1 /* 2 * Copyright 2013 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.example.android.interactivechart; 18 19 import android.content.Context; 20 import android.os.SystemClock; 21 import android.view.animation.DecelerateInterpolator; 22 import android.view.animation.Interpolator; 23 24 /** 25 * A simple class that animates double-touch zoom gestures. Functionally similar to a {@link 26 * android.widget.Scroller}. 27 */ 28 public class Zoomer { 29 /** 30 * The interpolator, used for making zooms animate 'naturally.' 31 */ 32 private Interpolator mInterpolator; 33 34 /** 35 * The total animation duration for a zoom. 36 */ 37 private int mAnimationDurationMillis; 38 39 /** 40 * Whether or not the current zoom has finished. 41 */ 42 private boolean mFinished = true; 43 44 /** 45 * The current zoom value; computed by {@link #computeZoom()}. 46 */ 47 private float mCurrentZoom; 48 49 /** 50 * The time the zoom started, computed using {@link android.os.SystemClock#elapsedRealtime()}. 51 */ 52 private long mStartRTC; 53 54 /** 55 * The destination zoom factor. 56 */ 57 private float mEndZoom; 58 Zoomer(Context context)59 public Zoomer(Context context) { 60 mInterpolator = new DecelerateInterpolator(); 61 mAnimationDurationMillis = context.getResources().getInteger( 62 android.R.integer.config_shortAnimTime); 63 } 64 65 /** 66 * Forces the zoom finished state to the given value. Unlike {@link #abortAnimation()}, the 67 * current zoom value isn't set to the ending value. 68 * 69 * @see android.widget.Scroller#forceFinished(boolean) 70 */ forceFinished(boolean finished)71 public void forceFinished(boolean finished) { 72 mFinished = finished; 73 } 74 75 /** 76 * Aborts the animation, setting the current zoom value to the ending value. 77 * 78 * @see android.widget.Scroller#abortAnimation() 79 */ abortAnimation()80 public void abortAnimation() { 81 mFinished = true; 82 mCurrentZoom = mEndZoom; 83 } 84 85 /** 86 * Starts a zoom from 1.0 to (1.0 + endZoom). That is, to zoom from 100% to 125%, endZoom should 87 * by 0.25f. 88 * 89 * @see android.widget.Scroller#startScroll(int, int, int, int) 90 */ startZoom(float endZoom)91 public void startZoom(float endZoom) { 92 mStartRTC = SystemClock.elapsedRealtime(); 93 mEndZoom = endZoom; 94 95 mFinished = false; 96 mCurrentZoom = 1f; 97 } 98 99 /** 100 * Computes the current zoom level, returning true if the zoom is still active and false if the 101 * zoom has finished. 102 * 103 * @see android.widget.Scroller#computeScrollOffset() 104 */ computeZoom()105 public boolean computeZoom() { 106 if (mFinished) { 107 return false; 108 } 109 110 long tRTC = SystemClock.elapsedRealtime() - mStartRTC; 111 if (tRTC >= mAnimationDurationMillis) { 112 mFinished = true; 113 mCurrentZoom = mEndZoom; 114 return false; 115 } 116 117 float t = tRTC * 1f / mAnimationDurationMillis; 118 mCurrentZoom = mEndZoom * mInterpolator.getInterpolation(t); 119 return true; 120 } 121 122 /** 123 * Returns the current zoom level. 124 * 125 * @see android.widget.Scroller#getCurrX() 126 */ getCurrZoom()127 public float getCurrZoom() { 128 return mCurrentZoom; 129 } 130 } 131