为啥要联动?快速定位方便选择,常见有新闻啊,外卖菜单啊。
右边的数据源格式
[
{
name:'分类1'
isType: true
},
{
name:'商品1'
isType: false
},
{
name:'商品2'
isType: false
},
{
name:'商品3'
isType: false
},
{
name:'分类2'
isType: true
},
{
name:'商品4'
isType: false
},
{
name:'商品5'
isType: false
},
...
]
左边RecyclerView 点击的监听
categoryAdapter.setListener(new HomeCategoryAdapter.OnItemClickListener() {
@Override
public void clicked(LzFoodType foodType, int position) {
categoryAdapter.setSelectedPos(position);
clickMenu = true;
int p = 0;
for (int i=0; i < foodAdapter.list.size(); i++) {
LzFood fo = foodAdapter.list.get(i);
if (fo.getName().equals(foodType.getName())) {
p = i;
break;
}
}
int first = layoutManagerFood.findFirstVisibleItemPosition();
int last = layoutManagerFood.findLastVisibleItemPosition();
if (p <= first) {
recyclerList.smoothScrollToPosition(p);
Log.d("lxf", ">>>>> 1 <<<<<<<");
} else if (p <= last) {
int top = recyclerList.getChildAt(p - first).getTop();
recyclerList.smoothScrollBy(0, top);
Log.d("lxf", ">>>>> 2 <<<<<<<");
} else {
recyclerList.scrollToPosition(p);
new Handler().postDelayed(new Runnable() {
@Override
public void run() {
int first2 = layoutManagerFood.findFirstVisibleItemPosition();
int last2 = layoutManagerFood.findLastVisibleItemPosition();
if (recyclerList.getChildAt(last2-first2) != null) {
int top = recyclerList.getChildAt(last2 - first2).getTop();
recyclerList.smoothScrollBy(0, top);
}
}
}, 50);
Log.d("lxf", ">>>>> 3 <<<<<<<");
}
}
});
右边列表 滚动监听
recyclerList.addOnScrollListener(new RecyclerView.OnScrollListener() {
@Override
public void onScrollStateChanged(@NonNull RecyclerView recyclerView, int newState) {
super.onScrollStateChanged(recyclerView, newState);
if (newState == RecyclerView.SCROLL_STATE_DRAGGING) {
clickMenu = false;
}
}
@Override
public void onScrolled(@NonNull RecyclerView recyclerView, int dx, int dy) {
super.onScrolled(recyclerView, dx, dy);
if (!clickMenu) {
int first = layoutManagerFood.findFirstVisibleItemPosition();
changeMenuSelected(first);
}
}
});
右边列表滚动时,对左边修改
通过右边列表显示的第一个可见item,来改变左边菜单
使用倒序遍历,总能找一个 isType 为 true 的 model
private void changeMenuSelected(int first){
int now = first;
LzFood food = null;
for (int i=first; i>=0; i--) {
LzFood f = foodAdapter.list.get(i);
if (f.isType){
now = i;
food = f;
break;
}
}
if (food == null) return;
for (int i=0; i<categoryAdapter.list.size(); i++) {
LzFoodType ft = categoryAdapter.list.get(i);
if (ft.getName().equals(food.getName())){
now = i;
break;
}
}
//notifyDataSetChanged() 在set中
categoryAdapter.setSelectedPos(now);
recyclerMenu.smoothScrollToPosition(now);
}
联动标记
标记是用户手动滚动列表,还是点击左边菜单滚动右边
private boolean clickMenu = false;
关于如何设置组头悬浮
由于未使用 ItemDecoration,所以可以使用 组头 的布局相对 recyclerView进行布局,然后修改内容即可。。。。