Set Drag Listener on SpannableString

Question

Im trying to set an OnDragListener to certain words of a TextView using SpannableString. Im able to add an OnClick Listener by using ClickableSpan

by doing

hashText.setSpan(new ClickableSpan() {

So I figured I would try the same but replace ClickableSpan with OnDragListener.

I'm able to read the different drag events, but I have not been able to isolate the drag events to the specific words I choose, as Im able to do with ClickableSpan.

hashText.setSpan(new View.OnDragListener() {
            @Override
            public boolean onDrag(View targetView, DragEvent event) {
              int action = event.getAction();
              TextView targetVariable = (TextView) targetView;
              String textGetter;
              textGetter = targetVariable.getText().toString();
              // boolean actionDropOutside = (DragEvent.ACTION_DRAG_ENDED != DragEvent.ACTION_DROP);
              switch (event.getAction()) {
                case DragEvent.ACTION_DRAG_STARTED:


                  Log.d(TAG, "DRAG STARTED");
                  break;
                case DragEvent.ACTION_DRAG_ENTERED:

                  ////create method that checks if text is empty if so lights up
                  //if (textGetter.equals("")) {
                    targetView.setBackgroundColor(CARD_SLECTED);
                    //lightupVariableCard(cardV);
                    Log.d(TAG, "DRAG ENTERED EMPTY TEXT");
                  //}

                  Log.d(TAG, "DRAG ENTERED" + targetVariable.getText().toString());
                  break;
                case DragEvent.ACTION_DRAG_EXITED:
                  targetView.setBackgroundColor(CARD_UNSLECTED);
                  Log.d(TAG, "DRAG EXITED");
                  break;

                case DragEvent.ACTION_DROP:
                  // Dropped, reassign View to ViewGroup
                  //if (textGetter.equals("")) {
                    TextView draggedView = (TextView) event.getLocalState();
                    ViewGroup owner = (ViewGroup) draggedView.getParent();
                    targetVariable.setText(draggedView.getText());
                    owner.setVisibility(View.INVISIBLE);
                    targetView.setBackgroundColor(CARD_UNSLECTED);
                    //fabDisplayCounter++;
                    //displayFab();
                    Log.d(TAG, "DRAG DROPPED");
                  //}
                  Log.d(TAG, "DRAG NOT POSSSIBLE HERE");
                  break;
                case DragEvent.ACTION_DRAG_ENDED:
//                if (actionDropOutside == true){
//                    Log.d(TAG, "DRAG DROPPED OUTSIDE TRUE");
//                }
                  Log.d(TAG, "DRAG ENDED");
                  //default:

              }
              return true;
            }


          }, matcher.start(), matcher.end(), i);
          the_question.setText(hashText);
          the_question.setMovementMethod(LinkMovementMethod.getInstance());
          //the_question.setOnDragListener(new MyDragListener(hashText.nextSpanTransition()));

Answer 1

I'm not a big expert in this field, never had to dig it out. But since you have no replies I try to give you some hint / direction.

I think what you need is a custom MovementMethod.

The android platform MovementMethod are managed here inside this package: https://github.com/android/platform_frameworks_base/tree/master/core/java/android/text/method

Specifically this interface: https://github.com/android/platform_frameworks_base/blob/master/core/java/android/text/method/MovementMethod.java

As you see it has a onTouchEvent() method.

ClickableSpan has an onClick method, but it only works because there's a LinkMovementMethod handling the touch events, looking for ClickableSpan and issuing the onClick() on them.

See: https://github.com/android/platform_frameworks_base/blob/master/core/java/android/text/method/LinkMovementMethod.java

which extend: https://github.com/android/platform_frameworks_base/blob/master/core/java/android/text/method/ScrollingMovementMethod.java

which extend https://github.com/android/platform_frameworks_base/blob/master/core/java/android/text/method/BaseMovementMethod.java

but this last is not really related with touches.

ScrollingMovementMethod use the class Touch to delegate the touch event handling, you can see this class here: https://github.com/android/platform_frameworks_base/blob/master/core/java/android/text/method/Touch.java

Looking at the code very quickly I think you can extend the LinkMovementMethod and add the drag detection there. Then create a new Span type for the Drag and call the dragging methods inside it.

I know I did not gave you a solution but I hope I pointed you in the right direction.