Use Picasso to get a callback with a Bitmap

问题

I\'m using Picasso to download images for my app.

I\'m in a situation where I need to access the Bitmap first before it\'s loaded into the ImageView. The presence of the Downloader.Response class seems to suggest this is possible, but I can\'t find any use examples. I don\'t want to write a bunch more code to asynchronously handle this one particular case if it\'s possible to do with Picasso.

Can anyone show me how to do it?

回答1:

Found the answer on github in case anyone is wondering:

private Target target = new Target() {
      @Override
      public void onBitmapLoaded(Bitmap bitmap, Picasso.LoadedFrom from) {
      }

      @Override
      public void onBitmapFailed(Drawable errorDrawable) {
      }

      @Override
      public void onPrepareLoad(Drawable placeHolderDrawable) {
      }
}

private void someMethod() {
   Picasso.with(this).load("url").into(target);
}

@Override 
public void onDestroy() {  // could be in onPause or onStop
   Picasso.with(this).cancelRequest(target);
   super.onDestroy();
}

The post recommends not using an anonymous callback, and instead using an instance variable for target.

回答2:

taken from here:

Picasso.with(this)
    .load(url)
    .into(new Target() {
        @Override
        public void onBitmapLoaded (final Bitmap bitmap, Picasso.LoadedFrom from){
            /* Save the bitmap or do something with it here */

            //Set it in the ImageView
            theView.setImageBitmap(bitmap); 
        }
});

Updated (May 04, 2016):

            Picasso.with(this)
                .load(youUrl)
                .into(new Target() {
                    @Override
                    public void onBitmapLoaded(Bitmap bitmap, Picasso.LoadedFrom from) {

                    }

                    @Override
                    public void onBitmapFailed(Drawable errorDrawable) {

                    }

                    @Override
                    public void onPrepareLoad(Drawable placeHolderDrawable) {

                    }
                });

Updated (November 22, 2016)

or using a strong reference for Target so that it wont be garbage collected

Target target = new Target() {
            @Override
            public void onBitmapLoaded(Bitmap bitmap, Picasso.LoadedFrom from) {

            }

            @Override
            public void onBitmapFailed(Drawable errorDrawable) {

            }

            @Override
            public void onPrepareLoad(Drawable placeHolderDrawable) {

            }
        };


void foo() {
        Picasso.with(getContext()).load(getUrl()).into(target);
}

Kotlin

object: com.squareup.picasso.Target {
                  override fun onBitmapFailed(e: java.lang.Exception?, errorDrawable: Drawable?) {
                    TODO("not implemented") //To change body of created functions use File | Settings | File Templates.
                }

                  override fun onPrepareLoad(placeHolderDrawable: Drawable?) {
                    TODO("not implemented") //To change body of created functions use File | Settings | File Templates.
                  }

                  override fun onBitmapLoaded(bitmap: Bitmap?, from: Picasso.LoadedFrom?) {

                  }
                }

回答3:

What can be easy than next:

val url: String = "https://...."
val bitmap: Bitmap = Picasso.with(context).load(url).get()

Should be called from not the main thread!

or with RxJava 2:

fun getBitmapSingle(picasso: Picasso, url: String): Single<Bitmap> = Single.create {
    try {
        if (!it.isDisposed) {
            val bitmap: Bitmap = picasso.load(url).get()
            it.onSuccess(bitmap)
        }
    } catch (e: Throwable) {
        it.onError(e)
    }
}

Retrieve Bitmap:

getBitmapSingle(Picasso.with(context), "https:/...")
                .subscribeOn(Schedulers.io())
                .observeOn(AndroidSchedulers.mainThread())
                .subscribe({ bitmap ->
                // val drawable = BitmapDrawable(context, bitmap)
                }, Throwable::printStackTrace)

I used Picasso v.2.5.2

回答4:

I thought maybe some of you would like an RxJava version of the above answer... Here it is:

    public static Observable<Bitmap> loadBitmap(Picasso picasso, String imageUrl) {
    return Observable.create(new Observable.OnSubscribe<Bitmap>() {
        @Override
        public void call(Subscriber<? super Bitmap> subscriber) {
            Target target = new Target() {
                @Override
                public void onBitmapLoaded(Bitmap bitmap, Picasso.LoadedFrom from) {
                    subscriber.onNext(bitmap);
                    subscriber.onCompleted();
                }

                @Override
                public void onBitmapFailed(Drawable errorDrawable) {
                    subscriber.onError(new Exception("failed to load " + imageUrl));
                }

                @Override
                public void onPrepareLoad(Drawable placeHolderDrawable) {
                }
            };
            subscriber.add(new Subscription() {
                private boolean unSubscribed;

                @Override
                public void unsubscribe() {
                    picasso.cancelRequest(target);
                    unSubscribed = true;
                }

                @Override
                public boolean isUnsubscribed() {
                    return unSubscribed;
                }
            });
            picasso.load(imageUrl).into(target);
        }
    });
}

P.S. When subscribing, store the subscription reference on your activity, otherwise, target will be GC'd before you receive a response...

回答5:

with using target garbage collector run out your plans.so I do a trick with this sample code:

ImageView bitmapImageView = new ImageView(context);
picasso.with(context).load(url).into(bitmapImageView);
Bitmap bitmap = ((BitmapDrawable)bitmapImageView.getDrawable()).getBitmap();

now you can enjoy your bitmap; :))

来源：https://stackoverflow.com/questions/20181491/use-picasso-to-get-a-callback-with-a-bitmap