Android中SQLite的使用

Posted 2020-09-25 drinkMilk

一、如何创建数据库和表？

     自己的类继承抽象类SQLiteOpenHelper。

　 （1）修改中的构造方法中的super方法创建数据库

　 （2）第一个抽象方法用于创建表

二、如何进行增删改查，代码如下：

public class StudentDao {
    private StudentSqliteOpenHelper studentSqliteOpenHelper;

    public StudentDao(Context context){
        studentSqliteOpenHelper = new StudentSqliteOpenHelper(context);
    }
    //增
    public boolean add(Student student){
        SQLiteDatabase db = studentSqliteOpenHelper.getReadableDatabase();
        ContentValues values = new ContentValues();
        values.put("name",student.name);
        values.put("age",student.age);
        values.put("school",student.school);

        long result = db.insert("student", null, values);
        db.close();
        if(result != -1){
            return true;
        }else{
            return false;
        }
    }
    //删
    public int del(String name){
        SQLiteDatabase db = studentSqliteOpenHelper.getReadableDatabase();
        int delLines = db.delete("student", "name = ?", new String[]{name});
        db.close();
        return delLines;
    }

    //改
    public int update(Student student){
        SQLiteDatabase db = studentSqliteOpenHelper.getReadableDatabase();
        ContentValues values = new ContentValues();
        values.put("name",student.name);
        values.put("age",student.age);
        values.put("school",student.school);
        int result = db.update("student", values, "name = ?", new String[]{student.name});
        db.close();
        return result;
    }
    //查
    public ArrayList<Student> query(String name){
        SQLiteDatabase db = studentSqliteOpenHelper.getReadableDatabase();
        Cursor cursor = db.rawQuery("select * from student where name = ?", new String[]{name});
        ArrayList<Student> arrayList = new ArrayList<>();
        if(cursor != null && cursor.getCount() > 0){
            //遍历cursor
            while (cursor.moveToNext()){
                Student s = new Student();
                s.id = cursor.getLong(0);
                s.name = cursor.getString(1);
                s.age = cursor.getInt(2);
                s.school = cursor.getString(3);
                arrayList.add(s);
            }
        }
        db.close();
        return arrayList;
    }
}