Wsrtjtyk

I am adding buttons dynamically into a grid view through its adapter. Each button has the following listeners:

• on click listener: at the moment just printing into the console that the button was clicked


• on long click listener: starts a drag event


• on drag listener: handles the drag event
  In the grid adapter, I have an Arraylist<Button> which I add the buttons to it. My getView() method returns the appropriate view from the list.

The first drag and drop event is handled as expected. However, if I click on the buttons after that, they are unresponsive. I have to click ~10 times before all 10 messages get clicked into the console. Even then, I cannot long click on the buttons to drag them.

I followed many tutorials and many other suggestions related to using ViewHolders and inflating views in the getView() method of the BaseAdapter but non actually suits me since I am receiving my data from a database.

Here are my code snippets:

MainActivity.java

@Override

protected void onCreate(Bundle savedInstanceState) {

    super.onCreate(savedInstanceState);

    setContentView(R.layout.activity_main);



    GridView gridView = findViewById(R.id.gridView);

    GridAdapter adapter = new GridAdapter();

    gridView.setAdapter(adapter);



    for(int i = 0; i < 2; i++) {

        final String text = "Hello " + (i + 1);

        Button button = new Button(MainActivity.this);

        button.setText(text);

        adapter.addView(button);



        button.setOnClickListener(new View.OnClickListener() {

            @Override

            public void onClick(View v) {

                Log.d("TAG", "Button " + text + " pressed");

            }

        });



        button.setOnLongClickListener(new View.OnLongClickListener() {

            @Override

            public boolean onLongClick(View v) {

                View.DragShadowBuilder myShadow = new View.DragShadowBuilder(v);

                v.startDrag(null, myShadow, v, 0);

                return true;

            }

        });



        button.setOnDragListener(new DragEventListener());

        button.setTag("1" + i);

    }

}

DragEventListener.java

private class DragEventListener implements View.OnDragListener {

    @Override

    public boolean onDrag(View v, DragEvent event) {

        final int action = event.getAction();



        switch(action) {

            case DragEvent.ACTION_DRAG_STARTED:

                return v instanceof Button;

            case DragEvent.ACTION_DRAG_ENTERED:

                v.setVisibility(View.INVISIBLE);

                return true;

            case DragEvent.ACTION_DRAG_LOCATION:

                return true;

            case DragEvent.ACTION_DRAG_EXITED:

                v.setVisibility(View.VISIBLE);

                return true;

            case DragEvent.ACTION_DROP:

                if(event.getLocalState() == v) {

                    return false;

                }



                // this is the actual view being dropped

                View itemBeingDragged = (View) event.getLocalState();

                GridView itemsParent = (GridView) itemBeingDragged.getParent();



                GridAdapter adapter = (GridAdapter) itemsParent.getAdapter();

                adapter.swap(itemBeingDragged, v);



                return true;

            case DragEvent.ACTION_DRAG_ENDED:

                v.setVisibility(View.VISIBLE);

                return true;

        }

        return true;

    }

}

And finally the GridAdapter.java

public class GridAdapter extends BaseAdapter {

    private volatile ArrayList<View> children = new ArrayList<>();



    public void addView(View view) {

        children.add(view);

        notifyDataSetChanged();

    }



    public void swap(View v1, View v2){

        int indexOfV1 = children.indexOf(v1);

        int indexOfV2 = children.indexOf(v2);

        Collections.swap(children, indexOfV1, indexOfV2);

        notifyDataSetChanged();

    }



    @Override

    public int getCount() {

        return children.size();

    }



    @Override

    public Object getItem(int position) {

        return children.get(position);

    }



    @Override

    public long getItemId(int position) {

        return 0;

    }



    // create a new ImageView for each item referenced by the Adapter

    @Override

    public View getView(int position, View convertView, ViewGroup parent) {

        return children.get(position);

    }

}

Any idea what might be happening? I used to get an exception after some number of long clicks related to NPE but I am unable to reproduce it now to show the exception unfortunately.

I appreciate any help.