src/com/android/launcher3/ClickShadowView.java

/*
 * Copyright (C) 2014 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 com.android.launcher3;

import android.content.Context;
import android.graphics.Bitmap;
import android.graphics.Canvas;
import android.graphics.Color;
import android.graphics.Paint;
import android.view.View;
import android.view.ViewGroup;

public class ClickShadowView extends View {

    private static final int SHADOW_SIZE_FACTOR = 3;
    private static final int SHADOW_LOW_ALPHA = 30;
    private static final int SHADOW_HIGH_ALPHA = 60;

    private final Paint mPaint;

    private final float mShadowOffset;
    private final float mShadowPadding;

    private Bitmap mBitmap;

    public ClickShadowView(Context context) {
        super(context);
        mPaint = new Paint(Paint.FILTER_BITMAP_FLAG);
        mPaint.setColor(Color.BLACK);

        mShadowPadding = getResources().getDimension(R.dimen.blur_size_click_shadow);
        mShadowOffset = getResources().getDimension(R.dimen.click_shadow_high_shift);
    }

    /**
     * @return extra space required by the view to show the shadow.
     */
    public int getExtraSize() {
        return (int) (SHADOW_SIZE_FACTOR * mShadowPadding);
    }

    /**
     * Applies the new bitmap.
     * @return true if the view was invalidated.
     */
    public boolean setBitmap(Bitmap b) {
        if (b != mBitmap){
            mBitmap = b;
            invalidate();
            return true;
        }
        return false;
    }

    @Override
    protected void onDraw(Canvas canvas) {
        if (mBitmap != null) {
            mPaint.setAlpha(SHADOW_LOW_ALPHA);
            canvas.drawBitmap(mBitmap, 0, 0, mPaint);
            mPaint.setAlpha(SHADOW_HIGH_ALPHA);
            canvas.drawBitmap(mBitmap, 0, mShadowOffset, mPaint);
        }
    }

    public void animateShadow() {
        setAlpha(0);
        animate().alpha(1)
            .setDuration(FastBitmapDrawable.CLICK_FEEDBACK_DURATION)
            .setInterpolator(FastBitmapDrawable.CLICK_FEEDBACK_INTERPOLATOR)
            .start();
    }

    /**
     * Aligns the shadow with {@param view}
     * @param viewParent immediate parent of {@param view}. It must be a sibling of this view.
     */
    public void alignWithIconView(BubbleTextView view, ViewGroup viewParent) {
        float leftShift = view.getLeft() + viewParent.getLeft() - getLeft();
        float topShift = view.getTop() + viewParent.getTop() - getTop();
        int iconWidth = view.getRight() - view.getLeft();
        int iconHSpace = iconWidth - view.getCompoundPaddingRight() - view.getCompoundPaddingLeft();
        float drawableWidth = view.getIcon().getBounds().width();

        setTranslationX(leftShift
                + viewParent.getTranslationX()
                + view.getCompoundPaddingLeft() * view.getScaleX()
                + (iconHSpace - drawableWidth) * view.getScaleX() / 2  /* drawable gap */
                + iconWidth * (1 - view.getScaleX()) / 2  /* gap due to scale */
                - mShadowPadding  /* extra shadow size */
                );
        setTranslationY(topShift
                + viewParent.getTranslationY()
                + view.getPaddingTop() * view.getScaleY()  /* drawable gap */
                + view.getHeight() * (1 - view.getScaleY()) / 2  /* gap due to scale */
                - mShadowPadding  /* extra shadow size */
                );
    }
}