Issue #44 - Use Of Semaphore for avoiding unnecessary downloads/loads

nostra13 · Sep 23, 2012 · 87a4ee9 · 87a4ee9
1 parent 4137c10
commit 87a4ee9
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Showing 3 changed files with 47 additions and 10 deletions.
diff --git a/UniversalImageLoader/src/com/nostra13/universalimageloader/core/ImageLoader.java b/UniversalImageLoader/src/com/nostra13/universalimageloader/core/ImageLoader.java
@@ -6,6 +6,7 @@
 import java.util.WeakHashMap;
 import java.util.concurrent.ExecutorService;
 import java.util.concurrent.Executors;
+import java.util.concurrent.locks.ReentrantLock;
 
 import android.content.res.Configuration;
 import android.graphics.Bitmap;
@@ -42,6 +43,7 @@ public class ImageLoader {
 	private ImageLoadingListener emptyListener;
 
 	private Map<ImageView, String> cacheKeyForImageView = Collections.synchronizedMap(new WeakHashMap<ImageView, String>());
+	private Map<String, ReentrantLock> uriLocks = Collections.synchronizedMap(new WeakHashMap<String, ReentrantLock>());
 
 	private volatile static ImageLoader instance;
 
@@ -209,7 +211,7 @@ public void displayImage(String uri, ImageView imageView, DisplayImageOptions op
 			}
 
 			checkExecutors();
-			ImageLoadingInfo imageLoadingInfo = new ImageLoadingInfo(uri, imageView, targetSize, options, listener);
+			ImageLoadingInfo imageLoadingInfo = new ImageLoadingInfo(uri, imageView, targetSize, options, listener, getLockForUri(uri));
 			LoadAndDisplayImageTask displayImageTask = new LoadAndDisplayImageTask(configuration, imageLoadingInfo, new Handler());
 			boolean isImageCachedOnDisc = configuration.discCache.get(uri).exists();
 			if (isImageCachedOnDisc) {
@@ -327,4 +329,15 @@ private int getFieldValue(Object object, String fieldName) {
 		}
 		return value;
 	}
+
+	private ReentrantLock getLockForUri(String uri) {
+		synchronized (uriLocks) {
+			ReentrantLock lock = uriLocks.get(uri);
+			if (lock == null) {
+				lock = new ReentrantLock();
+				uriLocks.put(uri, lock);
+			}
+			return lock;
+		}
+	}
 }
diff --git a/UniversalImageLoader/src/com/nostra13/universalimageloader/core/ImageLoadingInfo.java b/UniversalImageLoader/src/com/nostra13/universalimageloader/core/ImageLoadingInfo.java
@@ -1,5 +1,7 @@
 package com.nostra13.universalimageloader.core;
 
+import java.util.concurrent.locks.ReentrantLock;
+
 import android.net.Uri;
 import android.widget.ImageView;
 
@@ -23,13 +25,15 @@ final class ImageLoadingInfo {
 	final ImageSize targetSize;
 	final DisplayImageOptions options;
 	final ImageLoadingListener listener;
+	final ReentrantLock loadFromUriLock;
 
-	public ImageLoadingInfo(String uri, ImageView imageView, ImageSize targetSize, DisplayImageOptions options, ImageLoadingListener listener) {
+	public ImageLoadingInfo(String uri, ImageView imageView, ImageSize targetSize, DisplayImageOptions options, ImageLoadingListener listener, ReentrantLock loadFromUriLock) {
 		this.uri = Uri.encode(uri, "@#&=*+-_.,:!?()/~'%");
 		this.imageView = imageView;
 		this.targetSize = targetSize;
 		this.options = options;
 		this.listener = listener;
+		this.loadFromUriLock = loadFromUriLock;
 		memoryCacheKey = MemoryCacheKeyUtil.generateKey(uri, targetSize);
 	}
 }
diff --git a/UniversalImageLoader/src/com/nostra13/universalimageloader/core/LoadAndDisplayImageTask.java b/UniversalImageLoader/src/com/nostra13/universalimageloader/core/LoadAndDisplayImageTask.java
@@ -32,6 +32,8 @@
 final class LoadAndDisplayImageTask implements Runnable {
 
 	private static final String LOG_START_DISPLAY_IMAGE_TASK = "Start display image task [%s]";
+	private static final String LOG_WAITING = "Image already is loading. Waiting... [%s]";
+	private static final String LOG_GET_IMAGE_FROM_MEMORY_CACHE_AFTER_WAITING = "...Get cached bitmap from memory after waiting. [%s]";
 	private static final String LOG_LOAD_IMAGE_FROM_INTERNET = "Load image from Internet [%s]";
 	private static final String LOG_LOAD_IMAGE_FROM_DISC_CACHE = "Load image from disc cache [%s]";
 	private static final String LOG_CACHE_IMAGE_IN_MEMORY = "Cache image in memory [%s]";
@@ -52,17 +54,35 @@ public LoadAndDisplayImageTask(ImageLoaderConfiguration configuration, ImageLoad
 
 	@Override
 	public void run() {
-		if (configuration.loggingEnabled) Log.i(ImageLoader.TAG, String.format(LOG_START_DISPLAY_IMAGE_TASK, imageLoadingInfo.memoryCacheKey));
+		if (configuration.loggingEnabled) {
+			Log.i(ImageLoader.TAG, String.format(LOG_START_DISPLAY_IMAGE_TASK, imageLoadingInfo.memoryCacheKey));
+			if (imageLoadingInfo.loadFromUriLock.isLocked()) {
+				Log.i(ImageLoader.TAG, String.format(LOG_WAITING, imageLoadingInfo.memoryCacheKey));
+			}
+		}
 
-		if (checkTaskIsNotActual()) return;
-		Bitmap bmp = tryLoadBitmap();
-		if (bmp == null) return;
+		imageLoadingInfo.loadFromUriLock.lock();
+		Bitmap bmp;
+		try {
+			if (checkTaskIsNotActual()) return;
 
-		if (checkTaskIsNotActual()) return;
-		if (imageLoadingInfo.options.isCacheInMemory()) {
-			if (configuration.loggingEnabled) Log.i(ImageLoader.TAG, String.format(LOG_CACHE_IMAGE_IN_MEMORY, imageLoadingInfo.memoryCacheKey));
+			bmp = ImageLoader.getInstance().getMemoryCache().get(imageLoadingInfo.memoryCacheKey);
+			if (bmp == null) {
+				bmp = tryLoadBitmap();
+				if (bmp == null) return;
 
-			configuration.memoryCache.put(imageLoadingInfo.memoryCacheKey, bmp);
+				if (checkTaskIsNotActual()) return;
+				if (imageLoadingInfo.options.isCacheInMemory()) {
+					if (configuration.loggingEnabled) Log.i(ImageLoader.TAG, String.format(LOG_CACHE_IMAGE_IN_MEMORY, imageLoadingInfo.memoryCacheKey));
+
+					configuration.memoryCache.put(imageLoadingInfo.memoryCacheKey, bmp);
+				}
+			} else {
+				if (configuration.loggingEnabled)
+					Log.i(ImageLoader.TAG, String.format(LOG_GET_IMAGE_FROM_MEMORY_CACHE_AFTER_WAITING, imageLoadingInfo.memoryCacheKey));
+			}
+		} finally {
+			imageLoadingInfo.loadFromUriLock.unlock();
 		}
 
 		if (checkTaskIsNotActual()) return;