how to highlight the selected Item of Recycler View?

Question

I have a Recycler View with the Images loaded from the Internal Storage. I want to Highlight the selected item when clicked. I tried a lot of thing but it was not working. Actually what I need is when I click any item in Recycler View that Item must go in My ArrayList and it should also get highlighted and again when I click or say unselect it must again become normal. Here is my Code:

public class Images extends Fragment {     private List<ImageHolder> imageList;     Cursor imageCursor;      RecyclerView recyclerView;     MyImageAdapter adapter;     ActionButton clickButton;     List<String> listofImages;     List<Integer> pos;     int columnIndex;     StringBuilder stringBuilder;     @Override     public View onCreateView(LayoutInflater inflater, ViewGroup container,   Bundle savedInstanceState) {         View rootlayout = inflater.inflate(R.layout.image, container, false);         listofImages=new ArrayList<String>();         pos=new ArrayList<Integer>();         stringBuilder=new StringBuilder();         ContentResolver imageResolver = getActivity().getContentResolver();         Uri imageUri = android.provider.MediaStore.Images.Media.EXTERNAL_CONTENT_URI;         String projection[]={MediaStore.Images.Thumbnails._ID,MediaStore.Images.Media.TITLE};         imageCursor = getActivity().managedQuery(imageUri, projection, null, null, null);          clickButton= (ActionButton) rootlayout.findViewById(R.id.action_button);          recyclerView = (RecyclerView) rootlayout.findViewById(R.id.recycler_view_image);         adapter = new MyImageAdapter(getActivity(), getImageList());          recyclerView.setAdapter(adapter);         recyclerView.setLayoutManager(new LinearLayoutManager(getActivity()));          recyclerView.addOnItemTouchListener(new RecyclerTouchListener(getActivity(),recyclerView,new RecyclerTouchListener.ClickListener() {             @Override             public void onClick(View view, int position) {                TextView tv= (TextView) view.findViewById(R.id.list_text_all);                     int flag=0;                      String[] projection = {MediaStore.Images.Media.DATA};                     imageCursor = getActivity().managedQuery(MediaStore.Images.Media.EXTERNAL_CONTENT_URI,                             projection,                              null,                                    null,                             null);                     columnIndex = imageCursor.getColumnIndexOrThrow(MediaStore.Images.Media.DATA);                     imageCursor.moveToPosition(position);                     // Get image filename                     String imagePath = imageCursor.getString(columnIndex);                     if (listofImages.contains(imagePath)){                         Log.d("Contains Test","Yes");                         listofImages.remove(imagePath);                         pos.remove(position);                     } else {                         listofImages.add(imagePath);                         pos.add(position);                         Log.d("Contains Test","No");                     }                  String s=listofImages.size()+" "+imagePath;                 Log.d("Inserted",s);             }              @Override             public void onLongClick(View view, int position) {}         }));          clickButton.setOnClickListener(new View.OnClickListener() {             @Override             public void onClick(View v) {                 for (int i=0;i<listofImages.size();i++){                     stringBuilder.append(listofImages.get(i)+"\n");                 }                 Toast.makeText(getActivity(),stringBuilder,Toast.LENGTH_LONG).show();             }         });          return rootlayout;     }      public List<ImageHolder> getImageList() {         imageList=new ArrayList<ImageHolder>();          if(imageCursor!=null && imageCursor.moveToFirst()){             int titleColumn = imageCursor.getColumnIndex                     (android.provider.MediaStore.Images.Media.TITLE);             int idColumn = imageCursor.getColumnIndex                     (android.provider.MediaStore.Images.Media._ID);              do {                 ImageHolder img=new ImageHolder();                 img.id=imageCursor.getLong(idColumn);                 img.title=imageCursor.getString(titleColumn);                  img.iconid= imageCursor.getInt(idColumn);                   imageList.add(img);             }             while (imageCursor.moveToNext());         }          return  imageList;     } } 

This is my Adapter Class:

public class MyImageAdapter extends RecyclerView.Adapter<MyImageAdapter.MyViewHolder> {     Context context;     private LayoutInflater inflater;     List<ImageHolder> data= Collections.emptyList();     private ClickListener clickListener;     int width,height;      public MyImageAdapter(Context context, List<ImageHolder> data1) {         inflater = LayoutInflater.from(context);         this.data=data1;         this.context=context;     }      @Override     public MyViewHolder onCreateViewHolder(ViewGroup parent, int viewType) {         View view = inflater.inflate(R.layout.all_row, parent, false);         MyViewHolder holder=new MyViewHolder(view);         return holder;     }      @Override     public void onBindViewHolder(MyViewHolder holder, int position) {         try{             ImageHolder current=data.get(position);             holder.title.setText(current.title);              Log.d("Imageid:"+current.iconid,"");             Uri IMAGE_URI = Uri.withAppendedPath(MediaStore.Images.Media.EXTERNAL_CONTENT_URI, "" + current.iconid);              Bitmap bitmap = Bitmap.createScaledBitmap(decodeUri(IMAGE_URI), 200, 200, true);             holder.img.setImageBitmap(bitmap);         }         catch(Exception e){}     }     public void deleteRecyclerData(int position){         data.remove(position);         notifyItemRemoved(position);     }       private Bitmap decodeUri(Uri selectedImage) throws FileNotFoundException {         BitmapFactory.Options o = new BitmapFactory.Options();         o.inJustDecodeBounds = true;         BitmapFactory.decodeStream(                context.getContentResolver().openInputStream(selectedImage), null, o);          final int REQUIRED_SIZE = 100;          int width_tmp = o.outWidth, height_tmp = o.outHeight;         int scale = 1;         while (true) {             if (width_tmp / 2 < REQUIRED_SIZE || height_tmp / 2 < REQUIRED_SIZE) {                 break;             }             width_tmp /= 2;             height_tmp /= 2;             scale *= 2;         }          BitmapFactory.Options o2 = new BitmapFactory.Options();         o2.inSampleSize = scale;         return BitmapFactory.decodeStream(                 context.getContentResolver().openInputStream(selectedImage), null, o2);     }     @Override     public int getItemCount() {         return data.size();     }      public class MyViewHolder extends RecyclerView.ViewHolder implements View.OnClickListener{         TextView title;       // TextView artist;         ImageView img;         CheckBox checkBox;          public MyViewHolder(View itemView) {             super(itemView);             title= (TextView) itemView.findViewById(R.id.list_text_all);             img= (ImageView) itemView.findViewById(R.id.list_image_all);             img.setOnClickListener(this);         }          @Override         public void onClick(View v) {}     }     public interface ClickListener{         public void itemClicked(View view, int position);     } } 

Answer 1

You can use a StateListDrawable to achieve the desired effect.

Example

Create a new Drawable resource file in your drawable directory with the following content:

selector_row.xml

<?xml version="1.0" encoding="utf-8"?> <selector xmlns:android="http://schemas.android.com/apk/res/android">     <!-- Color when the row is selected -->     <item android:drawable="@android:color/darker_gray" android:state_pressed="false" android:state_selected="true" />     <!-- Standard background color -->     <item android:drawable="@android:color/white" android:state_selected="false" /> </selector> 

Now simply use this StateListDrawable as the background in the row-layout of your RecyclerView

row_recyclerview.xml

<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"     android:layout_width="match_parent"     android:layout_height="wrap_content"     android:background="@drawable/selector_row">      <!-- row content -->  </RelativeLayout> 

Now as soon as the onClick() method in your adapter is called you simply need to do the following:

// myBackground is the RelativeLayout root of your row myBackground.setSelected(true); 

The rows' background will have the color (in this case darker_gray) as long as you call myBackground.setSelected(false). Of course you should create a SparseBooleanArray for example in order to know which row is selected and which isn't since the rows will be reused when scrolling.

Edit: Remember selected items
The idea behind the SparseBooleanArray is to remember the items which are selected. Following a sample on how to use it:

public class MyImageAdapter extends RecyclerView.Adapter<MyImageAdapter.MyViewHolder> {      private SparseBooleanArray selectedItems;      // Other stuff [...]      @Override     public void onBindViewHolder(MyViewHolder holder, int position) {         // Set the selected state of the row depending on the position         holder.myBackground.setSelected(selectedItems.get(position, false));     }      public class MyViewHolder extends RecyclerView.ViewHolder implements View.OnClickListener{          @Override         public void onClick(View v) {               // Save the selected positions to the SparseBooleanArray                if (selectedItems.get(getAdapterPosition(), false)) {                   selectedItems.delete(getAdapterPosition());                   myBackground.setSelected(false);               }               else {                   selectedItems.put(getAdapterPosition(), true);                   myBackground.setSelected(true);               }         }     } }