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ItemShadowDecorator.java
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ItemShadowDecorator.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.ColorDrawable;
import android.graphics.drawable.Drawable;
import android.graphics.drawable.NinePatchDrawable;
import android.support.v4.view.ViewCompat;
import android.support.v7.widget.RecyclerView;
import android.view.View;
/**
* Item decoration which draws drop shadow of each item views.
*/
public class ItemShadowDecorator extends RecyclerView.ItemDecoration {
private final NinePatchDrawable mShadowDrawable;
private final Rect mShadowPadding = new Rect();
/**
* Constructor.
*
* @param shadow 9-patch drawable used for drop shadow
*/
public ItemShadowDecorator(NinePatchDrawable shadow) {
mShadowDrawable = shadow;
mShadowDrawable.getPadding(mShadowPadding);
}
@Override
public void onDraw(Canvas c, RecyclerView parent, RecyclerView.State state) {
final int childCount = parent.getChildCount();
if (childCount == 0) {
return;
}
int savedCount = c.save(Canvas.CLIP_SAVE_FLAG);
c.clipRect(
parent.getLeft() + Math.max(0, parent.getPaddingLeft() - mShadowPadding.left),
parent.getTop()/* + Math.max(0, parent.getPaddingTop() - mShadowPadding.top)*/,
parent.getRight() - Math.max(0, parent.getPaddingRight() - mShadowPadding.right),
parent.getBottom()/* - Math.max(0, parent.getPaddingBottom() - mShadowPadding.bottom)*/);
for (int i = 0; i < childCount; i++) {
final View child = parent.getChildAt(i);
if (!shouldDrawDropShadow(child)) {
continue;
}
final int tx = (int) (ViewCompat.getTranslationX(child) + 0.5f);
final int ty = (int) (ViewCompat.getTranslationY(child) + 0.5f);
final int left = child.getLeft() - mShadowPadding.left;
final int right = child.getRight() + mShadowPadding.right;
final int top = child.getTop() - mShadowPadding.top;
final int bottom = child.getBottom() + mShadowPadding.bottom;
mShadowDrawable.setBounds(left + tx, top + ty, right + tx, bottom + ty);
mShadowDrawable.draw(c);
}
c.restoreToCount(savedCount);
}
private static boolean shouldDrawDropShadow(View child) {
if (child.getVisibility() != View.VISIBLE) {
return false;
}
if (ViewCompat.getAlpha(child) != 1.0f) {
return false;
}
Drawable background = child.getBackground();
if (background == null) {
return false;
}
if (background instanceof ColorDrawable) {
//noinspection RedundantCast
if (((ColorDrawable) background).getAlpha() == 0) {
return false;
}
}
return true;
}
@Override
public void getItemOffsets(Rect outRect, View view, RecyclerView parent, RecyclerView.State state) {
outRect.set(0, 0, 0, 0);
}
}