Implementing Multi-Type RecyclerView Adapter with Drag-and-Scale Functionality in Android

After reading this article, readers will understand the basic usage of the MultiItem library for implementing a multi‑type RecyclerView adapter with cross‑RecyclerView item dragging and scaling, primarily used for office‑software style panels.

Effect screenshots (images omitted).

Usage – Drag functionality The drag process is handled via an ItemDragHelper and callbacks to ItemDragListener . Example initialization:

@Override
protected void onCreate(Bundle savedInstanceState) {
    // …
    dragHelper = new ItemDragHelper(horizontalRecycler);
    dragHelper.setOnItemDragListener(new OnBaseDragListener());
}
...
public boolean dispatchTouchEvent(MotionEvent ev) {
    return dragHelper.onTouch(ev) || super.dispatchTouchEvent(ev);
}

Register a data source that implements ItemData :

baseItemAdapter.register(TextDragBean.class, new TextViewDragManager());

Start dragging an item:

dragHelper.startDrag(viewHolder);

Implement a drag listener to receive callbacks, e.g., when dragging finishes:

class OnBaseDragListener extends OnItemDragListener {
    @Override
    public void onDragFinish(RecyclerView recyclerView, int itemRecyclerPos, int itemPos) {
        super.onDragFinish(recyclerView, itemRecyclerPos, itemPos);
        String text = String.format("Drag start list %s item %s end list %s item %s\n\nData:%s",
                originalRecyclerPosition, originalItemPosition, itemRecyclerPos, itemPos, dragItemData);
        Toast.makeText(PanelActivity.this, text, Toast.LENGTH_SHORT).show();
    }
}

General item drag control The data source must implement the ItemDrag interface, which defines methods isCanMove() , isCanChangeRecycler() , and isCanDrag() to control moving, switching between RecyclerViews, and enabling drag.

Double‑tap zoom Instantiate ViewScaleHelper and set the content, horizontal and vertical views, then toggle the scale mode:

// Instantiate scaling helper
ViewScaleHelper scaleHelper = new ViewScaleHelper();
scaleHelper.setContentView(contentView);
scaleHelper.setHorizontalView(horizontalRecycler);
scaleHelper.addVerticalView(verticalView);
// Toggle scaling
scaleHelper.toggleScaleModel(); // or startScaleModel()/stopScaleModel()

Other customizations can be achieved by overriding methods in ItemDragListener , such as scale retrieval, move limits, scroll speeds, and floating view drawing.

Main process analysis The implementation follows the logic of Android’s ItemTouchHelper : generate a floating view using WindowManager and ImageView , calculate scrolling for both horizontal and vertical RecyclerViews, compute item position swaps based on touch coordinates, and apply view scaling.

In summary, this is a beta‑level implementation that provides a functional drag‑and‑scale feature for multi‑type RecyclerViews; readers are encouraged to explore the source code for deeper understanding and further refinement.