我想在回收器视图中选择多个项目，当选择它时，我想将该项目的复选框的可见性设置为可见。所以，只要我能够设置onlongClickListner使用接口和处理onLongClick片段中的事件。
每当用户长按任何项目时，应用程序onCLick逻辑被改变。不久之后，单击应用程序将在另一个活动中打开该项目，但是在长按之后onClick的逻辑改变了，可以设置任何我想要的。我想在长按后选中与该项目对应的复选框。并想从arrayList这是在回收者视图中加载的。
Fragment
...
@Override
public void onclick(int position) {
if (!isSelectionMode) {
Intent intent = new Intent(getActivity(), FullPhoto.class);
intent.putExtra("uri", arrayList.get(position).getUri());
startActivity(intent);
}
}
//Support fun to turn selectionMode on, onLongClick event.
@Override
public void onLongClick() {
isSelectionMode = true;
}
...
Adapter
...
public static class MyViewHolder extends RecyclerView.ViewHolder implements View.OnClickListener,View.OnLongClickListener {
private final ImageView img;
public CheckBox selection;
OnImageClickListner listner;
OnImageLongClickListener longClickListener;
public MyViewHolder(@NonNull View itemView, OnImageClickListner listner,OnImageLongClickListener longClickListener) {
super(itemView);
this.listner = listner;
this.longClickListener = longClickListener;
itemView.setOnLongClickListener(this); //onLongClickListener is set to all of the RecyclerView Items for once rather than setting on each item in BindViewHolder for repeated times
itemView.setOnClickListener(this); //onClickListener is set to all of the RecyclerView Items for once rather than setting on each item in BindViewHolder for repeated times
img = itemView.findViewById(R.id.img);
selection = itemView.findViewById(R.id.checkbox);
}
@Override
public void onClick(View v) {
listner.onclick(getAdapterPosition()); //Returning the current clicked position
}
@Override
public boolean onLongClick(View v) {
longClickListener.onLongClick();
return true;
}
}
// inner class ends
public interface OnImageClickListner{ //Interface to generate call back when user clicked an image.
void onclick(int position);
}
public interface OnImageLongClickListener{ //Interface to generate call back when user long clicked an image.
void onLongClick();
}
...
在这种情况下，我无法理解如何实现选择跟踪器。我可以通过以下方式获取适配器位置getAdapterPosition()然后我可以从中删除该元素arrayList在该指数上。但是，我想突出显示该复选框position。在这种情况下我无法实现代码。
我尝试过的事情
我确实尝试通过View v from onLongClick(View v)然后通过selection复选框到onCLick()事件。但是，这没有用。
我想从回收者视图中选择项目并将可见性设置为VISIBLE对于选定的项目。
------ Update ------
现在，我可以借助事件方法中的少量编辑将复选框的可见性设置为可见。
Fragment
@Override
public void onclick(int position, CheckBox selection) {
if (!isSelectionMode) {
Intent intent = new Intent(getActivity(), FullPhoto.class);
intent.putExtra("uri", arrayList.get(position).getUri());
startActivity(intent);
}
else
{
selection.setVisibility(View.VISIBLE);
selection.setChecked(true);
}
}
Where selection是一个复选框，传递自MyViewHolder来自适配器的类。但是，由于回收商观点的本质，我得到了双重选择。还有一个奇怪的问题是，在选择项目后，如果我向下滚动，选择将随机更改。
在此图像中，如您所见，我只选择了 4 个图像，但是当我向下滚动时，其他图像也被选择，当我再次向上滚动时，它弄乱了我选择的项目。
照片适配器
public class PhotosAdapter extends RecyclerView.Adapter<PhotosAdapter.MyViewHolder> {
public Context context;
ArrayList<ImageModel> arrayList;
Activity activity;
OnImageClickListner listener;
OnImageLongClickListener longClickListener;
/*=============================================================== CONSTRUCTOR ===============================================================*/
public PhotosAdapter(Context context, ArrayList<ImageModel> arrayList, Activity activity, OnImageClickListner listner, OnImageLongClickListener longClickListener) {
this.context = context;
this.arrayList = arrayList;
this.activity = activity;
this.listener = listner;
this.longClickListener = longClickListener;
}
/*=============================================================== OVERRIDDEN METHODS ===============================================================*/
@NonNull
@Override
public MyViewHolder onCreateViewHolder(@NonNull ViewGroup parent, int viewType) { //This methods returns single_view.xml as a view for RecyclerView.
View view = LayoutInflater.from(parent.getContext()).inflate(R.layout.single_view, parent, false);
return new MyViewHolder(view, listener, longClickListener);
}
@Override
public void onBindViewHolder(@NonNull MyViewHolder holder, int position) { //Binding the uris with each view depending upon the position of current view.
activity.runOnUiThread(() -> GlideApp.with(context)
.load(Uri.parse(arrayList.get(position).getUri()))
.apply(RequestOptions.overrideOf(150, 150)) //It overrides the value of original image and reduces it to the visible thumbnail size.
.diskCacheStrategy(DiskCacheStrategy.RESOURCE) //Then it caches the reduced size thumbnail for faster loading speed.
.into(holder.img));
}
@Override
public int getItemCount() {
return arrayList.size();
}
/*=============================================================== INNER VIEW HOLDER CLASS ===============================================================*/
public static class MyViewHolder extends RecyclerView.ViewHolder implements View.OnClickListener, View.OnLongClickListener {
private final ImageView img;
public CheckBox selection;
OnImageClickListner listener;
OnImageLongClickListener longClickListener;
public final SparseBooleanArray selectedItems; ///////////////////////////////// ADDED LINE /////////////////////////////////
public MyViewHolder(@NonNull View itemView, OnImageClickListner listener, OnImageLongClickListener longClickListener) {
super(itemView);
this.listener = listener;
this.longClickListener = longClickListener;
itemView.setOnLongClickListener(this); //onLongClickListener is set to all of the RecyclerView Items for once rather than setting on each item in BindViewHolder for repeated times
itemView.setOnClickListener(this); //onClickListener is set to all of the RecyclerView Items for once rather than setting on each item in BindViewHolder for repeated times
img = itemView.findViewById(R.id.img);
selection = itemView.findViewById(R.id.checkbox);
selectedItems = new SparseBooleanArray(); ///////////////////////////////// ADDED LINE /////////////////////////////////
}
@Override
public void onClick(View v) {
listener.onclick(getAdapterPosition(), selection); //Returning the current clicked position and selection checkbox to the implemented method.
}
@Override
public boolean onLongClick(View v) {
longClickListener.onLongClick(getAdapterPosition(), v); //Returning the current clicked position and view to the implemented method.
return true;
}
//////////////////////////////////////////////////////////////////////////// ADDED LINES ////////////////////////////////////////////////////////////////////////////
boolean isSelected(int position) {
return getSelectedItems().contains(position);
}
public void toggleSelection(int position) {
if (selectedItems.get(position, false)) {
selectedItems.delete(position);
} else {
selectedItems.put(position, true);
}
notifyItemChanged(position);
}
public void selectAll() {
for (int i = 0; i < getItemCount(); i++) {
if (!(selectedItems.get(i, false))) {
selectedItems.put(i, true);
}
notifyItemChanged(i);
}
notifyDataSetChanged();
}
public void clearSelection() {
List<Integer> selection = getSelectedItems();
selectedItems.clear();
for (Integer i : selection) {
notifyItemChanged(i);
}
}
public int getSelectedItemCount() {
return selectedItems.size();
}
public List<Integer> getSelectedItems() {
List<Integer> items = new ArrayList<>(selectedItems.size());
for (int i = 0; i < selectedItems.size(); ++i) {
items.add(selectedItems.keyAt(i));
}
return items;
}
} //INNER CLASS ENDS
/*=============================================================== INTERFACES ===============================================================*/
public interface OnImageClickListner { //Interface to generate call back when user clicked an image.
void onclick(int position, CheckBox selection);
}
public interface OnImageLongClickListener { //Interface to generate call back when user long clicked an image.
void onLongClick(int position, View v);
}
}
这就是导致双重或多重选择的原因。 Recyclerview 以这种方式工作，视图被回收。
因此，每次视图膨胀时，您都必须隐藏、选中或取消选中每个项目。
所以在onbindViewholder你必须setChecked()根据您的情况，为 true 或 false。
我解决这个问题的方法是： 不要将视图传递给父片段，而是以这种方式将检查逻辑保留在适配器中：
if (isItemSelected){
selection.setChecked(true);
}else{
selection.setChecked(false);
}
这样，检查和取消检查就会很完美。
- 更新 -
创建一个可选择的适配器类来提供isSelected()方法如下
可选适配器
public abstract class SelectableAdapter<VH extends RecyclerView.ViewHolder> extends RecyclerView.Adapter<VH> {
private static final String TAG = SelectableAdapter.class.getSimpleName();
private final SparseBooleanArray selectedItems;
SelectableAdapter() {
selectedItems = new SparseBooleanArray();
}
boolean isSelected(int position) {
return getSelectedItems().contains(position);
}
public void toggleSelection(int position) {
if (selectedItems.get(position, false)) {
selectedItems.delete(position);
} else {
selectedItems.put(position, true);
}
notifyItemChanged(position);
}
public void selectAll() {
for (int i = 0; i < getItemCount(); i++) {
if (!(selectedItems.get(i, false))) {
selectedItems.put(i, true);
}
notifyItemChanged(i);
}
notifyDataSetChanged();
}
public void clearSelection() {
List<Integer> selection = getSelectedItems();
selectedItems.clear();
for (Integer i : selection) {
notifyItemChanged(i);
}
}
public int getSelectedItemCount() {
return selectedItems.size();
}
public List<Integer> getSelectedItems() {
List<Integer> items = new ArrayList<>(selectedItems.size());
for (int i = 0; i < selectedItems.size(); ++i) {
items.add(selectedItems.keyAt(i));
}
return items;
}
}
让您的适配器延长selectableAdapter如下：
适配器类
public class RecyclerViewAdapter extends SelectableAdapter<RclAdapter.ViewHolder>
关于片段的使用toggleSelection将位置设置为选定或未选定。
@Override
public void onclick(int position) {
if (!isSelectionMode) {
Intent intent = new Intent(getActivity(), FullPhoto.class);
intent.putExtra("uri", arrayList.get(position).getUri());
startActivity(intent);
}
else
{
// Use the adapter instance here
adapter.toggleSelection(position);
}
}
记住toggleSelection通知适配器并调用onBindViewHolder.
在适配器中：onBindViewHolder实现选择逻辑以显示和隐藏复选框。
如果您只将其设置为View.VISIBLE并且不要将其设置为View.GONE对于那些没有被选中的，你仍然会遇到同样的问题。