從另一個活動中的一個活動打開數據庫

Question

我想重用我在主要活動中創建的數據庫。但是我無法獲得第二個活動來引用數據庫。

主要acitivy代碼：

public class StoreAccount extends AppCompatActivity { 
static final int READ_BLOCK_SIZE = 100; 

@Override 
protected void onCreate(Bundle savedInstanceState) { 
    super.onCreate(savedInstanceState); 
    setContentView(R.layout.activity_store_account); 


    final AccountDB db1 = new AccountDB(this); 


    Button buttonSave = (Button) findViewById(R.id.buttonSave); 
    buttonSave.setOnClickListener(new View.OnClickListener() { 
     public void onClick(View v) { 
      EditText account = (EditText) findViewById(R.id.editTextAccount); 
      String acc = account.getText().toString(); 
      EditText username = (EditText) findViewById(R.id.editTextUsername); 
      String user = username.getText().toString(); 
      EditText password = (EditText) findViewById(R.id.editTextPassword); 
      String pass = password.getText().toString(); 
      EditText days = (EditText) findViewById(R.id.editTextDays); 
      int expiry = Integer.parseInt(days.getText().toString()); 
      /** 
      * CRUD Operations 
      * */ 
      // add Accounts 

      db1.addAccount(new Account(acc, user, pass, expiry)); 
      //db.addBook(new Book("Android Programming: The Big Nerd Ranch Guide", "Bill Phillips and Brian Hardy")); 
      //db.addBook(new Book("Learn Android App Development", "Wallace Jackson")); 


      // get all accounts 
      List<Account> list1 = db1.getAllAccounts(); 

      // delete one account 
      db1.deleteAccount(list1.get(0)); 

      // get all accounts 
      db1.getAllAccounts(); 

     } 

    }); 
} 

次活動

public class AccountView extends StoreAccount { 
//@Override 
protected void onCreate(Bundle savedInstanceState, SQLiteDatabase db) { 
    super.onCreate(savedInstanceState); 
    setContentView(R.layout.activity_account_view); 

    Context context = getApplicationContext(); 
    context.getDatabasePath(AccountDb.AccountDb); 
    //AccountDB db1 = new AccountDB(this); 
    List<Account> list1 = db1.getAllAccounts(); 

} 

}

數據庫代碼

public class AccountDB extends SQLiteOpenHelper { 
// Database Version 
private static final int DATABASE_VERSION = 1; 
// Database Name 
private static final String DATABASE_NAME = "AccountDB"; 

public AccountDB(Context context) { 
    super(context, DATABASE_NAME, null, DATABASE_VERSION); 
} 

@Override 
public void onCreate(SQLiteDatabase db) { 
    // SQL statement to create account table 
    String CREATE_ACCOUNT_TABLE = "CREATE TABLE accounts (" + 
      "id INTEGER PRIMARY KEY AUTOINCREMENT, " + 
      "account TEXT, " + 
      "username TEXT, " + 
      "password TEXT, " + 
      "expiry INTEGER)"; 

    // create accounts table 
    db.execSQL(CREATE_ACCOUNT_TABLE); 
} 

@Override 
public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) { 
    // Drop older accounts table if existed 
    db.execSQL("DROP TABLE IF EXISTS accounts"); 

    // create fresh accounts table 
    this.onCreate(db); 
} 
//--------------------------------------------------------------------- 

/** 
* CRUD operations (create "add", read "get", update, delete) account + get all accounts + delete all accounts 
*/ 

// Accounts table name 
private static final String TABLE_ACCOUNTS = "accounts"; 

// Accounts Table Columns names 
private static final String KEY_ID = "id"; 
private static final String KEY_ACCOUNT = "account"; 
private static final String KEY_USERNAME = "username"; 
private static final String KEY_PASSWORD = "password"; 
private static final String KEY_DAYS = "expiry"; 

private static final String[] COLUMNS = {KEY_ID, KEY_ACCOUNT, KEY_USERNAME, KEY_PASSWORD, KEY_DAYS}; 

public void addAccount(Account account) { 
    Log.d("addAccount", account.toString()); 
    // 1. get reference to writable DB 
    SQLiteDatabase db = this.getWritableDatabase(); 

    // 2. create ContentValues to add key "column"/value 
    ContentValues values = new ContentValues(); 
    values.put(KEY_ACCOUNT, account.getAccount()); // get account 
    values.put(KEY_USERNAME, account.getUsername()); // get username 
    values.put(KEY_PASSWORD, account.getPassword()); // get password 
    values.put(KEY_DAYS, account.getDays()); // get expiry 

    // 3. insert 
    db.insert(TABLE_ACCOUNTS, // table 
      null, //nullColumnHack 
      values); // key/value -> keys = column names/ values = column values 

    // 4. close 
    db.close(); 
} 

public Account getAccount(int id) { 

    // 1. get reference to readable DB 
    SQLiteDatabase db = this.getReadableDatabase(); 

    // 2. build query 
    Cursor cursor = 
      db.query(TABLE_ACCOUNTS, // a. table 
        COLUMNS, // b. column names 
        " id = ?", // c. selections 
        new String[]{String.valueOf(id)}, // d. selections args 
        null, // e. group by 
        null, // f. having 
        null, // g. order by 
        null); // h. limit 

    // 3. if we got results get the first one 
    if (cursor != null) 
     cursor.moveToFirst(); 

    // 4. build account object 
    Account account = new Account(); 
    account.setId(Integer.parseInt(cursor.getString(0))); 
    account.setAccount(cursor.getString(1)); 
    account.setUsername(cursor.getString(2)); 
    account.setPassword(cursor.getString(3)); 
    account.setDays(Integer.parseInt(cursor.getString(4))); 

    Log.d("getAccount(" + id + ")", account.toString()); 

    // 5. return account 
    return account; 
} 

// Get All Accounts 
public List<Account> getAllAccounts() { 
    List<Account> accounts = new LinkedList<Account>(); 

    // 1. build the query 
    String query = "SELECT * FROM " + TABLE_ACCOUNTS; 

    // 2. get reference to writable DB 
    SQLiteDatabase db = this.getWritableDatabase(); 
    Cursor cursor = db.rawQuery(query, null); 

    // 3. go over each row, build account and add it to list 
    Account account = null; 
    if (cursor.moveToFirst()) { 
     do { 
      account = new Account(); 
      account.setId(Integer.parseInt(cursor.getString(0))); 
      account.setAccount(cursor.getString(1)); 
      //account.setUsername(cursor.getString(2)); 
      //account.setPassword(cursor.getString(3)); 
      //account.setDays(Integer.parseInt(cursor.getString(4))); 

      // Add account to accounts 
      accounts.add(account); 
     } while (cursor.moveToNext()); 
    } 

    Log.d("getAllAccounts()", accounts.toString()); 

    // return accounts 
    return accounts; 
} 

// Updating single account 
public int updateAccount(Account account) { 

    // 1. get reference to writable DB 
    SQLiteDatabase db = this.getWritableDatabase(); 

    // 2. create ContentValues to add key "column"/value 
    ContentValues values = new ContentValues(); 
    values.put("account", account.getAccount()); // get account 
    values.put("username", account.getUsername()); // get username 
    values.put("password", account.getPassword()); // get password 
    values.put("expiry", account.getDays()); // get expiry 

    // 3. updating row 
    int i = db.update(TABLE_ACCOUNTS, //table 
      values, // column/value 
      KEY_ID + " = ?", // selections 
      new String[]{String.valueOf(account.getId())}); //selection args 

    // 4. close 
    db.close(); 

    return i; 

} 

// Deleting single account 
public void deleteAccount(Account account) { 

    // 1. get reference to writable DB 
    SQLiteDatabase db = this.getWritableDatabase(); 

    // 2. delete 
    db.delete(TABLE_ACCOUNTS, 
      KEY_ID + " = ?", 
      new String[]{String.valueOf(account.getId())}); 

    // 3. close 
    db.close(); 

    Log.d("deleteAccount", account.toString()); 

} 

public int getRowCount() { 
    String countQuery = "SELECT * FROM " + TABLE_ACCOUNTS; 
    SQLiteDatabase db = this.getReadableDatabase(); 
    Cursor cursor = db.rawQuery(countQuery, null); 
    int cnt = cursor.getCount(); 
    cursor.close(); 
    return cnt; 


} 


} 

Answer 1

使數據庫類的對象在你的AccountView活動和訪問您的數據庫類方法

AccountDB accountdb = new AccountDB(this); 
List<Account> list1 = accountdb.getAllAccounts();