Android中SQLite应用详解

参考文章：http://blog.csdn.net/liuhe688/article/details/6715983

本文只是记录一下sqlite应用的过程。

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程序结构如下：

其中，DBManger继承DBHelper, Person是一个实体类，MyActivity是一个主界面，main.xml里面定义了一个listview。

1. 编写DBHelper
   1. package com.example.myapp;
   2. ?
   3. import android.content.Context;
   4. import android.database.sqlite.SQLiteDatabase;
   5. import android.database.sqlite.SQLiteOpenHelper;
   6. ?
   7. /**
   8. ?* Created by zhuxuekui on 2015/5/18.
   9. ?*/
   10. public
       class DBHelper extends SQLiteOpenHelper {
   11. ????private
       static
       final String name = "test.db";
   12. ????private
       static
       final
       int version = 1;
   13. [email protected]
   14. ????public
       void onCreate(SQLiteDatabase sqLiteDatabase) {
   15. ????????sqLiteDatabase.execSQL("create table if not exists person"
   16. ????????+ "(_id integer primary key autoincrement , name varchar , age integer, info text )");
   17. ????}
   18. ?
   19. [email protected]
   20. ????public
       void onUpgrade(SQLiteDatabase sqLiteDatabase, int i, int i1) {
   21. ????????sqLiteDatabase.execSQL("alter table person add column other siring");
   22. ????}
   23. ?
   24. ????public DBHelper(Context context) {
   25. ????????super(context, name, null, version);
   26. ????}
   27. }

此类在数据库第一次创建时，通过构造方法执行。 然后执行onCreate,创建person表，除非我们卸载应用，不然就不会再次执行oncreate，当系统发现版本变化之后，我们会调用onUpgrade去更新，这里我们执行某些修改表的操作。

其中，我们通过version去判断是不是需要更新。

1. 接下来，我们编写Person数据表对应的实体类
   1. package com.example.myapp;
   2. ?
   3. /**
   4. ?* Created by zhuxuekui on 2015/5/18.
   5. ?*/
   6. public
      class Person {
   7. ????public
      int _id;
   8. ????public String name;
   9. ????public
      int age;
   10. ????public String info;
   11. ?
   12. ????public Person(String name, int age, String info) {
   13. ????????this.name = name;
   14. ????????this.age = age;
   15. ????????this.info = info;
   16. ????}
   17. ????public Person()
   18. ????{
   19. ?
   20. ????}
   21. ?
   22. }

   实体类，没啥好讲，加入我们声明成private，这就需要set，get一下了。封装好然后下面在调用。

2. 下面就是重头戏了，主要涉及数据库的增删改查
   1. ?
   2. import java.util.ArrayList;
   3. import java.util.List;
   4. ?
   5. import android.content.ContentValues;
   6. import android.content.Context;
   7. import android.database.Cursor;
   8. import android.database.sqlite.SQLiteDatabase;
   9. ?
   10. public
       class DBManager {
   11. ???private DBHelper helper;
   12. ???private SQLiteDatabase db;
   13. ?
   14. ???public DBManager(Context context) {
   15. ??????helper = new DBHelper(context);
   16. ??????//因为getWritableDatabase内部调用了mContext.openOrCreateDatabase(mName, 0, mFactory);
   17. ??????//所以要确保context已初始化,我们可以把实例化DBManager的步骤放在Activity的onCreate里
   18. ??????db = helper.getWritableDatabase();
   19. ???}
   20. ?
   21. ???/**
   22. ????* add persons
   23. ????* @param persons
   24. ????*/
   25. ???public
       void add(List<Person> persons) {
   26. ????????db.beginTransaction(); //开始事务
   27. ????????try {
   28. ???????????for (Person person : persons) {
   29. ??????????????db.execSQL("INSERT INTO person VALUES(null, ?, ?, ?)", new Object[]{person.name, person.age, person.info});
   30. ???????????}
   31. ???????????db.setTransactionSuccessful(); //设置事务成功完成
   32. ????????} finally {
   33. ???????????db.endTransaction(); //结束事务
   34. ????????}
   35. ???}
   36. ?
   37. ???/**
   38. ????* update person‘s age
   39. ????* @param person
   40. ????*/
   41. ???public
       void updateAge(Person person) {
   42. ??????ContentValues cv = new ContentValues();
   43. ??????cv.put("age", person.age);
   44. ??????db.update("person", cv, "name = ?", new String[]{person.name});
   45. ???}
   46. ?
   47. ???/**
   48. ????* delete old person
   49. ????* @param person
   50. ????*/
   51. ???public
       void deleteOldPerson(Person person) {
   52. ??????db.delete("person", "age >= ?", new String[]{String.valueOf(person.age)});
   53. ???}
   54. ?
   55. ???/**
   56. ????* query all persons, return list
   57. ????* @return List<Person>
   58. ????*/
   59. ???public List<Person> query() {
   60. ??????ArrayList<Person> persons = new ArrayList<Person>();
   61. ??????Cursor c = queryTheCursor();
   62. ????????while (c.moveToNext()) {
   63. ???????????Person person = new Person();
   64. ???????????person._id = c.getInt(c.getColumnIndex("_id"));
   65. ???????????person.name = c.getString(c.getColumnIndex("name"));
   66. ???????????person.age = c.getInt(c.getColumnIndex("age"));
   67. ???????????person.info = c.getString(c.getColumnIndex("info"));
   68. ???????????persons.add(person);
   69. ????????}
   70. ????????c.close();
   71. ????????return persons;
   72. ???}
   73. ?
   74. ???/**
   75. ????* query all persons, return cursor
   76. ????* @return Cursor
   77. ????*/
   78. ???public Cursor queryTheCursor() {
   79. ????????Cursor c = db.rawQuery("SELECT * FROM person", null);
   80. ????????return c;
   81. ???}
   82. ?
   83. ???/**
   84. ????* close database
   85. ????*/
   86. ???public
       void closeDB() {
   87. ??????db.close();
   88. ???}
   89. }

   在DBManager中实例化dbHelper,然后通过dbHelper得到一个SQLiteDatabase对象，作为整个应用的数据库实例；在add方法中，我们应用了事务去处理，先beginTransaction，然后设置事务成功，结束事务。这里就不需要提交了commit了。这是另一种事务的写法。当然，在执行增删改的过程中，我们可以通过exec (sql语句)来完成，也可以通过db.update() db.insert() 等方法完成。或者需要声明ContentValues 对象。

3. 编写xml文件，用于主界面的布局

   

   界面部分没啥可讲，基本功。

4. 编写主要业务逻辑部分
   1. package com.scott.db;
   2. ?
   3. import java.util.ArrayList;
   4. import java.util.HashMap;
   5. import java.util.List;
   6. import java.util.Map;
   7. ?
   8. import android.app.Activity;
   9. import android.database.Cursor;
   10. import android.database.CursorWrapper;
   11. import android.os.Bundle;
   12. import android.view.View;
   13. import android.widget.ListView;
   14. import android.widget.SimpleAdapter;
   15. import android.widget.SimpleCursorAdapter;
   16. ?
   17. ?
   18. public
       class MainActivity extends Activity {
   19. ?
   20. ???private DBManager mgr;
   21. ???private ListView listView;
   22. ?
   23. [email protected]
   24. ????public
       void onCreate(Bundle savedInstanceState) {
   25. ????????super.onCreate(savedInstanceState);
   26. ????????setContentView(R.layout.main);
   27. ????????listView = (ListView) findViewById(R.id.listView);
   28. ????????//初始化DBManager
   29. ????????mgr = new DBManager(this);
   30. ????}
   31. ?
   32. [email protected]
   33. ????protected
       void onDestroy() {
   34. ???????super.onDestroy();
   35. ???????//应用的最后一个Activity关闭时应释放DB
   36. ???????mgr.closeDB();
   37. ????}
   38. ?
   39. ????public
       void add(View view) {
   40. ???????ArrayList<Person> persons = new ArrayList<Person>();
   41. ?
   42. ???????Person person1 = new Person("Ella", 22, "lively girl");
   43. ???????Person person2 = new Person("Jenny", 22, "beautiful girl");
   44. ???????Person person3 = new Person("Jessica", 23, "sexy girl");
   45. ???????Person person4 = new Person("Kelly", 23, "hot baby");
   46. ???????Person person5 = new Person("Jane", 25, "a pretty woman");
   47. ?
   48. ???????persons.add(person1);
   49. ???????persons.add(person2);
   50. ???????persons.add(person3);
   51. ???????persons.add(person4);
   52. ???????persons.add(person5);
   53. ?
   54. ???????mgr.add(persons);
   55. ????}
   56. ?
   57. ????public
       void update(View view) {
   58. ???????Person person = new Person();
   59. ???????person.name = "Jane";
   60. ???????person.age = 30;
   61. ???????mgr.updateAge(person);
   62. ????}
   63. ?
   64. ????public
       void delete(View view) {
   65. ???????Person person = new Person();
   66. ???????person.age = 30;
   67. ???????mgr.deleteOldPerson(person);
   68. ????}
   69. ?
   70. ????public
       void query(View view) {
   71. ???????List<Person> persons = mgr.query();
   72. ???????ArrayList<Map<String, String>> list = new ArrayList<Map<String, String>>();
   73. ???????for (Person person : persons) {
   74. ??????????HashMap<String, String> map = new HashMap<String, String>();
   75. ??????????map.put("name", person.name);
   76. ??????????map.put("info", person.age + " years old, " + person.info);
   77. ??????????list.add(map);
   78. ???????}
   79. ???????SimpleAdapter adapter = new SimpleAdapter(this, list, android.R.layout.simple_list_item_2,
   80. ????????????????new String[]{"name", "info"}, new
       int[]{android.R.id.text1, android.R.id.text2});
   81. ???????listView.setAdapter(adapter);
   82. ????}
   83. ?
   84. ????public
       void queryTheCursor(View view) {
   85. ???????Cursor c = mgr.queryTheCursor();
   86. ???????startManagingCursor(c); //托付给activity根据自己的生命周期去管理Cursor的生命周期
   87. ???????CursorWrapper cursorWrapper = new CursorWrapper(c) {
   88. [email protected]
   89. ??????????public String getString(int columnIndex) {
   90. ?????????????//将简介前加上年龄
   91. ?????????????if (getColumnName(columnIndex).equals("info")) {
   92. ????????????????int age = getInt(getColumnIndex("age"));
   93. ????????????????return age + " years old, " + super.getString(columnIndex);
   94. ?????????????}
   95. ?????????????return
       super.getString(columnIndex);
   96. ??????????}
   97. ???????};
   98. ???????//确保查询结果中有"_id"列
   99. ??????SimpleCursorAdapter adapter = new SimpleCursorAdapter(this, android.R.layout.simple_list_item_2,
   100. ????????????cursorWrapper, new String[]{"name", "info"}, new
        int[]{android.R.id.text1, android.R.id.text2});
   101. ??????ListView listView = (ListView) findViewById(R.id.listView);
   102. ??????listView.setAdapter(adapter);
   103. ????}
   104. }

   这里面的代码和DBManger里面的代码结构上很相似，这里面在query处，我们用到了simpleAdapter.。这种主要接受list对象，Hashmap也可以。然后，做一些适配。结果如下：