SelectionTracker
是 Android Jetpack 中的一个组件,用于跟踪和管理用户在 RecyclerView 或其他列表视图中的选择状态。它可以帮助开发者实现多选功能,并且能够轻松地获取当前选中的项目。
SelectionTracker
提供了简单的 API 来跟踪和管理选择状态。Adapter
和 ViewHolder
结合使用,实现复杂的选择逻辑。SelectionTracker
主要有以下几种类型:
以下是一个使用 SelectionTracker
实现多选功能的示例代码:
public class MyAdapter extends RecyclerView.Adapter<MyAdapter.ViewHolder> {
private List<Item> items;
private SelectionTracker<Long> selectionTracker;
public MyAdapter(List<Item> items) {
this.items = items;
this.selectionTracker = new SelectionTracker.Builder<>("my-selection-tracker",
recyclerView,
new StableIdKeyProvider(recyclerView),
new MyItemDetailsLookup(recyclerView),
StorageStrategy.createLongStorage())
.build();
}
@NonNull
@Override
public ViewHolder onCreateViewHolder(@NonNull ViewGroup parent, int viewType) {
View view = LayoutInflater.from(parent.getContext()).inflate(R.layout.item_layout, parent, false);
return new ViewHolder(view);
}
@Override
public void onBindViewHolder(@NonNull ViewHolder holder, int position) {
Item item = items.get(position);
holder.textView.setText(item.getText());
holder.itemView.setSelected(selectionTracker.hasSelection(item.getId()));
}
@Override
public int getItemCount() {
return items.size();
}
public class ViewHolder extends RecyclerView.ViewHolder {
TextView textView;
public ViewHolder(@NonNull View itemView) {
super(itemView);
textView = itemView.findViewById(R.id.textView);
}
}
private static class MyItemDetailsLookup extends ItemDetailsLookup<Long> {
private RecyclerView recyclerView;
public MyItemDetailsLookup(RecyclerView recyclerView) {
this.recyclerView = recyclerView;
}
@Override
public ItemDetails<Long> getItemDetails(MotionEvent e) {
View view = findChildViewUnder(e.getX(), e.getY());
if (view != null) {
return ((ViewHolder) recyclerView.getChildViewHolder(view)).getItemDetails();
}
return null;
}
private View findChildViewUnder(float x, float y) {
final int childCount = recyclerView.getChildCount();
for (int i = childCount - 1; i >= 0; i--) {
final View child = recyclerView.getChildAt(i);
if (x >= child.getLeft() && x <= child.getRight() &&
y >= child.getTop() && y <= child.getBottom()) {
return child;
}
}
return null;
}
}
private static class MyItemDetails extends ItemDetailsLookup.ItemDetails<Long> {
private long id;
public MyItemDetails(long id) {
this.id = id;
}
@Override
public int getPosition() {
return (int) id;
}
@Override
public long getSelectionKey() {
return id;
}
}
}
Android Jetpack - SelectionTracker
Adapter
没有正确通知 RecyclerView
数据变化。notifyDataSetChanged()
或其他适当的通知方法。ItemView
的 setSelected()
方法没有正确调用。onBindViewHolder
中正确调用 setSelected()
方法。SelectionTracker
初始化时参数不正确。SelectionTracker.Builder
的参数是否正确,特别是 ItemDetailsLookup
和 StorageStrategy
。通过以上内容,你应该能够全面了解 SelectionTracker
的基础概念、优势、类型、应用场景以及常见问题的解决方法。
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