android - 使用 picasso 加载图像时淡入动画

Question

我想在 Imageview 上加载图像时显示淡入淡出效果。我正在使用 picasso 缓存图像并在 ImageView 中显示。我已经搜索了很多，但找不到任何解决方案。

我之前使用过，我知道在某些版本中他们有 .fade(int Duration) 方法在加载时淡化图像，但我再也找不到这个方法了。

这就是我现在正在做的事情

Picasso.with(context)
                .load(viewHolder.data.imageList.get(0).url)
                .networkPolicy(NetworkPolicy.OFFLINE)
                .placeholder(R.drawable.a_place_holder_list_view)
                .error(R.drawable.a_place_holder_list_view)
                .into(viewHolder.ivUser, context.loadImage(viewHolder.ivUser, viewHolder.data.imageList.get(0).url));


public Callback loadImage(RoundedImageView ivUser, String url) {
    return new callback(ivUser, url);
}

public class callback implements Callback {

    RoundedImageView imageView;
    String url;

    public callback(RoundedImageView imageView, String url) {
        this.imageView = imageView;
        this.url = url;
    }

    @Override
    public void onSuccess() {

    }

    @Override
    public void onError() {
        Picasso.with(BaseActivity.this)
                .load(url)
                .placeholder(R.drawable.a_place_holder_list_view)
                .error(R.drawable.a_place_holder_list_view)
                .into(imageView, new Callback() {
                    @Override
                    public void onSuccess() {

                    }

                    @Override
                    public void onError() {
                        Log.v("Picasso", "Could not fetch image");
                    }
                });
    }
}

请帮助我，我已经被困了很长时间了。提前致谢。

Answer 1

引用 Jake Wharton 的回答 here :

If the image comes from anywhere except the memory cache the fade should be automatically applied.

如果您查看 PicassoDrawable类

boolean fade = loadedFrom != MEMORY && !noFade;
if (fade) {
  this.placeholder = placeholder;
  animating = true;
  startTimeMillis = SystemClock.uptimeMillis();
}
.
.
.
@Override public void draw(Canvas canvas) {
if (!animating) {
  super.draw(canvas);
} else {
.
.
.

fade effect 已经应用于从 n/w 而不是内存/缓存加载的图像和 FADE_DURATION = 200f;//毫秒

要强制淡出，再次引用 jake wharton 的回答 here :

You can specify noFade() and then always play an animation in the image loaded callback. You can also rely on the callback being called synchronously to determine if an animation needs played.

final AtomicBoolean playAnimation = new AtomicBoolean(true);
Picasso.with(context).load(..).into(imageView, new Callback() {
  @Override public void onLoad() {
    if (playAnimation.get()) {
      //play fade
      Animation fadeOut = new AlphaAnimation(0, 1);
      fadeOut.setInterpolator(new AccelerateInterpolator());
      fadeOut.setDuration(1000);
      imageView.startAnimation(fadeOut);

      Animation fadeOutPlaceholder = new AlphaAnimation(1, 0);
      fadeOutPlaceholder.setInterpolator(new AccelerateInterpolator());
      fadeOutPlaceholder.setDuration(1000);
      placeHolderImageView.startAnimation(fadeOutPlaceholder);
    }
  }
  //..
});
playAnimation.set(false);