public abstract class BitmapTransformation extends java.lang.Object implements Transformation<android.graphics.Bitmap>
Transformation
for transforming Bitmap
s that abstracts away dealing with Resource
objects for subclasses.
Use cases will look something like this:
public class FillSpace extends BitmapTransformation {
private static final String ID = "com.bumptech.glide.transformations.FillSpace";
private static final byte[] ID_BYTES = ID.getBytes(Charset.forName("UTF-8"));
@Override
public Bitmap transform(BitmapPool pool, Bitmap toTransform, int outWidth, int outHeight) {
if (toTransform.getWidth() == outWidth && toTransform.getHeight() == outHeight) {
return toTransform;
}
return Bitmap.createScaledBitmap(toTransform, outWidth, outHeight, true);
}
@Override
public boolean equals(Object o) {
return o instanceof FillSpace;
}
@Override
public int hashCode() {
return ID.hashCode();
}
@Override
public void updateDiskCacheKey(MessageDigest messageDigest) {
messageDigest.update(ID_BYTES);
}
}
Using the fully qualified class name as a static final String
(not Class.getName()
to avoid proguard obfuscation) is an easy way to implement Key.updateDiskCacheKey(java.security.MessageDigest)
} correctly. If additional arguments are
required they can be passed in to the constructor of the Transformation
and then used to
update the MessageDigest
passed in to Key.updateDiskCacheKey(MessageDigest)
. If arguments are primitive types, they can typically easily
be serialized using ByteBuffer
. String
types can be serialized with
String.getBytes(Charset)
using the constant Key.CHARSET
.
As with all Transformation
s, all subclasses must implement Object.equals(Object)
and Object.hashCode()
for memory caching to work correctly.
CHARSET, STRING_CHARSET_NAME
Constructor and Description |
---|
BitmapTransformation() |
Modifier and Type | Method and Description |
---|---|
protected abstract android.graphics.Bitmap |
transform(BitmapPool pool,
android.graphics.Bitmap toTransform,
int outWidth,
int outHeight)
Transforms the given
Bitmap based on the given dimensions and returns
the transformed result. |
Resource<android.graphics.Bitmap> |
transform(android.content.Context context,
Resource<android.graphics.Bitmap> resource,
int outWidth,
int outHeight)
Transforms the given resource and returns the transformed resource.
|
clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait
equals, hashCode, updateDiskCacheKey
@NonNull public final Resource<android.graphics.Bitmap> transform(@NonNull android.content.Context context, @NonNull Resource<android.graphics.Bitmap> resource, int outWidth, int outHeight)
Transformation
If the original resource object is not returned, the original resource will be recycled and it's internal resources may be reused. This means it is not safe to rely on the original resource or any internal state of the original resource in any new resource that is created. Usually this shouldn't occur, but if absolutely necessary either the original resource object can be returned with modified internal state, or the data in the original resource can be copied into the transformed resource.
If a Transformation is updated, Key.equals(Object)
, Key.hashCode()
, and Key.updateDiskCacheKey(java.security.MessageDigest)
should all change. If you're using a simple
String key an easy way to do this is to append a version number to your key. Failing to do so
will mean users may see images loaded from cache that had the old version of the Transformation
applied. Changing the return values of those methods will ensure that the cache key has changed
and therefore that any cached resources will be re-generated using the updated Transformation.
During development you may need to either using DiskCacheStrategy.NONE
or make sure Key.updateDiskCacheKey(java.security.MessageDigest)
changes each time you make a change to the
Transformation. Otherwise the resource you request may be loaded from disk cache and your
Transformation may not be called.
transform
in interface Transformation<android.graphics.Bitmap>
context
- The Application contextresource
- The resource to transform.outWidth
- The width of the view or target the resource will be displayed in, or Target.SIZE_ORIGINAL
to indicate the original resource
width.outHeight
- The height of the view or target the resource will be displayed in, or Target.SIZE_ORIGINAL
to indicate the original resource
height.protected abstract android.graphics.Bitmap transform(@NonNull BitmapPool pool, @NonNull android.graphics.Bitmap toTransform, int outWidth, int outHeight)
Bitmap
based on the given dimensions and returns
the transformed result.
The provided Bitmap, toTransform, should not be recycled or returned to the pool. Glide will automatically recycle and/or reuse toTransform if the transformation returns a different Bitmap. Similarly implementations should never recycle or return Bitmaps that are returned as the result of this method. Recycling or returning the provided and/or the returned Bitmap to the pool will lead to a variety of runtime exceptions and drawing errors. See #408 for an example. If the implementation obtains and discards intermediate Bitmaps, they may safely be returned to the BitmapPool and/or recycled.
outWidth and outHeight will never be Target.SIZE_ORIGINAL
, this class converts them to be the
size of the Bitmap we're going to transform before calling this method.
pool
- A BitmapPool
that can be used
to obtain and return intermediate Bitmap
s used in this transformation. For every
Bitmap
obtained from the pool during this transformation, a Bitmap
must also be returned.toTransform
- The Bitmap
to transform.outWidth
- The ideal width of the transformed bitmap (the transformed width does not need
to match exactly).outHeight
- The ideal height of the transformed bitmap (the transformed height does not
need to match exactly).