Android项目中如何在一个数据库里建立多张表，很多新手对此不是很清楚，为了帮助大家解决这个难题，下面小编将为大家详细讲解，有这方面需求的人可以来学习下，希望你能有所收获。
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：
1 public class CommDB { 2 3 public static final String DATABASE_NAME = "myDatabase"; //数据库名称 4 5 public static final int DATABASE_VERSION = 1; 6 //创建该数据库下学生表的语句 7 private static final String CREATE_TABLE_Students = 8 "CREATE TABLE if not exists " + StudentDB.SQLITE_TABLE + " (" + 9 StudentDB.KEY_ROWID + " integer PRIMARY KEY autoincrement," +10 StudentDB.KEY_AGE + "," +11 StudentDB.KEY_GENDER + "," +12 StudentDB.KEY_NAME + "," +13 " UNIQUE (" + StudentDB.KEY_NAME +"));";//暂时规定不能重名14 //创建该数据库下教师表的语句15 private static final String CREATE_TABLE_Teachers =16 "CREATE TABLE if not exists " + TeacherDB.SQLITE_TABLE + " (" +17 TeacherDB.KEY_ROWID + " integer PRIMARY KEY autoincrement," +18 TeacherDB.KEY_AGE + "," +19 TeacherDB.KEY_GENDER + "," +20 TeacherDB.KEY_NAME + "," +21 " UNIQUE (" + TeacherDB.KEY_AGE +"));";22 private final Context context;
23 private DatabaseHelper DBHelper;24 private SQLiteDatabase db;25 29 public CommDB(Context ctx)30 {31 this.context = ctx;32 this.DBHelper = new DatabaseHelper(this.context);33 }34 35 private static class DatabaseHelper extends SQLiteOpenHelper
36 {37 DatabaseHelper(Context context)
38 {39 super(context, DATABASE_NAME, null, DATABASE_VERSION);40 }41 42 @Override43 public void onCreate(SQLiteDatabase db)
44 {45 db.execSQL(CREATE_TABLE_Students);//创建学生表46 db.execSQL(CREATE_TABLE_Teachers);//创建教师表 47 }48 49 @Override50 public void onUpgrade(SQLiteDatabase db, int oldVersion,
51 int newVersion)
52 {
53 // Adding any table mods to this guy here54 }55 }
56 57 63 public CommDB open() throws SQLException
64 {65 this.db = this.DBHelper.getWritableDatabase();66 return this;67 }68 69 73 public void close()
74 {75 this.DBHelper.close();76 }77 }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：
1 public class GApplication extends Application { 2 private CommDB comDBHelper; 3 4 @Override 5 public void onCreate() { 6 // TODO Auto-generated method stub 7 super.onCreate(); 8 comDBHelper = new CommDB(this); 9 comDBHelper.open();10 }11 12 }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();
}
}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;
}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;
}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() {
}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 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，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。
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