How to set border for android recyclerview grid layout.

Question

I want a view that looks like this , a border without spacing between items.

Currently my view looks like this, i am using a recyclerview with card view layout.

below is my code for each individual item

single_item_homepage xml:

<android.support.v7.widget.CardView xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="95dp"
android:layout_height="95dp"
android:layout_margin="8dp"
>

    <LinearLayout
    android:layout_width="match_parent"
    android:layout_height="wrap_content"
    android:orientation="vertical">

    <ImageView
        android:id="@+id/imageViewCategory"
        android:layout_width="match_parent"
        android:layout_height="75dp"
        />

    <TextView
        android:text="Shirt"
        android:id="@+id/textViewCategory"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_gravity="center_horizontal"
        android:textSize="15sp"/>


    </LinearLayout>

</android.support.v7.widget.CardView>

HomePage activity:

public class HomepageActivity extends AppCompatActivity {


private RecyclerView recyclerView;
private ImageAdapter imageAdapter;

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_homepage);

    recyclerView = findViewById(R.id.recyclerView);
    imageAdapter = new ImageAdapter(this);

    recyclerView.setHasFixedSize(true);
    recyclerView.setLayoutManager(new GridLayoutManager(HomepageActivity.this,3));
    recyclerView.setAdapter(imageAdapter);

    }
}

this is my adapter class:

public class ImageAdapter extends RecyclerView.Adapter<ImageAdapter.ImageViewHolder> {


private Context context;

public ImageAdapter(Context context) {
    this.context = context;
}

private int[] resourceId = new int[] {R.drawable.shirt,R.drawable.sleeveless,R.drawable.outerwear,
        R.drawable.sweater,R.drawable.pants,R.drawable.shorts,R.drawable.skirt,R.drawable.dresses,
        R.drawable.shoes,R.drawable.bags,R.drawable.accessories,R.drawable.swimwear
};

private String[] names = new String[]{
        "Shirts","Sleevless","Outerwear","Sweater","Pants","Shorts","Skirts","Dresses","Shoes","Bags","Accessories","Swimwear"
};



@NonNull
@Override
public ImageAdapter.ImageViewHolder onCreateViewHolder(@NonNull ViewGroup parent, int viewType) {
    View v = LayoutInflater.from(context).inflate(R.layout.single_item_homepage,parent,false);
    return new ImageViewHolder(v);
}

@Override
public void onBindViewHolder(@NonNull ImageAdapter.ImageViewHolder holder, int position) {
    String currName = names[position];
    int currResource = resourceId[position];
    holder.categoryName.setText(currName);
    holder.categoryImage.setImageResource(currResource);

}

@Override
public int getItemCount() {
    return names.length;
}

class ImageViewHolder extends RecyclerView.ViewHolder {

    TextView categoryName;
    ImageView categoryImage;


    public ImageViewHolder(View itemView) {
        super(itemView);

        categoryName = itemView.findViewById(R.id.textViewCategory);
        categoryImage = itemView.findViewById(R.id.imageViewCategory);
        }
    }
}

is there a way to change the recyclerview border ? Thanks in advance :)

Answer

HomepageActivity.java

recyclerView = findViewById(R.id.recyclerView);
imageAdapter = new ImageAdapter(this);

recyclerView.setHasFixedSize(true);
recyclerView.addItemDecoration(new DividerItemDecoration(this,
                DividerItemDecoration.HORIZONTAL))
recyclerView.addItemDecoration(new DividerItemDecoration(this,
                DividerItemDecoration.VERTICAL))
recyclerView.setLayoutManager(new GridLayoutManager(HomepageActivity.this,2));
recyclerView.setAdapter(imageAdapter);

single_item_homepage.xml

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="wrap_content"
    android:foreground="?android:selectableItemBackground"
    android:orientation="vertical"
    android:padding="@dimen/fifteen_dp">

    <ImageView
        android:id="@+id/ivGraphItemThumb"
        android:layout_width="match_parent"
        android:layout_height="125dp"
        tools:src="@drawable/ic_recent_exce" />

    <TextView
        android:id="@+id/tvMenu"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_gravity="center"
        android:textColor="@color/black"
        android:textSize="@dimen/fifteen_sp"
        tools:text="Item 1" />
</LinearLayout>

Answer

Add below code to set divider line for GridLayoutManager of RecylcerView.

recyclerView.addItemDecoration(new GridLayoutItemDecoration(2));

Use below GridLayoutItemDecoration class.

public class GridLayoutItemDecoration extends RecyclerView.ItemDecoration {
    private int space;

    public GridLayoutItemDecoration(int space) {
        this.space = space;
    }

    @Override
    public void getItemOffsets(Rect outRect, View view, RecyclerView parent, RecyclerView.State state) {
        int position = parent.getChildLayoutPosition(view);

        /// Only for GridLayoutManager 
        GridLayoutManager manager = (GridLayoutManager) parent.getLayoutManager();

        if (parent.getChildLayoutPosition(view) < manager.getSpanCount())
            outRect.top = space;

        if (position % 2 != 0) {
            outRect.right = space;
        }

        outRect.left = space;
        outRect.bottom = space;
    }
}

Remove CardView and margin of root layout and set background color (white in your case) from the single_item_homepage xml.

Set background color (gray in your case) of RecyclerView which will be display as color of divider line.

Answer

If you used childCount-1 in drawVertical and drawHorizontal in DividerItemDecoration, it won't work for GridLayoutManager.

I've modified DividerItemDecoration class, adding support for GridLayoutManager with just inner dividers. It can also supports the normal LinearLayoutManager.

You can try it out.

MiddleDividerItemDecoration

https://gist.github.com/Veeyikpong/a376c6128e603b0dee316670a74b345b

How to use?

GridLayoutManager

//MiddleDivideritemDecoration.ALL means both vertical and horizontal dividers
//You can also use MiddleDividerItemDecoration.VERTICAL / MiddleDividerItemDecoration.HORIZONTAL if you just want horizontal / vertical dividers
recyclerView.addItemDecoration(MiddleDividerItemDecoration(context!!, MiddleDividerItemDecoration.ALL))
recyclerView.layoutManager = GridLayoutManager(context!!, 3)
recyclerView.adapter = customAdapter

For complete usage, you can refer to https://gist.github.com/Veeyikpong/a376c6128e603b0dee316670a74b345b#gistcomment-2897799

EDITED: This will only worked for transparent background.