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?
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;
}
}
}
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));
}
}
如果你想将它与Android数据绑定结合使用，请查看https://github.com/evant/binding-collection-adapter -它是迄今为止我所见过的多种视图类型RecyclerView的最佳解决方案。
你可以这样使用它
var items: AsyncDiffPagedObservableList<BaseListItem> =
AsyncDiffPagedObservableList(GenericDiff)
val onItemBind: OnItemBind<BaseListItem> =
OnItemBind { itemBinding, _, item -> itemBinding.set(BR.item, item.layoutRes) }
然后在列表所在的布局中
<androidx.recyclerview.widget.RecyclerView
android:layout_width="match_parent"
android:layout_height="0dp"
android:layout_weight="1"
app:enableAnimations="@{false}"
app:scrollToPosition="@{viewModel.scrollPosition}"
app:itemBinding="@{viewModel.onItemBind}"
app:items="@{viewModel.items}"
app:reverseLayoutManager="@{true}"/>
你的列表项必须实现BaseListItem接口，它看起来像这样:
interface BaseListItem {
val layoutRes: Int
}
项目视图应该看起来像这样:
<layout xmlns:android="http://schemas.android.com/apk/res/android">
<data>
<variable
name="item"
type="...presentation.somescreen.list.YourListItem"/>
</data>
...
</layout>
YourListItem实现BaseListItem。
为不同的布局创建不同的ViewHolder
RecyclerView可以有任意数量的viewholders，但为了更好的可读性，让我们看看如何创建一个有两个viewholders的viewholders。
这可以通过三个简单的步骤来完成
覆盖公共int getItemViewType(int position)
在onCreateViewHolder()方法中根据ViewType返回不同的ViewHolders
根据onBindViewHolder()方法中的itemViewType填充视图
下面是一小段代码片段:
public class YourListAdapter extends RecyclerView.Adapter<RecyclerView.ViewHolder> {
private static final int LAYOUT_ONE = 0;
private static final int LAYOUT_TWO = 1;
@Override
public int getItemViewType(int position)
{
if(position==0)
return LAYOUT_ONE;
else
return LAYOUT_TWO;
}
@Override
public RecyclerView.ViewHolder onCreateViewHolder(ViewGroup parent, int viewType) {
View view = null;
RecyclerView.ViewHolder viewHolder = null;
if(viewType==LAYOUT_ONE)
{
view = LayoutInflater.from(parent.getContext()).inflate(R.layout.one,parent,false);
viewHolder = new ViewHolderOne(view);
}
else
{
view = LayoutInflater.from(parent.getContext()).inflate(R.layout.two,parent,false);
viewHolder= new ViewHolderTwo(view);
}
return viewHolder;
}
@Override
public void onBindViewHolder(RecyclerView.ViewHolder holder, final int position) {
if(holder.getItemViewType() == LAYOUT_ONE)
{
// Typecast Viewholder
// Set Viewholder properties
// Add any click listener if any
}
else {
ViewHolderOne vaultItemHolder = (ViewHolderOne) holder;
vaultItemHolder.name.setText(displayText);
vaultItemHolder.name.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
.......
}
});
}
}
//**************** VIEW HOLDER 1 ******************//
public class ViewHolderOne extends RecyclerView.ViewHolder {
public TextView name;
public ViewHolderOne(View itemView) {
super(itemView);
name = (TextView)itemView.findViewById(R.id.displayName);
}
}
//**************** VIEW HOLDER 2 ******************//
public class ViewHolderTwo extends RecyclerView.ViewHolder {
public ViewHolderTwo(View itemView) {
super(itemView);
..... Do something
}
}
}
getItemViewType(int position)是键。
在我看来，创建这种recyclerView的起点是这个方法的知识。因为这个方法是可选的，所以默认情况下它在RecylerView类中是不可见的，这使得许多开发人员(包括我)不知道从哪里开始。
一旦您知道了这个方法的存在，创建这样的RecyclerView将是小菜一菜。
让我们看一个例子来证明我的观点。如果你想显示两个布局
在交替的位置上这样做
@Override
public int getItemViewType(int position)
{
if(position%2==0) // Even position
return LAYOUT_ONE;
else // Odd position
return LAYOUT_TWO;
}
相关链接:
看看我已经实现了这个项目。
你可以使用这个图书馆:https://github.com/vivchar/RendererRecyclerViewAdapter
mRecyclerViewAdapter = new RendererRecyclerViewAdapter(); /* Included from library */
mRecyclerViewAdapter.registerRenderer(new SomeViewRenderer(SomeModel.TYPE, this));
mRecyclerViewAdapter.registerRenderer(...); /* You can use several types of cells */
对于每一个项目，你应该实现一个ViewRenderer, ViewHolder, SomeModel:
ViewHolder -它是回收器视图的一个简单视图持有者。
SomeModel -它是你的模型与ItemModel接口
public class SomeViewRenderer extends ViewRenderer<SomeModel, SomeViewHolder> {
public SomeViewRenderer(final int type, final Context context) {
super(type, context);
}
@Override
public void bindView(@NonNull final SomeModel model, @NonNull final SomeViewHolder holder) {
holder.mTitle.setText(model.getTitle());
}
@NonNull
@Override
public SomeViewHolder createViewHolder(@Nullable final ViewGroup parent) {
return new SomeViewHolder(LayoutInflater.from(getContext()).inflate(R.layout.some_item, parent, false));
}
}
有关更多详细信息，您可以查看文档。
