RecyclerView滚动到位置并获取该视图 [英] RecyclerView scroll to position and get that view
问题描述
我想将列表项自动滚动到回收器视图的顶部（firstVisible项），并在该位置获取视图，以便可以从片段中突出显示它。
所以，这是我的片段代码的要旨：
私人无效activateNewListItem（int position）{
mLayoutManager（）。scrollToPositionWithOffset（position，0）;
RecyclerView.ViewHolder viewHolder = mRecyclerView.findViewHolderForLayoutPosition（position）;
View view = viewHolder.getItemView（）;
view.setBackgroundColor（getResources（）。getColor（R.color.esr_light_grey））;
}
如果职位为 1 ， 2 ， 3 ， 4 等， mRecyclerView.findViewHolderForPosition（位置）返回一个有效的ViewHolder，
，因为我想RecyclerView已经为dataSet中的那些索引绘制了ViewHolders。
但是，如果我通过职位如 25 ， mRecyclerView.findViewHolderForPosition（position）返回null，因为我假设尚未绘制，即使我调用 mLayoutManager.scrollToPositionWithOffset（position，0）在它上面。
我该怎么做才能实现这两件事？
-
将dataSet索引
position的列表项滚动到firstVisibleItem。 / p> -
获取该listItem的View或ViewHolder对象，因此我可以更改背景或其他内容。
不是在其他地方访问ViewHolder，而是在适配器项布局xml文件中使用自定义选择器背景，而是在您的适配器中跟踪位置适配器作为选定位置，并在滚动完成后调用notifydatasetchanged（）/ notifyItemRangeChanged（）使其突出显示。您已经具有scrollToPosition（）方法，并具有滚动侦听器以跟踪滚动状态。
选择器背景示例：item_selector.xml
< ;? xml version = 1.0 encoding = utf-8？>
<选择器xmlns：android =
http://schemas.android.com/apk/res/android\">
< item android：state_activated = true
android：drawable = @ color / primary_dark />
< item android：drawable = @ android：color / transparent />
< / selector>
将其设置为项目xml的背景
< RelativeLayout xmlns：android = http://schemas.android.com/apk/res/android
android：id = @ + id / container_list_item
android：layout_width = match_parent
android：layout_height = match_parent
android：background = @ drawable / item_selector>
< ---您在此处的布局项目--->
< / RelativeLayout>
您的适配器代码：
公共类SampleAdapter扩展了RecyclerView.Adapter< SampleAdapter.ViewHolder> {
私人最终字串[]清单；
private int lastCheckedPosition = -1;
public SampleAdapter（String [] list）{
this.list = list;
}
@Override
public ViewHolder onCreateViewHolder（ViewGroup parent，int viewType）{
View view = View.inflate（parent.getContext（），R.layout .sample_layout，null）；
ViewHolder持有者=新的ViewHolder（view）;
退税持有人；
}
@Override
public void onBindViewHolder（ViewHolderholder，int position）{
holder.choiceName.setText（list [position]）;
holder.containerView.setSelected（position == lastCheckedPosition）;
}
@Override
public int getItemCount（）{
return list.length;
}
公共类ViewHolder扩展了RecyclerView.ViewHolder {
@Bind（R.id.choice_name）
TextView choiceName;
@Bind（R.id。container_list_item）
查看containerView;
public ViewHolder（View itemView）{
super（itemView）;
ButterKnife.bind（this，itemView）;
itemView.setOnClickListener（new View.OnClickListener（）{
@Override
public void onClick（View v）{
lastCheckedPosition = getAdapterPosition（）;
notifyItemRangeChanged（0 ，list.length）;
}
}）；
}
}
}
要滚动到任意位置：
recyclerview.scrollToPosition（position）
让我知道是否有帮助。
I want to auto scroll a list item to top (firstVisible item) in my recycler view and get the view at that position, so I can highlight it, from my fragment.
So, this is the gist of my fragment code :
private void activateNewListItem(int position) {
mLayoutManager().scrollToPositionWithOffset(position, 0);
RecyclerView.ViewHolder viewHolder = mRecyclerView.findViewHolderForLayoutPosition(position);
View view = viewHolder.getItemView();
view.setBackgroundColor(getResources().getColor(R.color.esr_light_grey));
}
If position is 1,2,3,4 etc, mRecyclerView.findViewHolderForPosition(position) returns a valid ViewHolder,
because I guess RecyclerView has drawn ViewHolders for those indexes in dataSet.
However, if I pass in position as say, 25, mRecyclerView.findViewHolderForPosition(position) returns null, because I assume, it hasn't been drawn yet, even thoughI called mLayoutManager.scrollToPositionWithOffset(position, 0) above it.
What can I do to achieve these two things?
Scroll the list item of dataSet index
positionto firstVisibleItem.Get the View or ViewHolder object of that listItem, so I can change the background or whatever.
Instead of accessing ViewHolder somewhere else, go for a custom selector background in your adapters item layout xml file instead, track the position in your adapter as selected position and call notifydatasetchanged()/notifyItemRangeChanged() to highlight it once the scroll is complete. You already have the scrollToPosition() method, have a scroll listener to track the scroll state.
Example for selector background : item_selector.xml
<?xml version="1.0" encoding="utf-8"?>
<selector xmlns:android=
"http://schemas.android.com/apk/res/android">
<item android:state_activated="true"
android:drawable="@color/primary_dark" />
<item android:drawable="@android:color/transparent" />
</selector>
Set it as background to your item xml
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:id="@+id/container_list_item"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:background="@drawable/item_selector">
<--- Your layout items here --->
</RelativeLayout>
Your adapter code :
public class SampleAdapter extends RecyclerView.Adapter<SampleAdapter.ViewHolder> {
private final String[] list;
private int lastCheckedPosition = -1;
public SampleAdapter(String[] list) {
this.list = list;
}
@Override
public ViewHolder onCreateViewHolder(ViewGroup parent, int viewType) {
View view = View.inflate(parent.getContext(), R.layout.sample_layout, null);
ViewHolder holder = new ViewHolder(view);
return holder;
}
@Override
public void onBindViewHolder(ViewHolder holder, int position) {
holder.choiceName.setText(list[position]);
holder.containerView.setSelected(position == lastCheckedPosition);
}
@Override
public int getItemCount() {
return list.length;
}
public class ViewHolder extends RecyclerView.ViewHolder {
@Bind(R.id.choice_name)
TextView choiceName;
@Bind(R.id. container_list_item)
View containerView;
public ViewHolder(View itemView) {
super(itemView);
ButterKnife.bind(this, itemView);
itemView.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
lastCheckedPosition = getAdapterPosition();
notifyItemRangeChanged(0, list.length);
}
});
}
}
}
To scroll to any position :
recyclerview.scrollToPosition(position)
Let me know if this helps.
这篇关于RecyclerView滚动到位置并获取该视图的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！
