要实现在Android中显示未在本地数据库中的相关项目,并且不中断分页,可以使用以下方法:
List projectList = new ArrayList<>();
RecyclerView recyclerView = findViewById(R.id.recyclerView);
recyclerView.setLayoutManager(new LinearLayoutManager(this));
ProjectAdapter adapter = new ProjectAdapter();
recyclerView.setAdapter(adapter);
PagedList.Config config = new PagedList.Config.Builder()
.setPageSize(10)
.setEnablePlaceholders(false)
.build();
DataSource.Factory dataSourceFactory = new DataSource.Factory() {
@Override
public DataSource create() {
return new PageKeyedDataSource() {
@Override
public void loadInitial(@NonNull LoadInitialParams params, @NonNull LoadInitialCallback callback) {
// 在这里加载第一页数据,并将其传递给callback
List initialData = projectList.subList(0, Math.min(projectList.size(), params.requestedLoadSize));
callback.onResult(initialData, null, 1);
}
@Override
public void loadBefore(@NonNull LoadParams params, @NonNull LoadCallback callback) {
// 不需要实现
}
@Override
public void loadAfter(@NonNull LoadParams params, @NonNull LoadCallback callback) {
// 在这里加载下一页数据,并将其传递给callback
int nextPage = params.key + 1;
int start = params.key * params.requestedLoadSize;
int end = Math.min(projectList.size(), start + params.requestedLoadSize);
List pageData = projectList.subList(start, end);
callback.onResult(pageData, nextPage);
}
};
}
};
PagedList pagedList = new LivePagedListBuilder<>(dataSourceFactory, config).build();
pagedList.observe(this, new Observer>() {
@Override
public void onChanged(PagedList projects) {
adapter.submitList(projects);
}
});
class ProjectAdapter extends PagedListAdapter {
protected ProjectAdapter() {
super(DIFF_CALLBACK);
}
@NonNull
@Override
public ProjectViewHolder onCreateViewHolder(@NonNull ViewGroup parent, int viewType) {
LayoutInflater inflater = LayoutInflater.from(parent.getContext());
View view = inflater.inflate(R.layout.item_project, parent, false);
return new ProjectViewHolder(view);
}
@Override
public void onBindViewHolder(@NonNull ProjectViewHolder holder, int position) {
Project project = getItem(position);
if (project != null) {
holder.bind(project);
}
}
private static DiffUtil.ItemCallback DIFF_CALLBACK = new DiffUtil.ItemCallback() {
@Override
public boolean areItemsTheSame(@NonNull Project oldItem, @NonNull Project newItem) {
return oldItem.getId() == newItem.getId();
}
@Override
public boolean areContentsTheSame(@NonNull Project oldItem, @NonNull Project newItem) {
return oldItem.equals(newItem);
}
};
}
class ProjectViewHolder extends RecyclerView.ViewHolder {
private TextView titleTextView;
ProjectViewHolder(@NonNull View itemView) {
super(itemView);
titleTextView = itemView.findViewById(R.id.titleTextView);
}
void bind(Project project) {
titleTextView.setText(project.getTitle());
}
}
通过这种方法,你可以显示并分页加载相关项目,即使它们尚未存储在本地数据库中。