Use ReadWriteLock to allow multiple threads to decode tiles while preventing simultaneous recycling
diff --git a/library/src/main/java/com/davemorrissey/labs/subscaleview/decoder/SkiaImageRegionDecoder.java b/library/src/main/java/com/davemorrissey/labs/subscaleview/decoder/SkiaImageRegionDecoder.java
index c3ffb6c..9d216f6 100644
--- a/library/src/main/java/com/davemorrissey/labs/subscaleview/decoder/SkiaImageRegionDecoder.java
+++ b/library/src/main/java/com/davemorrissey/labs/subscaleview/decoder/SkiaImageRegionDecoder.java
@@ -11,17 +11,24 @@
import java.io.InputStream;
import java.util.List;
+import java.util.concurrent.locks.ReadWriteLock;
+import java.util.concurrent.locks.ReentrantReadWriteLock;
/**
* Default implementation of {@link com.davemorrissey.labs.subscaleview.decoder.ImageRegionDecoder}
* using Android's {@link android.graphics.BitmapRegionDecoder}, based on the Skia library. This
* works well in most circumstances and has reasonable performance due to the cached decoder instance,
* however it has some problems with grayscale, indexed and CMYK images.
+ *
+ * A {@link ReadWriteLock} is used to delegate responsibility for multi threading behaviour to the
+ * {@link BitmapRegionDecoder} instance, whilst allowing this class to block until no tiles are being
+ * loaded before recycling the decoder. In practice, {@link BitmapRegionDecoder} is single threaded
+ * so this has no real impact on performance.
*/
public class SkiaImageRegionDecoder implements ImageRegionDecoder {
private BitmapRegionDecoder decoder;
- private final Object decoderLock = new Object();
+ private final ReadWriteLock decoderLock = new ReentrantReadWriteLock(true);
private static final String FILE_PREFIX = "file://";
private static final String ASSET_PREFIX = FILE_PREFIX + "/android_asset/";
@@ -90,25 +97,42 @@
@Override
public Bitmap decodeRegion(Rect sRect, int sampleSize) {
- synchronized (decoderLock) {
- BitmapFactory.Options options = new BitmapFactory.Options();
- options.inSampleSize = sampleSize;
- options.inPreferredConfig = bitmapConfig;
- Bitmap bitmap = decoder.decodeRegion(sRect, options);
- if (bitmap == null) {
- throw new RuntimeException("Skia image decoder returned null bitmap - image format may not be supported");
+ decoderLock.readLock().lock();
+ try {
+ if (decoder != null && !decoder.isRecycled()) {
+ BitmapFactory.Options options = new BitmapFactory.Options();
+ options.inSampleSize = sampleSize;
+ options.inPreferredConfig = bitmapConfig;
+ Bitmap bitmap = decoder.decodeRegion(sRect, options);
+ if (bitmap == null) {
+ throw new RuntimeException("Skia image decoder returned null bitmap - image format may not be supported");
+ }
+ return bitmap;
+ } else {
+ throw new IllegalStateException("Cannot decode region after decoder has been recycled");
}
- return bitmap;
+ } finally {
+ decoderLock.readLock().unlock();
}
}
@Override
public boolean isReady() {
- return decoder != null && !decoder.isRecycled();
+ decoderLock.readLock().lock();
+ try {
+ return decoder != null && !decoder.isRecycled();
+ } finally {
+ decoderLock.readLock().unlock();
+ }
}
@Override
public void recycle() {
- decoder.recycle();
+ decoderLock.writeLock().lock();
+ try {
+ decoder.recycle();
+ } finally {
+ decoderLock.writeLock().unlock();
+ }
}
}