Various utilities for animation and graphics.

AnimationUtils.java

package com.odbol.utils;

/**
 * Various utilities for animation and graphics.
 */
public class AnimationUtils {

  /**
   * Interpolate a value with specified extrema, to a new value between new extrema.
   *
   * @param value the current value
   * @param inputMin minimum the input value can reach
   * @param inputMax maximum the input value can reach
   * @param outputMin minimum the output value can reach
   * @param outputMax maximum the output value can reach
   */
  public static float map(float value, float inputMin, float inputMax, float outputMin, float outputMax) {
    return outputMin + (outputMax - outputMin) * ((value - inputMin) / (inputMax - inputMin));
  }

  /**
   * Same as {@link #map}, but clamps the values so they never exceed the extrema.
   */
  public static float mapClamped(float value, float inputMin, float inputMax, float outputMin, float outputMax) {
    return Math.max(outputMin, Math.min(outputMax, map(value, inputMin, inputMax, outputMin, outputMax)));
  }

  /***
   * Interpolate between values a and b.
   */
  public static float lerp(float a, float b, float fraction)
  {
    return (float) ((a * (1.0 - fraction)) + (b * fraction));
  }
}

RxUtils.java

package com.odbol.utils;

import android.animation.Animator;
import android.animation.AnimatorListenerAdapter;
import androidx.dynamicanimation.animation.DynamicAnimation;
import androidx.dynamicanimation.animation.DynamicAnimation.OnAnimationEndListener;
import io.reactivex.rxjava3.core.Single;

public class RxUtils {

  /**
   * Starts an animation and completes once the animation finishes.
   *
   * The observed value is true if the animation ended, false if it was canceled.
   */
  public static Single<Boolean> startAnimationAndWaitForEnd(Animator animator) {
    return Single.create(emitter -> {
      animator.addListener(new AnimatorListenerAdapter() {
        @Override
        public void onAnimationCancel(Animator animation) {
          animator.removeListener(this);
          emitter.onSuccess(false);
        }

        @Override
        public void onAnimationEnd(Animator animation) {
          animator.removeListener(this);
          emitter.onSuccess(true);
        }
      });
      animator.start();
    });
  }

  /**
   * Starts an animation and completes once the animation finishes.
   *
   * The observed value is true if the animation ended, false if it was canceled.
   */
  public static <T extends DynamicAnimation<T>> Single<Boolean> startAnimationAndWaitForEnd(DynamicAnimation<T> animator) {
    return Single.create(emitter -> {
      animator.addEndListener(new OnAnimationEndListener() {
        @Override
        public void onAnimationEnd(DynamicAnimation animation, boolean canceled, float value, float velocity) {
          animator.removeEndListener(this);
          emitter.onSuccess(!canceled);
        }
      });
      animator.start();
    });
  }
}