Android之轻量数据库SQLite

2019-11-08 00:17:22

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来源：转载

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SQLite学习

一个朋友问我SQLite运用的怎么样我就给他说了一下步骤。我就有回顾了一下顺便再练习练习但是实际写起来还真有点手生啦！我就抓紧敲了起来以下就是源码:

MySQLite

package com.example.android_sqlite;import android.content.Context;import android.database.sqlite.SQLiteDatabase;import android.database.sqlite.SQLiteOpenHelper;import android.widget.Toast;/* 创建Sqlite帮助类*/public class MySqlite extends SQLiteOpenHelper { public static final String CREATE_BOOK = "create table Book(" + "id integer PRimary key autoincrement, " + "author text, " + "price real, " + "pages integer, " + "name text)"; private Context mContext; public static final String CREATE_CATEGORY = "create table Category(" + "id integer primary key autoincrement, " + "category_name text, " + "category_code integer)"; public MySqlite(Context context, String name, SQLiteDatabase.CursorFactory factory, int version) { super(context, name, factory, version); mContext = context; } @Override public void onCreate(SQLiteDatabase db) {//创建方法 db.execSQL(CREATE_BOOK); db.execSQL(CREATE_CATEGORY); Toast.makeText(mContext, "建表成功", Toast.LENGTH_SHORT).show(); } @Override public void onUpgrade(SQLiteDatabase db, int i, int i1) {//升级方法 //如果表已经存在就删除重新调用oncreate方法 db.execSQL("drop table if exists Book"); db.execSQL("drop table if exists Category"); onCreate(db); }}

MainActivity

package com.example.android_sqlite;import android.content.ContentValues;import android.database.Cursor;import android.database.sqlite.SQLiteDatabase;import android.support.v7.app.AppCompatActivity;import android.os.Bundle;import android.util.Log;import android.view.View;import android.widget.ArrayAdapter;import android.widget.Button;import android.widget.ListView;import android.widget.SimpleAdapter;import android.widget.Toast;import java.util.ArrayList;import java.util.HashMap;import java.util.List;import java.util.Map;import java.util.Objects;/* android内置数据库sqlite的使用步骤： 1.创建数据库使用SqliteOpenHelp帮助类（创建、升级） 2.通过ContentValues对象取出数据库的数据 */public class MainActivity extends AppCompatActivity implements View.OnClickListener { private Button btcreat; private MySqlite mySqlite; private Button Add_data, Delete_data, retr_data, Updata; private ListView listView; @Override protected void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.activity_main); creatSql(); initView(); } private void creatSql() { //初始化数据库填写需要创建的数据库的名字游标用null先代替版本是1 mySqlite = new MySqlite(this, "BookStore.db", null, 2); } private void initView() { btcreat = (Button) findViewById(R.id.btcreat); btcreat.setOnClickListener(this); Add_data = (Button) findViewById(R.id.Add_data); Add_data.setOnClickListener(this); Delete_data = (Button) findViewById(R.id.Delete_data); Delete_data.setOnClickListener(this); retr_data = (Button) findViewById(R.id.retr_data); retr_data.setOnClickListener(this); Updata = (Button) findViewById(R.id.Updata); Updata.setOnClickListener(this); listView = (ListView) findViewById(R.id.lv); } @Override public void onClick(View view) { //创建数据库帮助对象 SQLiteDatabase db = mySqlite.getWritableDatabase(); //添加数据对象 ContentValues values = new ContentValues(); switch (view.getId()) { case R.id.btcreat: //调用getWritableDatabase方法会创建数据库 mySqlite.getWritableDatabase(); Toast.makeText(this, "创建数据库", Toast.LENGTH_SHORT).show(); break; case R.id.Add_data: //开始添加第一条数据 values.put("name", "HELLO ANDROID"); values.put("author", "X-X-X"); values.put("pages", "448"); values.put("price", "47.00"); db.insert("Book", null, values); values.clear(); //插入第二条数据 values.put("name", "爱上编程"); values.put("author", "X1-X1-X1"); values.put("pages", "500"); values.put("price", "60.00"); db.insert("Book", null, values); break; case R.id.Delete_data: db.delete("Book", "pages > ?", new String[]{"449"}); break; case R.id.retr_data: //数据的查询返回的是cursor对象从cursor中得到数据 Cursor cursor = db.query("Book", null, null, null, null, null, null); //遍历cursor对象 if (cursor.moveToFirst()) { do { String name = cursor.getString(cursor.getColumnIndex("name")); String author = cursor.getString(cursor.getColumnIndex("author")); int pages = cursor.getInt(cursor.getColumnIndex("pages")); double price = cursor.getDouble(cursor.getColumnIndex("price")); List<Map<String, Object>> list = new ArrayList<>(); Map<String, Object> map = new HashMap<>(); map.put("姓名", name); map.put("作者", author); map.put("页数", pages); map.put("价格", price); list.add(map); SimpleAdapter simpleAdapter = new SimpleAdapter(this, list, R.layout.item_layout, new String[]{"姓名", "作者", "页数", "价格"}, new int[]{R.id.name, R.id.author, R.id.pages, R.id.price}); listView.setAdapter(simpleAdapter); } while (cursor.moveToNext()); } break; case R.id.Updata: values.put("pages", "500"); db.update("Book", values, "author = ?", new String[]{"X-X-X"}); break; } }}

activity_main

<?xml version="1.0" encoding="utf-8"?><LinearLayout xmlns:android="http://schemas.android.com/apk/res/android" xmlns:tools="http://schemas.android.com/tools" android:layout_width="match_parent" android:layout_height="match_parent" android:orientation="vertical" tools:context="com.example.android_sqlite.MainActivity"> <TextView android:layout_width="match_parent" android:layout_height="wrap_content" android:gravity="center" android:text="Android之Sqlite数据库" android:textColor="@android:color/black" /> <View android:layout_width="match_parent" android:layout_height="1dp" android:background="@android:color/holo_blue_bright" /> <Button android:id="@+id/btcreat" android:layout_width="match_parent" android:layout_height="wrap_content" android:text="创建数据库" /> <Button android:id="@+id/Add_data" android:layout_width="match_parent" android:layout_height="wrap_content" android:text="插入数据" /> <Button android:id="@+id/Delete_data" android:layout_width="match_parent" android:layout_height="wrap_content" android:text="删除数据" /> <Button android:id="@+id/retr_data" android:layout_width="match_parent" android:layout_height="wrap_content" android:text="查询数据" /> <Button android:id="@+id/Updata" android:layout_width="match_parent" android:layout_height="wrap_content" android:text="更新数据" /> <ListView android:id="@+id/lv" android:layout_width="match_parent" android:layout_height="match_parent" /></LinearLayout>

item_layout

<?xml version="1.0" encoding="utf-8"?><LinearLayout xmlns:android="http://schemas.android.com/apk/res/android" android:layout_width="match_parent" android:layout_height="match_parent" android:orientation="vertical"> <TextView android:id="@+id/name" android:layout_width="match_parent" android:layout_height="wrap_content" /> <TextView android:id="@+id/author" android:layout_width="match_parent" android:layout_height="wrap_content" /> <TextView android:id="@+id/pages" android:layout_width="match_parent" android:layout_height="wrap_content" /> <TextView android:id="@+id/price" android:layout_width="match_parent" android:layout_height="wrap_content" /></LinearLayout>

粘贴以上源码就可以运行啦！效果图就不上了，手机没有root不能录屏。

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