Package 

Class SkiaPooledImageRegionDecoder

  • All Implemented Interfaces:
    com.pdfview.subsamplincscaleimageview.decoder.ImageRegionDecoder 
    
public class SkiaPooledImageRegionDecoder
 implements ImageRegionDecoder

    An implementation of ImageRegionDecoder using a pool of BitmapRegionDecoders, to provide true parallel loading of tiles. This is only effective if parallel loading has been enabled in the view by calling setExecutor with a multi-threaded Executor instance.

    One decoder is initialised when the class is initialised. This is enough to decode base layer tiles. Additional decoders are initialised when a subregion of the image is first requested, which indicates interaction with the view. Creation of additional encoders stops when allowAdditionalDecoder returns false. The default implementation takes into account the file size, number of CPU cores, low memory status and a hard limit of 4. Extend this class to customise this.

    WARNING: This class is highly experimental and not proven to be stable on a wide range of devices. You are advised to test it thoroughly on all available devices, and code your app to use SkiaImageRegionDecoder on old or low powered devices you could not test.

    • Field Summary

      Fields 
      Modifier and Type Field Description
      private static boolean debug

    • Method Summary

      Modifier and Type Method Description
      static void setDebug(boolean debug) Controls logging of debug messages.
      Point init(Context context, @NonNull() Uri uri) Initialises the decoder pool.
      Bitmap decodeRegion(@NonNull() Rect sRect, int sampleSize) Acquire a read lock to prevent decoding overlapping with recycling, then check the pool stillexists and acquire a decoder to load the requested region.
      synchronized boolean isReady() Holding a read lock to avoid returning true while the pool is being recycled, this returnstrue if the pool has at least one decoder available.
      synchronized void recycle() Wait until all read locks held by decodeRegion are released, then recycleand destroy the pool.

      • Methods inherited from class com.pdfview.subsamplincscaleimageview.decoder.ImageRegionDecoder

        init

      • Methods inherited from class java.lang.Object

        clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

    • Constructor Detail

      • SkiaPooledImageRegionDecoder

        SkiaPooledImageRegionDecoder()

      • SkiaPooledImageRegionDecoder

        SkiaPooledImageRegionDecoder(Bitmap.Config bitmapConfig)

    • Method Detail

      • setDebug

         static void setDebug(boolean debug)

        Controls logging of debug messages. All instances are affected.

        Parameters:
        debug - true to enable debug logging, false to disable.

      • init

        @NonNull() Point init(Context context, @NonNull() Uri uri)

        Initialises the decoder pool. This method creates one decoder on the current thread and usesit to decode the bounds, then spawns an independent thread to populate the pool with anadditional three decoders. The thread will abort if recycle is called.

      • decodeRegion

        @NonNull() Bitmap decodeRegion(@NonNull() Rect sRect, int sampleSize)

        Acquire a read lock to prevent decoding overlapping with recycling, then check the pool stillexists and acquire a decoder to load the requested region. There is no check whether the poolcurrently has decoders, because it's guaranteed to have one decoder after init is called and be null once recycle is called. In practice the view can't call thismethod until after init, so there will be no blocking on an empty pool.

      • isReady

         synchronized boolean isReady()

        Holding a read lock to avoid returning true while the pool is being recycled, this returnstrue if the pool has at least one decoder available.

      • recycle

         synchronized void recycle()

        Wait until all read locks held by decodeRegion are released, then recycleand destroy the pool. Elsewhere, when a read lock is acquired, we must check the pool is not null.