Develop Reference

Caching Images and strings using Retrofit, okhttp, picasso

I am working on an app with a lot of dynamic and changing content.
I pull all my data from my server when the app is loading.
As a result, nearly every activity/fragment is loading separately which will cause the user to wait a lot of time for each "page" to load individually.
My goal is to create one loading page when the app starts while being responssible for all the downloading and will disk cache all the images and info(strings) and ti pull them at the right time. (or at least to most of it)
I had the chance to use retrofit, okhttp and Picasso as a single additional library, I know though that they can work together and to be synced and that disk cacheing is available through at least two of this libraries (picasso and okhttp) I'm not sure though which one should do which part and how I can sync them together.
I will appreciate every Tip/Guidance, thanks ahead.

okhttp provides support for cache control headers. I've implemented them in an app before to provide a cache when network is flaky using this guide like so:
int cacheSize = 10 * 1024 * 1024; // 10 MiB
Cache cache = new Cache(cacheDirectory, cacheSize);
client = new OkHttpClient.Builder()
.cache(cache)
.build();
As Retrofit uses okhttp internally (if you're using the latest at least), you don't configure any caching for it. Just use the okhttp client you just configured:
RestAdapter restAdapter = new RestAdapter.Builder()
.setClient(new OkClient(client))
.setServer("http://example.com")
...
.build();
Picasso automatically caches images using some default cache size limit. You can change Picasso's default, and I've found some answers here and here. You could set the cache size in the onCreate of your application:
Picasso.Builder builder = new Picasso.Builder(this);
builder.downloader(new OkHttpDownloader(this,Integer.MAX_VALUE));
Picasso picasso = builder.build();
picasso.setIndicatorsEnabled(true);
picasso.setLoggingEnabled(true);
Picasso.setSingletonInstance(picasso);
Picasso also lets you prefetch images earlier on in an app's lifecycle if you have the time to begin with (say, on a loading screen) and want to make later parts of the app load quicker. To do that, I would use the fetch method from the Picasso builder to get the images, but not insert them into any ImageViews. You can Google it too, but there's a quick answer here which explains the background behind this:
Picasso.with(getApplicationContext())
.load(url)
.fetch();
IIRC you need to make sure you fetch the same sized and transformed image as you try and retrieve later, because Picasso caches the transformed image result rather than the raw downloaded image.

Load image from URL to imageView as well as Cache

Hi i am new beginner in android. I want to insert image in imageView from URL but whenever one time it is loaded from URL in imageView then second time it should be insert without internet means it would be stored in cache as well.

for this you can use picasso Library
You can download it from Picasso Library site simply put this jar file into libs folder. It will manage all property of Image.
http://square.github.io/picasso/
String imgURL = "Your URL";
ivmage = (ImageView) findViewById(R.id.imageView1);
Picasso.with(MainActivity.this).load(imgURL).into(ivmage);

You can use Picasso Library.
By Using Picasso, The Advantages are
Handling ImageView recycling and download cancelation in an adapter.
Complex image transformations with minimal memory use.
Automatic memory and disk caching.
To load Image from Url
Picasso.with(context).load(url).into(imageView);
Refer this link for Api : Picasso

you can use Glide https://github.com/bumptech/glide
Glide.with(this).load("imageURl").into(imageView);

I suggest picasso library for doing this. here is the detailed documentation of picasso library.
ex:
Picasso.with(context).load("http://i.imgur.com/DvpvklR.png").into(imageView);
or you can make use of volley's ImageLoader. here you can find the documentation for Volley's image loading.
ex :
// Retrieves an image specified by the URL, displays it in the UI.
ImageRequest request = new ImageRequest(url,
new Response.Listener<Bitmap>() {
#Override
public void onResponse(Bitmap bitmap) {
mImageView.setImageBitmap(bitmap);
}
}, 0, 0, null,
new Response.ErrorListener() {
public void onErrorResponse(VolleyError error) {
mImageView.setImageResource(R.drawable.image_load_error);
}
});
// Access the RequestQueue through your singleton class.
MySingleton.getInstance(this).addToRequestQueue(request);
if you are using volley. then you have to cache images manually. picasso will cache images by default.

Picasso with OkHttp?

How to write picasso with Okhttp?
My code is given below but it is showing Error. By the way I am having confusion that picasso uses by default OkHttp or should I write it in code also?
OkHttpClient okHttpClient = new OkHttpClient();
RestAdapter restAdapter = new RestAdapter.Builder().setClient(new OkClient(okHttpClient)).build();
OkHttpDownloader downloader = new OkHttpDownloader(okHttpClient);
Picasso picasso = new Picasso.Builder(context).downloader(downloader).build();
Picasso.with(context).load("http://192.168.0.15:1337/offers/" + image_url.get(position)).resize(350, 100).centerCrop().into(holder.imageView);

No, you don't need to do things like that. OkHttp is a thing, which just make HTTP connection and loading files, for example, JSON easier. You should use it in separate thread, otherwise, you'll get an NetworkOnMainThreadException.
If you just need to download image, you won't need specific HTTP connection. Just use Picasso, for example, in onCreate() of the Activity, and enjoy the result.
All you need to do is:
Picasso.with(context)
.load("http://192.168.0.15:1337/offers/" + image_url.get(position))
.resize(350, 100)
.centerCrop()
.into(holder.imageView);

Loading images using picasso on a slow connection

I am using Picasso to load images for a listview.
The problem is internet connection is slow.
How can I change load timeout time in Picasso?
My code is :
Picasso.with(context)
.load(MainActivity.WEBSITE + book_item.Image)
.resize(final_thumb_width, final_thumb_height)
.into(new PicassoTarget(book_item,item.img, item.title));

You could possibly try something like this in your MainActivity's onCreate (or whereever you want to create the Picasso Builder
Picasso picasso;
OkHttpClient okHttpClient;
okHttpClient = new OkHttpClient();
okHttpClient.setConnectTimeout(10, TimeUnit.SECONDS);
picasso = new Picasso.Builder(this)
.downloader(new OkHttpDownloader(okHttpClient))
.build();
That should give Picasso a timeout of ten seconds. Configure it to your needs.
Full Disclosure: I don't use a timeout. I just noticed this in the API. This may be completely wrong lol.

You have two options:
Subclass a Downloader class. Check this for reference implementation
Preconfigure OkHttpClient with timeouts and pass it to Picasso

How to implement my own disk cache with picasso library - Android?

I'm using picasso library to load images for my app. But I don't how to implement my own disk (sdcard) caching with picasso library.

Picasso uses the HTTP client for disk caching and if one is already configured it will use that instead of installing its own.
For the built-in UrlConnection the docs for installing a cache are here: https://developer.android.com/reference/android/net/http/HttpResponseCache.html
If you are using OkHttp then you just call setCache:
http://square.github.io/okhttp/2.x/okhttp/com/squareup/okhttp/OkHttpClient.html#setCache-com.squareup.okhttp.Cache-

#Dax, to save files in custom cache directory using OkHttp, I would code something like this -
OkHttpClient okHttpClient = new OkHttpClient();
File customCacheDirectory = new File(Environment.getExternalStorageDirectory().getAbsoluteFile() + "/MyCache");
okHttpClient.setCache(new Cache(customCacheDirectory, Integer.MAX_VALUE));
OkHttpDownloader okHttpDownloader = new OkHttpDownloader(okHttpClient);
Picasso picasso = new Picasso.Builder(mainActivity).downloader(okHttpDownloader).build();
picasso.load(imageURL).into(viewHolder.image);
Hope this helps.