Question

Been struggling with this for a while now. Basically i have extended the application class so that it creates a simple linkedlist in the hope that this list would be accessible across various activities. But for can’t seem to get the information out of the linkedlist when i need it.

I’m not sure if this is even possible (although i don’t see why it wouldn’t) or if I am just making some stupid mistakes when dealing with the linkedlist.

Extending the appllication class (GlobalData)

package com.example.testing;

import java.util.LinkedList;
import android.app.Application;
import android.widget.Toast;

public class GlobalData extends Application {

public static LinkedList<String> EmployeeList;

@Override
public void onCreate(){
    super.onCreate();
    createLinkedList();
}

public void createLinkedList(){
    // create a linked list

    LinkedList<String> EmployeeList = new LinkedList<String>();
    String emp1 ="john", emp2="adam";
    EmployeeList.add(emp1);
    EmployeeList.add(emp2);

    String boo;
     boo = EmployeeList.getFirst();

    //This works, displays the name ok.
    Toast.makeText(getApplicationContext(), "("+boo+")" ,Toast.LENGTH_LONG).show();
}

}

The main where i would like to be able to access the linkedlist.

package com.example.testing;

import android.os.Bundle;
import android.app.Activity;
import android.widget.TextView;
import android.widget.Toast;

public class MainActivity extends Activity {

protected GlobalData globalData;

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

    // Get the application instance
    globalData = (GlobalData)getApplication();  

    String boo;
    boo = GlobalData.EmployeeList.getFirst();

    //This doesn't work & im not sure why.
    Toast.makeText(getApplicationContext(), "("+boo+")" ,Toast.LENGTH_LONG).show();     

}
}

Probably should mention that i’m just getting started with this stuff, so apologies if this is a completely idiotic question.

I can’t understand why I am not able to access the contents of that list, if i modify the script so that the GlobalData class contains a string variable the above code(with a few alterations) works fine. So why would the variable be accessible but the linked list not?

Thanks

Answer 1

In this line you are creating a new instance of the list instead of using the one you’ve created as a member of the class:

LinkedList<String> EmployeeList = new LinkedList<String>();

Simply change this line to :

EmployeeList = new LinkedList<String>();