无法将LinearLayoutManager转换为GridLayoutManager

Question

if (mLayoutManager instanceof GridLayoutManager) {
                        ((GridLayoutManager) mLayoutManager).setSpanSizeLookup(new GridLayoutManager.SpanSizeLookup() {
                            @Override
                            public int getSpanSize(int position) {
                                return listResultAdapter.isHeaderOrFooter(position) ? ((GridLayoutManager) mLayoutManager).getSpanCount() : 1;
                            }
                        });
                    }

上面的代码崩溃了，它说java.lang.ClassCastException: android.support.v7.widget.LinearLayoutManager不能转换为android.support.v7.widget.GridLayoutManager

我发现下面这条线造成了坠机

((GridLayoutManager) mLayoutManager).getSpanCount()

避免崩溃的解决方案是什么？

mLayoutManager被声明为LinearLayoutManager

Answer 1

您还应该在getSpanSize中进行类检查

public int getSpanSize(int position) {
     return mLayoutManager instanceof GridLayoutManager && listResultAdapter.isHeaderOrFooter(position) 
             ? ((GridLayoutManager) mLayoutManager).getSpanCount() : 1;
}