转发：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);}@Overridepublic void onCreate(SQLiteDatabase db) {db.execSQL(CREATE_TABLE_Students);//创建学生表db.execSQL(CREATE_TABLE_Teachers);//创建教师表 }@Overridepublic 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;@Overridepublic void onCreate() {// TODO Auto-generated method stubsuper.onCreate();comDBHelper = new CommDB(this);comDBHelper.open();}}

3.在manifest.xml文件中添加Application

<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"package="com.example.fxjzzyo.phome"><uses-permission android:name="android.permission.INTERNET" /><application
        android:allowBackup="true"android:icon="@mipmap/ic_launcher"android:label="@string/app_name"android:name=".application.GApplication"android:supportsRtl="true"android:theme="@style/Theme.AppCompat.Light.NoActionBar"><activity android:name=".activity.LoginActivity"><intent-filter><action android:name="android.intent.action.MAIN" /><category   android:name="android.intent.category.LAUNCHER" /></intent-filter></activity><activity android:name=".activity.MainActivity" /><activity android:name=".activity.RegiserActivity"></activity></application></manifest>

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);}@Overridepublic void onCreate(SQLiteDatabase db) {}@Overridepublic 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 exceptione.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);}@Overridepublic void onCreate(SQLiteDatabase db) {// Log.w(TAG, DATABASE_CREATE);// db.execSQL(DATABASE_CREATE);}@Overridepublic 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 exceptione.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ticketIDpublic 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，在Activity中调用

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>();@Overrideprotected 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());}}@Overrideprotected void onDestroy() {// TODO Auto-generated method stubsuper.onDestroy();if (studentDB != null) {studentDB.close();}if (teacherDB != null) {teacherDB.close();}}@Overridepublic 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。

原文地址：http://www.cnblogs.com/crashmaker/p/3368812.html

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