android 44 SQLiteOpenHelper

2022-10-24 15:14:52

java

package com.sxt.day06_10;

import java.util.ArrayList;

import com.sxt.day06_10.entity.StudentBean;

import android.os.Bundle;

import android.app.Activity;

import android.content.Context;

import android.view.Menu;

import android.view.View;

import android.view.ViewGroup;

import android.widget.BaseAdapter;

import android.widget.ListView;

import android.widget.TextView;

public class MainActivity extends Activity {

    StudentDBHelper mDao;

    ListView mlvStudent;

    ArrayList<StudentBean> mStudents;

    StudentAdapter mAdapter;

    @Override

    protected void onCreate(Bundle savedInstanceState) {

        super.onCreate(savedInstanceState);

        setContentView(R.layout.activity_main);

        mDao=new StudentDBHelper(this);

        initData();

        initView();

    }

    private void initView() {

        mlvStudent=(ListView) findViewById(R.id.lvStudent);

        mAdapter=new StudentAdapter(mStudents, this, mDao);

        mlvStudent.setAdapter(mAdapter);

    }

    private void initData() {

        mStudents=mDao.queryAll();

    }

    class StudentAdapter extends BaseAdapter{

        ArrayList<StudentBean> students;

        Context context;

        StudentDBHelper dao;

        public StudentAdapter(ArrayList<StudentBean> students, Context context,//Context是Activity的父类

                StudentDBHelper dao) {

            super();

            this.students = students;

            this.context = context;

            this.dao = dao;

        }

        public void remove(int position){//列表的删除

            dao.deleteRecord(students.get(position).getId());

            students.remove(position);

            notifyDataSetChanged();

        }

        public void add(StudentBean bean){//列表的增加

            students.add(bean);

            notifyDataSetChanged();

            dao.insertRecored(bean);

        }

        public void update(int position,StudentBean bean){

            students.set(position, bean);

            notifyDataSetChanged();

            dao.updateRecord(bean);

        }

        @Override

        public int getCount() {

            return students.size();

        }

        @Override

        public Object getItem(int position) {

            // TODO Auto-generated method stub

            return null;

        }

        @Override

        public long getItemId(int position) {

            // TODO Auto-generated method stub

            return 0;

        }

        @Override

        public View getView(int position, View convertView, ViewGroup parent) {

            ViewHolder holder=null;

            if(convertView==null){

                //缓存第一屏的所有convertView（比如10个）

                convertView=View.inflate(context, R.layout.item_student, null);

                holder=new ViewHolder();

                holder.tvName=(TextView) convertView.findViewById(R.id.tvName);

                holder.tvSex=(TextView) convertView.findViewById(R.id.tvSex);

                holder.tvBirthday=(TextView) convertView.findViewById(R.id.tvBirthday);

                holder.tvHeight=(TextView) convertView.findViewById(R.id.tvHeight);

                convertView.setTag(holder);

            }else{

                //滚屏的时候获取缓存的所有convertView（比如10个）

                holder=(ViewHolder) convertView.getTag();

            }

            //修改成新的

            StudentBean bean=students.get(position);

            holder.tvName.setText(bean.getName());

            holder.tvSex.setText(bean.getSex());

            holder.tvBirthday.setText(bean.getBirthday());

            holder.tvHeight.setText(bean.getHeight()+"");

            return convertView;

        }

        class ViewHolder{

            TextView tvName,tvSex,tvBirthday,tvHeight;

        }

    }

}

package com.sxt.day06_10;

import java.util.ArrayList;

import com.sxt.day06_10.entity.StudentBean;

import android.content.ContentValues;

import android.content.Context;

import android.database.Cursor;

import android.database.sqlite.SQLiteDatabase;

import android.database.sqlite.SQLiteDatabase.CursorFactory;

import android.database.sqlite.SQLiteOpenHelper;

public class StudentDBHelper extends SQLiteOpenHelper {

    private static final String DB_NAME="students.db";

    static final String TABLE_NAME="student";

    static final String ID="_id";

    static final String NAME="name";

    static final String SEX="sex";

    static final String BIRTHDAY="birthday";

    static final String HEIGHT="height";

    public StudentDBHelper(Context context) {

        super(context, DB_NAME, null, 1);

    }

    @Override

    public void onCreate(SQLiteDatabase db) {

        String sql="create table if not exists "+TABLE_NAME+"("

            +ID+" integer primary key autoincrement,"

            +NAME+" varchar(50),"

            +SEX+" varchar(2),"

            +BIRTHDAY+" datetext,"

            +HEIGHT+" real)";

        db.execSQL(sql);

        insertRecords(db);

    }

    private void insertRecords(SQLiteDatabase db) {

        ContentValues values=new ContentValues();

        values.put(NAME, "张飞");

        values.put(SEX, "男");

        values.put(BIRTHDAY, "1990-5-5");

        values.put(HEIGHT, 1.99);

        db.insert(TABLE_NAME, null, values);

        values=new ContentValues();

        values.put(NAME, "王菲");

        values.put(SEX, "女");

        values.put(BIRTHDAY, "1990-8-5");

        values.put(HEIGHT, 1.69);

        db.insert(TABLE_NAME, null, values);

        values=new ContentValues();

        values.put(NAME, "刘亦菲");

        values.put(SEX, "女");

        values.put(BIRTHDAY, "1991-5-5");

        values.put(HEIGHT, 1.7);

        db.insert(TABLE_NAME, null, values);

        values=new ContentValues();

        values.put(NAME, "李菲");

        values.put(SEX, "女");

        values.put(BIRTHDAY, "1992-5-5");

        values.put(HEIGHT, 1.72);

        db.insert(TABLE_NAME, null, values);

        values=new ContentValues();

        values.put(NAME, "田菲");

        values.put(SEX, "男");

        values.put(BIRTHDAY, "1993-5-5");

        values.put(HEIGHT, 1.78);

        db.insert(TABLE_NAME, null, values);

    }

    @Override

    public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {

        // TODO Auto-generated method stub

    }

    /**

     * 向表中增加一条记录

     * @param bean

     * @return

     */

    public int insertRecored(StudentBean bean){

        ContentValues values=new ContentValues();

        values.put(NAME, bean.getName());

        values.put(SEX, bean.getSex());

        values.put(BIRTHDAY, bean.getBirthday());

        values.put(HEIGHT, bean.getHeight());

        SQLiteDatabase db = getWritableDatabase();//getWritableDatabase()是SQLiteOpenHelper的方法

        long count = db.insert(TABLE_NAME, null, values);

        return (int) count;//插入的行数

    }

    /**

     * 删除指定id的记录

     * @param id

     * @return

     */

    public int deleteRecord(int id){

        SQLiteDatabase db = getWritableDatabase();

        int count = db.delete(TABLE_NAME, ID+"=?", new String[]{""+id});

        return count;//删除的行号

    }

    public int updateRecord(StudentBean bean){

        ContentValues values=new ContentValues();

        values.put(NAME, bean.getName());

        values.put(SEX, bean.getSex());

        values.put(BIRTHDAY, bean.getBirthday());

        values.put(HEIGHT, bean.getHeight());

        SQLiteDatabase db = getWritableDatabase();

        int count = db.update(TABLE_NAME, values, ID+"=?", new String[]{bean.getId()+""});//ID+"=?"是条件，new String[]{bean.getId()+""是填充占位符?

        return count;

    }

    public ArrayList<StudentBean> queryAll(){

        SQLiteDatabase db = getReadableDatabase();

        Cursor c = db.query(TABLE_NAME, null, null, null, null, null, null);//全查询，没有条件

        ArrayList<StudentBean> students=new ArrayList<StudentBean>();

        while(c.moveToNext()){

            int id=c.getInt(0);

            String name=c.getString(c.getColumnIndex(NAME));

            String sex=c.getString(c.getColumnIndex(SEX));

            String birthday=c.getString(c.getColumnIndex(BIRTHDAY));

            double height=c.getDouble(c.getColumnIndex(HEIGHT));

            StudentBean bean=new StudentBean(id, name, sex, birthday, height);

            students.add(bean);

        }

        return students;

    }

    public StudentBean queryRecord(int id){

        SQLiteDatabase db = getReadableDatabase();

        Cursor c = db.query(TABLE_NAME, null, ID+"=?", new String[]{""+id}, null,null,null);

        if(c.moveToNext()){

            String name=c.getString(c.getColumnIndex(NAME));

            String sex=c.getString(c.getColumnIndex(SEX));

            String birthday=c.getString(c.getColumnIndex(BIRTHDAY));

            double height=c.getDouble(c.getColumnIndex(HEIGHT));

            StudentBean bean=new StudentBean(id, name, sex, birthday, height);

            return bean;

        }

        return null;

    }

}

main.xml

<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"

    android:layout_width="match_parent"

    android:layout_height="match_parent">

    <ListView

        android:id="@+id/lvStudent"

        android:layout_width="match_parent"

        android:layout_height="match_parent"

        android:dividerHeight="5dp"/>

</RelativeLayout>

item_student.xml

<?xml version="1.0" encoding="utf-8"?>

<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"

    android:layout_width="match_parent"

    android:layout_height="wrap_content" >

    <TextView

        android:id="@+id/tvName"

        android:layout_width="wrap_content"

        android:layout_height="wrap_content"

        android:textSize="18sp"

        android:text="张飞"

        android:layout_marginLeft="5dp"/>

    <TextView

        android:id="@+id/tvSex"

        android:layout_alignParentRight="true"

        android:layout_width="wrap_content"

        android:layout_height="wrap_content"

        android:textSize="18sp"

        android:text="男"

        android:layout_marginLeft="5dp"/>

   <TextView

        android:id="@+id/tvBirthday"

        android:layout_below="@id/tvName"

        android:layout_alignParentLeft="true"

        android:layout_width="wrap_content"

        android:layout_height="wrap_content"

        android:textSize="18sp"

        android:text="1990-5-5"

        android:layout_marginLeft="5dp"/>

    <TextView

        android:id="@+id/tvHeight"

        android:layout_below="@id/tvSex"

        android:layout_alignParentRight="true"

        android:layout_width="wrap_content"

        android:layout_height="wrap_content"

        android:textSize="18sp"

        android:text="1.99米"

        android:layout_marginLeft="5dp"/>

</RelativeLayout>

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