Question

当我执行下面的代码时，它总是让我“无效”，即使我用一个预定的字符串替换usertry ..我的查询中是否有语法问题？

check login方法在另一个检查有效登录的类中

    public void checklogin(String usertry){


    DatabaseHelper dbh = new DatabaseHelper(LoginActivity.this);
    DatabaseAdapter dba = new DatabaseAdapter(LoginActivity.this);
    db= dbh.getReadableDatabase();
    TextView usernametry = (TextView) findViewById(R.id.usernametry);
     usertry = usernametry.getText().toString();

    Cursor mCursor = db.query(dba.TABLE_USERS,new String[]{dba.COLUMN_ID,dba.COLUMN_NAME},  dba.COLUMN_NAME + "=" + "?", new String[]{usertry},null,null,null,null);

     if  (mCursor.moveToFirst()){
         Toast.makeText(LoginActivity.this, "Yaaaay", Toast.LENGTH_LONG).show();
     }

      Toast.makeText(LoginActivity.this, "invalid", Toast.LENGTH_LONG).show();                  
        }
}

这是我的数据库适配器类：

  public class DatabaseAdapter {

public static final String COLUMN_ID = "ID";
public static final String COLUMN_NAME = "Name";
public static final String COLUMN_AGE = "Age";
public static final String COLUMN_GENDER = "Gender";
public static final String COLUMN_WEIGHT = "Weight";
public static final String COLUMN_HEIGHT = "Height";
public static final String COLUMN_ACTIVITY = "Activitylevel";
public static final String COLUMN_CALORIES = "numCal";
public static final String FOOD_ID = "food_ID";
public static final String FOOD_NAME = "food_name";
public static final String FOOD_CALS = "food_cals";
public static final String FOOD_FAT = "food_fat";
public static final String FOOD_PRO = "food_protein";
public static final String FOOD_CRAB = "food_crabs";

public static final String TABLE_USERS = "users";
public static final String TABLE_FOOD = "food";
private static final int DATABASE_VERSION = 1;
private static final String DATABASE_NAME = "nutriwellness.db";

private static final String CREATE_TABLE_USERS = "create table users( id integer primary key autoincrement, "
        + "Name text, Age integer, Gender text, Weight text, Height text, Activitylevel text, numCal float );";

private static final String CREATE_TABLE_FOOD = "create table food( food_ID integer primary key autoincrement,"
        + "food_name text,food_cals integer, food_fat integer, food_protein integer, food_crabs integer );";

private SQLiteDatabase database;
private DatabaseHelper dbHelper;

private String[] allColumnsofuserstable = { COLUMN_ID, COLUMN_NAME,
        COLUMN_AGE, COLUMN_GENDER, COLUMN_WEIGHT, COLUMN_HEIGHT };

private String[] allColumnoffoodtable = { FOOD_ID, FOOD_NAME, FOOD_FAT,
        FOOD_PRO, FOOD_CRAB };


public DatabaseAdapter(Context context) {

    dbHelper = new DatabaseHelper(context);
}

public static class DatabaseHelper extends SQLiteOpenHelper {

    public DatabaseHelper(Context context) {
        super(context, DATABASE_NAME, null, 5);
    }

    @Override
    public void onCreate(SQLiteDatabase db) {
        try {
            db.execSQL(CREATE_TABLE_USERS);
            db.execSQL(CREATE_TABLE_FOOD);
        } catch (SQLException e) {

            e.printStackTrace();
        }
    }

    @Override
    public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
        Log.w(DatabaseHelper.class.getName(),
                "Upgrading database from version " + oldVersion
                        + "to version " + newVersion);

        db.execSQL("DROP TABLE IF EXISTS users");
        onCreate(db);

    }

}

public DatabaseAdapter open() throws SQLException {
    database = dbHelper.getWritableDatabase();
    return this;
}

public void close() {
    dbHelper.close();
}

// create a user
public long createUser(String name, String age, String gender,
        String weight, String height, String level, float calnum) {

    ContentValues values = new ContentValues();
    values.put(COLUMN_NAME, name);
    values.put(COLUMN_AGE, age);

    values.put(COLUMN_GENDER, gender);

    values.put(COLUMN_WEIGHT, weight);
    values.put(COLUMN_HEIGHT, height);
    values.put(COLUMN_ACTIVITY, level);
    values.put(COLUMN_CALORIES, calnum);

    return database.insert(TABLE_USERS, COLUMN_ID, values);
}

// delete a user by ID
public boolean deleteUser(long rowId) {
    return database.delete(TABLE_USERS, COLUMN_ID + "=" + rowId, null) > 0;
}

// retrieve a list of all users
public Cursor getAllUsers() {
    return database.query(TABLE_USERS, allColumnsofuserstable, null, null,
            null, null, null);

}

// retrieve a particular user
public Cursor getUser(long rowId) throws SQLException {
    Cursor mCursor = database.query(true, TABLE_USERS,
            allColumnsofuserstable, COLUMN_ID + "=" + rowId, null, null,
            null, null, null);
    if (mCursor != null) {
        mCursor.moveToFirst();
    }
    return mCursor;

}

// update a user
public boolean updateUser(long rowId, String Name, int age, String gender,
        String weight, String height, String level, float calnum) {
    ContentValues values = new ContentValues();
    values.put(COLUMN_NAME, Name);
    values.put(COLUMN_AGE, age);

    values.put(COLUMN_GENDER, gender);

    values.put(COLUMN_WEIGHT, weight);
    values.put(COLUMN_HEIGHT, height);
    values.put(COLUMN_ACTIVITY, level);
    values.put(COLUMN_CALORIES, calnum);
    return database.update(TABLE_USERS, values, COLUMN_ID + "=" + rowId,
            null) > 0;
}


// FOOD METHODS !

//Create a new food row
public long createFood(String name, int food_cal, int food_fat, int food_proteins, int food_carbs){
    ContentValues Fvalues = new ContentValues();
    Fvalues.put(FOOD_NAME, name);
    Fvalues.put(FOOD_CALS, food_cal);
Fvalues.put(FOOD_FAT, food_fat);
    Fvalues.put(FOOD_PRO, food_proteins);
    Fvalues.put(FOOD_CRAB, food_carbs);
    return database.insert(TABLE_FOOD, FOOD_ID, Fvalues);       
}


// delete a Food by ID
public boolean deleteFood(long rowId) {
    return database.delete(TABLE_FOOD, FOOD_ID + "=" + rowId, null) > 0;
}
// retrieve a list of all FOOD
public Cursor getAllfood() {
    return database.query(TABLE_FOOD, allColumnoffoodtable, null, null,
            null, null, null);

}

// Retrieve a specific Food


public Cursor getFood(long rowId) throws SQLException {
    Cursor mCursor = database.query(true, TABLE_FOOD,
            allColumnoffoodtable, FOOD_ID + "=" + rowId, null, null,
            null, null, null);
    if (mCursor != null) {
        mCursor.moveToFirst();
    }
    return mCursor;

}

// Update a food

public boolean updateFood(long rowId,String name, int food_cal, int food_fat, int food_proteins, int food_carbs){
    ContentValues Fvalues = new ContentValues();
    Fvalues.put(FOOD_NAME, name);
    Fvalues.put(FOOD_CALS, food_cal);
Fvalues.put(FOOD_FAT, food_fat);
    Fvalues.put(FOOD_PRO, food_proteins);
    Fvalues.put(FOOD_CRAB, food_carbs);
    return database.update(TABLE_FOOD, Fvalues, FOOD_ID+"="+rowId, null)>0; 
}
}

Answer 1

显然，即使您的查询有效，也会始终显示此Toast消息。你应该尝试类似的东西：

if  (mCursor.moveToFirst()){
         Toast.makeText(LoginActivity.this, "Yaaaay", Toast.LENGTH_LONG).show();
     }else{
         Toast.makeText(LoginActivity.this, "invalid", Toast.LENGTH_LONG).show();
     }

但我想这不是真正的问题，但我没有看到任何其他问题。也许我们需要看看你的DatabaseAdapter类。

Sqlite查询的语法？

1 个答案: