1 /* 2 * Copyright (C) 2009 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 android.view.animation; 18 19 import android.content.Context; 20 import android.content.res.TypedArray; 21 import android.util.AttributeSet; 22 23 /** 24 * An interpolator where the change starts backward then flings forward. 25 */ 26 public class AnticipateInterpolator implements Interpolator { 27 private final float mTension; 28 29 public AnticipateInterpolator() { 30 mTension = 2.0f; 31 } 32 33 /** 34 * @param tension Amount of anticipation. When tension equals 0.0f, there is 35 * no anticipation and the interpolator becomes a simple 36 * acceleration interpolator. 37 */ 38 public AnticipateInterpolator(float tension) { 39 mTension = tension; 40 } 41 42 public AnticipateInterpolator(Context context, AttributeSet attrs) { 43 TypedArray a = context.obtainStyledAttributes(attrs, 44 com.android.internal.R.styleable.AnticipateInterpolator); 45 46 mTension = 47 a.getFloat(com.android.internal.R.styleable.AnticipateInterpolator_tension, 2.0f); 48 49 a.recycle(); 50 } 51 52 public float getInterpolation(float t) { 53 // a(t) = t * t * ((tension + 1) * t - tension) 54 return t * t * ((mTension + 1) * t - mTension); 55 } 56 } 57
