src/com/android/colorpicker/ColorStateDrawable.java

/*
 * Copyright (C) 2013 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.colorpicker;

import android.graphics.Color;
import android.graphics.PorterDuff;
import android.graphics.drawable.Drawable;
import android.graphics.drawable.LayerDrawable;

/**
 * A drawable which sets its color filter to a color specified by the user, and changes to a
 * slightly darker color when pressed or focused.
 */
public class ColorStateDrawable extends LayerDrawable {

    private static final float PRESSED_STATE_MULTIPLIER = 0.70f;

    private int mColor;

    public ColorStateDrawable(Drawable[] layers, int color) {
        super(layers);
        mColor = color;
    }

    @Override
    protected boolean onStateChange(int[] states) {
        boolean pressedOrFocused = false;
        for (int state : states) {
            if (state == android.R.attr.state_pressed || state == android.R.attr.state_focused) {
                pressedOrFocused = true;
                break;
            }
        }

        if (pressedOrFocused) {
            super.setColorFilter(getPressedColor(mColor), PorterDuff.Mode.SRC_ATOP);
        } else {
            super.setColorFilter(mColor, PorterDuff.Mode.SRC_ATOP);
        }

        return super.onStateChange(states);
    }

    /**
     * Given a particular color, adjusts its value by a multiplier.
     */
    private static int getPressedColor(int color) {
        float[] hsv = new float[3];
        Color.colorToHSV(color, hsv);
        hsv[2] = hsv[2] * PRESSED_STATE_MULTIPLIER;
        return Color.HSVToColor(hsv);
    }

    @Override
    public boolean isStateful() {
        return true;
    }
}