sdk/sources/android-25/android/view/animation/OvershootInterpolator.java

   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
  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      */
  47     public OvershootInterpolator(float tension) {
  48         mTension = tension;
  49     }
  50
  51     public OvershootInterpolator(Context context, AttributeSet attrs) {
  52         this(context.getResources(), context.getTheme(), attrs);
  53     }
  54
  55     /** @hide */
  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
  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
  78     public long createNativeInterpolator() {
  79         return NativeInterpolatorFactoryHelper.createOvershootInterpolator(mTension);
  80     }
  81 }