Fade in animation while loading image Using Picasso

问题

I want to show a fade effect when image is loading on Imageview. I am using picasso to cache image and display in image view. I have searched alot for this but couldnt find any solution.

I have used earlier before and i know in some version they had .fade(int Duration) method to fade image while loading but i couldnt find this method anymore.

Here is what i am doing now

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");
                    }
                });
    }
}

Please help me i have been stuck in this for quite long time. Thanks in advance.

回答1:

Quoting Jake Wharton's answer here:

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

If you check the PicassoDrawable class

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 is already applied for images loaded from n/w and not memory/cache and FADE_DURATION = 200f; //ms

To force fade, again quoting jake wharton's answer 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);

回答2:

You can simply do

Picasso.with(context).load(url).fetch(new Callback(){
            @Override
            public void onSuccess() {
                imageView.setAlpha(0f);
                Picasso.with(context).load(url).into(imageView);
                imageView.animate().setDuration(300).alpha(1f).start();
            }

            @Override
            public void onError() {

            }
        });

回答3:

I do this:

Picasso.get().load(url).fit().noFade().centerInside().into(imageView, new Callback() {

                @Override
                public void onSuccess() {
                    imageView.setAlpha(0f);
                    imageView.animate().setDuration(200).alpha(1f).start();
                }

                @Override
                public void onError(Exception e) {
                }
            });

来源：https://stackoverflow.com/questions/34488556/fade-in-animation-while-loading-image-using-picasso