android框架搭建——封装一个属于自己的数据存储工具类（SQLite篇）

当我们缓存本地的数据存在一对多（一个name对应多个values）的情况时，sharedPreferences已经无法胜任存储的工作了。此时我们需要使用SQLite来进行本地缓存。
直接使用SQlite进行存储时，每次执行插入，查询，删除操作都要写一大堆代码，很麻烦，所以我们对SQLite进行一下简单的封装，下面给出例子：
在这个例子中，我们要存储同学的姓名，年龄，指导老师，家庭地址，手机号等数据。
步骤一：创建SQLiteOpenHelper类，用于建表操作：

DBHelper.java:

public class DBHelper extends SQLiteOpenHelper {
private static final String DB_NAME = "student.db";
private static final int version = 1;
private static final String SQL_CREATE = "create table student_info(_id integer primary key autoincrement,student_id integer,name text,age integer,teacher text,address text,phone long)";
private static final String SQL_DROP = "drop table if exists student_info";

public DBHelper(Context context) {
super(context, DB_NAME, null, version);
}

@Override
public void onCreate(SQLiteDatabase db) {
db.execSQL(SQL_CREATE);
}

@Override
public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
db.execSQL(SQL_DROP);
db.execSQL(SQL_CREATE);
}
}

步骤二：写一个学生信息的bean：

studentInfo.java:

public class SudentInfo {
private int id;
private String name;
private int age;
private String teacher;
private String address;
private long phone;

public int getId() {
return id;
}

public void setId(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;
}

public String getTeacher() {
return teacher;
}

public void setTeacher(String teacher) {
this.teacher = teacher;
}

public String getAddress() {
return address;
}

public void setAddress(String address) {
this.address = address;
}

public long getPhone() {
return phone;
}

public void setPhone(long phone) {
this.phone = phone;
}

}

步骤三：写一个增删改查的接口：

StudentDAO.java:

/**数据访问接口
* Created by 95 on 2015/10/21.
*/
public interface StudentDAO {
/**
* 插入学生信息
*/
public void insertStudent(StudentInfo studentInfo);

/**
* 删除学生
*/
public void deleteStudent(String name);

/**
* 更新学生
*/
public void updateThread(String name);

/**
* 查询学生信息(同一老师对应多个学生)
*/
public List<StudentInfo> getStudents(String teacher);
/*
* 查询学生信息(一个名字对应一个学生)
*/
public StudentInfo getStudent(String name);

/**\
* 学生信息是否存在
* @return
*/
public boolean isExists(String name);
}

步骤四：写一个实现增删改查接口的类：

/**
* 数据访问接口实现
* Created by 95 on 2015/10/21.
*/

public class StudentDAOImpl implements StudentDAO {
private DBHelper mHelpter = null;

public StudentDAOImpl(Context context) {
mHelpter = new DBHelper(context);
}

@Override
public void insertStudent(StudentInfo studentInfo) {
SQLiteDatabase db = mHelpter.getWritableDatabase();
db.execSQL("insert into student_info(student_id,name,age,teacher,adderess,phone) values(?,?,?,?,?,?)",
new Object[]{studentInfo.getId(), studentInfo.getName(), studentInfo.getAge(), studentInfo.getTeacher(), studentInfo.getAddress(),studentInfo.getPhone()});
db.close();
}

@Override
public void deleteStudent(String name) {
SQLiteDatabase db = mHelpter.getWritableDatabase();
db.execSQL("delete from student_info where name = ? ",
new Object[]{name});
db.close();
}

@Override
public void updateStudent(String name,int age,String teacher,String address,long phone) {
SQLiteDatabase db = mHelpter.getWritableDatabase();
db.execSQL("update student_info set age = ?,teacher = ?,adderess = ?,phone = ? where name = ?",
new Object[]{age,teacher,address,phone,name});
db.close();
}

@Override
public List<StudentInfo> getStudents(String teacher) {
SQLiteDatabase db = mHelpter.getWritableDatabase();
List<StudentInfo> list = new ArrayList<StudentInfo>();
Cursor c = db.rawQuery("select * from student_info where teacher = ?", new String[]{teacher});
while (c.moveToNext()) {
StudentInfo student = new StudentInfo();
student.setId(c.getInt(c.getColumnIndex("student_id")));
student.setName(c.getString(c.getColumnIndex("name")));
student.setAge(c.getInt(c.getColumnIndex("age")));
student.setAddress(c.getString(c.getColumnIndex("address")));
student.setPhone(c.getLong(c.getColumnIndex("phone")));
list.add(student);
}
c.close();
db.close();

return list;
}
@Override
public StudentInfo getStudent(String name) {
SQLiteDatabase db = mHelpter.getWritableDatabase();
StudentInfo student = new StudentInfo();
Cursor c = db.rawQuery("select * from student_info where name = ?", new String[]{name});
while (c.moveToNext()) {
student.setId(c.getInt(c.getColumnIndex("student_id")));
student.setAge(c.getInt(c.getColumnIndex("age")));
student.setAddress(c.getString(c.getColumnIndex("address")));
student.setTeacher(c.getString(c.getColumnIndex("teacher")));
student.setPhone(c.getLong(c.getColumnIndex("phone")));
}
c.close();
db.close();
return student;
}

@Override
public boolean isExists(String name) {
SQLiteDatabase db = mHelpter.getWritableDatabase();
List<StudentInfo> list = new ArrayList<StudentInfo>();
Cursor c = db.rawQuery("select * from student_info where name = ? ", new String[]{name});
boolean isExists = c.moveToNext();
c.close();
db.close();
return isExists;
}
}

ok,在使用SQLite进行学生数据的本地缓存的时候，只要用几行代码就可以完成增删改查操作了，封装完成！