Getter and Setters not working?

问题

I've got two classes right now: RemindersDAO.java and ViewLocalReminders.java.

I'm trying to get access to a variable that's in ViewLocalReminders.java and I'm trying to call it from RemindersDAO.java. I'm doing this by using the getter/setter method combo. However, for some reason, my variable value keeps getting set to 0 in the getter method. Here's the code:

ViewLocalReminders.java

public class ViewLocalReminders extends SherlockListActivity {

private long reminderID;

    public void onCreate(Bundle SavedInstance) {

    reminderID = 16;
    setReminderID(reminderID);      

    }

    public void setReminderID(long id) {
        id = reminderID;
        System.out.println("Reminder ID Value in Setter: " + reminderID);
    }

    public long getReminderID() {
        return reminderID;
        System.out.println("Reminder ID Value in Getter: " + reminderID);
    }

}

RemindersDAO.java

public class RemindersDAO extends SQLiteOpenHelper {

    @SuppressWarnings("deprecation")
    public Cursor getRowByID(Activity activity) {
    String[] from = { _ID, NAME };

    ViewLocalReminders viewLocalReminders = new ViewLocalReminders();
    long reminderID = viewLocalReminders.getReminderID();
    System.out.println("Value of Reminder ID in RemindersDAO: " + reminderID);

    }

}

This is the output that I'm getting for all my System.out.printlns:

Reminder ID Value in Setter: 16
Reminder ID Value in Getter: 0
Reminder ID Value in RemindersDAO: 0

So obviously, something's happening between the setter and getter methods. The value of reminderID is 16 in the setter method, the way it should be. However, the value goes to 0 in the getter method. Consequently, the value is still 0 when I call the getter method in RemindersDAO.java. What am I doing wrong here? Thanks for your help! :)

回答1:

here:

public void setReminderID(long id) {
    id = reminderID;  //<-- wrong, should be the other way around
    System.out.println("Reminder ID Value in Setter: " + reminderID);
}

You should use reminderID = id instead

Also:

public void onCreate(Bundle SavedInstance) {

    reminderID = 16;           //one of these two lines..
    setReminderID(reminderID); //..should do it      

}

No need to set the reminderId twice

回答2:

Your setter should look like this:

 public void setReminderID(long id) {
    reminderID = id;
    System.out.println("Reminder ID Value in Setter: " + reminderID);
}

Your remainderID variable should be on the left. The way you had it written, id was being set to reminderID.

Also, in your getter:

public long getReminderID() {
    return reminderID;
    System.out.println("Reminder ID Value in Getter: " + reminderID);
}

Since the System.out.println is after the return, then you shouldn't ever see the output. Return will end the function right there.

回答3:

you have

id = remainderID;

it should be

 remainderID = id;

回答4:

You're assignment of the reminder id is backwards

id = reminderID;

should read

reminderID = id;

in you setReminderID method

回答5:

public void setReminderID(long id) {
    this.reminderID = id;
    System.out.println("Reminder ID Value in Setter: " + reminderID);
}

回答6:

try using this

this.remainderId = id;

instead of

remainderId = id;

in your model or domain.

回答7:

Your setter method seems wrong. You need to use your IDE's auto generation to create these methods.

回答8:

I see that you accepted the answer. However, I think I know the problem about your getter-setter bug. It's about the order and order matters...it's like you're giving the instruction step-by-step.

Let me explain...

The first one, your setter method, did a mistake. (See marked comment/s)

public void setReminderID(long id) {
        id = reminderID; // --> your argument is id. reminderId field value should be changed not the other way around.
        System.out.println("Reminder ID Value in Setter: " + reminderID);
    }

Here's the correct setter.

public void setReminderID(long id) {
    reminderID = id; // --> "id" is your parameter and that's the reminderID's new value.
    System.out.println("Reminder ID Value in Setter: " + reminderID);
}

Next, about the getter. The reason why there's a bug in getter is because you have a wrong order. (See marked comment/s)

public long getReminderID() {
    return reminderID;
    System.out.println("Reminder ID Value in Getter: " + reminderID); // --> putting this line code after "return" results an error and therefore you won't be able to obtain a number or value!
}

Here's the correct getter. Look carefully the difference.

public long getReminderID() {
    System.out.println("Reminder ID Value in Getter: " + reminderID); // --> Anycode before "return" value will be fine.
    return reminderID; // --> Always put the "return" value at the last line within a getter method.
}

I hope you can use this correction for your future project in case whenever you need to apply the getter-setter method when you're programming. Remember that it's very important because ordering of the code matters and know where you direct the value changes. Questions?

回答9:

Thanks for all your help you guys. I wasn't able to figure out why my getters and setters weren't working, even though I followed all of your guys' suggestions. I'm guessing it has something to do with the fact that reminderID is taken in as an argument of a constructor. Either way, I solved my problem by using Android's Bundle and transferring my variables from one activity to another through that.

Again, thanks for all your help! :)

来源：https://stackoverflow.com/questions/12593490/getter-and-setters-not-working

标签

java

android

getter-setter