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);
            }
        }
    }
}