未在Android应用程序中使用SQLite创建java表

Question

我尝试在应用程序中使用sqlite创建一个表

这是我的密码：

public class DatabaseHandler extends SQLiteOpenHelper {

    // All Static variables
    // Database Version
    private static final int DATABASE_VERSION = 1;

    // Database Name
    private static final String DATABASE_NAME = "安卓_api";

    // Login table name
    private static final String TABLE_LOGIN = "login";

    // Login Table Columns names
    private static final String KEY_ID = "id";
    private static final String KEY_NAME = "name";
    private static final String KEY_EMAIL = "email";
    private static final String KEY_UID = "uid";
    private static final String KEY_CREATED_AT = "created_at";
    private static final String KEY_TOTAL_USAGE = "total_usage";


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

    // Creating Tables
    @Override
    public void onCreate(SQLiteDatabase db) {
        String CREATE_LOGIN_TABLE = "CREATE TABLE " + TABLE_LOGIN + "("
                + KEY_ID + " INTEGER PRIMARY KEY," 
                + KEY_NAME + " TEXT,"
                + KEY_EMAIL + " TEXT UNIQUE,"
                + KEY_UID + " TEXT,"
                + KEY_CREATED_AT + " TEXT,"
                + KEY_TOTAL_USAGE + " TEXT);";
        db.execSQL(CREATE_LOGIN_TABLE);
    }

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

        // Create tables again
        onCreate(db);
    }

    /**
     * Storing user details in database
     * */
    public void addUser(String name, String email, String uid, String created_at) {
        SQLiteDatabase db = this.getWritableDatabase();


        ContentValues values = new ContentValues();
        values.put(KEY_NAME, name); // Name
        values.put(KEY_EMAIL, email); // Email
        values.put(KEY_UID, uid); // Email
        values.put(KEY_CREATED_AT, created_at); // Created At
    //    values.put(KEY_TOTAL_USAGE, total_usage); // Total_usage

        // Inserting Row
        db.insert(TABLE_LOGIN, null, values);

        db.close(); // Closing database connection
    }

    /**
     * Storing user details in database
     * */
    public void updateUser(String email, String total_usage) {
        String selectQuery = "UPDATE login SET total_usage = 132 WHERE email = 'sampleMail'";

        SQLiteDatabase db = this.getWritableDatabase();

        db.execSQL(selectQuery);

        db.setTransactionSuccessful();
        db.close(); 
    }

    /**
     * Getting user data from database
     * */
    public HashMap<String, String> getUserDetails(){
        HashMap<String,String> user = new HashMap<String,String>();
        String selectQuery = "SELECT  * FROM " + TABLE_LOGIN;

        SQLiteDatabase db = this.getReadableDatabase();
        Cursor cursor = db.rawQuery(selectQuery, null);
        // Move to first row
        cursor.moveToFirst();
        if(cursor.getCount() > 0){
            user.put("name", cursor.getString(1));
            user.put("email", cursor.getString(2));
            user.put("uid", cursor.getString(3));
            user.put("created_at", cursor.getString(4));
        }
        cursor.close();
        db.close();
        // return user
        return user;
    }

    /**
     * Getting user login status
     * return true if rows are there in table
     * */
    public int getRowCount() {
        String countQuery = "SELECT  * FROM " + TABLE_LOGIN;
        SQLiteDatabase db = this.getReadableDatabase();
        Cursor cursor = db.rawQuery(countQuery, null);
        int rowCount = cursor.getCount();
        db.close();
        cursor.close();

        // return row count
        return rowCount;
    }

    /**
     * Re crate database
     * Delete all tables and create them again
     * */
    public void resetTables(){
        SQLiteDatabase db = this.getWritableDatabase();
        // Delete All Rows
        db.delete(TABLE_LOGIN, null, null);
        db.close();
    }

}

我的问题是：为什么表login从未创建过？我做错什么了吗？解决这样的问题不可能这么难。我在使用Sqlite时遇到了很多困难。如果有人能帮助我，那就太好了。Im使用phpmyadmin作为数据库

应用程序本身没有错误，logcat为空

我删除并运行了该应用程序10亿次，但它不起作用

也许这个信息有用：当我在终端中键入adb时，它不会被识别

为什么从未调用onCreate（）方法？如果我误用了一些术语，请原谅，因为我在一周内都没有解决这个问题，这让我发疯了：(

我在代码中使用了这个：http://www.安卓hive.info/2012/01/安卓-login-and-registration-with-php-mysql-and-sqlite/

---

以下代码不起作用：

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

Answer 1

在调用SQLiteOpenHelper类的getWritableDatabase（）或getReadableDatabase（）方法之前，不会创建数据库

您可以做的是存储一个变量字段 SQLiteDatabase db; 然后在构造函数调用db = db.getWriteableDatabase()/readable();

我想这会解决你的问题：）

编辑：尝试以下操作：

private SQLiteDatabase db;

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

public void open(){
     db = getWritableDatabase();
}

然后像这样做：

DatabaseHandler dh = new DatabaseHandler();
dh.open()

如果这仍然不起作用，试试看 https://www.google.se/?gws_rd=ssl#q=android+sqlite+oncreate+not+called

祝你好运