使用RecyclerView创建动态列表:
当我们创建一个RecyclerView时。适配器我们必须指定ViewHolder，它将绑定到适配器。
public class MyAdapter extends RecyclerView.Adapter<MyAdapter.ViewHolder> {
private String[] mDataset;
public MyAdapter(String[] myDataset) {
mDataset = myDataset;
}
public static class ViewHolder extends RecyclerView.ViewHolder {
public TextView mTextView;
public ViewHolder(TextView v) {
super(v);
mTextView = v;
}
}
@Override
public MyAdapter.ViewHolder onCreateViewHolder(ViewGroup parent, int viewType) {
View v = LayoutInflater.from(parent.getContext()).inflate(R.layout.some_layout, parent, false);
//findViewById...
ViewHolder vh = new ViewHolder(v);
return vh;
}
@Override
public void onBindViewHolder(ViewHolder holder, int position) {
holder.mTextView.setText(mDataset[position]);
}
@Override
public int getItemCount() {
return mDataset.length;
}
}
有可能创建多个视图类型的RecyclerView吗?
我是这样做的。我传递了“fragmentType”，并创建了两个ViewHolders，在此基础上，我在一个适配器中相应地分类了我的布局，可以有不同的布局和布局管理器
private Context mContext;
protected IOnLoyaltyCardCategoriesItemClicked mListener;
private String fragmentType;
private View view;
public LoyaltyCardsCategoriesRecyclerViewAdapter(Context context, IOnLoyaltyCardCategoriesItemClicked itemListener, String fragmentType) {
this.mContext = context;
this.mListener = itemListener;
this.fragmentType = fragmentType;
}
public class LoyaltyCardCategoriesFragmentViewHolder extends RecyclerView.ViewHolder implements View.OnClickListener {
private ImageView lc_categories_iv;
private TextView lc_categories_name_tv;
private int pos;
public LoyaltyCardCategoriesFragmentViewHolder(View v) {
super(v);
view.setOnClickListener(this);
lc_categories_iv = (ImageView) v.findViewById(R.id.lc_categories_iv);
lc_categories_name_tv = (TextView) v.findViewById(R.id.lc_categories_name_tv);
}
public void setData(int pos) {
this.pos = pos;
lc_categories_iv.setImageResource(R.mipmap.ic_launcher);
lc_categories_name_tv.setText("Loyalty Card Categories");
}
@Override
public void onClick(View view) {
if (mListener != null) {
mListener.onLoyaltyCardCategoriesItemClicked(pos);
}
}
}
public class MyLoyaltyCardsFragmentTagViewHolder extends RecyclerView.ViewHolder implements View.OnClickListener {
public ImageButton lc_categories_btn;
private int pos;
public MyLoyaltyCardsFragmentTagViewHolder(View v) {
super(v);
lc_categories_btn = (ImageButton) v.findViewById(R.id.lc_categories_btn);
lc_categories_btn.setOnClickListener(this);
}
public void setData(int pos) {
this.pos = pos;
lc_categories_btn.setImageResource(R.mipmap.ic_launcher);
}
@Override
public void onClick(View view) {
if (mListener != null) {
mListener.onLoyaltyCardCategoriesItemClicked(pos);
}
}
}
@NonNull
@Override
public RecyclerView.ViewHolder onCreateViewHolder(ViewGroup parent, int viewType) {
if (fragmentType.equalsIgnoreCase(Constants.LoyaltyCardCategoriesFragmentTag)) {
view = LayoutInflater.from(mContext).inflate(R.layout.loyalty_cards_categories_frag_item, parent, false);
return new LoyaltyCardCategoriesFragmentViewHolder(view);
} else if (fragmentType.equalsIgnoreCase(Constants.MyLoyaltyCardsFragmentTag)) {
view = LayoutInflater.from(mContext).inflate(R.layout.my_loyalty_cards_categories_frag_item, parent, false);
return new MyLoyaltyCardsFragmentTagViewHolder(view);
} else {
return null;
}
}
@Override
public void onBindViewHolder(@NonNull RecyclerView.ViewHolder holder, int position) {
if (fragmentType.equalsIgnoreCase(Constants.LoyaltyCardCategoriesFragmentTag)) {
((LoyaltyCardCategoriesFragmentViewHolder) holder).setData(position);
} else if (fragmentType.equalsIgnoreCase(Constants.MyLoyaltyCardsFragmentTag)) {
((MyLoyaltyCardsFragmentTagViewHolder) holder).setData(position);
}
}
@Override
public int getItemCount() {
return 7;
}
下面的代码不是伪代码。我已经测试过了，它对我很有效。
我想在我的recyclerview中创建一个headerview，然后在用户可以点击的标题下面显示一个图片列表。
我在我的代码中使用了一些开关，不知道这是否是最有效的方法，所以请随意给出您的评论:
public class ViewHolder extends RecyclerView.ViewHolder{
//These are the general elements in the RecyclerView
public TextView place;
public ImageView pics;
//This is the Header on the Recycler (viewType = 0)
public TextView name, description;
//This constructor would switch what to findViewBy according to the type of viewType
public ViewHolder(View v, int viewType) {
super(v);
if (viewType == 0) {
name = (TextView) v.findViewById(R.id.name);
decsription = (TextView) v.findViewById(R.id.description);
} else if (viewType == 1) {
place = (TextView) v.findViewById(R.id.place);
pics = (ImageView) v.findViewById(R.id.pics);
}
}
}
@Override
public ViewHolder onCreateViewHolder(ViewGroup parent,
int viewType)
{
View v;
ViewHolder vh;
// create a new view
switch (viewType) {
case 0: //This would be the header view in my Recycler
v = LayoutInflater.from(parent.getContext())
.inflate(R.layout.recyclerview_welcome, parent, false);
vh = new ViewHolder(v,viewType);
return vh;
default: //This would be the normal list with the pictures of the places in the world
v = LayoutInflater.from(parent.getContext())
.inflate(R.layout.recyclerview_picture, parent, false);
vh = new ViewHolder(v, viewType);
v.setOnClickListener(new View.OnClickListener(){
@Override
public void onClick(View v) {
Intent intent = new Intent(mContext, nextActivity.class);
intent.putExtra("ListNo",mRecyclerView.getChildPosition(v));
mContext.startActivity(intent);
}
});
return vh;
}
}
//Overridden so that I can display custom rows in the recyclerview
@Override
public int getItemViewType(int position) {
int viewType = 1; //Default is 1
if (position == 0) viewType = 0; //If zero, it will be a header view
return viewType;
}
@Override
public void onBindViewHolder(ViewHolder holder, int position) {
//position == 0 means it's the info header view on the Recycler
if (position == 0) {
holder.name.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
Toast.makeText(mContext,"name clicked", Toast.LENGTH_SHORT).show();
}
});
holder.description.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
Toast.makeText(mContext,"description clicked", Toast.LENGTH_SHORT).show();
}
});
//This means it is beyond the headerview now as it is no longer 0. For testing purposes, I'm alternating between two pics for now
} else if (position > 0) {
holder.place.setText(mDataset[position]);
if (position % 2 == 0) {
holder.pics.setImageDrawable(mContext.getResources().getDrawable(R.drawable.pic1));
}
if (position % 2 == 1) {
holder.pics.setImageDrawable(mContext.getResources().getDrawable(R.drawable.pic2));
}
}
}
是的，这是可能的。只需实现getItemViewType()，并照顾onCreateViewHolder()中的viewType参数。
所以你可以这样做:
public class MyAdapter extends RecyclerView.Adapter<RecyclerView.ViewHolder> {
class ViewHolder0 extends RecyclerView.ViewHolder {
...
public ViewHolder0(View itemView){
...
}
}
class ViewHolder2 extends RecyclerView.ViewHolder {
...
public ViewHolder2(View itemView){
...
}
@Override
public int getItemViewType(int position) {
// Just as an example, return 0 or 2 depending on position
// Note that unlike in ListView adapters, types don't have to be contiguous
return position % 2 * 2;
}
@Override
public RecyclerView.ViewHolder onCreateViewHolder(ViewGroup parent, int viewType) {
switch (viewType) {
case 0: return new ViewHolder0(...);
case 2: return new ViewHolder2(...);
...
}
}
@Override
public void onBindViewHolder(final RecyclerView.ViewHolder holder, final int position) {
switch (holder.getItemViewType()) {
case 0:
ViewHolder0 viewHolder0 = (ViewHolder0)holder;
...
break;
case 2:
ViewHolder2 viewHolder2 = (ViewHolder2)holder;
...
break;
}
}
}
比以往任何时候都简单，忘记ViewTypes。不建议在一个适配器中使用多个视图类型。这将使代码混乱，并打破单一责任原则，因为现在适配器需要处理逻辑来知道要填充哪个视图。
现在，想象一下在大型团队中工作，每个团队都必须在这些视图类型中的一种功能中工作。如果在不同视图类型中工作的所有团队都使用同一个适配器，那将是一团糟。这是使用ConcatAdapter解决的，其中隔离了适配器。逐个编码，然后将它们合并到一个视图中。
在recyclerview:1.2.0-alpha04中，您现在可以使用ConcatAdapter。
如果你需要一个具有不同viewTypes的视图，你可以为每个部分编写适配器，并使用ConcatAdapter将它们合并到一个recyclerview中。
ConcatAdapter
这张图片显示了一个recyclerview拥有的三种不同的视图类型，页眉，内容和页脚。
你只需要为每个section创建一个适配器，然后使用ConcatAdapter将它们合并到一个recyclerview中:
val firstAdapter: FirstAdapter = …
val secondAdapter: SecondAdapter = …
val thirdAdapter: ThirdAdapter = …
val concatAdapter = ConcatAdapter(firstAdapter, secondAdapter,
thirdAdapter)
recyclerView.adapter = concatAdapter
这就是你需要知道的。如果您想处理加载状态，例如在某些加载发生后删除最后一个适配器，您可以使用LoadState。
欲了解更多深入信息，请关注Florina Muntenescu的帖子https://medium.com/androiddevelopers/merge-adapters-sequentially-with-mergeadapter-294d2942127a
使用Kotlin，视图类型的实现变得更加容易。下面是这个light库https://github.com/Link184/KidAdapter的示例
recyclerView.setUp {
withViewType {
withLayoutResId(R.layout.item_int)
withItems(mutableListOf(1, 2, 3, 4, 5, 6))
bind<Int> { // this - is adapter view hoder itemView, it - current item
intName.text = it.toString()
}
}
withViewType("SECOND_STRING_TAG") {
withLayoutResId(R.layout.item_text)
withItems(mutableListOf("eight", "nine", "ten", "eleven", "twelve"))
bind<String> {
stringName.text = it
}
}
}
