Android data storage (6) and SQLite database use instances

1. Create a subclass of sqliteopenhelper.

Package COM. tao. sqlitedb; import android. content. context; import android. database. SQLite. sqlitedatabase; import android. database. SQLite. sqliteopenhelper; public class dbopenhelper extends sqliteopenhelper {Private Static string db_name = "test. DB "; Private Static int db_version = 1; Public dbopenhelper (context) {super (context, db_name, null, db_version);} // called when the database is created, create a Table @ overridepublic void oncreate (sqlitedatabase dB) {// create three fields in the table, _ ID: db.exe csql ("create table tbl_person (_ id integer primary key autoincrement, name varchar (20), age integer )");} // called when the database version is upgraded. For example, when the software is upgraded, a new field or table must be added to a table in the original database, modify the Database @ overridepublic void onupgrade (sqlitedatabase dB, int oldversion, int newversion ){//}}

2. In order to reflect the object-oriented features and implement MVC, we will create a mode person

public class Person {private int _id;private String name;private int age;public Person() {}public Person(int _id, String name, int age) {this._id = _id;this.name = name;this.age = age;}public int get_id() {return _id;}public void set_id(int _id) {this._id = _id;}public String getName() {return name;}public void setName(String name) {this.name = name;}public int getAge() {return age;}public void setAge(int age) {this.age = age;}}

3. Implement MVC, encapsulate business methods, and become Controller

Package COM. tao. sqlitedb; import Java. util. arraylist; import Java. util. list; import android. content. context; import android. database. cursor; import android. database. SQLite. sqlitedatabase; public class dbmanager {private dbopenhelper helper; private sqlitedatabase dB; Public dbmanager (context) {helper = new dbopenhelper (context); // because getwritabledatabase internally calls mcontext. openorcreatedatabase (mname, 0 ,// Mfactory); // to ensure that the context has been initialized, we can put the steps for instantiating dbmanager in oncreate of activity DB = helper. getwritabledatabase ();}/*** Add a record ** @ Param person */Public void add (person) mongodb.exe csql ("insert into tbl_person values (null ,?,?) ", New object [] {person. getname (), person. getage ()});}/*** add multiple records ** @ Param persons */Public void adds (list <person> Persons) {dB. begintransaction (); try {for (person P: Persons) mongodb.exe csql ("insert into tbl_person values (null ,?,?) ", New object [] {P. getname (), P. getage ()});} dB. settransactionsuccessful ();} catch (exception e) {e. printstacktrace ();} finally {dB. endtransaction () ;}}/*** update a record ** @ Param person */Public void Update (person) mongodb.exe csql ("Update tbl_person set name = ?, Age =? Where _ id =? ", New object [] {person. getname (), person. getage (), person. get_id ()});}/*** delete a record ** @ Param person */Public void Delete (int id) mongodb.exe csql ("delete from tbl_person where _ id =? ", New object [] {ID});}/*** query a record */public person queryone (INT _ id) {person = new person (); cursor c = dB. rawquery ("select * From tbl_person where _ id =? ", New string [] {_ ID +" "}); While (C. movetonext () {person. set_id (C. getint (C. getcolumnindex ("_ id"); person. setname (C. getstring (C. getcolumnindex ("name"); person. setage (C. getint (C. getcolumnindex ("Age");} C. close (); Return person;}/*** query multiple records ** @ return list <person> */public list <person> querydetail () {arraylist <person> Persons = new arraylist <person> (); cursor c = dB. rawquery ("select * From tbl_person", null); While (C. movetonext () {person = new person (); person. set_id (C. getint (C. getcolumnindex ("_ id"); person. setname (C. getstring (C. getcolumnindex ("name"); person. setage (C. getint (C. getcolumnindex ("Age"); persons. add (person);} C. close (); return persons ;}}

4. Database Encapsulation has been completed, so we can simply use it now.

package com.tao.sqlitedb;import java.util.ArrayList;import java.util.HashMap;import java.util.List;import java.util.Map;import android.R.integer;import android.app.Activity;import android.database.sqlite.SQLiteDatabase;import android.os.Bundle;import android.util.Log;import android.view.View;import android.view.ViewGroup.LayoutParams;import android.widget.Button;import android.widget.EditText;import android.widget.ListView;import android.widget.SimpleAdapter;public class SqliteDBActivity extends Activity {private EditText ed1;private EditText ed2;private EditText ed3;private ListView listView;private DBManager dbManager;@Overridepublic void onCreate(Bundle savedInstanceState) {super.onCreate(savedInstanceState);setContentView(R.layout.main);dbManager=new DBManager(this);ed1=(EditText)findViewById(R.id.ed1);ed2=(EditText)findViewById(R.id.ed2);ed3=(EditText)findViewById(R.id.ed3);listView=(ListView)findViewById(R.id.listView);}public void add(View view){Person person=new Person(ed1.getText().toString().trim(), Integer.parseInt(ed2.getText().toString().trim()));dbManager.add(person);}public void delete(View view){dbManager.delete(Integer.parseInt(ed3.getText().toString().trim()));}public void update(View view){Person person=new Person(Integer.parseInt(ed3.getText().toString().trim()),ed1.getText().toString().trim(), Integer.parseInt(ed2.getText().toString().trim()));dbManager.update(person);}public void queryOne(View view){Person person=dbManager.queryOne(Integer.parseInt(ed3.getText().toString().trim()));List<Person> persons=new ArrayList<Person>();persons.add(person);setListView(persons);}public void queryMany(View view){List<Person> persons=dbManager.queryMany();setListView(persons);}public void setListView(List<Person> persons){List<Map<String, Object>> list=new ArrayList<Map<String,Object>>();for(Person p:persons){Map<String, Object> map=new HashMap<String, Object>();map.put("id", p.get_id());map.put("name", p.getName());map.put("age", p.getAge());list.add(map);}SimpleAdapter adapter=new SimpleAdapter(this, list, R.layout.cell, new String[]{"id","name","age"}, new int[]{R.id.text1,R.id.text2,R.id.text3});    listView.setAdapter(adapter);}}

Main. xml

<? XML version = "1.0" encoding = "UTF-8"?> <Linearlayout xmlns: Android = "http://schemas.android.com/apk/res/android" Android: layout_width = "fill_parent" Android: layout_height = "fill_parent" Android: Orientation = "vertical"> <edittext Android: id = "@ + ID/ED1" Android: hint = "name" Android: layout_width = "fill_parent" Android: layout_height = "wrap_content"/> <edittext Android: id = "@ + ID/ED2" Android: hint = "Age" Android: Numeric = "integer" Android: layout_width = "fill_parent" Android: layout_height = "wrap_content"/> <edittext Android: Id = "@ + ID/ed3" Android: hint = "ID" Android: Numeric = "integer" Android: layout_width = "fill_parent" Android: layout_height = "wrap_content"/> <linearlayout Android: Orientation = "horizontal" Android: layout_width = "fill_parent" Android: layout_height = "wrap_content"> <button Android: text = "add" Android: onclick = "add" Android: layout_width = "wrap_content" Android: layout_height = "wrap_content"/> <button Android: text = "exclude" Android: onclick = "delete" Android: layout_width = "wrap_content" Android: layout_height = "wrap_content"/> <button Android: layout_width = "fill_parent" Android: layout_height = "wrap_content" Android: text = "modify" Android: onclick = "Update"/> </linearlayout> <linearlayout Android: Orientation = "horizontal" Android: layout_width = "fill_parent" Android: layout_height = "wrap_content"> <button Android: TEXT = "query" Android: onclick = "queryone" Android: layout_width = "wrap_content" Android: layout_height = "wrap_content"/> <button Android: TEXT = "query multiple items" Android: onclick = "querymedia" Android: layout_width =" wrap_content "Android: layout_height =" wrap_content "/> </linearlayout> <listview Android: id = "@ + ID/listview" Android: layout_width = "fill_parent" Android: layout_height = "wrap_content"> </listview> </linearlayout>

The layout file cell. xml of listview

<?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="horizontal" >    <TextView         android:id="@+id/text1"        android:layout_width="wrap_content"        android:layout_height="wrap_content"/>    <TextView         android:id="@+id/text2"        android:layout_width="wrap_content"        android:layout_height="wrap_content"/>        <TextView         android:id="@+id/text3"        android:layout_width="wrap_content"        android:layout_height="wrap_content"/></LinearLayout>