Andre Andre - 6 months ago 39
Android Question

Building a 9 patch drawable at runtime

I am successfully building a 9patch drawable at runtime on Android 3.0+ using the excellent gist provided by Brian Griffey (found here).

Essentially I load the raw (no patches) graphic file from the network and the filename contains the cap insets that I need to use in order to scale the image accordingly. I then use these values with the class found above and apply the image as a background to a variety of elements (such as

TextView
,
ImageButton
,
Button
,
ViewGroup
, etc).

This works perfectly as you can see here:

Android 3.0+ result

However, running the same code on Android 2.3.x yields the result:

Android 2.x result

I've looked through the source code used in Android to parse a 9patch image (here and here) but have found no method of getting this to work correctly. I've tried just about everything I could throw at it to no avail.

For the record, the 9patch consists of three columns on each axis, one fixed, one stretchable and one fixed.

Here's hoping someone else has solved this problem before.

Thanks in advance.

EDIT I am only interested in duplicating this behavior on Android 2.3 and above (I originally had 2.x).

EDIT #2 This gist describes exactly what I'm trying to do + Source image: source image

EDIT #3 The size of the image is 22px/58px (width/height) and the insets are 14/6/14/6 (top/left/bottom/right).

Answer

Putting together all I've spotted so far, and honing it a bit:

  • There doesn't seem to be a difference in the Res_png_9patch structure (which the byte chunk goes into) between android versions (see http://code.metager.de/source/xref/android), so that doesn't look like the cause.

  • Other answers about nine patch drawables suggest that each region (especially stretchable ones) should be at least 2x2 pixels (if not 3x3), but outside of that smaller is better.

  • However, the way some of the byte chunk is allocated looks like it could be updated. Try setting the 4th byte to 9 (the number of patches, I think), adding 7 more NO_COLORs to the the end and moving its size up to 56 + (7 x 4) = 84 bytes

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