Android recyclerview-selection Implementation?

Question

I'm currently trying to implement the new recyclerview-selection APIs from Android Support Library 28.0.0-alpha1, and am running into some issues. My goal is to have a RecyclerView, with the ability to select multiple rows, show a Contextual Action Bar, and perform actions on them, such as "delete" or "share"

I'll try and furnish enough code to give a good idea of what's going on, but I can always respond with more if necessary.

In my Fragment which contains the RecyclerView I'm concerned with, I am initiating a SelectionTracker, and setting it on my RecyclerView.Adapter, like so:

private void buildRecyclerView() {
    sheetsAdapter = new SheetsAdapter(getContext(), this, sheets);
    gridManager = new GridLayoutManager(getContext(), getResources().getInteger(R.integer.grid_span_count));

    ItemOffsetDecoration itemDecoration = new ItemOffsetDecoration(getContext(), R.dimen.item_offset);
    sheetsRecycler.addItemDecoration(itemDecoration);
    sheetsRecycler.setLayoutManager(gridManager);
    sheetsRecycler.setAdapter(sheetsAdapter);
    sheetsRecycler.setHasFixedSize(true);

    SelectionTracker selectionTracker = new SelectionTracker.Builder<>(
        "sheet_selection",
        sheetsRecycler,
        new StableIdKeyProvider(sheetsRecycler),
        new SheetDetailsLookup(sheetsRecycler),
        StorageStrategy.createLongStorage()
    )
    .withOnContextClickListener(this)
    .build();

    sheetsAdapter.setSelectionTracker(selectionTracker);
}

This Fragment also implements OnContextClickListener, in order to listen for long-clicks on the items in my RecyclerView:

@Override
public boolean onContextClick(@NonNull MotionEvent e) {
    if (actionMode != null) {
        return false;
    }

    // Start the CAB using the ActionMode.Callback defined below
    if (getActivity() != null) {
        actionMode = ((AppCompatActivity) getActivity()).startSupportActionMode(actionModeCallback);
    }

    return true;
}

And it should show my CAB, like this:

private ActionMode.Callback actionModeCallback = new ActionMode.Callback() {

    @Override
    public boolean onCreateActionMode(ActionMode mode, Menu menu) {
        MenuInflater inflater = mode.getMenuInflater();
        inflater.inflate(R.menu.sheets_cab_menu, menu);

        return true;
    }

    @Override
    public boolean onPrepareActionMode(ActionMode mode, Menu menu) {
        return false;
    }

    @Override
    public boolean onActionItemClicked(ActionMode mode, MenuItem item) {
        switch (item.getItemId()) {
            case  R.id.delete:
                Toast.makeText(getContext(), R.string.sheets_delete, Toast.LENGTH_SHORT).show();
                mode.finish();
                return true;
            default:
                return false;
        }
    }

    @Override
    public void onDestroyActionMode(ActionMode mode) {
        actionMode = null;
    }
};

My SheetDetailsLookup looks like this:

public class SheetDetailsLookup extends ItemDetailsLookup<Long> {

    private RecyclerView recyclerView;

    SheetDetailsLookup(RecyclerView recyclerView) {
        super();

        this.recyclerView = recyclerView;
    }

    @Nullable
    @Override
    public ItemDetails<Long> getItemDetails(@NonNull MotionEvent e) {
        View view = recyclerView.findChildViewUnder(e.getX(), e.getY());
        if (view != null) {
            RecyclerView.ViewHolder holder = recyclerView.getChildViewHolder(view);
            if (holder instanceof SheetsAdapter.SheetViewHolder) {
                return ((SheetsAdapter.SheetViewHolder) holder).getItemDetails();
            }
        }
        return null;
    }
}

And in my SheetViewHolder, I update the view to show that it has been selected:

if (selectionTracker.isSelected(sheet.uid)) {
    layout.setBackgroundResource(R.color.md_grey_700);
} else {
    layout.setBackgroundResource(android.R.color.transparent);
}

As well as:

public SheetItemDetails getItemDetails() {
    return new SheetItemDetails(getAdapterPosition(), mSheets.get(getAdapterPosition()).uid);
}

Where SheetItemDetails is simply:

public class SheetItemDetails extends ItemDetailsLookup.ItemDetails<Long> {

    private int position;
    private Long key;

    SheetItemDetails(int position, Long key) {
        this.position = position;
        this.key = key;
    }

    @Override
    public int getPosition() {
        return position;
    }

    @Nullable
    @Override
    public Long getSelectionKey() {
        return key;
    }
}

I've implemented all of the things mentioned in the API specification, but am now running into troubles. My CAB doesn't show up when I select an item... and the app usually crashes. Crashes occur whenever I try to "back out" of selections,and then long-click to start another selection, with this stack trace:

java.lang.IllegalStateException
    at android.support.v4.util.Preconditions.checkState(Preconditions.java:130)
    at android.support.v4.util.Preconditions.checkState(Preconditions.java:142)
    at androidx.recyclerview.selection.GestureSelectionHelper.start(GestureSelectionHelper.java:76)
    at androidx.recyclerview.selection.SelectionTracker$Builder$4.run(SelectionTracker.java:742)
    at androidx.recyclerview.selection.TouchInputHandler.onLongPress(TouchInputHandler.java:136)
    at androidx.recyclerview.selection.GestureRouter.onLongPress(GestureRouter.java:95)
    at android.view.GestureDetector.dispatchLongPress(GestureDetector.java:779)
    at android.view.GestureDetector.access$200(GestureDetector.java:40)
    at android.view.GestureDetector$GestureHandler.handleMessage(GestureDetector.java:293)
    at android.os.Handler.dispatchMessage(Handler.java:106)
    at android.os.Looper.loop(Looper.java:164)
    at android.app.ActivityThread.main(ActivityThread.java:6656)
    at java.lang.reflect.Method.invoke(Native Method)
    at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:438)
    at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:823)

Also, I've now lost the ability to "short-click" on one of my items, to launch a detail view... Which I had working just fine until now.

What have I done wrong?

1. `withOnContextClickListener` is not for long-click 2.your `getItemDetails` returns a new instance every time. Can you paste the entire code? — wangqi060934, Jun 01 '18 at 03:12
I'm facing the short-click trouble too. I'm using Kotlin and ParcelableStorage for the item key and everything is working fine but the simple click listener event. How did you solve this? — Jose Ricardo Citerio Alcala, Jan 02 '19 at 02:17
Override `getItemId` and set `setHasStableIds(true)` in your adapter. — MrOnyszko, Aug 05 '19 at 18:31

score 6 · Answer 1 · answered Nov 11 '18 at 18:18

6

I recently started looking at this library and got stuck on the same exception. The problem occurs when the SelectionTracker attempts to get an id from your custom RecyclerView.Adapter subclass. To fix the problem, first call setHasStableIds(true) in its constructor. Then override getItemId() to return an id for the given position parameter.

answered Nov 11 '18 at 18:18

Code-Apprentice

81,660
23
145
268

can you please recomend a tutorial – EdgeDev Feb 07 '19 at 11:50
@Micklo_Nerd I started by reading the official documentation for recyclerview-selection on http://d.android.com. Then I figured out the solution to this problem by diving into the source code. – Code-Apprentice Feb 07 '19 at 17:04
3

@Micklo_Nerd Yes, I found it complicated as well. – Code-Apprentice Feb 07 '19 at 20:17
I implemented a much simpler implementation that works for me https://edgedevstudio.com/recyclerview-item-multi-select-tutorial/ – EdgeDev Feb 07 '19 at 21:32

score 3 · Answer 2 · edited May 20 '18 at 23:24

New library looks complicated for now, indeed. I would wait the new final version before starting to implement over it. Surely, you can experiment with it, but I suggest you not use it in your app for now.

There's only one nice, new feature: the continuous multi-selection by moving the finger or mouse.

However, I found these examples:

In the meantime, I strongly suggest to use a library like mine: FlexibleAdapter which comes from more than 3 years of "selection experience", where it does NOT bind the item when (de)selection occurs! The multi-selection is simple to use with an ActionModeHelper to simplify your code with the ActionMode. Read the related Wiki page.

Currently, the selection is saved in a Set, but it might be delegated to the adapter item itself in the future. However, you can use 'selections' with this extension.

Maybe this will help, it's a modern implementation using Kotlin that showcases quite a few things that can be achieved with this library: https://github.com/ExpensiveBelly/RecyclerViewSelection — ExpensiveBelly, May 16 '21 at 19:01

score 0 · Answer 3 · answered Apr 07 '18 at 08:19

0

The selection package is still in alpha, the documentation is quite poor and it's not really clear how to use it. I tried myself but I had similar problems, at the end I used the SmartRecyclerView

answered Apr 07 '18 at 08:19

greywolf82

21,813
18
54
108

nowadays (from Sep, 2018), it has a stable 1.0.0 release – A. Petrov Nov 20 '18 at 08:53

A. Petrov · Answer 4 · 2018-11-20T08:50:27.273

0

Two things:

1) to reach the click on items, you need to implement an OnItemActivatedListener<K> listener and pass a reference to it onto the tracker builder. After that you can receive 'touches' on an items.

2) to show Contextual Action Bar menu different approach is required: you need to implement an SelectionTracker.SelectionObserver and pass it to the tracker after creation: tracker.addObserver(.... After that, you can receive a selection change events in that observer (via onSelectionChanged callback). For instance, when selection starts (!tracker.getSelection().isEmpty() => show CAB) and selection ends (tracker.getSelection().isEmpty() hide CAB). If you want to control for single/multiple items selection, tracker must be supplemented with SelectionTracker.SelectionPredicate instance (via .withSelectionPredicate( builder method).

and also, as @Code-Apprentice suggests, you need to provide correct ID's from getItemId() while you construct an ItemDetailsLookup.ItemDetails provider (this eliminates an Exception).

edited Nov 20 '18 at 08:50

answered Nov 20 '18 at 08:41

A. Petrov

910
13
18

Where does the `getItemId()` method come from? It no longer exists in the RecyclerView Selection library in version `1.1.0-alpha01`. – Edric Dec 14 '18 at 03:23
@Edric, this method is came from an Adapter. Override it, and provide from it correct id's of an Adapter hosted items. If Adapter do not provide an Id's, SelectionTracker do not know what to do with selection events - it can not hook into an items. – A. Petrov Dec 14 '18 at 07:14
Typically, you need to provide the result from `Adapter`'s `getItemId()` via the overridden method `getSelectionKey()` of `ItemDetailsLookup.ItemDetails`. It is done while you write your own `ViewHolder` implementation. – A. Petrov Dec 14 '18 at 07:23

Android recyclerview-selection Implementation?

4 Answers4