OrigamiAnimationView.java

package com.facebook.origami;

import android.content.Context;
import android.util.AttributeSet;
import android.view.View;
import android.widget.FrameLayout;

import com.facebook.rebound.SimpleSpringListener;
import com.facebook.rebound.Spring;
import com.facebook.rebound.SpringConfig;
import com.facebook.rebound.SpringSystem;
import com.facebook.rebound.SpringUtil;

public class OrigamiAnimationView extends FrameLayout {

  private final SpringSystem springSystem;
  private final Spring photoZoomSpring;
  private final Spring fadeSpring;
  private final View story;
  private final View photo;

  public OrigamiAnimationView(Context context) {
    this(context, null);
  }

  public OrigamiAnimationView(Context context, AttributeSet attrs) {
    this(context, attrs, 0);
  }

  public OrigamiAnimationView(Context context, AttributeSet attrs, int defStyle) {
    super(context, attrs, defStyle);

    // Hook up variables to your views here
    story = null;
    photo = null;

    springSystem = SpringSystem.create();

    photoZoomSpring = springSystem.createSpring()
        .setSpringConfig(SpringConfig.withBouncinessAndSpeed(7, 2))
        .addListener(new SimpleSpringListener() {
          @Override
          public void onSpringUpdate(Spring spring) {
            setPhotoZoomProgress((float) spring.getCurrentValue());
          }
        });

    fadeSpring = springSystem.createSpring()
        .setSpringConfig(SpringConfig.withBouncinessAndSpeed(15, 2))
        .addListener(new SimpleSpringListener() {
          @Override
          public void onSpringUpdate(Spring spring) {
            setFadeProgress((float) spring.getCurrentValue());
          }
        });
  }

  // photoZoom transition

  public void photoZoom(boolean on) {
    photoZoomSpring.setEndValue(on ? 1 : 0);
  }

  public void setPhotoZoomProgress(float progress) {
    float alpha2 = transition(progress, 1f, 0f);
    story.setOpacity(alpha2);

    float scale2 = transition(progress, 0.4797f, 0.55f);
    photo.setScaleX(scale2);
    photo.setScaleY(scale2);

    float yPosition2 = transition(progress, -186f, 0f);
    photo.setTranslationY(yPosition2);

    float scale2 = transition(progress, 1f, 0.97f);
    story.setScaleX(scale2);
    story.setScaleY(scale2);

    float rotation2 = transition(progress, 0f, 30f);
    photo.setRotation(rotation2);
  }

  // fade transition

  public void fade(boolean on) {
    fadeSpring.setEndValue(on ? 1 : 0);
  }

  public void setFadeProgress(float progress) {
    float alpha2 = transition(progress, 1f, 0.3f);
    photo.setOpacity(alpha2);
  }

  // Utilities

  public float transition (float progress, float startValue, float endValue) {
    return (float) SpringUtil.mapValueFromRangeToRange(progress, 0, 1, startValue, endValue);
  }

}