Volley Image Caching

Question

I am trying to understand Volley\'s image caching. I have a fragment with gridview inside it, which will load around 12-30 images. There images are retrieved from server and

Answer 1

A very rude way but it works :)

package it.dataware.passaeprendi.app.util;

import android.graphics.Bitmap;
import android.graphics.BitmapFactory;
import android.os.Environment;
import android.util.LruCache;

import com.android.volley.VolleyLog;
import com.android.volley.toolbox.ImageLoader;

import java.io.File;
import java.io.FileNotFoundException;
import java.io.FileOutputStream;
import java.io.IOException;
import java.util.Date;

// https://stackoverflow.com/questions/14053338/save-bitmap-in-android-as-jpeg-in-external-storage-in-a-folder
// https://stackoverflow.com/questions/8710515/reading-an-image-file-into-bitmap-from-sdcard-why-am-i-getting-a-nullpointerexc

public class DiskBitmapCache implements ImageLoader.ImageCache {
private File   cacheDir;

// ...
private  static final String CACHE_PATH      = "dataware/passaeprendi/imagechache/";
private  static final String CACHE_FULL_PATH = Environment.getExternalStorageDirectory() + "/" + CACHE_PATH;
private  static final int    MAX_IMAGE_AGE   = 5; // in days

private  static final BitmapFactory.Options options = new BitmapFactory.Options();
static {
options.inPreferredConfig = Bitmap.Config.ARGB_8888;
}

public DiskBitmapCache() {
    cacheDir = new File(CACHE_FULL_PATH);
    cacheDir.mkdirs();
}

private static  ImageLoader.ImageCache imageLoaderCache = new ImageLoader.ImageCache() {
    private final LruCache mCache = new LruCache<>(30);

    public void putBitmap(String url, Bitmap bitmap) {
        mCache.put(url, bitmap);
    }
    public Bitmap getBitmap(String url) {
        return mCache.get(url);
    }
};

public Bitmap getBitmap(String url) {

    final String volleyFileName = getFilenameForKey(url);

    final Bitmap bitmapL1 = imageLoaderCache.getBitmap(volleyFileName);
    if (bitmapL1 != null) {
        // VolleyLog.d("taken from cache L1 :" + url + " -> " + volleyFileName + ".");
        return bitmapL1;
    }

    final File volleyCacheFile = new File(cacheDir, volleyFileName);

    if (!volleyCacheFile.exists()) {
        return null;
    }

    // =======================================
    // age check
    // =======================================

    long diff = new Date().getTime() - volleyCacheFile.lastModified();

    if (diff > MAX_IMAGE_AGE * 24 * 60 * 60 * 1000) {
        volleyCacheFile.delete();
        return null;
    }

    // =======================================
    // load from disk
    // =======================================

    Bitmap bitmap = BitmapFactory.decodeFile(volleyCacheFile.getAbsolutePath(), options);

    if (bitmap != null) {
        //     VolleyLog.d("taken from cache L2 :" + url + " -> " + volleyFileName + ".");
        imageLoaderCache.putBitmap(volleyFileName, bitmap);
    }

    // VolleyLog.d("taken from cache L2 :" + url + " -> " + volleyFileName + ".");
    return bitmap;
}

public void putBitmap(String url, Bitmap bitmap) {
    final String volleyFileName = getFilenameForKey(url);

    File volleyCacheFile = new File(cacheDir, volleyFileName);

    try {
        // ...
        FileOutputStream fos = null;
        volleyCacheFile.createNewFile();
        fos = new FileOutputStream(volleyCacheFile, false);
        bitmap.compress(Bitmap.CompressFormat.JPEG, 100, fos);
        fos.flush();
        fos.close();
    } catch (FileNotFoundException e) {
        e.printStackTrace();
    } catch (IOException e) {
        e.printStackTrace();
    }
}

// Volley creates a filename for the url with the following function, so we'll use the same function
// for translating the url back to said filename
private String getFilenameForKey(String key) {
    int firstHalfLength = key.length() / 2;

    // ..
    String  localFilename   = String.valueOf(key.substring(0, firstHalfLength)  .hashCode());
            localFilename  += String.valueOf(key.substring(firstHalfLength)     .hashCode());
            localFilename  += ".jpg";

    return localFilename;
}
}    

I hope will help someone.