下面是一个使用MVVM架构和RecyclerView动态加载数据的Android代码示例:
首先,创建一个Model类来表示数据项:
public class Item {
private String name;
public Item(String name) {
this.name = name;
}
public String getName() {
return name;
}
}
接下来,创建一个ViewModel类来管理数据和业务逻辑:
public class ItemViewModel extends ViewModel {
private MutableLiveData> items;
public LiveData> getItems() {
if (items == null) {
items = new MutableLiveData<>();
loadItems();
}
return items;
}
private void loadItems() {
// 模拟从网络或数据库加载数据
List- itemList = new ArrayList<>();
for (int i = 0; i < 10; i++) {
itemList.add(new Item("Item " + i));
}
items.setValue(itemList);
}
public void loadMoreItems() {
// 模拟加载更多数据
List
- currentItems = items.getValue();
if (currentItems != null) {
List
- newItems = new ArrayList<>();
int currentSize = currentItems.size();
for (int i = currentSize; i < currentSize + 10; i++) {
newItems.add(new Item("Item " + i));
}
currentItems.addAll(newItems);
items.setValue(currentItems);
}
}
}
然后,在Activity或Fragment中使用ViewModel和RecyclerView来展示数据:
public class MainActivity extends AppCompatActivity {
private RecyclerView recyclerView;
private ItemAdapter adapter;
private ItemViewModel itemViewModel;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
recyclerView = findViewById(R.id.recyclerView);
recyclerView.setLayoutManager(new LinearLayoutManager(this));
adapter = new ItemAdapter();
recyclerView.setAdapter(adapter);
itemViewModel = new ViewModelProvider(this).get(ItemViewModel.class);
itemViewModel.getItems().observe(this, new Observer>() {
@Override
public void onChanged(List- items) {
adapter.setItems(items);
}
});
// 模拟初始加载数据
itemViewModel.loadMoreItems();
// 监听RecyclerView滚动事件,当滑动到底部时加载更多数据
recyclerView.addOnScrollListener(new RecyclerView.OnScrollListener() {
@Override
public void onScrolled(@NonNull RecyclerView recyclerView, int dx, int dy) {
super.onScrolled(recyclerView, dx, dy);
LinearLayoutManager layoutManager = (LinearLayoutManager) recyclerView.getLayoutManager();
int visibleItemCount = layoutManager.getChildCount();
int totalItemCount = layoutManager.getItemCount();
int firstVisibleItemPosition = layoutManager.findFirstVisibleItemPosition();
if (visibleItemCount + firstVisibleItemPosition >= totalItemCount && firstVisibleItemPosition >= 0) {
itemViewModel.loadMoreItems();
}
}
});
}
}
最后,创建一个RecyclerView的Adapter类来展示数据:
public class ItemAdapter extends RecyclerView.Adapter {
private List- items;
public void setItems(List
- items) {
this.items = items;
notifyDataSetChanged();
}
@NonNull
@Override
public ItemViewHolder onCreateViewHolder(@NonNull ViewGroup parent, int viewType) {
View view = LayoutInflater.from(parent.getContext()).inflate(R.layout.item_layout, parent, false);
return new ItemViewHolder(view);
}
@Override
public void onBindViewHolder(@NonNull ItemViewHolder holder, int position) {
Item item = items.get(position);
holder.nameTextView.setText(item.getName());
}
@Override
public int getItemCount() {
return items != null ? items.size() : 0;
}
public static class ItemViewHolder extends RecyclerView.ViewHolder {
private TextView nameTextView;
public ItemViewHolder(@NonNull View itemView) {
super(itemView);
nameTextView = itemView.findViewById(R.id.nameTextView);
}
}
}
以上代码示例使用了LiveData和ViewModel来管理数据和状态,通过RecyclerView的滚动事件来实现动态加载数据。在Activity或Fragment中,通过观察ViewModel的LiveData来更新RecyclerView的数据,在滑动到底部时通过ViewModel的方法加载更多数据。同时,在Adapter中通过调用notifyDataSetChanged()方法来通知RecyclerView更新数据。
请注意,以上代码示例仅为演示MVVM和RecyclerView动态加载数据的一种方法,实际项目中可能还需要处理更多的情况,如错误处理、空数据处理