Android項目中，在一個數據庫裏創建多張表
一，建立一個公共的DBAdapter;數據庫
爲了在整個程序運行期間調用該公共的數據庫，咱們定義了一個擴展自Application的CommDB類：app
1，建立惟一的數據庫：ide
1 public class CommDB {
2
3 public static final String DATABASE_NAME = "myDatabase"; //數據庫名稱
4
5 public static final int DATABASE_VERSION = 1;
6 //建立該數據庫下學生表的語句
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 +"));";//暫時規定不能重名
14 //建立該數據庫下教師表的語句
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 /**
26 * Constructor
27 * @param ctx
28 */
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 @Override
43 public void onCreate(SQLiteDatabase db)
44 {
45 db.execSQL(CREATE_TABLE_Students);//建立學生表
46 db.execSQL(CREATE_TABLE_Teachers);//建立教師表
47 }
48
49 @Override
50 public void onUpgrade(SQLiteDatabase db, int oldVersion,
51 int newVersion)
52 {
53 // Adding any table mods to this guy here
54 }
55 }
56
57 /**
58 * open the db
59 * @return this
60 * @throws SQLException
61 * return type: DBAdapter
62 */
63 public CommDB open() throws SQLException
64 {
65 this.db = this.DBHelper.getWritableDatabase();
66 return this;
67 }
68
69 /**
70 * close the db
71 * return type: void
72 */
73 public void close()
74 {
75 this.DBHelper.close();
76 }
77 }
2，在app開始運行時，建立上述的數據庫，並建立對應的數據表：fetch
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，分別建立對應的數據表；this
1，創建學生數據表類：spa
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();
}
}
/**
* 建立學生表的字段
* @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;
}
/**
* 刪除表的所有字段數據
* @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;
}
/**
* 根據名稱刪除表中的數據
* @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() {
}
/**
* 獲取表中的全部字段
* @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，建立教師數據表類：.net
public class TeacherDB { public static final String KEY_ROWID = "_id"; public static final String KEY_AGE = "age"; public static final String KEY_GENDER = "gender";// 還要保留
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() {
} // 掃描時進行判斷本地數據庫是否有此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，調用public class ShowActivity extends Activity {code
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", "小鈴"); teacherDB.createTeacher("40", "男", "何SIR"); teacherDB.createTeacher("45", "女", "MRS謝"); 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，結果驗證；orm
10-25 16:50:10.321: E/stList value(3953): 阿武
10-25 16:50:10.321: E/stList value(3953): 小鈴
10-25 16:50:10.321: E/trList value(3953): 何SIR
10-25 16:50:10.321: E/trList value(3953): MRS謝rem
五，注意事項：
此例子中插入數據庫的數據是以年齡做爲惟一字段，當插入的數據中，年齡字段有重複時，數據庫會報錯，此例子只爲說明如何在一個數據庫中創建多張表，所以，在實際項目中，通常以某個實體的ID做爲惟一字段，且插入前必須通過判斷；
另外，數據庫的關閉，咱們選擇在onDestroy()方法中調用。
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