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;
}
这是非常简单直接的。
只需在适配器中重写getItemViewType()方法。根据数据返回不同的itemViewType值。例如，考虑一个Person类型的对象，其成员为male，如果isMale为真，则返回1,isMale为假，则在getItemViewType()方法中返回2。
现在来到createViewHolder (ViewGroup parent, int viewType)，在不同的viewType的基础上，你可以膨胀不同的布局文件。像下面这样:
if (viewType == 1){
View view = LayoutInflater.from(parent.getContext()).inflate(R.layout.male, parent, false);
return new AdapterMaleViewHolder(view);
}
else{
View view = LayoutInflater.from(parent.getContext()).inflate(R.layout.female, parent, false);
return new AdapterFemaleViewHolder(view);
}
在onBindViewHolder (VH holder,int position)检查holder是AdapterFemaleViewHolder或AdapterMaleViewHolder的实例，并相应地分配值。
ViewHolder可能是这样的
class AdapterMaleViewHolder extends RecyclerView.ViewHolder {
...
public AdapterMaleViewHolder(View itemView){
...
}
}
class AdapterFemaleViewHolder extends RecyclerView.ViewHolder {
...
public AdapterFemaleViewHolder(View itemView){
...
}
}
首先，必须创建两个布局XML文件。之后，在recyclerview适配器中，TYPE_CALL和TYPE_EMAIL是两个静态值，分别为适配器类中的1和2。
现在在Recycler视图Adapter类级别定义两个静态值，例如:private static int TYPE_EMAIL = 2;
现在创建多个视图的视图持有者，如下所示:
class CallViewHolder extends RecyclerView.ViewHolder {
private TextView txtName;
private TextView txtAddress;
CallViewHolder(@NonNull View itemView) {
super(itemView);
txtName = itemView.findViewById(R.id.txtName);
txtAddress = itemView.findViewById(R.id.txtAddress);
}
}
class EmailViewHolder extends RecyclerView.ViewHolder {
private TextView txtName;
private TextView txtAddress;
EmailViewHolder(@NonNull View itemView) {
super(itemView);
txtName = itemView.findViewById(R.id.txtName);
txtAddress = itemView.findViewById(R.id.txtAddress);
}
}
现在在recyclerview适配器的onCreateViewHolder和onBindViewHolder方法中编写如下代码:
@NonNull
@Override
public RecyclerView.ViewHolder onCreateViewHolder(@NonNull ViewGroup viewGroup, int viewType) {
View view;
if (viewType == TYPE_CALL) { // for call layout
view = LayoutInflater.from(context).inflate(R.layout.item_call, viewGroup, false);
return new CallViewHolder(view);
} else { // for email layout
view = LayoutInflater.from(context).inflate(R.layout.item_email, viewGroup, false);
return new EmailViewHolder(view);
}
}
@Override
public void onBindViewHolder(@NonNull RecyclerView.ViewHolder viewHolder, int position) {
if (getItemViewType(position) == TYPE_CALL) {
((CallViewHolder) viewHolder).setCallDetails(employees.get(position));
} else {
((EmailViewHolder) viewHolder).setEmailDetails(employees.get(position));
}
}
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
您可以通过使getItemViewType()返回该位置的预期viewType值来处理multipleViewTypes RecyclerAdapter。
我准备了一个MultipleViewTypeAdapter用于构造一个MCQ列表的考试，它可能抛出一个可能有两个或多个有效答案(复选框选项)和一个单一答案问题(单选按钮选项)的问题。
为此，我从API响应中获得问题的类型，并使用它来决定我必须为该问题显示哪个视图。
public class MultiViewTypeAdapter extends RecyclerView.Adapter {
Context mContext;
ArrayList<Question> dataSet;
ArrayList<String> questions;
private Object radiobuttontype1;
//Viewholder to display Questions with checkboxes
public static class Checkboxtype2 extends RecyclerView.ViewHolder {
ImageView imgclockcheck;
CheckBox checkbox;
public Checkboxtype2(@NonNull View itemView) {
super(itemView);
imgclockcheck = (ImageView) itemView.findViewById(R.id.clockout_cbox_image);
checkbox = (CheckBox) itemView.findViewById(R.id.clockout_cbox);
}
}
//Viewholder to display Questions with radiobuttons
public static class Radiobuttontype1 extends RecyclerView.ViewHolder {
ImageView clockout_imageradiobutton;
RadioButton clockout_radiobutton;
TextView sample;
public radiobuttontype1(View itemView) {
super(itemView);
clockout_imageradiobutton = (ImageView) itemView.findViewById(R.id.clockout_imageradiobutton);
clockout_radiobutton = (RadioButton) itemView.findViewById(R.id.clockout_radiobutton);
sample = (TextView) itemView.findViewById(R.id.sample);
}
}
public MultiViewTypeAdapter(ArrayList<QueDatum> data, Context context) {
this.dataSet = data;
this.mContext = context;
}
@NonNull
@Override
public RecyclerView.ViewHolder onCreateViewHolder(@NonNull ViewGroup viewGroup, int viewType) {
if (viewType.equalsIgnoreCase("1")) {
View view = LayoutInflater.from(viewGroup.getContext()).inflate(R.layout.clockout_radio_list_row, viewGroup, false);
return new radiobuttontype1(view);
} else if (viewType.equalsIgnoreCase("2")) {
View view = LayoutInflater.from(viewGroup.getContext()).inflate(R.layout.clockout_cbox_list_row, viewGroup, false);
view.setHorizontalFadingEdgeEnabled(true);
return new Checkboxtype2(view);
} else if (viewType.equalsIgnoreCase("3")) {
View view = LayoutInflater.from(viewGroup.getContext()).inflate(R.layout.clockout_radio_list_row, viewGroup, false);
return new Radiobuttontype1(view);
} else if (viewType.equalsIgnoreCase("4")) {
View view = LayoutInflater.from(viewGroup.getContext()).inflate(R.layout.clockout_radio_list_row, viewGroup, false);
return new Radiobuttontype1(view);
} else if (viewType.equalsIgnoreCase("5")) {
View view = LayoutInflater.from(viewGroup.getContext()).inflate(R.layout.clockout_radio_list_row, viewGroup, false);
return new Radiobuttontype1(view);
}
return null;
}
@Override
public void onBindViewHolder(@NonNull RecyclerView.ViewHolder viewHolder, int viewType) {
if (viewType.equalsIgnoreCase("1")) {
options = dataSet.get(i).getOptions();
question = dataSet.get(i).getQuestion();
image = options.get(i).getValue();
((radiobuttontype1) viewHolder).clockout_radiobutton.setChecked(false);
((radiobuttontype1) viewHolder).sample.setText(question);
//Loading image bitmap in the ViewHolder's View
Picasso.with(mContext)
.load(image)
.into(((radiobuttontype1) viewHolder).clockout_imageradiobutton);
} else if (viewType.equalsIgnoreCase("2")) {
options = (ArrayList<Clockout_questions_Option>) dataSet.get(i).getOptions();
question = dataSet.get(i).getQuestion();
image = options.get(i).getValue();
//Loading image bitmap in the ViewHolder's View
Picasso.with(mContext)
.load(image)
.into(((Checkboxtype2) viewHolder).imgclockcheck);
} else if (viewType.equalsIgnoreCase("3")) {
//Fit data to viewHolder for ViewType 3
} else if (viewType.equalsIgnoreCase("4")) {
//Fit data to viewHolder for ViewType 4
} else if (viewType.equalsIgnoreCase("5")) {
//Fit data to viewHolder for ViewType 5
}
}
@Override
public int getItemCount() {
return dataSet.size();
}
/**
* Returns viewType for that position by picking the viewType value from the
* dataset
*/
@Override
public int getItemViewType(int position) {
return dataSet.get(position).getViewType();
}
}
你可以避免在onBindViewHolder()中基于多个条件的viewHolder数据填充，通过为不同位置的viewHolder中相似的视图分配相同的id。
