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/*
* 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 android.view.animation.Interpolator;
// Animation calculates a value according to the current input time.
//
// 1. First we need to use setDuration(int) to set the duration of the
// animation. The duration is in milliseconds.
// 2. Then we should call start(). The actual start time is the first value
// passed to calculate(long).
// 3. Each time we want to get an animation value, we call
// calculate(long currentTimeMillis) to ask the Animation to calculate it.
// The parameter passed to calculate(long) should be nonnegative.
// 4. Use get() to get that value.
//
// In step 3, onCalculate(float progress) is called so subclasses can calculate
// the value according to progress (progress is a value in [0,1]).
//
// Before onCalculate(float) is called, There is an optional interpolator which
// can change the progress value. The interpolator can be set by
// setInterpolator(Interpolator). If the interpolator is used, the value passed
// to onCalculate may be (for example, the overshoot effect).
//
// The isActive() method returns true after the animation start() is called and
// before calculate is passed a value which reaches the duration of the
// animation.
//
// The start() method can be called again to restart the Animation.
//
abstract public class Animation {
private static final long ANIMATION_START = -1;
private static final long NO_ANIMATION = -2;
private long mStartTime = NO_ANIMATION;
private int mDuration;
private Interpolator mInterpolator;
public void setInterpolator(Interpolator interpolator) {
mInterpolator = interpolator;
}
public void setDuration(int duration) {
mDuration = duration;
}
public void start() {
mStartTime = ANIMATION_START;
}
public void setStartTime(long time) {
mStartTime = time;
}
public boolean isActive() {
return mStartTime != NO_ANIMATION;
}
public void forceStop() {
mStartTime = NO_ANIMATION;
}
public boolean calculate(long currentTimeMillis) {
if (mStartTime == NO_ANIMATION) return false;
if (mStartTime == ANIMATION_START) mStartTime = currentTimeMillis;
int elapse = (int) (currentTimeMillis - mStartTime);
float x = Utils.clamp((float) elapse / mDuration, 0f, 1f);
Interpolator i = mInterpolator;
onCalculate(i != null ? i.getInterpolation(x) : x);
if (elapse >= mDuration) mStartTime = NO_ANIMATION;
return mStartTime != NO_ANIMATION;
}
abstract protected void onCalculate(float progress);
}
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