我正在尝试重用我在主要活动中创建的数据库。但我不能让第二个活动引用数据库。
主要活动代码：
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();
}
});
}
第二项活动
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();
}
}
数据库代码
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;
}
}
答案 0 :(得分：0)
在AccountView Activity中创建Database类的对象并访问数据库类方法
AccountDB accountdb = new AccountDB(this);
List<Account> list1 = accountdb.getAllAccounts();