refactor: ImageDownloader Improvement

* Handling of Null Image links is now taken care by the ImageDownloader AsyncTaskLoader. * Reading and Writing Bitmaps to Memory cache is now taken care by the ImageDownloader AsyncTaskLoader.
kaushiknsanji · Oct 22, 2019 · 30f8dcc · 30f8dcc
1 parent 46ef6ab
commit 30f8dcc
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diff --git a/app/src/main/java/com/example/kaushiknsanji/bookslibrary/BookDetailActivity.java b/app/src/main/java/com/example/kaushiknsanji/bookslibrary/BookDetailActivity.java
@@ -30,7 +30,6 @@
 import android.support.v7.app.AppCompatActivity;
 import android.text.Layout;
 import android.text.TextUtils;
-import android.util.Log;
 import android.view.MenuItem;
 import android.view.View;
 import android.view.ViewGroup;
@@ -46,8 +45,6 @@
 import com.example.kaushiknsanji.bookslibrary.utils.TextAppearanceUtility;
 import com.example.kaushiknsanji.bookslibrary.workers.ImageDownloaderFragment;
 
-import java.text.ParseException;
-
 /**
  * Activity class that displays the {@link BookInfo} Item data selected in the List/Grid View.
  * The Item data is received via an Intent and the corresponding view components in the
@@ -417,17 +414,12 @@ private void updatePagesInfo(int pageCount, String bookType) {
      *                               retrieved from the Item's {@link BookInfo} Object
      */
     private void updateBookImage(String imageLinkForDetailInfo) {
-        if (!TextUtils.isEmpty(imageLinkForDetailInfo)) {
-            //Loading the Image when link is present
-            ImageDownloaderFragment
-                    .newInstance(this.getSupportFragmentManager(), mBookImageView.getId())
-                    .executeAndUpdate(mBookImageView,
-                            imageLinkForDetailInfo,
-                            mBookImageView.getId());
-        } else {
-            //Resetting to the default Book image when link is absent
-            mBookImageView.setImageResource(R.drawable.ic_book);
-        }
+        //Loading the Image when link is present
+        ImageDownloaderFragment
+                .newInstance(this.getSupportFragmentManager(), mBookImageView.getId())
+                .executeAndUpdate(mBookImageView,
+                        imageLinkForDetailInfo,
+                        mBookImageView.getId());
     }
 
     /**

diff --git a/app/src/main/java/com/example/kaushiknsanji/bookslibrary/BookImageActivity.java b/app/src/main/java/com/example/kaushiknsanji/bookslibrary/BookImageActivity.java
@@ -21,7 +21,6 @@
 import android.support.annotation.Nullable;
 import android.support.v4.app.NavUtils;
 import android.support.v7.app.AppCompatActivity;
-import android.text.TextUtils;
 import android.view.MenuItem;
 import android.widget.ImageView;
 
@@ -56,19 +55,13 @@ protected void onCreate(@Nullable Bundle savedInstanceState) {
 
         //Loading the Image to be shown from the Intent received
         Intent bookImageIntent = getIntent();
-        String imageLinkForBookImageInfo = bookImageIntent.getStringExtra(BOOK_INFO_ITEM_IMAGE_STR_KEY);
-        if (!TextUtils.isEmpty(imageLinkForBookImageInfo)) {
-            //Loading the Image when link is present
-            ImageDownloaderFragment
-                    .newInstance(getSupportFragmentManager(), bookImageView.getId())
-                    .executeAndUpdate(bookImageView,
-                            imageLinkForBookImageInfo,
-                            bookImageView.getId());
-        } else {
-            //Resetting to the default Book image when link is absent
-            //(This case can only occur if there is a problem with network connectivity)
-            bookImageView.setImageResource(R.drawable.ic_book);
-        }
+
+        //Loading the Image when link is present
+        ImageDownloaderFragment
+                .newInstance(getSupportFragmentManager(), bookImageView.getId())
+                .executeAndUpdate(bookImageView,
+                        bookImageIntent.getStringExtra(BOOK_INFO_ITEM_IMAGE_STR_KEY),
+                        bookImageView.getId());
 
     }
 

diff --git a/app/src/main/java/com/example/kaushiknsanji/bookslibrary/utils/ImageUtility.java b/app/src/main/java/com/example/kaushiknsanji/bookslibrary/utils/ImageUtility.java
@@ -22,8 +22,6 @@
 import android.text.TextUtils;
 import android.util.Log;
 
-import com.example.kaushiknsanji.bookslibrary.cache.BitmapImageCache;
-
 import java.io.BufferedInputStream;
 import java.io.ByteArrayOutputStream;
 import java.io.IOException;
@@ -97,11 +95,6 @@ public static Bitmap downloadFromURL(String imageURLStr) {
                     Log.e(LOG_TAG, "Error occurred while closing the Image Input Stream\n", e);
                 }
             }
-
-            //Adding the Bitmap to Memory Cache if generated
-            if (bitmap != null) {
-                BitmapImageCache.addBitmapToCache(imageURLStr, bitmap);
-            }
         }
 
         //Returning the Bitmap Image downloaded

diff --git a/app/src/main/java/com/example/kaushiknsanji/bookslibrary/workers/ImageDownloader.java b/app/src/main/java/com/example/kaushiknsanji/bookslibrary/workers/ImageDownloader.java
@@ -18,8 +18,12 @@
 
 import android.content.Context;
 import android.graphics.Bitmap;
+import android.support.annotation.Nullable;
 import android.support.v4.content.AsyncTaskLoader;
+import android.text.TextUtils;
+import android.util.Log;
 
+import com.example.kaushiknsanji.bookslibrary.cache.BitmapImageCache;
 import com.example.kaushiknsanji.bookslibrary.utils.ImageUtility;
 import com.example.kaushiknsanji.bookslibrary.utils.NetworkUtility;
 
@@ -31,6 +35,9 @@
  */
 public class ImageDownloader extends AsyncTaskLoader<Bitmap> {
 
+    //Constant used for logs
+    private static final String LOG_TAG = ImageDownloader.class.getSimpleName();
+
     //Stores the Image URL String from which the Image needs to be downloaded
     private String mImageURLStr;
 
@@ -42,9 +49,9 @@ public class ImageDownloader extends AsyncTaskLoader<Bitmap> {
      *
      * @param context     used to retrieve the application context.
      * @param imageURLStr String containing the Image URL from
-     *                    which the image needs to be downloaded
+     *                    which the image needs to be downloaded. Can be {@code null}.
      */
-    public ImageDownloader(Context context, String imageURLStr) {
+    public ImageDownloader(Context context, @Nullable String imageURLStr) {
         super(context);
         mImageURLStr = imageURLStr;
     }
@@ -58,15 +65,36 @@ public ImageDownloader(Context context, String imageURLStr) {
      */
     @Override
     public Bitmap loadInBackground() {
-        //Proceeding to download when the Internet Connectivity is established
-        if (NetworkUtility.isNetworkConnected(getContext())) {
-            //Downloading the Image from URL and returning the Bitmap
-            Bitmap downloadedBitmap = ImageUtility.downloadFromURL(mImageURLStr);
-            if (downloadedBitmap != null) {
-                //Uploading the Bitmap to GPU for caching in background thread (for faster loads)
-                downloadedBitmap.prepareToDraw();
+        if (!TextUtils.isEmpty(mImageURLStr)) {
+            //When we have the Image URL
+            try {
+                //Proceeding to download when the Internet Connectivity is established
+                if (NetworkUtility.isNetworkConnected(getContext())) {
+                    //Looking up for the Image in Memory Cache
+                    Bitmap cachedBitmap = BitmapImageCache.getBitmapFromCache(mImageURLStr);
+                    if (cachedBitmap != null) {
+                        //When Bitmap image was present in Memory Cache, return the Bitmap retrieved
+                        return cachedBitmap;
+                    } else {
+                        //When Bitmap image was NOT present in Memory Cache, download the Image from URL
+                        Bitmap downloadedBitmap = ImageUtility.downloadFromURL(mImageURLStr);
+                        if (downloadedBitmap != null) {
+                            //On Successful download
+
+                            //Uploading the Bitmap to GPU for caching in background thread (for faster loads)
+                            downloadedBitmap.prepareToDraw();
+
+                            //Adding the downloaded Bitmap to cache
+                            BitmapImageCache.addBitmapToCache(mImageURLStr, downloadedBitmap);
+
+                            return downloadedBitmap; //Returning the Bitmap downloaded
+                        }
+                    }
+                }
+            } catch (Exception e) {
+                Log.e(LOG_TAG, "loadInBackground: Failed while downloading the bitmap for the URL "
+                        + mImageURLStr, e);
             }
-            return downloadedBitmap; //Returning the Bitmap downloaded
         }
 
         //For all else, returning null
@@ -171,16 +199,16 @@ public void onCanceled(Bitmap data) {
      */
     private void releaseResources() {
         //Invalidating the Loader data
-        if (mDownloadedBitmap != null) {
-            mDownloadedBitmap = null;
-        }
+        mDownloadedBitmap = null;
+        mImageURLStr = null;
     }
 
     /**
      * Method that returns the Image URL String from which this loader downloads the image
      *
      * @return The Image URL String from which this loader downloads the image
      */
+    @Nullable
     public String getImageURLStr() {
         return mImageURLStr;
     }

diff --git a/...src/main/java/com/example/kaushiknsanji/bookslibrary/workers/ImageDownloaderFragment.java b/...src/main/java/com/example/kaushiknsanji/bookslibrary/workers/ImageDownloaderFragment.java
@@ -17,14 +17,18 @@
 package com.example.kaushiknsanji.bookslibrary.workers;
 
 
+import android.content.Context;
+import android.content.ContextWrapper;
 import android.graphics.Bitmap;
 import android.os.Bundle;
 import android.support.annotation.NonNull;
+import android.support.annotation.Nullable;
 import android.support.v4.app.Fragment;
 import android.support.v4.app.FragmentActivity;
 import android.support.v4.app.FragmentManager;
 import android.support.v4.app.LoaderManager;
 import android.support.v4.content.Loader;
+import android.text.TextUtils;
 import android.widget.ImageView;
 
 import com.example.kaushiknsanji.bookslibrary.R;
@@ -83,44 +87,122 @@ public static ImageDownloaderFragment newInstance(FragmentManager fragmentManage
      * if necessary
      *
      * @param imageView   The ImageView Component on which the Image needs to be updated
-     * @param imageURLStr String containing the Image URL whose Image needs to be downloaded and updated
+     * @param imageURLStr String containing the Image URL whose Image needs to be downloaded and updated. Can be {@code null}.
      * @param loaderId    Integer identifier used while creating this Fragment
      */
-    public void executeAndUpdate(ImageView imageView, String imageURLStr, int loaderId) {
+    public void executeAndUpdate(ImageView imageView, @Nullable String imageURLStr, int loaderId) {
+        //Delegating to other overloaded method with the derived instance for LoaderManager
+        executeAndUpdate(imageView, imageURLStr, loaderId, obtainLoaderManager(imageView));
+    }
+
+    /**
+     * Method that loads the Image from Memory Cache or downloads the Image from the URL passed
+     * if necessary
+     *
+     * @param imageView   The ImageView Component on which the Image needs to be updated
+     * @param imageURLStr String containing the Image URL whose Image needs to be downloaded and updated. Can be {@code null}.
+     * @param loaderId    Integer identifier used while creating this Fragment
+     * @param loaderManager Instance of {@link LoaderManager} to use for downloading the image
+     */
+    public void executeAndUpdate(ImageView imageView, @Nullable String imageURLStr, int loaderId, LoaderManager loaderManager) {
         //Saving the parameters passed
         mImageView = imageView;
         mImageURLStr = imageURLStr;
 
-        //Looking up for the Image in Memory Cache for the given URL
-        Bitmap bitmap = BitmapImageCache.getBitmapFromCache(mImageURLStr);
-        if (bitmap != null) {
-            //When Bitmap image was present in Memory Cache, update the ImageView
-            mImageView.setImageBitmap(bitmap);
+        if (loaderManager == null) {
+            //When we do not have the LoaderManager instance for downloading the Image
+            //throw a Runtime Exception
+            throw new IllegalStateException("LoaderManager is not attached.");
+        }
+
+        //Retrieving the loader at the loaderId if any
+        ImageDownloader imageDownloader = getImageDownloader(loaderId, loaderManager);
+
+        //Resetting the ImageView to the default Book Image for lazy loading
+        mImageView.setImageResource(R.drawable.ic_book);
+
+        //Boolean to check if we need to restart the loader
+        boolean isNewImageURLStr = false;
+        if (imageDownloader != null) {
+            //When we have a previously registered loader
+
+            //Setting the Loader to be restarted when the Image URL passed is
+            //not the same as that of the loader
+            isNewImageURLStr = !TextUtils.equals(mImageURLStr, imageDownloader.getImageURLStr());
+        }
+
+        if (isNewImageURLStr) {
+            //Restarting the Loader when the ImageURL is new
+            loaderManager.restartLoader(loaderId, null, this);
         } else {
-            //Resetting the ImageView to the default Book Image for lazy loading
-            mImageView.setImageResource(R.drawable.ic_book);
+            //Invoking the Loader AS-IS if the ImageURL is the same
+            //or if the Loader is not yet registered with the loaderId passed
+            loaderManager.initLoader(loaderId, null, this);
+        }
 
-            //Starting the download when Bitmap image is not available from Memory Cache: START
-            LoaderManager loaderManager = ((FragmentActivity) mImageView.getContext()).getSupportLoaderManager();
-            boolean isNewImageURLStr = false; //Boolean to check if we need to restart the loader
-            Loader<Bitmap> loader = loaderManager.getLoader(loaderId); //Getting the loader at the loaderId
-            if (loader instanceof ImageDownloader) {
-                //Validating the loader and casting to ImageDownloader
-                ImageDownloader imageDownloader = (ImageDownloader) loader;
-                //Checking for inequality of the Image URL with the one from the loader
-                isNewImageURLStr = !mImageURLStr.equals(imageDownloader.getImageURLStr());
-            }
-
-            if (isNewImageURLStr) {
-                //Restarting the Loader when the ImageURL is new
-                loaderManager.restartLoader(loaderId, null, this);
-            } else {
-                //Invoking the Loader AS-IS if the ImageURL is the same
-                //or if the Loader is not yet registered with the loaderId passed
-                loaderManager.initLoader(loaderId, null, this);
-            }
-            //Starting the download when Bitmap image is not available from Memory Cache: END
+    }
+
+    /**
+     * Method that returns the instance of the {@link ImageDownloader} for the
+     * Loader Id {@code loaderId} passed.
+     *
+     * @param loaderId      The Id of the Loader whose Loader instance needs to be looked up
+     * @param loaderManager Instance of {@link LoaderManager}
+     * @return Instance of {@link ImageDownloader} if found; else {@code null}
+     */
+    @Nullable
+    private ImageDownloader getImageDownloader(int loaderId, LoaderManager loaderManager) {
+        //Getting the loader at the loaderId
+        Loader<Bitmap> loader = loaderManager.getLoader(loaderId);
+        if (loader instanceof ImageDownloader) {
+            //Returning the ImageDownloader instance
+            return (ImageDownloader) loader;
+        } else {
+            //Returning NULL when not found
+            return null;
+        }
+    }
+
+    /**
+     * Method that retrieves the {@link FragmentActivity} instance required
+     * for obtaining the {@link LoaderManager} instance.
+     *
+     * @param context The {@link Context} to retrieve the Activity from.
+     * @return Instance of the {@link FragmentActivity} is any; else {@code null}
+     */
+    @Nullable
+    private FragmentActivity obtainActivity(@Nullable Context context) {
+        if (context == null) {
+            //Return Null when Null
+            return null;
+        } else if (context instanceof FragmentActivity) {
+            //Return the FragmentActivity instance when Context is of type FragmentActivity
+            return (FragmentActivity) context;
+        } else if (context instanceof ContextWrapper) {
+            //Recall with the Base Context when Context is of type ContextWrapper
+            return obtainActivity(((ContextWrapper) context).getBaseContext());
+        }
+        //Returning Null when we could not derive the Activity instance from the given Context
+        return null;
+    }
+
+    /**
+     * Method that retrieves the {@link LoaderManager} instance for the given view {@code imageView}
+     *
+     * @param imageView The {@link ImageView} to retrieve the {@link LoaderManager} from.
+     * @return Instance of {@link LoaderManager} when the {@link FragmentActivity} was derivable
+     * from {@code imageView}; else {@code null}
+     */
+    @Nullable
+    private LoaderManager obtainLoaderManager(ImageView imageView) {
+        //Obtaining the Activity from the ImageView
+        FragmentActivity activity = obtainActivity(imageView.getContext());
+        if (activity != null) {
+            //When we have the Activity, return the LoaderManager instance
+            return activity.getSupportLoaderManager();
         }
+        //Returning Null when Activity could not be derived from ImageView
+        return null;
     }
 
     /**