Passing an arraylist from an activity to a java class in Android

Question

I have an arraylist in MainActivity and I have a java class which is not an acitivity . How can i pass this arraylist to this class ? My arraylist:

public List<String>  types = new ArrayList<String>();

and i filled in MainAcitivity. then i have to use in a java class which is name ExpandableListAdapter. Here is part of the java class which i have to do change in it and i tried to create new activity object but it didn't work.

public class ExpandableListAdapter extends BaseExpandableListAdapter {


 public View getChildView(int groupPosition, final int childPosition,
        boolean isLastChild, View convertView, ViewGroup parent) {

     MainActivity m=new MainActivity();

    Integer[]  mIcons = {R.drawable.car_1,R.drawable.car_2,R.drawable.car_3,R.drawable.car_4,R.drawable.car_5,R.drawable.car_6,R.drawable.car_7,R.drawable.car_8,R.drawable.car_9,R.drawable.car_10}

    Integer[] mIcons_2 = new Integer [m.types.size()];

    for(int i=0; i<m.types.size(); i++){

    mIcons_2[i]= mIcons[ Integer.parseInt(m.types.get(i))];



}



    final String childText = (String) getChild(groupPosition, childPosition);

    if (convertView == null) {
        LayoutInflater infalInflater = (LayoutInflater) this._context
                .getSystemService(Context.LAYOUT_INFLATER_SERVICE);
        convertView = infalInflater.inflate(R.layout.drawer_list_item, null);
    }

    ImageView iconn =(ImageView)convertView.findViewById(R.id.thumbNail);

    iconn.setImageResource(mIcons_2[childPosition]);


  TextView txtListChild = (TextView) convertView
            .findViewById(R.id.textView);

    txtListChild.setTextColor(Color.BLUE);

  txtListChild.setText(childText);
    return convertView;
}

I created a navigation drawer with an expandable listview also i try to put different icons on every item. This ExpandableListAdapter class is about that but my problem is about how can i pass the types ArrayList from the MainActivity to the ExpandableListAdapter java class? I know that using intent works when pass the values one activity to other activity but i didn't know about passing one activity to a java class.

Answer 1

Pass it using the constructor as follows:

public class ExpandableListAdapter extends BaseExpandableListAdapter {
    private final List<String> typesList;

    public ExpandableListAdapter(List<String> typesList) {
        this.typesList = typesList;
    }
    ...
    ...
}

Alternatively, you can also use a setter like:

public class ExpandableListAdapter extends BaseExpandableListAdapter {
    private List<String> typesList;

    public void setTypesList(List<String> typesList) {
        this.typesList = typesList;
    }
    ...
    ...
}

Then you can set the types anytime by calling adapter.setTypesList()

Answer 2

Declare a List in your adapter class

// Declaration :

 public List<String> list = new ArrayList<String>();

Constructor will help you to pass the arraylist as params.

 ExpandableListAdapter(List<String>  types){
 this.list = types
 }

You can pass the arraylist as follows :

  new ExpandableListAdapter(types);

Answer 3

I will suggest you to call the constructor of the non activity class having an array List as its parameter Lets suppose my Non-Activity class be Class B

B obj=new B(Activity context,types);

And don't forget to declare the same constructor in B class