How to use backbutton to unselect all item in gridview?

Question

i'm using backbutton as interface from activity but it's not working properly for me because on backpress showing 0 size of arraylist

// here is the activity class from where i'm getting backbutton interface..

 public class Multiple_Images extends AppCompatActivity {


@Override
public void onBackPressed() {
        if(twice ==true){

         Intent intent =new Intent(this,MainActivity.class);
          startActivity(intent);
                           }ImageAdapter imageAdapter =new ImageAdapter(this);
      imageAdapter.onBackPress();
  Toast.makeText(this, "Press twice", Toast.LENGTH_SHORT).show();
    twice =true;
    new Handler().postDelayed(new Runnable() {
        @Override
        public void run() {

            twice =false; }   }, 2000); }}

//here is the adapter class here i'm using backbutton

public class ImageAdapter extends BaseAdapter implements onBackPressListener {
    ArrayList<String> selectedArraylist ;
    @Override
    public boolean onBackPress() {

        selectedArraylist.clear();

        Toast.makeText(context, "All values unselected", Toast.LENGTH_SHORT).show();

        return true;
    }

    @Override
    public View getView(int i, View view, ViewGroup viewGroup) {
        urimodel=new ArrayList<>();

        final ImageView imageGrid ;
        Activity activity = (Activity) context;
        actionMode = activity.startActionMode(new Actionmode());

        final GridModel gridModel=(GridModel) this.getItem(i);

        if(view==null) {
            view = LayoutInflater.from(context).inflate(R.layout.model, null);
            selectedArraylist    =new ArrayList<>();
        }

        final CardView cardView=   (CardView)view.findViewById(R.id.cardview_image);
        imageGrid = (ImageView) view.findViewById(R.id.grid_image);
        //   gridText = (TextView) view.findViewById(R.id.grid_text);

        imageGrid.setScaleType(ImageView.ScaleType.CENTER_CROP);
        //  imageGrid.setScaleType(ImageView.ScaleType.CENTER_CROP);

        Picasso.get().load(gridModel.getImage()).resize(200,200).into(imageGrid);

        if (selectedArraylist.contains(gridModel.getImage_text())) {

            cardView.setCardBackgroundColor(CARD_SELECTED_COLOR);

        }else {

            cardView.setCardBackgroundColor(Color.WHITE);
        }
        return view;
    }
}

Answer 1

Simply you can do this inside onBackPressed

@Override
public void onBackPressed() {

    if (twice == true) {

        super.onBackPressed(); //this backs to the previous activity, if you want to stay with Intent, add finish() after startActivity()
        return;
    } else {

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

            if (gridView.isItemChecked(i)) {

                gridView.setItemChecked(i, false);
            }
        }
        //selectedArraylist.clear(); this is clearing your array of selected items
    }
    twice = true;
    new Handler().postDelayed(new Runnable() {
        @Override
        public void run() {

            twice = false;
        }
    }, 2000);
}

I don't know, why did you put selectedArraylist =new ArrayList<>(); in adapter getView() method. getView() is fired every time, when a new list item is inflated, that mean every time, when you are changing adapters source, scrolling list this method is called, and every time you are initialize you array, and all data inside lost. You should treat an adapter class just like a tool for displaying items, and all actions like above make outside adapter.

Answer 2

pretty much easy, I give you my own project code, hope it help you.

StudentFragment.java:

private void MultiSelected_Student(int position) {
    Student data = adapter_class.getItem(position);
    if (data != null) {
        if (selectedIds.contains(data)) selectedIds.remove(data);
        else selectedIds.add(data);
    }
}

private void Remove_MultiSelected() {
    try {
        selectedIds.clear();
    } catch (Exception e) {
        e.printStackTrace();
    }
}

public void Group_UnSelect() {
    Remove_MultiSelected();
    MultiSelected = false;
    fab.setVisibility(View.GONE);
    homeeActivity.studentsMultiSelect = false;
    notifyy();
}

private void notifyy() {
    adapter_class.notifyDataSetChanged();
}

HomeActivity.java:

public boolean studentsMultiSelect = false;

@Override
public void onBackPressed() {
    if (studentsMultiSelect) {
        studentFragment.Group_UnSelect();
    } else {
        super.onBackPressed();
    }
}