str4 = space.getText().toString();

String str5;
str5 = wen.getText().toString();
Dao  dao = new Dao(Main2Activity.this);
dao.insert(str1,str2,str3,str4,str5);