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。
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