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 flings forward and overshoots the last value
32  * then comes back.
33  */
34 @HasNativeInterpolator
35 public class OvershootInterpolator extends BaseInterpolator implements NativeInterpolatorFactory {
36     private final float mTension;
37 
OvershootInterpolator()38     public OvershootInterpolator() {
39         mTension = 2.0f;
40     }
41 
42     /**
43      * @param tension Amount of overshoot. When tension equals 0.0f, there is
44      *                no overshoot and the interpolator becomes a simple
45      *                deceleration interpolator.
46      */
OvershootInterpolator(float tension)47     public OvershootInterpolator(float tension) {
48         mTension = tension;
49     }
50 
OvershootInterpolator(Context context, AttributeSet attrs)51     public OvershootInterpolator(Context context, AttributeSet attrs) {
52         this(context.getResources(), context.getTheme(), attrs);
53     }
54 
55     /** @hide */
OvershootInterpolator(Resources res, Theme theme, AttributeSet attrs)56     public OvershootInterpolator(Resources res, Theme theme, AttributeSet attrs) {
57         TypedArray a;
58         if (theme != null) {
59             a = theme.obtainStyledAttributes(attrs, R.styleable.OvershootInterpolator, 0, 0);
60         } else {
61             a = res.obtainAttributes(attrs, R.styleable.OvershootInterpolator);
62         }
63 
64         mTension = a.getFloat(R.styleable.OvershootInterpolator_tension, 2.0f);
65         setChangingConfiguration(a.getChangingConfigurations());
66         a.recycle();
67     }
68 
getInterpolation(float t)69     public float getInterpolation(float t) {
70         // _o(t) = t * t * ((tension + 1) * t + tension)
71         // o(t) = _o(t - 1) + 1
72         t -= 1.0f;
73         return t * t * ((mTension + 1) * t + mTension) + 1.0f;
74     }
75 
76     /** @hide */
77     @Override
createNativeInterpolator()78     public long createNativeInterpolator() {
79         return NativeInterpolatorFactoryHelper.createOvershootInterpolator(mTension);
80     }
81 }
82