Kuldeep Dubey Kuldeep Dubey - 5 months ago 74
Android Question

how to highlight the selected Item of Recycler View?

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

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(pos);
                  myBackground.setSelected(false);
              }
              else {
                  selectedItems.put(getAdapterPosition(), true);
                  myBackground.setSelected(true);
              }
        }
    }
}