Android onClick切换RecyclerView项

问题描述

按现在的方式运行此代码，我可以构建一个项目列表，在单击该项目时，背景将变为灰色，就像选中该项目一样。再次单击，背景恢复为白色。我遇到且无法弄清的问题是，如何像共享首选项一样将背景颜色永久保持灰色，所以当应用程序更改方向或退出时，所选项目保持选中状态，直到再次单击以取消选择？

public class CampingItemRecyclerViewAdapter extends RecyclerView.Adapter<CampingItemRecyclerViewAdapter.ViewHolder>{
int i;
public final List<CampingItem> campingItems;
ListListener listListener;

public CampingItemRecyclerViewAdapter(List<CampingItem> campingItems){
    this.campingItems = campingItems;
}

@NonNull
@Override
public ViewHolder onCreateViewHolder(@NonNull ViewGroup parent,int viewType) {
    View view = LayoutInflater.from(parent.getContext())
            .inflate(R.layout.recycler_item,parent,false);
    return new ViewHolder(view);
}

@Override
public void onBindViewHolder(@NonNull ViewHolder holder,int position) {

    final CampingItem campingItem = campingItems.get(position);
    if (campingItem != null){
        holder.campingItem = campingItem;
        holder.txtLine1.setText(campingItem.getItemName());
        holder.txtLine2.setText(campingItem.getItemCost());
        holder.txtLine3.setText(campingItem.getInStock());
        holder.txtLine4.setText(campingItem.getLocation());

        holder.root.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                if (i == 0){
                    v.setBackgroundColor(Color.GRAY);
                    i++;
                }
                else if (i == 1) {
                    v.setBackgroundColor(Color.WHITE);

                    i = 0;
                }

            }
        });
        holder.root.setOnLongClickListener(new View.OnLongClickListener() {
            @Override
            public boolean onLongClick(View v) {
                Bundle bundle = new Bundle();
                bundle.putInt("campingItem_pk",campingItem.get_id());

                CampingItemDetailsDialogFragment detailsFragment = new CampingItemDetailsDialogFragment();
                detailsFragment.setArguments(bundle);

                AppCompatActivity activity = (AppCompatActivity) v.getContext();
                activity.getSupportFragmentManager().beginTransaction()
                        .add(android.R.id.content,detailsFragment)
                        .addToBackStack(null)
                        .commit();
                return true;
            }
        });

    }
}

@Override
public int getItemCount() {
    return campingItems.size();
}


public void addItems(List<CampingItem> campingItems){
    this.campingItems.clear();
    this.campingItems.addAll(campingItems);
    notifyDataSetChanged();

}


public class ViewHolder extends RecyclerView.ViewHolder{
    public View root;
    public CampingItem campingItem;
    public TextView txtLine1,txtLine2,txtLine3,txtLine4;

    public ViewHolder(View itemView){
        super (itemView);
        root = itemView;
        txtLine1 = (TextView)root.findViewById(R.id.txtLine1);
        txtLine2 = (TextView)root.findViewById(R.id.txtLine2);
        txtLine3 = (TextView)root.findViewById(R.id.txtLine3);
        txtLine4 = (TextView)root.findViewById(R.id.txtLine4);



    }
}

}

public class MainActivityFragment extends Fragment {

View root;
private RecyclerView recyclerView;
private CampingItemRecyclerViewAdapter campingItemRecyclerViewAdapter;
private int columnCount = 1;

@Nullable
@Override
public View onCreateView(@NonNull LayoutInflater inflater,@Nullable ViewGroup container,@Nullable Bundle savedInstanceState) {

    root = inflater.inflate(R.layout.fragment_main,container,false);
    recyclerView = (RecyclerView)root.findViewById(R.id.recyclerView);
    return root;
}

@Override
public void onResume() {
    super.onResume();
    Context context = getContext();
    campingItemRecyclerViewAdapter = new CampingItemRecyclerViewAdapter(new ArrayList<CampingItem>());

    if(columnCount <= 1){
        recyclerView.setLayoutManager(new LinearLayoutManager(context));
    }else{
        recyclerView.setLayoutManager(new GridLayoutManager(context,columnCount));
    }

    recyclerView.setAdapter(campingItemRecyclerViewAdapter);
    recyclerView.setHasFixedSize(false);

    ViewModelProviders.of(this)
            .get(AllCampingItemsViewModel.class)
            .getCampingItemList(context)
            .observe(this,new Observer<List<CampingItem>>() {
                @Override
                public void onChanged(List<CampingItem> campingItems) {
                    if (campingItems != null){
                        campingItemRecyclerViewAdapter.addItems(campingItems);
                    }
                }
            });
}

}

public class MainActivity extends AppCompatActivity {
FragmentManager fm;
Toolbar toolbar;

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);
    toolbar = (Toolbar) findViewById(R.id.toolbar);
    toolbar.setTitle("Camping List");
    setSupportActionBar(toolbar);


    FloatingActionButton fab = findViewById(R.id.fab);
    fab.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View view) {
            fm = getSupportFragmentManager();
            fm.beginTransaction()
                    .add(android.R.id.content,new NewCampingItemDialogFragment())
                    .addToBackStack(null)
                    .commit();


        }
    });
}

}

解决方法

您要寻找的功能是 recyclerview-selection 库的一部分。看一下this。不幸的是，它是针对kotlin的，但是您应该可以在Java中毫无问题地重写它。