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;
                            }
                        });
                    }

上面的代码崩溃说 java.lang.ClassCastException: android.support.v7.widget.LinearLayoutManager cannot be cast to android.support.v7.widget.GridLayoutManager

我发现下面一行导致了崩溃

((GridLayoutManager) mLayoutManager).getSpanCount()

避免崩溃的解决方案是什么

mLayoutManager 声明为 LinearLayoutManager

Answer 1

您还应该在 getSpanSize:

中进行 class 检查

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