Android项目中,在一个数据库里建立多张表
一,创建一个公共的DBAdapter;
为了在整个程序运行期间调用该公共的数据库,我们定义了一个扩展自Application的CommDB类:
1,创建唯一的数据库:
public class CommDB { public static final String DATABASE_NAME = "myDatabase"; //数据库名称 public static final int DATABASE_VERSION = 1;
//创建该数据库下学生表的语句
private static final String CREATE_TABLE_Students =
"CREATE TABLE if not exists " + StudentDB.SQLITE_TABLE + " (" +
StudentDB.KEY_ROWID + " integer PRIMARY KEY autoincrement," +
StudentDB.KEY_AGE + "," +
StudentDB.KEY_GENDER + "," +
StudentDB.KEY_NAME + "," +
" UNIQUE (" + StudentDB.KEY_NAME +"));";//暂时规定不能重名
//创建该数据库下教师表的语句
private static final String CREATE_TABLE_Teachers =
"CREATE TABLE if not exists " + TeacherDB.SQLITE_TABLE + " (" +
TeacherDB.KEY_ROWID + " integer PRIMARY KEY autoincrement," +
TeacherDB.KEY_AGE + "," +
TeacherDB.KEY_GENDER + "," +
TeacherDB.KEY_NAME + "," +
" UNIQUE (" + TeacherDB.KEY_AGE +"));";
private final Context context;
private DatabaseHelper DBHelper;
private SQLiteDatabase db;
/**
* Constructor
* @param ctx
*/
public CommDB(Context ctx)
{
this.context = ctx;
this.DBHelper = new DatabaseHelper(this.context);
} private static class DatabaseHelper extends SQLiteOpenHelper
{
DatabaseHelper(Context context)
{
super(context, DATABASE_NAME, null, DATABASE_VERSION);
} @Override
public void onCreate(SQLiteDatabase db)
{
db.execSQL(CREATE_TABLE_Students);//创建学生表
db.execSQL(CREATE_TABLE_Teachers);//创建教师表
} @Override
public void onUpgrade(SQLiteDatabase db, int oldVersion,
int newVersion)
{
// Adding any table mods to this guy here
}
} /**
* open the db
* @return this
* @throws SQLException
* return type: DBAdapter
*/
public CommDB open() throws SQLException
{
this.db = this.DBHelper.getWritableDatabase();
return this;
} /**
* close the db
* return type: void
*/
public void close()
{
this.DBHelper.close();
}
}
2,在app开始运行时,创建上述的数据库,并创建对应的数据表:
public class GApplication extends Application {
private CommDB comDBHelper; @Override
public void onCreate() {
// TODO Auto-generated method stub
super.onCreate();
comDBHelper = new CommDB(this);
comDBHelper.open();
} }
二,分别创建对应的数据表;
1,建立学生数据表类:
public class StudentDB {
public static final String KEY_ROWID = "_id";
public static final String KEY_AGE = "age";
public static final String KEY_GENDER = "gender";
public static final String KEY_NAME = "name"; private static final String TAG = "StudentDbAdapter";
private DatabaseHelper mDbHelper;
private SQLiteDatabase mDb; // private static final String DATABASE_NAME = "Fortrun_Ticket11";
static final String SQLITE_TABLE = "StudentTable"; private final Context mCtx; private static class DatabaseHelper extends SQLiteOpenHelper { DatabaseHelper(Context context) { super(context, CommDB.DATABASE_NAME, null, CommDB.DATABASE_VERSION);
} @Override
public void onCreate(SQLiteDatabase db) { } @Override
public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
Log.w(TAG, "Upgrading database from version " + oldVersion + " to "
+ newVersion + ", which will destroy all old data");
db.execSQL("DROP TABLE IF EXISTS " + SQLITE_TABLE);
onCreate(db);
}
} public StudentDB(Context ctx) {
this.mCtx = ctx;
} public StudentDB open() throws SQLException { mDbHelper = new DatabaseHelper(mCtx);
mDb = mDbHelper.getWritableDatabase();
return this;
} public void close() {
if (mDbHelper != null) {
mDbHelper.close();
}
} /**
* 创建学生表的字段
* @param age
* @param gender
* @param name
* @return
*/
public long createStudent(String age, String gender, String name) {
long createResult = 0;
ContentValues initialValues = new ContentValues();
initialValues.put(KEY_AGE, age);
initialValues.put(KEY_GENDER, gender);
initialValues.put(KEY_NAME, name);
try {
createResult = mDb.insert(SQLITE_TABLE, null, initialValues);
} catch (Exception e) {
// TODO: handle exception
}
return createResult;
} /**
* 删除表的全部字段数据
* @return
*/
public boolean deleteAllStudents() {
int doneDelete = 0;
try {
doneDelete = mDb.delete(SQLITE_TABLE, null, null);
Log.w(TAG, Integer.toString(doneDelete));
Log.e("doneDelete", doneDelete + "");
} catch (Exception e) {
// TODO: handle exception
e.printStackTrace();
}
return doneDelete > 0;
} /**
* 根据名称删除表中的数据
* @param name
* @return
*/
public boolean deleteTicketByName(String name) {
int isDelete;
String[] tName;
tName = new String[] { name };
isDelete = mDb.delete(SQLITE_TABLE, KEY_AGE + "=?", tName);
Log.e("deleteTicket", "isDelete:" + isDelete + "||" + "ticketID="
+ name);
return isDelete > 0;
}
public void insertSomeTickets() { } /**
* 获取表中的所有字段
* @return
*/
public ArrayList<Student> fetchAll() { ArrayList<Student> allTicketsList = new ArrayList<Student>();
Cursor mCursor = null;
mCursor = mDb.query(SQLITE_TABLE, new String[] { KEY_ROWID, KEY_AGE,
KEY_GENDER, KEY_NAME }, null, null, null, null, null);
if (mCursor.moveToFirst()) {
do {
Student st = new Student();
st.setAge(mCursor.getString(mCursor
.getColumnIndexOrThrow(KEY_AGE)));
st.setGender(mCursor.getString(mCursor
.getColumnIndexOrThrow(KEY_GENDER)));
st.setName(mCursor.getString(mCursor
.getColumnIndexOrThrow(KEY_NAME)));
allTicketsList.add(st);
} while (mCursor.moveToNext());
}
if (mCursor != null && !mCursor.isClosed()) {
mCursor.close();
}
return allTicketsList;
} }
2,创建教师数据表类:
public class TeacherDB {
public static final String KEY_ROWID = "_id";
public static final String KEY_AGE = "age";
public static final String KEY_GENDER = "gender";// 还要保留
public static final String KEY_NAME = "name"; private static final String TAG = "TeacherDbAdapter";
private DatabaseHelper mDbHelper;
private SQLiteDatabase mDb; // private static final String DATABASE_NAME = "Fortrun_Ticket11";
static final String SQLITE_TABLE = "TeacherTable";
private static final int DATABASE_VERSION = 1; private final Context mCtx; private static class DatabaseHelper extends SQLiteOpenHelper { DatabaseHelper(Context context) { super(context, CommDB.DATABASE_NAME, null, CommDB.DATABASE_VERSION);
} @Override
public void onCreate(SQLiteDatabase db) {
// Log.w(TAG, DATABASE_CREATE);
// db.execSQL(DATABASE_CREATE);
} @Override
public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
Log.w(TAG, "Upgrading database from version " + oldVersion + " to "
+ newVersion + ", which will destroy all old data");
db.execSQL("DROP TABLE IF EXISTS " + SQLITE_TABLE);
onCreate(db);
}
} public TeacherDB(Context ctx) {
this.mCtx = ctx;
} public TeacherDB open() throws SQLException { mDbHelper = new DatabaseHelper(mCtx);
mDb = mDbHelper.getWritableDatabase();
return this;
} public void close() {
if (mDbHelper != null) {
mDbHelper.close();
}
} public long createTeacher(String age, String gender, String name) {
long createResult = 0;
ContentValues initialValues = new ContentValues();
initialValues.put(KEY_AGE, age);
initialValues.put(KEY_GENDER, gender);
initialValues.put(KEY_NAME, name);
try {
createResult = mDb.insert(SQLITE_TABLE, null, initialValues);
} catch (Exception e) {
// TODO: handle exception
}
return createResult;
} public boolean deleteAllTeachers() {
int doneDelete = 0;
try {
doneDelete = mDb.delete(SQLITE_TABLE, null, null);
Log.w(TAG, Integer.toString(doneDelete));
Log.e("doneDelete", doneDelete + "");
} catch (Exception e) {
// TODO: handle exception
e.printStackTrace();
}
return doneDelete > 0;
} public boolean deleteTeacherByName(String name) {
int isDelete;
String[] tName;
tName = new String[] { name };
isDelete = mDb.delete(SQLITE_TABLE, KEY_AGE + "=?", tName);
Log.e("deleteTicket", "isDelete:" + isDelete + "||" + "ticketID="
+ name);
return isDelete > 0;
}
public void insertSomeTickets() { } // 扫描时进行判断本地数据库是否有此ticketID
public ArrayList<Teacher> fetchAll() { ArrayList<Teacher> allTeacherList = new ArrayList<Teacher>();
Cursor mCursor = null;
mCursor = mDb.query(SQLITE_TABLE, new String[] { KEY_ROWID, KEY_AGE,
KEY_GENDER, KEY_NAME }, null, null, null, null, null);
if (mCursor.moveToFirst()) {
do {
Teacher st = new Teacher();
st.setAge(mCursor.getString(mCursor
.getColumnIndexOrThrow(KEY_AGE)));
st.setGender(mCursor.getString(mCursor
.getColumnIndexOrThrow(KEY_GENDER)));
st.setName(mCursor.getString(mCursor
.getColumnIndexOrThrow(KEY_NAME)));
allTeacherList.add(st);
} while (mCursor.moveToNext());
}
if (mCursor != null && !mCursor.isClosed()) {
mCursor.close();
}
return allTeacherList;
} }
三,调用public class ShowActivity extends Activity {
private StudentDB studentDB;
private TeacherDB teacherDB;
private List<Student> stList = new ArrayList<Student>();
private List<Teacher> trList = new ArrayList<Teacher>(); @Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_show);
studentDB = new StudentDB(this);
studentDB.open(); teacherDB = new TeacherDB(this);
teacherDB.open(); studentDB.createStudent("28", "男", "阿武");
studentDB.createStudent("24", "女", "小铃"); teacherDB.createTeacher("40", "男", "何SIR");
teacherDB.createTeacher("45", "女", "MRS谢");
stList = studentDB.fetchAll();
trList = teacherDB.fetchAll();
for (int i = 0; i < stList.size(); i++) {
Log.e("stList value", stList.get(i).getName());
}
for (int i = 0; i < trList.size(); i++) {
Log.e("trList value", trList.get(i).getName());
}
}
@Override
protected void onDestroy() {
// TODO Auto-generated method stub
super.onDestroy();
if (studentDB != null) {
studentDB.close();
}
if (teacherDB != null) {
teacherDB.close();
}
} @Override
public boolean onCreateOptionsMenu(Menu menu) {
// Inflate the menu; this adds items to the action bar if it is present.
getMenuInflater().inflate(R.menu.show, menu);
return true;
} }
四,结果验证;
10-25 16:50:10.321: E/stList value(3953): 阿武
10-25 16:50:10.321: E/stList value(3953): 小铃
10-25 16:50:10.321: E/trList value(3953): 何SIR
10-25 16:50:10.321: E/trList value(3953): MRS谢
五,注意事项:
此例子中插入数据库的数据是以年龄作为唯一字段,当插入的数据中,年龄字段有重复时,数据库会报错,此例子只为说明如何在一个数据库中建立多张表,因此,在实际项目中,一般以某个实体的ID作为唯一字段,且插入前必须经过判断;
另外,数据库的关闭,我们选择在onDestroy()方法中调用。
Android项目中,在一个数据库里建立多张表的更多相关文章
- XamarinSQLite教程在Xamarin.Android项目中提取数据库文件
XamarinSQLite教程在Xamarin.Android项目中提取数据库文件 由于不能直接打开该文件,开发者需要先将数据库文件从Android系统中提取出来.操作步骤如下. (5)选择MyDoc ...
- XamarinSQLite教程在Xamarin.Android项目中定位数据库文件
XamarinSQLite教程在Xamarin.Android项目中定位数据库文件 实际开发中,经常需要验证数据库操作的正确性.这个时候,需要打开数据库文件,进行确认.下面是如何找到MyDocumen ...
- XamarinSQLite教程在Xamarin.Android项目中使用数据库
XamarinSQLite教程在Xamarin.Android项目中使用数据库 在Xamarin.Android项目中使用预设数据库的具体操作步骤如下: (1)创建一个Xamarin.Android项 ...
- Android项目中如何用好构建神器Gradle?(转)
最近在忙团队并行开发的事情,主要是将各个团队的代码分库,一方面可以降低耦合,为后面模块插件化做铺垫,另一方面采用二进制编译,可以加快编译速度.分库遇到了一些问题,很多都要通过Gradle脚本解决,所以 ...
- 在Android项目中使用Java8
前言 在过去的文章中我介绍过Java8的一些新特性,包括: Java8新特性第1章(Lambda表达式) Java8新特性第2章(接口默认方法) Java8新特性第3章(Stream API) 之前由 ...
- Android 项目中文件夹的说明与作用(转)
(转自:http://blog.csdn.net/goodshot/article/details/11529731) Android 项目中文件夹的作用 1. src:存放所有的*.java源程序. ...
- 对Android项目中的文件夹进行解释
对Android项目中的文件夹进行解释: · src:里面存放的是Activity程序,或者是以后的其他组件,在此文件夹之中建立类的时候一定要注意,包名称不能是一级. · gen:此文件夹中的内容是自 ...
- android项目中如何加载已有so库 <转>
1,在项目根目录下建立文件夹libs/armeabi文件夹 2,将so库放入 libs/armeabi文件夹 注意事项: 1,如果采用静态注册的方式请注意C文件中严格按照命名规则 Java_packa ...
- android项目中刷新activity界面
android项目中在sqlite数据库插入/更新/删除数据后: 1. 刷新当前activity界面数据(手动刷新): 在activity类下新增一个refresh()方法: /** * 刷新, 这样 ...
随机推荐
- 张洋:浅析PageRank算法
本文引自http://blog.jobbole.com/23286/ 很早就对Google的PageRank算法很感兴趣,但一直没有深究,只有个轮廓性的概念.前几天趁团队outing的机会,在动车上看 ...
- phpcms v9 标签含义整理
{template "content","header"} ---------- 调用根目录下phpcms\template\content\header ...
- Gbase配置
喵了个咪的.到目前为止,自己已经用过SQL SERVER,My SQL,Oracle,SQLite,加上南大通用GBASE 五种数据库了.虽然每种都用的不深 注:GBASE提供了C的API,查看手册即 ...
- [Laravel-Swagger]如何在 Laravel 项目中使用 Swagger
如何在 Laravel 项目中使用 Swagger http://swagger.io/getting-started/ 安装依赖 swagger-php composer require zirco ...
- CMD命令小结
C:\Windows\Explorer.exe “文件具体目录(要加文件后缀名)”,(Explorer.exe后有一个空格,例如C:\Windows\Explorer.exe C:\temp\New ...
- JDK 对应的设计模式
一.设计模式是什么 (1)反复出现问题的解决方案 (2)增强软件的灵活性 (3)适应软件不断变化二.学习JDK中设计模式的好处 (1)借鉴优秀代码的设计,有助于提高代码设计能力 (2)JDK的设计中体 ...
- activity启动模式区别和优化
初学android的开发人员,可能会经常忽略这个重要的设置. Activity一共有以下四种launchMode:1.standard2.singleTop3.singleTask4.singleIn ...
- SQL入门经典(七) 之脚本和批处理
什么是脚本.我们前面学的CREATE TABLE <table name> ,USE <database name>这些都是脚本,为什么用脚本.脚本存储到文件中并且可以重复利用 ...
- HTML5按钮的点击态问题
开始在网页上实现点击态是mousedown mouseup来实现但是手机HTML5实现点击态怎么就不可以了呢 经过查资料才知道手机浏览器来实现点击态是通过 touchstart touchend实现
- TclError: no display name and no $DISPLAY environment variable
%matplotlib inline 或 %matplotlib notebook