[移动开发]RecylcerView getItemViewType position一直是0

记录一下：
https://blog.csdn.net/qq_26075861/article/details/86685293
在RecyclerView外层套上一层RelativeLayout即可

https://blog.csdn.net/Moonlighting_/article/details/52385267
@Override
protected void onMeasure(int widthSpec, int heightSpec) {
int expandSpec = MeasureSpec.makeMeasureSpec(Integer.MAX_VALUE >> 2, MeasureSpec.AT_MOST);
super.onMeasure(widthSpec, expandSpec);
}

https://blog.csdn.net/the_spring/article/details/54236996
1.getItemCount()返回值<=0 ;
2.设置LayoutManager ;
3.被ScrollView嵌套
ok重点说一下第三点
recyclerview 25可以被scrollview嵌套，可以正常显示
recyclerview 23被scrollview嵌套时，无法正常显示

getItemCount()返回值<=0 ;肯定是对的。其他几个没有验证。
我再来补充一种情况：
由于我们经常会使用开源的第三方的RecycleView，并且我们可能还会把他的代码抄下来：
于是：

 @Override
        public int getItemViewType(int position) {
            if (isRefreshHeader(position)) {
                return TYPE_REFRESH_HEADER;
            }

            if (isLoadMoreFooter(position)) {
                return TYPE_LOAD_MORE_FOOTER;
            }
            int adjPosition = position - 1;
            int adapterCount;
            if (adapter != null) {
                adapterCount = adapter.getItemCount();
                if (adjPosition < adapterCount) {
                    int type = adapter.getItemViewType(adjPosition);
                    if (isReservedItemViewType(type)) {
                        throw new IllegalStateException("PullToRefreshRecyclerView require itemViewType in adapter should be less than 10000 ");
                    }
                    return type;
                }
            }
            return 0;
        }

比如PullRecyclerView的代码中，你的Adpater是被他wrap了一层的。
由于他默认认为有header，所以position固定-1。
这个问题，如果你遇到了类似的问题也可以往别人的源码中查一下。

https://my.oschina.net/caomenglong/blog/747197
https://github.com/amardeshbd/android-recycler-view-wrap-content


<android.support.v7.widget.RecyclerView
android:id="@+id/my_recycler_view"
android:layout_width=“match_parent”
android:layout_height=“wrap_content”
tools:listitem="@layout/row_list_item">

        </android.support.v7.widget.RecyclerView>

    </RelativeLayout>

mRecyclerView.setHasFixedSize(true);

    // use a linear layout manager
    mLayoutManager = new LinearLayoutManager(getContext());
    mLayoutManager.setOrientation(LinearLayoutManager.VERTICAL);
    mRecyclerView.setLayoutManager(mLayoutManager);

    // Disabled nested scrolling since Parent scrollview will scroll the content.
    mRecyclerView.setNestedScrollingEnabled(false);

    // specify an adapter (see also next example)
    mAdapter = new SimpleListAdapter(DataSetProvider.generateDataset());
    mRecyclerView.setAdapter(mAdapter);