Android項目中，在一個數據庫裏創建多張表

時間 2019-12-06

原文原文鏈接

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：code

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 {blog

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；rem

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get

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。