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SimpleListDividerDecorator.java
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SimpleListDividerDecorator.java
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/*
* Copyright (C) 2015 Haruki Hasegawa
*
* 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 com.h6ah4i.android.widget.advrecyclerview.decoration;
import android.graphics.Canvas;
import android.graphics.Rect;
import android.graphics.drawable.Drawable;
import android.support.annotation.Nullable;
import android.support.v4.view.ViewCompat;
import android.support.v7.widget.RecyclerView;
import android.view.View;
/**
* Item decoration which draws item divider between each items.
*/
public class SimpleListDividerDecorator extends RecyclerView.ItemDecoration {
private final Drawable mHorizontalDrawable;
private final Drawable mVerticalDrawable;
private final int mHorizontalDividerHeight;
private final int mVerticalDividerWidth;
private final boolean mOverlap;
/**
* Constructor.
*
* @param divider horizontal divider drawable
* @param overlap whether the divider is drawn overlapped on bottom of the item.
*/
public SimpleListDividerDecorator(@Nullable Drawable divider, boolean overlap) {
this(divider, null, overlap);
}
/**
* Constructor.
*
* @param horizontalDivider horizontal divider drawable
* @param verticalDivider vertical divider drawable
* @param overlap whether the divider is drawn overlapped on bottom (or right) of the item.
*/
public SimpleListDividerDecorator(@Nullable Drawable horizontalDivider, @Nullable Drawable verticalDivider, boolean overlap) {
mHorizontalDrawable = horizontalDivider;
mVerticalDrawable = verticalDivider;
mHorizontalDividerHeight = (mHorizontalDrawable != null) ? mHorizontalDrawable.getIntrinsicHeight() : 0;
mVerticalDividerWidth = (mVerticalDrawable != null) ? mVerticalDrawable.getIntrinsicWidth() : 0;
mOverlap = overlap;
}
@Override
public void onDrawOver(Canvas c, RecyclerView parent, RecyclerView.State state) {
final int childCount = parent.getChildCount();
if (childCount == 0) {
return;
}
final float xPositionThreshold = (mOverlap) ? 1.0f : (mVerticalDividerWidth + 1.0f); // [px]
final float yPositionThreshold = (mOverlap) ? 1.0f : (mHorizontalDividerHeight + 1.0f); // [px]
final float zPositionThreshold = 1.0f; // [px]
for (int i = 0; i < childCount - 1; i++) {
final View child = parent.getChildAt(i);
final View nextChild = parent.getChildAt(i + 1);
if ((child.getVisibility() != View.VISIBLE) ||
(nextChild.getVisibility() != View.VISIBLE)) {
continue;
}
// check if the next item is placed at the bottom or right
final float childBottom = child.getBottom() + ViewCompat.getTranslationY(child);
final float nextChildTop = nextChild.getTop() + ViewCompat.getTranslationY(nextChild);
final float childRight = child.getRight() + ViewCompat.getTranslationX(child);
final float nextChildLeft = nextChild.getLeft() + ViewCompat.getTranslationX(nextChild);
if (!(((mHorizontalDividerHeight != 0) && (Math.abs(nextChildTop - childBottom) < yPositionThreshold)) ||
((mVerticalDividerWidth != 0) && (Math.abs(nextChildLeft - childRight) < xPositionThreshold)))) {
continue;
}
// check if the next item is placed on the same plane
final float childZ = ViewCompat.getTranslationZ(child) + ViewCompat.getElevation(child);
final float nextChildZ = ViewCompat.getTranslationZ(nextChild) + ViewCompat.getElevation(nextChild);
if (!(Math.abs(nextChildZ - childZ) < zPositionThreshold)) {
continue;
}
final float childAlpha = ViewCompat.getAlpha(child);
final float nextChildAlpha = ViewCompat.getAlpha(nextChild);
final int tx = (int) (ViewCompat.getTranslationX(child) + 0.5f);
final int ty = (int) (ViewCompat.getTranslationY(child) + 0.5f);
if (mHorizontalDividerHeight != 0) {
final int left = child.getLeft();
final int right = child.getRight();
final int top = child.getBottom() - (mOverlap ? mHorizontalDividerHeight : 0);
final int bottom = top + mHorizontalDividerHeight;
mHorizontalDrawable.setAlpha((int) ((0.5f * 255) * (childAlpha + nextChildAlpha) + 0.5f));
mHorizontalDrawable.setBounds(left + tx, top + ty, right + tx, bottom + ty);
mHorizontalDrawable.draw(c);
}
if (mVerticalDividerWidth != 0) {
final int left = child.getRight() - (mOverlap ? mVerticalDividerWidth : 0);
final int right = left + mVerticalDividerWidth;
final int top = child.getTop();
final int bottom = child.getBottom();
mVerticalDrawable.setAlpha((int) ((0.5f * 255) * (childAlpha + nextChildAlpha) + 0.5f));
mVerticalDrawable.setBounds(left + tx, top + ty, right + tx, bottom + ty);
mVerticalDrawable.draw(c);
}
}
}
@Override
public void getItemOffsets(Rect outRect, View view, RecyclerView parent, RecyclerView.State state) {
if (mOverlap) {
outRect.set(0, 0, 0, 0);
} else {
outRect.set(0, 0, mVerticalDividerWidth, mHorizontalDividerHeight);
}
}
}