src/com/android/gallery3d/anim/AlphaAnimation.java

/*
 * Copyright (C) 2010 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.gallery3d.anim;

import com.android.gallery3d.common.Utils;
import com.android.gallery3d.glrenderer.GLCanvas;

public class AlphaAnimation extends CanvasAnimation {
    private final float mStartAlpha;
    private final float mEndAlpha;
    private float mCurrentAlpha;

    public AlphaAnimation(float from, float to) {
        mStartAlpha = from;
        mEndAlpha = to;
        mCurrentAlpha = from;
    }

    @Override
    public void apply(GLCanvas canvas) {
        canvas.multiplyAlpha(mCurrentAlpha);
    }

    @Override
    public int getCanvasSaveFlags() {
        return GLCanvas.SAVE_FLAG_ALPHA;
    }

    @Override
    protected void onCalculate(float progress) {
        mCurrentAlpha = Utils.clamp(mStartAlpha
                + (mEndAlpha - mStartAlpha) * progress, 0f, 1f);
    }
}