Android Picasso将所有图像预取到磁盘上

Question

I want to prefetch images using Picasso and save them all to disk upon opening the app (no lazy loading on the fly). To make sure the cache is big enough I am using the following code in my Application onCreate

ContextWrapper cw = new ContextWrapper(getApplicationContext());
// path to /data/data/yourapp/app_data/imageDir
File directory = cw.getDir("imageDir", Context.MODE_PRIVATE);

OkHttpClient client = new OkHttpClient.Builder()
        .cache(new Cache(directory, Integer.MAX_VALUE))
        .build();
OkHttp3Downloader okHttp3Downloader = new OkHttp3Downloader(client);
Picasso.Builder builder = new Picasso.Builder(this);
builder.downloader(okHttp3Downloader);
Picasso built = builder.build();
built.setIndicatorsEnabled(false);
built.setLoggingEnabled(false);
Picasso.setSingletonInstance(built);

So here I set my cache size to Integer.MAX_VALUE which should be big enough ;)

I use code similar to this line to prefetch the image: Picasso.with(context).load(url).fetch(); .

Now when I kill my internet and mobile data, no images are loaded even though the my code is fetching items. Any ideas why?

Answer 1

Maybe the problem is loosing state. Did you try to extend Application class (like this ) and keep Picasso instance here?

In similar situation when I needed to fetch lots of images, I save them to internal memory (not just in some cache) - to prevent from reloading, and save uri's to files into SQLite and then use Picasso to work with such URI's. (don't forget to check that user don't delete anything).

Answer 2

最后，我创建了自己的图像管理器，用于下载和存储图像（仍然使用毕加索下载它们）。

Answer 3

Here is my approach:

In Application's onCreate method do:

Picasso picasso = new Picasso.Builder(this)
        .downloader(new OkHttp3Downloader(this,Integer.MAX_VALUE))
        .build();
picasso.setIndicatorsEnabled(BuildConfig.DEBUG);
picasso.setLoggingEnabled(BuildConfig.DEBUG);
Picasso.setSingletonInstance(picasso);

And then wherever you want to load your images call this for each image's url:

Picasso.with(context).load(url).fetch();

From doc:

fetch()

Asynchronously fulfills the request without a ImageView or Target. This is useful when you want to warm up the cache with an image.

You can even pass in callback to check for possible errors