How to programmatically re-apply a 9-patch image to an ImageView?

Question

I have an activity that has an ImageView defined inside a HorizontalScrollView. The image source is a 9-patch file that is constrained to stretch only the right edge to fill

Answer 1

9-patch images seem to only work when they're set as a View's background image. So:

• instead of android:src, set android:background in your layout XML, and
• call setBackgroundResource() when you want to change the image.

You can also use a plain View instead of an ImageView if you want; it doesn't really matter much.

Answer 2

Move this: ImageView imgResultMap = (ImageView)findViewById(R.id.imgResultMap); to a global intialized in the onCreate method. Otherwise the device has to search for the view and find it every time it is tapped.

and try calling imgResultMap.invalidate(); before you return from the onDoubleTap method (http://developer.android.com/reference/android/view/View.html#invalidate())

Answer 3

EDIT: After doing some research, I have it figured out. Instead of just manipulating the bitmap, I need to also include the 9-patch chunk, which is not part of the bitmap image, to re-construct a new 9-patch drawable. See sample code below:

    ...
 else {
        // Zoom out
        zoom = 1;
        Bitmap mapBitmapScaled = mapBitmap; 
        // Load the 9-patch data chunk and apply to the view
        byte[] chunk = mapBitmap.getNinePatchChunk();
        NinePatchDrawable mapNinePatch = new NinePatchDrawable(getResources(), 
            mapBitmapScaled, chunk, new Rect(), null);
        imgResultMap.setImageDrawable(mapNinePatch);
 }

  ....

EDIT #2: For those who looks at my solution here, also take a look at Kai's suggestions below regarding memory management. Very useful information.

Answer 4

Also another solution is to set image programmatically as ImageResource and set scaleType

imageView.setImageResource(R.drawable.favorite_driver_icon);
imageView.setScaleType(ScaleType.FIT_XY);

Answer 5

Why don't you just include two different scaled images and switch between them using imgResultMap.setImageResource(resId) when zooming? Also note that you are loading & creating Bitmaps in UIThread which is not a good way to provide smooth user experience, at least preload the bitmap only once during onCreate() and cache that.