1 /* 2 * Copyright (C) 2010 The Android Open Source Project 3 * 4 * Licensed under the Apache License, Version 2.0 (the "License"); 5 * you may not use this file except in compliance with the License. 6 * You may obtain a copy of the License at 7 * 8 * http://www.apache.org/licenses/LICENSE-2.0 9 * 10 * Unless required by applicable law or agreed to in writing, software 11 * distributed under the License is distributed on an "AS IS" BASIS, 12 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 13 * See the License for the specific language governing permissions and 14 * limitations under the License. 15 */ 16 17 package com.android.gallery3d.anim; 18 19 import android.view.animation.Interpolator; 20 21 import com.android.gallery3d.common.Utils; 22 23 // Animation calculates a value according to the current input time. 24 // 25 // 1. First we need to use setDuration(int) to set the duration of the 26 // animation. The duration is in milliseconds. 27 // 2. Then we should call start(). The actual start time is the first value 28 // passed to calculate(long). 29 // 3. Each time we want to get an animation value, we call 30 // calculate(long currentTimeMillis) to ask the Animation to calculate it. 31 // The parameter passed to calculate(long) should be nonnegative. 32 // 4. Use get() to get that value. 33 // 34 // In step 3, onCalculate(float progress) is called so subclasses can calculate 35 // the value according to progress (progress is a value in [0,1]). 36 // 37 // Before onCalculate(float) is called, There is an optional interpolator which 38 // can change the progress value. The interpolator can be set by 39 // setInterpolator(Interpolator). If the interpolator is used, the value passed 40 // to onCalculate may be (for example, the overshoot effect). 41 // 42 // The isActive() method returns true after the animation start() is called and 43 // before calculate is passed a value which reaches the duration of the 44 // animation. 45 // 46 // The start() method can be called again to restart the Animation. 47 // 48 abstract public class Animation { 49 private static final long ANIMATION_START = -1; 50 private static final long NO_ANIMATION = -2; 51 52 private long mStartTime = NO_ANIMATION; 53 private int mDuration; 54 private Interpolator mInterpolator; 55 setInterpolator(Interpolator interpolator)56 public void setInterpolator(Interpolator interpolator) { 57 mInterpolator = interpolator; 58 } 59 setDuration(int duration)60 public void setDuration(int duration) { 61 mDuration = duration; 62 } 63 start()64 public void start() { 65 mStartTime = ANIMATION_START; 66 } 67 setStartTime(long time)68 public void setStartTime(long time) { 69 mStartTime = time; 70 } 71 isActive()72 public boolean isActive() { 73 return mStartTime != NO_ANIMATION; 74 } 75 forceStop()76 public void forceStop() { 77 mStartTime = NO_ANIMATION; 78 } 79 calculate(long currentTimeMillis)80 public boolean calculate(long currentTimeMillis) { 81 if (mStartTime == NO_ANIMATION) return false; 82 if (mStartTime == ANIMATION_START) mStartTime = currentTimeMillis; 83 int elapse = (int) (currentTimeMillis - mStartTime); 84 float x = Utils.clamp((float) elapse / mDuration, 0f, 1f); 85 Interpolator i = mInterpolator; 86 onCalculate(i != null ? i.getInterpolation(x) : x); 87 if (elapse >= mDuration) mStartTime = NO_ANIMATION; 88 return mStartTime != NO_ANIMATION; 89 } 90 onCalculate(float progress)91 abstract protected void onCalculate(float progress); 92 } 93