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.Resources; 21 import android.content.res.Resources.Theme; 22 import android.content.res.TypedArray; 23 import android.util.AttributeSet; 24 25 import com.android.internal.R; 26 import com.android.internal.view.animation.HasNativeInterpolator; 27 import com.android.internal.view.animation.NativeInterpolatorFactory; 28 import com.android.internal.view.animation.NativeInterpolatorFactoryHelper; 29 30 /** 31 * An interpolator where the change starts backward then flings forward. 32 */ 33 @HasNativeInterpolator 34 public class AnticipateInterpolator extends BaseInterpolator implements NativeInterpolatorFactory { 35 private final float mTension; 36 37 public AnticipateInterpolator() { 38 mTension = 2.0f; 39 } 40 41 /** 42 * @param tension Amount of anticipation. When tension equals 0.0f, there is 43 * no anticipation and the interpolator becomes a simple 44 * acceleration interpolator. 45 */ 46 public AnticipateInterpolator(float tension) { 47 mTension = tension; 48 } 49 50 public AnticipateInterpolator(Context context, AttributeSet attrs) { 51 this(context.getResources(), context.getTheme(), attrs); 52 } 53 54 /** @hide */ 55 public AnticipateInterpolator(Resources res, Theme theme, AttributeSet attrs) { 56 TypedArray a; 57 if (theme != null) { 58 a = theme.obtainStyledAttributes(attrs, R.styleable.AnticipateInterpolator, 0, 0); 59 } else { 60 a = res.obtainAttributes(attrs, R.styleable.AnticipateInterpolator); 61 } 62 63 mTension = a.getFloat(R.styleable.AnticipateInterpolator_tension, 2.0f); 64 setChangingConfiguration(a.getChangingConfigurations()); 65 a.recycle(); 66 } 67 68 public float getInterpolation(float t) { 69 // a(t) = t * t * ((tension + 1) * t - tension) 70 return t * t * ((mTension + 1) * t - mTension); 71 } 72 73 /** @hide */ 74 @Override 75 public long createNativeInterpolator() { 76 return NativeInterpolatorFactoryHelper.createAnticipateInterpolator(mTension); 77 } 78 } 79
