如果您只想将图像从完全透明变淡为完全不透明，则只需执行以下操作:

If you just want to fade the image in from fully-transparent to fully-opaque, then just do the following:

ImageLayer faceLayer;
void init() {
  Image faceImage = assetManager().getImage("images/face.png");
  faceLayer = graphics().createImageLayer(faceImage);
  graphics().rootLayer().add(faceLayer);
}

void update(float delta) {
  float alpha = calcAlpha(delta);
  faceLayer.setAlpha(alpha);
}

alpha范围从0(完全透明)到1(完全不透明).

Where alpha ranges from 0 (fully transparent) to 1 (fully opaque).