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/*
* Copyright (C) 2009 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.launcher2;
import android.os.Handler;
import android.os.SystemClock;
/**
* Provides an animation between 0.0f and 1.0f over a given duration.
*/
class SymmetricalLinearTween {
private static final int FPS = 30;
private static final int FRAME_TIME = 1000 / FPS;
Handler mHandler;
int mDuration;
TweenCallback mCallback;
boolean mRunning;
long mBase;
boolean mDirection;
float mValue;
/**
* @param duration milliseconds duration
* @param callback callbacks
*/
public SymmetricalLinearTween(boolean initial, int duration, TweenCallback callback) {
mValue = initial ? 1.0f : 0.0f;
mDirection = initial;
mDuration = duration;
mCallback = callback;
mHandler = new Handler();
}
/**
* Starts the tweening.
*
* @param direction If direction is true, the value goes towards 1.0f. If direction
* is false, the value goes towards 0.0f.
*/
public void start(boolean direction) {
start(direction, SystemClock.uptimeMillis());
}
/**
* Starts the tweening.
*
* @param direction If direction is true, the value goes towards 1.0f. If direction
* is false, the value goes towards 0.0f.
* @param baseTime The time to use as zero for this animation, in the
* {@link SystemClock.uptimeMillis} time base. This allows you to
* synchronize multiple animations.
*/
public void start(boolean direction, long baseTime) {
if (direction != mDirection) {
if (!mRunning) {
mBase = baseTime;
mRunning = true;
mCallback.onTweenStarted();
long next = SystemClock.uptimeMillis() + FRAME_TIME;
mHandler.postAtTime(mTick, next);
} else {
// reverse direction
long now = SystemClock.uptimeMillis();
long diff = now - mBase;
mBase = now + diff - mDuration;
}
mDirection = direction;
}
}
Runnable mTick = new Runnable() {
public void run() {
long base = mBase;
long now = SystemClock.uptimeMillis();
long diff = now-base;
int duration = mDuration;
float val = diff/(float)duration;
if (!mDirection) {
val = 1.0f - val;
}
if (val > 1.0f) {
val = 1.0f;
} else if (val < 0.0f) {
val = 0.0f;
}
float old = mValue;
mValue = val;
mCallback.onTweenValueChanged(val, old);
int frame = (int)(diff / FRAME_TIME);
long next = base + ((frame+1)*FRAME_TIME);
if (diff < duration) {
mHandler.postAtTime(this, next);
}
if (diff >= duration) {
mCallback.onTweenFinished();
mRunning = false;
}
}
};
}