packages/SystemUI/src/com/android/systemui/statusbar/policy/KeyguardUserSwitcherScrim.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.systemui.statusbar.policy;

import android.graphics.Canvas;
import android.graphics.Color;
import android.graphics.ColorFilter;
import android.graphics.Paint;
import android.graphics.PixelFormat;
import android.graphics.RadialGradient;
import android.graphics.Rect;
import android.graphics.Shader;
import android.graphics.drawable.Drawable;
import android.util.LayoutDirection;
import android.view.View;

import com.android.systemui.R;

/**
 * Gradient background for the user switcher on Keyguard.
 */
public class KeyguardUserSwitcherScrim extends Drawable
        implements View.OnLayoutChangeListener {

    private static final float OUTER_EXTENT = 2.5f;
    private static final float INNER_EXTENT = 0.75f;

    private int mDarkColor;
    private int mTop;
    private Paint mRadialGradientPaint = new Paint();

    public KeyguardUserSwitcherScrim(View host) {
        host.addOnLayoutChangeListener(this);
        mDarkColor = host.getResources().getColor(
                R.color.keyguard_user_switcher_background_gradient_color);
    }

    @Override
    public void draw(Canvas canvas) {
        boolean isLtr = getLayoutDirection() == LayoutDirection.LTR;
        Rect bounds = getBounds();
        float width = bounds.width() * OUTER_EXTENT;
        float height = (mTop + bounds.height()) * OUTER_EXTENT;
        canvas.translate(0, -mTop);
        canvas.scale(1, height/width);
        canvas.drawRect(isLtr ? bounds.right - width : 0, 0,
                isLtr ? bounds.right : bounds.left + width, width, mRadialGradientPaint);
    }

    @Override
    public void setAlpha(int alpha) {
    }

    @Override
    public void setColorFilter(ColorFilter cf) {
    }

    @Override
    public int getOpacity() {
        return PixelFormat.TRANSLUCENT;
    }

    @Override
    public void onLayoutChange(View v, int left, int top, int right, int bottom, int oldLeft,
            int oldTop, int oldRight, int oldBottom) {
        if (left != oldLeft || top != oldTop || right != oldRight || bottom != oldBottom) {
            int width = right - left;
            float radius = width * OUTER_EXTENT;
            boolean isLtr = getLayoutDirection() == LayoutDirection.LTR;
            mRadialGradientPaint.setShader(
                    new RadialGradient(isLtr ? width : 0, 0, radius,
                            new int[] { mDarkColor, Color.TRANSPARENT},
                            new float[] { Math.max(0f, width * INNER_EXTENT / radius), 1f},
                            Shader.TileMode.CLAMP));
            mTop = top;
        }
    }
}