Picasso Load Image into Target

问题

I'm using Picasso to download various images. Usually, I just display these in an ImageView but in this situation, I want to hold a strong reference to them so that I can use them in different places without having to refer back to the cache or re-download them. Here is how I am attempting to do that (note that there is more to this class - I've just narrowed it down to the parts that are relevant to this question):

public class MapLayer {

    private Context mContext;
    private String mType;
    private Drawable mIcon = null;

    public MapLayer (Context context, String type) {
        mContext = context;
        mType = type;
        downloadIcon();
    }

    public Drawable getIcon() {return mIcon;}

    private void downloadIcon() {

        String url = mContext.getString(R.string.maps_icon_url).replace("${type}", mType));

        Target target = new Target() {
            @Override
            public void onBitmapLoaded(Bitmap bitmap, Picasso.LoadedFrom from) {
                Log.d(TAG, "on bitmap loaded");
                mIcon = new BitmapDrawable(mContext.getResources(), bitmap);
            }

            @Override
            public void onBitmapFailed(Drawable errorDrawable) {
                Log.d(TAG, "on bitmap failed");
            }

            @Override
            public void onPrepareLoad(Drawable placeHolderDrawable) {
                Log.d(TAG, "on prepare load");
                mIcon = placeHolderDrawable;
            }
        };

        ImageDownloader.getSharedInstance().load(url).into(target);
    }
}

In every case, I get the output:

on prepare load

but nothing else. My icon is always null. I know this from other classes where I call getIcon().

What am I missing here? Thanks for any help.

回答1:

Picasso holds Target instance with a weak reference, So your Target seems to be garbage collected.
see: https://github.com/square/picasso/issues/352

It is better to hold Target as an instance field.

public class MapLayer {

    ...

    private Target target;

    private void downloadIcon() {

        ...

        target = new Target() {
            ...
        };

        ImageDownloader.getSharedInstance().load(url).into(target);
    }
}

回答2:

Its because Picasso only keeps a weak reference to the Target object.

If you want to have a strong reference I'd recommend tagging the Target to the View.
Here is a solution for your problem.

来源：https://stackoverflow.com/questions/38617505/picasso-load-image-into-target

标签

android

picasso