Customizing the DividerItemDecoration class so we can remove divider / decorator after the last item

DividerItemDecoration.java

/*
 * Copyright (C) 2016 The Android Open Source Project
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package android.support.v7.widget;

import android.content.Context;
import android.content.res.TypedArray;
import android.graphics.Canvas;
import android.graphics.Rect;
import android.graphics.drawable.Drawable;
import android.support.annotation.NonNull;
import android.util.Log;
import android.view.View;
import android.widget.LinearLayout;

/**
 * DividerItemDecoration is a {@link RecyclerView.ItemDecoration} that can be used as a divider
 * between items of a {@link LinearLayoutManager}. It supports both {@link #HORIZONTAL} and
 * {@link #VERTICAL} orientations.
 *
 * <pre>
 *     mDividerItemDecoration = new DividerItemDecoration(recyclerView.getContext(),
 *             mLayoutManager.getOrientation());
 *     recyclerView.addItemDecoration(mDividerItemDecoration);
 * </pre>
 */
public class DividerItemDecoration extends RecyclerView.ItemDecoration {

    public static final int HORIZONTAL = LinearLayout.HORIZONTAL;
    public static final int VERTICAL = LinearLayout.VERTICAL;

    private static final String TAG = "DividerItem";
    private static final int[] ATTRS = new int[]{android.R.attr.listDivider};

    private Drawable mDivider;

    /**
     * Current orientation. Either {@link #HORIZONTAL} or {@link #VERTICAL}.
     */
    private int mOrientation;

//    private final Rect mBounds = new Rect();

    private final boolean mIsShowInLastItem;

    /**
     * Creates a divider {@link RecyclerView.ItemDecoration} that can be used with a
     * {@link LinearLayoutManager}.
     *
     * @param context          Current context, it will be used to access resources.
     * @param orientation      Divider orientation. Should be {@link #HORIZONTAL} or {@link #VERTICAL}.
     * @param isShowInLastItem Whether show the divider in last item.
     */
    public DividerItemDecoration(Context context, int orientation, boolean isShowInLastItem) {
        final TypedArray a = context.obtainStyledAttributes(ATTRS);
        mDivider = a.getDrawable(0);
        if (mDivider == null) {
            Log.w(TAG, "@android:attr/listDivider was not set in the theme used for this "
                    + "DividerItemDecoration. Please set that attribute all call setDrawable()");
        }
        a.recycle();
        setOrientation(orientation);
        this.mIsShowInLastItem = isShowInLastItem;
    }

    /**
     * Sets the orientation for this divider. This should be called if
     * {@link RecyclerView.LayoutManager} changes orientation.
     *
     * @param orientation {@link #HORIZONTAL} or {@link #VERTICAL}
     */
    public void setOrientation(int orientation) {
        if (orientation != HORIZONTAL && orientation != VERTICAL) {
            throw new IllegalArgumentException(
                    "Invalid orientation. It should be either HORIZONTAL or VERTICAL");
        }
        mOrientation = orientation;
    }

    /**
     * Sets the {@link Drawable} for this divider.
     *
     * @param drawable Drawable that should be used as a divider.
     */
    public void setDrawable(@NonNull Drawable drawable) {
        if (drawable == null) {
            throw new IllegalArgumentException("Drawable cannot be null.");
        }
        mDivider = drawable;
    }

    @Override
    public void onDraw(Canvas c, RecyclerView parent, RecyclerView.State state) {
        if (parent.getLayoutManager() == null || mDivider == null) {
            return;
        }
        if (mOrientation == VERTICAL) {
            drawVertical(c, parent);
        } else {
            drawHorizontal(c, parent);
        }
    }

    private void drawVertical(Canvas canvas, RecyclerView parent) {
        canvas.save();
        final int left;
        final int right;
        if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.LOLLIPOP && parent.getClipToPadding()) {
            left = parent.getPaddingLeft();
            right = parent.getWidth() - parent.getPaddingRight();
            canvas.clipRect(left, parent.getPaddingTop(), right,
                    parent.getHeight() - parent.getPaddingBottom());
        } else {
            left = 0;
            right = parent.getWidth();
        }

        int childCount;
        if (mIsShowInLastItem) {
            childCount = parent.getChildCount();
        } else {
            childCount = parent.getChildCount() - 1;
        }
        for (int i = 0; i < childCount; i++) {
            final View child = parent.getChildAt(i);
//                parent.getDecoratedBoundsWithMargins(child, mBounds);
//                final int bottom = mBounds.bottom + Math.round(child.getTranslationY());
            int decoratedBottom = parent.getLayoutManager().getDecoratedBottom(child);
            final int bottom = decoratedBottom + Math.round(child.getTranslationY());
            final int top = bottom - mDivider.getIntrinsicHeight();
            mDivider.setBounds(left, top, right, bottom);
            mDivider.draw(canvas);
        }
        canvas.restore();
    }

    private void drawHorizontal(Canvas canvas, RecyclerView parent) {
        canvas.save();
        final int top;
        final int bottom;
        if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.LOLLIPOP && parent.getClipToPadding()) {
            top = parent.getPaddingTop();
            bottom = parent.getHeight() - parent.getPaddingBottom();
            canvas.clipRect(parent.getPaddingLeft(), top,
                    parent.getWidth() - parent.getPaddingRight(), bottom);
        } else {
            top = 0;
            bottom = parent.getHeight();
        }

        int childCount;
        if (mIsShowInLastItem) {
            childCount = parent.getChildCount();
        } else {
            childCount = parent.getChildCount() - 1;
        }
        for (int i = 0; i < childCount; i++) {
            final View child = parent.getChildAt(i);
//                parent.getLayoutManager().getDecoratedBoundsWithMargins(child, mBounds);
//                final int right = mBounds.right + Math.round(child.getTranslationX());
            int decoratedRight = parent.getLayoutManager().getDecoratedRight(child);
            final int right = decoratedRight + Math.round(child.getTranslationX());
            final int left = right - mDivider.getIntrinsicWidth();
            mDivider.setBounds(left, top, right, bottom);
            mDivider.draw(canvas);
        }
        canvas.restore();
    }

    @Override
    public void getItemOffsets(Rect outRect, View view, RecyclerView parent, RecyclerView.State state) {
        if (mDivider == null) {
            outRect.setEmpty();
            return;
        }

        int itemPosition = ((RecyclerView.LayoutParams) view.getLayoutParams()).getViewLayoutPosition();
        int itemCount = state.getItemCount();

        if (mIsShowInLastItem) {
            if (mOrientation == VERTICAL) {
                outRect.set(0, 0, 0, mDivider.getIntrinsicHeight());
            } else {
                outRect.set(0, 0, mDivider.getIntrinsicWidth(), 0);
            }
        } else if (itemPosition == itemCount - 1) {
            // We didn't set the last item when mIsShowInLastItem's value is false.
            outRect.setEmpty();
        } else {
            if (mOrientation == VERTICAL) {
                outRect.set(0, 0, 0, mDivider.getIntrinsicHeight());
            } else {
                outRect.set(0, 0, mDivider.getIntrinsicWidth(), 0);
            }
        }
    }
}

Credit by https://stackoverflow.com/questions/46215810/recyclerview-remove-divider-decorator-after-the-last-item

The getClipToPadding() method in ViewGroup.java is added in API 21. So we refactor the drawVertical and drawHorizontal method.

We add the mIsShowInLastItem variable to control the logic of showing divider in last item.

works perfect

Thanks! Can we use the code in commercial apps?

Thanks a lot!!!

Thanks! Can we use the code in commercial apps?

Sure. :)

Thx A lot !!!,, helpfull

thanks!!

I have been using this code for 2 years, but currently noticed that adding a picture can sometimes produce removing a space before the last item (and after the last), if isShowInLastItem == false. If use DividerItemDecoration, all spaces will be equal, but we will have the last space visible. I think,

    } else if (itemPosition == itemCount - 1) {
        // We didn't set the last item when isShowInLastItem's value is false.
        outRect.setEmpty();
    }

works wrong, but I am not sure. Every time I add a picture before plus sign (in a last but one position).

UPDATE

Sorry, I found a mistake in my code. When I added a picture, I used notifyItemInserted(position) to update a list. But in my case it was position = list.lastIndex (this is wrong). So, it made double refreshing and called outRect.setEmpty(); twice. By the way, after removing outRect.setEmpty(); all dividers were drawn the same way.

Thanks @johnwatsondev , I am using this in to Kotlin code and Here i had converted it to Kotlin: https://gist.github.com/bipinvaylu/2714d9d429dc72b0108c05be52b609e0