lottie/src/main/java/com/airbnb/lottie/FillContent.java

package com.airbnb.lottie;

import android.graphics.Canvas;
import android.graphics.Matrix;
import android.graphics.Paint;
import android.graphics.Path;

import java.util.ArrayList;
import java.util.List;

class FillContent implements DrawingContent, BaseKeyframeAnimation.AnimationListener {
  private final Path path = new Path();
  private final Paint paint = new Paint(Paint.ANTI_ALIAS_FLAG);
  private final List<PathContent> paths = new ArrayList<>();
  private final KeyframeAnimation<Integer> colorAnimation;
  private final KeyframeAnimation<Integer> opacityAnimation;
  private final LottieDrawable lottieDrawable;

  FillContent(final LottieDrawable lottieDrawable, BaseLayer layer, ShapeFill fill) {
    this.lottieDrawable = lottieDrawable;
    if (fill.getColor() == null || fill.getOpacity() == null ) {
      colorAnimation = null;
      opacityAnimation = null;
      return;
    }

    path.setFillType(fill.getFillType());

    colorAnimation = fill.getColor().createAnimation();
    colorAnimation.addUpdateListener(this);
    layer.addAnimation(colorAnimation);
    opacityAnimation = fill.getOpacity().createAnimation();
    opacityAnimation.addUpdateListener(this);
    layer.addAnimation(opacityAnimation);
  }

  @Override public void onValueChanged() {
    lottieDrawable.invalidateSelf();
  }

  @Override public void setContents(List<Content> contentsBefore, List<Content> contentsAfter) {
    for (int i = 0; i < contentsAfter.size(); i++) {
      Content content = contentsAfter.get(i);
      if (content instanceof PathContent) {
        paths.add((PathContent) content);
      }
    }
  }

  @Override public void draw(Canvas canvas, Matrix parentMatrix, int parentAlpha) {
    paint.setColor(colorAnimation.getValue());
    int alpha = (int) ((parentAlpha / 255f * opacityAnimation.getValue() / 100f) * 255);
    paint.setAlpha(alpha);

    path.reset();
    for (int i = 0; i < paths.size(); i++) {
      path.addPath(paths.get(i).getPath(), parentMatrix);
    }

    canvas.drawPath(path, paint);
  }
}