StackOverflowError when using touchExpansion

• I have searched existing issues and this is not a duplicate

Issues and Steps to Reproduce

I need to add a recyclerView in the toolbar of my activity, and I cannot call setContentView() with the LithoView. Currently, I’m trying to add the generated LithoView as a sub child to an existing LinearLayout. However, this sends the renderer into an infinite number of recursive calls and overflows the stack.

Expected Behavior

I expect the LinearLayout to add the LithoView as a child.

Link to Code

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

        Toolbar toolbar = (Toolbar) findViewById(R.id.toolbar);
        setSupportActionBar(toolbar);

        LinearLayout layout = toolbar.findViewById(R.id.tagLinearLayout);
        final ComponentContext context = new ComponentContext(this);
        RecyclerBinder binder = new RecyclerBinder(context, new LinearLayoutInfo(this,
            LinearLayout.HORIZONTAL, true));
        final Component component = Recycler.create(context)
                .binder(binder)
                .build();
        layout.addView(LithoView.create(context, component));
    }

[yuntao]

I work with @vinc3m1 and did some investigation into this issue.

This touch expansion related StackOverflowError (SOE) can be reproduced at both Litho layer and plain Android view layer. When touch expansion is set on any root Litho component, this logic propagates down to Android view layer and triggers a programmatically possible infinite loop condition in TouchDelegates and causes the SOE.

At Litho layer, the SOE can be triggered by setting touchExpansionDip and clickHandler on any root component. For example, both layout specs below produce the SOE when set as the root component to a LithoView:

@LayoutSpec
public class ColumnItemSpec {
  @OnCreateLayout
  static Component onCreateLayout(ComponentContext c) {
    return Column.create(c)
        .touchExpansionDip(ALL, 24)
        .clickHandler(ColumnItem.onClick(c))
        .build();
  }
  @OnEvent(ClickEvent.class)
  static void onClick(ComponentContext c, @FromEvent View view) {
  }
}

@LayoutSpec
public class TextItemSpec {
  @OnCreateLayout
  static Component onCreateLayout(ComponentContext c) {
    return Text.create(c)
        .text("Hello world")
        .touchExpansionDip(ALL, 24)
        .clickHandler(TextItem.onClick(c))
        .build();
  }
  @OnEvent(ClickEvent.class)
  static void onClick(ComponentContext c, @FromEvent View view) {
  }
}

At plain Android view layer, touch expansion is achieved by using a TouchDelegate in between a parent view group and a child view. It is programmatically possible to set a view’s TouchDelegate to delegate to itself, as seen below. This causes an infinite loop of forwarding touch event to the view itself and thus the SOE.

View anyView = findViewById(R.id.any_view);
anyView.post(new Runnable() {
    @Override
    public void run() {
        Rect expandRect = new Rect();
        anyView.getHitRect(expandRect);
        expandRect.left -= 100;
        expandRect.top -= 100;
        expandRect.right += 100;
        expandRect.bottom += 100;
        anyView.setTouchDelegate(new TouchDelegate(expandRect, anyView));
        // Correct way is to set touch expansion on containing child view:
        // anyView.setTouchDelegate(new TouchDelegate(expandRect, childView));
    }
});

Suggestions on what could be done as fixes:

1. Update Litho docs on touch expansion to indicate that touch expansion should not be set on the root component and will not work. If touch expansion is desired on the root LithoView, then android.view.TouchDelegate should be used instead and the parent view group is also needed.

2. Apply fix to ComponentHost class where we handle touch expansion to skip when the touch expansion is being set on a LithoView itself:

void maybeRegisterTouchExpansion(int index, MountItem mountItem) {  
    if (this == MountItem.getContent()) {
        return;
    }
    ...
}

void maybeUnregisterTouchExpansion(int index, MountItem mountItem) {
    if (this == MountItem.getContent()) {
        return;
    }
    ...
}

[sushshring]

It seems I found the root cause of this. When touched, it did not seem to like the touchExpansion option at all. I don’t understand why that is the issue, but once I got rid of that it renders just fine now.