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LruCache with different size

Last exercise show Gallery with cached bitmaps using LruCache.

There is no specific size or formula that suits all applications, it's up to you to analyze your usage and come up with a suitable solution. A cache that is too small causes additional overhead with no benefit, a cache that is too large can once again cause java.lang.OutOfMemory exceptions and leave the rest of your app little memory to work with.

In this exercise, there are two Gallery widgets on screen, both with cached bitmaps using LruCache. The upper one with smaller cache size and the lower one with bigger cache size. There are more than 200 photos in /test/ directory. The upper small cache size gallery always re-load the cache. The lower one with bigger size of cache can keep bitmaps in cache, but when the cached memory get large, it crash the app!.

package com.example.androidgallery; import java.io.File; import java.lang.ref.WeakReference; import java.util.ArrayList; import android.os.AsyncTask; import android.os.Bundle; import android.os.Environment; import android.app.Activity; import android.app.ActivityManager; import android.content.Context; import android.graphics.Bitmap; import android.graphics.BitmapFactory; import android.util.LruCache; import android.view.Gravity; import android.view.View; import android.view.ViewGroup; import android.widget.BaseAdapter; import android.widget.Gallery; import android.widget.ImageView; import android.widget.LinearLayout; public class MainActivity extends Activity { public abstract class CacheGalleryBaseAdapter extends BaseAdapter { ArrayList<String> GalleryFileList; Context context; CacheGalleryBaseAdapter(Context cont){ context = cont; GalleryFileList = new ArrayList<String>(); } abstract Bitmap abstractGetBitmapFromMemCache(String key); abstract BitmapWorkerTask abstractStartBitmapWorkerTask(ImageView imageView); @Override public int getCount() { return GalleryFileList.size(); } @Override public Object getItem(int position) { return GalleryFileList.get(position); } @Override public long getItemId(int position) { return position; } @Override public View getView(int position, View convertView, ViewGroup parent) { ImageView imageView = new ImageView(context); //--- // Use the path as the key to LruCache final String imageKey = GalleryFileList.get(position); final Bitmap bm = abstractGetBitmapFromMemCache(imageKey); if (bm == null){ BitmapWorkerTask task = abstractStartBitmapWorkerTask(imageView); task.execute(imageKey); } LinearLayout layout = new LinearLayout(context); layout.setLayoutParams(new Gallery.LayoutParams(250, 250)); layout.setGravity(Gravity.CENTER); imageView.setLayoutParams(new Gallery.LayoutParams(200, 200)); imageView.setScaleType(ImageView.ScaleType.CENTER_CROP); imageView.setImageBitmap(bm); layout.addView(imageView); return layout; } public void add(String newitem){ GalleryFileList.add(newitem); } } public class CacheGalleryBaseAdapter_SmallSize extends CacheGalleryBaseAdapter{ CacheGalleryBaseAdapter_SmallSize(Context cont) { super(cont); } @Override Bitmap abstractGetBitmapFromMemCache(String key) { return getBitmapFromMemCache_SmallSize(key); } @Override BitmapWorkerTask abstractStartBitmapWorkerTask(ImageView imageView) { return (new BitmapWorkerTask_SmallSize(imageView)); } } public class CacheGalleryBaseAdapter_BigSize extends CacheGalleryBaseAdapter{ CacheGalleryBaseAdapter_BigSize(Context cont) { super(cont); } @Override Bitmap abstractGetBitmapFromMemCache(String key) { return getBitmapFromMemCache_BigSize(key); } @Override BitmapWorkerTask abstractStartBitmapWorkerTask(ImageView imageView) { return(new BitmapWorkerTask_BigSize(imageView)); } } CacheGalleryBaseAdapter_SmallSize myFastGallery1BaseAdapter; CacheGalleryBaseAdapter_BigSize myFastGallery2BaseAdapter; Gallery myFastGallery1, myFastGallery2; private LruCache<String, Bitmap> mMemoryCache_SmallSize; private LruCache<String, Bitmap> mMemoryCache_BigSize; @Override public void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.activity_main); myFastGallery1 = (Gallery)findViewById(R.id.fastgallery1); myFastGallery2 = (Gallery)findViewById(R.id.fastgallery2); myFastGallery1BaseAdapter = new CacheGalleryBaseAdapter_SmallSize(this); myFastGallery2BaseAdapter = new CacheGalleryBaseAdapter_BigSize(this); String ExternalStorageDirectoryPath = Environment .getExternalStorageDirectory() .getAbsolutePath(); String targetPath = ExternalStorageDirectoryPath + "/test/"; File targetDirector = new File(targetPath); File[] files = targetDirector.listFiles(); for (File file : files){ myFastGallery1BaseAdapter.add(file.getPath()); myFastGallery2BaseAdapter.add(file.getPath()); } myFastGallery1.setAdapter(myFastGallery1BaseAdapter); myFastGallery2.setAdapter(myFastGallery2BaseAdapter); // Get memory class of this device, exceeding this amount will throw an // OutOfMemory exception. final int memClass = ((ActivityManager)getSystemService(Context.ACTIVITY_SERVICE)).getMemoryClass(); final int cacheSize_SmallSize = 1024 * 1024 * memClass / 12; mMemoryCache_SmallSize = new LruCache_customSize(cacheSize_SmallSize); final int cacheSize_BigSize = 1024 * 1024 * memClass; mMemoryCache_BigSize = new LruCache_customSize(cacheSize_BigSize); } class LruCache_customSize extends LruCache<String, Bitmap>{ public LruCache_customSize(int maxSize) { super(maxSize); // TODO Auto-generated constructor stub } protected int sizeOf(String key, Bitmap bitmap) { // The cache size will be measured in bytes rather than number of items. return bitmap.getByteCount(); } } abstract class BitmapWorkerTask extends AsyncTask<String, Void, Bitmap>{ private final WeakReference<ImageView> imageViewReference; public BitmapWorkerTask(ImageView imageView) { // Use a WeakReference to ensure the ImageView can be garbage collected imageViewReference = new WeakReference<ImageView>(imageView); } @Override protected void onPostExecute(Bitmap bitmap) { if (imageViewReference != null && bitmap != null) { final ImageView imageView = (ImageView)imageViewReference.get(); if (imageView != null) { imageView.setImageBitmap(bitmap); } } } } public Bitmap getBitmapFromMemCache_SmallSize(String key) { return (Bitmap) mMemoryCache_SmallSize.get(key); } public Bitmap getBitmapFromMemCache_BigSize(String key) { return (Bitmap) mMemoryCache_BigSize.get(key); } class BitmapWorkerTask_SmallSize extends BitmapWorkerTask{ public BitmapWorkerTask_SmallSize(ImageView imageView) { super(imageView); // TODO Auto-generated constructor stub } @Override protected Bitmap doInBackground(String... params) { final Bitmap bitmap = decodeSampledBitmapFromUri(params[0], 200, 200); if( getBitmapFromMemCache_SmallSize(String.valueOf(params[0])) == null){ mMemoryCache_SmallSize.put(String.valueOf(params[0]), bitmap); } return bitmap; } } class BitmapWorkerTask_BigSize extends BitmapWorkerTask{ public BitmapWorkerTask_BigSize(ImageView imageView) { super(imageView); // TODO Auto-generated constructor stub } @Override protected Bitmap doInBackground(String... params) { final Bitmap bitmap = decodeSampledBitmapFromUri(params[0], 200, 200); if( getBitmapFromMemCache_BigSize(String.valueOf(params[0])) == null){ mMemoryCache_BigSize.put(String.valueOf(params[0]), bitmap); } return bitmap; } } public Bitmap decodeSampledBitmapFromUri(String path, int reqWidth, int reqHeight) { Bitmap bm = null; // First decode with inJustDecodeBounds=true to check dimensions final BitmapFactory.Options options = new BitmapFactory.Options(); options.inJustDecodeBounds = true; BitmapFactory.decodeFile(path, options); // Calculate inSampleSize options.inSampleSize = calculateInSampleSize(options, reqWidth, reqHeight); // Decode bitmap with inSampleSize set options.inJustDecodeBounds = false; bm = BitmapFactory.decodeFile(path, options); return bm; } public int calculateInSampleSize( BitmapFactory.Options options, int reqWidth, int reqHeight) { // Raw height and width of image final int height = options.outHeight; final int width = options.outWidth; int inSampleSize = 1; if (height > reqHeight || width > reqWidth) { if (width > height) { inSampleSize = Math.round((float)height / (float)reqHeight); } else { inSampleSize = Math.round((float)width / (float)reqWidth); } } return inSampleSize; } }

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android" xmlns:tools="http://schemas.android.com/tools" android:layout_width="match_parent" android:layout_height="match_parent" android:orientation="vertical"> <TextView android:layout_width="fill_parent" android:layout_height="wrap_content" android:text="Gallery with Small Cache Size" /> <Gallery android:id="@+id/fastgallery1" android:layout_width="fill_parent" android:layout_height="wrap_content" /> <TextView android:layout_width="fill_parent" android:layout_height="wrap_content" android:text="Gallery with Big Cache Size" /> <Gallery android:id="@+id/fastgallery2" android:layout_width="fill_parent" android:layout_height="wrap_content" /> </LinearLayout>

modify AndroidManifest.xml to have minSdkVersion and targetSdkVersion of "13".