Not able to select multiple gridview items

Question

I have an image gallery app . I can select only a single image at a time right now. But I want to be able to select multiple images and deleting them at a time. I tried some code based on this problem How to do multiselect functionality on grid view items on tap? but I am not sure why it is not working. Any suggestions?

PhotosActivity.java

public class PhotosActivity extends AppCompatActivity {
    int int_position;
    private GridView gridView;
    GridViewAdapter adapter;
    ArrayList<Model_images> al_menu = new ArrayList<>();
    private ArrayList<Integer> mSelected = new ArrayList<Integer>();
    boolean boolean_folder;

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

        final ImageButton button1 = (ImageButton) findViewById(R.id.button1);
        final ImageButton button2 = (ImageButton) findViewById(R.id.button2);
        final ImageButton button3 = (ImageButton) findViewById(R.id.button3);
        final ImageButton button4 = (ImageButton) findViewById(R.id.button4);
        final ImageButton button5 = (ImageButton) findViewById(R.id.button5);
        button1.setVisibility(View.GONE);
        button2.setVisibility(View.GONE);
        button3.setVisibility(View.GONE);
        button4.setVisibility(View.GONE);
        button5.setVisibility(View.GONE);

        gridView = (GridView) findViewById(android.R.id.list);
        int_position = getIntent().getIntExtra("value", 0);
        adapter = new GridViewAdapter(this, al_images, int_position);
        gridView.setAdapter(adapter);

        gridView.setOnItemClickListener(new AdapterView.OnItemClickListener() {
            @Override
            public void onItemClick(AdapterView<?> parent, View view, int position, long id) {
                String abc = "file://" + al_images.get(int_position).getAl_imagepath().get(position);

                Intent i = new Intent(getApplicationContext(), FullImageActivity.class);
                i.putExtra("id", position);
                i.putExtra("folderPosition", int_position);
                i.putExtra("abc", abc);
                startActivity(i);
            }
        });

        gridView.setOnItemLongClickListener(new AdapterView.OnItemLongClickListener() {
            @Override
            public boolean onItemLongClick(AdapterView<?> parent, View view, final int position, long id) {
                Integer position1 = new Integer(position);
                if(mSelected.contains(position1)) {
                    mSelected.remove(position1); // remove item from list
                    // update view (v) state here
                    // eg: remove highlight
                }
                else {
                    mSelected.add(position1); // add item to list
                    // update view (v) state here
                    // eg: add highlight
                }
}

Answer 1

1. Take a field selected in the model class. whenever an item is selected set selected=true and notifyAdapter .

2. in your onBindViewHolder() of adapter if item isSelected change background of the view (dont forget to write the else block ).

3. Also to delete the items maintain a separate list of the objects in the adapter or activity.

In Your Code : I would suggest rather than maintaining positions maintain list of objects . Use the above 2 steps to make change in the view of items when selected . hope it helps.