Comparison between decodefiledescriptor () and bimap than decodefile ()

Key points:
1. Use decodefiledescriptor () to generate bimap, which saves memory than decodefile ().

Bitmap bmp = BitmapFactory.decodeFile(imageFile, opts);imageView.setImageBitmap(bmp);

Replace

1 FileInputStream is = = new FileInputStream(path);2 bmp = BitmapFactory.decodeFileDescriptor(is.getFD(), null, opts);

 

Cause:
View the bitmapfactory source code and compare the implementation of the two. We can find that decodefile () is used to generate bitmap in the form of a stream.

Decodefile source code:

 

 

 1 public static Bitmap decodeFile(String pathName, Options opts) { 2     Bitmap bm = null; 3     InputStream stream = null; 4     try { 5         stream = new FileInputStream(pathName); 6         bm = decodeStream(stream, null, opts); 7     } catch (Exception e) { 8         /*  do nothing. 9             If the exception happened on open, bm will be null.10         */11     } finally {12         if (stream != null) {13             try {14                 stream.close();15             } catch (IOException e) {16                 // do nothing here17             }18         }19     }20     return bm;21 }

 

Decodefiledescriptor source code, you can find the native local method decodefiledescriptor, generate bitmap through the underlying layer

Decodefiledescriptor source code:

 1 public static Bitmap decodeFileDescriptor(FileDescriptor fd, Rect outPadding, Options opts) { 2        if (nativeIsSeekable(fd)) { 3            Bitmap bm = nativeDecodeFileDescriptor(fd, outPadding, opts); 4            if (bm == null && opts != null && opts.inBitmap != null) { 5                throw new IllegalArgumentException("Problem decoding into existing bitmap"); 6            } 7            return finishDecode(bm, outPadding, opts); 8        } else { 9            FileInputStream fis = new FileInputStream(fd);10            try {11                return decodeStream(fis, outPadding, opts);12            } finally {13                try {14                    fis.close();15                } catch (Throwable t) {/* ignore */}16            }17        }18    }19  20 private static native Bitmap nativeDecodeFileDescriptor(FileDescriptor fd,Rect padding, Options opts);

I can't give a reasonable explanation of what actually involves underlying virtual machines.

 

Comparison between decodefiledescriptor () and bimap than decodefile ()