Do you know why calling view.draw() on a scrollview draws the screen
disregarding the current scrollY and assumes the scrollview is at the
beginning always?
On Jun 24, 10:14 am, Romain Guy <romain...@android.com> wrote:
> The drawing cache is per view, so if you need to capture several views
> (sibling, and not a subtree like you are doing in your example) if
> would be better to allocate a single bitmap. This works of course only
> if all the views have the same size.
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> On Thu, Jun 23, 2011 at 5:06 PM,rukiman<ruksh...@optushome.com.au> wrote:
> > I am suspecting using the view cache system causes the view system to
> > allocate memory for the view.
> > Now lets say I can to capture 3 views, does that mean memory is
> > allocated for 3 views worth of caches if I don't destroy the cache?
>
> > Also I noticed through profiling that this code runs around 100ms
> > view.setDrawingCacheEnabled(true);
> > view.setDrawingCacheQuality(View.DRAWING_CACHE_QUALITY_HIGH);
> > view.setDrawingCacheBackgroundColor(Color.BLACK);
> > Bitmap bitmap = view.getDrawingCache();
> > Bitmap retVal = bitmap == null ? null :
> > bitmap.copy(bitmap.getConfig(), false);
> > view.destroyDrawingCache();
> > view.setDrawingCacheEnabled(false);
> > return retVal;
>
> > while this runs at around 60ms
> > mCanvas.setBitmap(mBitmapCapture);
> > view.draw(mCanvas);
> > Bitmap retVal = mBitmapCapture;
>
> > I have to capture a few views and trying to speed them as quick as
> > possible and at the same time not use much memory. I guess the slight
> > speed difference is in enabling and destroying the view drawing cache?
> > What is the effect of not destroying it? Does that mean it will suffer
> > from my approach above that is double the workload on each frame as
> > well?
>
> > Going back to my approach my code is just as I pasted it, should I be
> > saving the canvas and restoring it in the dispatchDraw? Any help is
> > appreciated. Thanks.
>
> > On Jun 24, 9:47 am, Romain Guy <romain...@android.com> wrote:
> >> It's either because you don't properly save/restore the state of your
> >> offline Canvas or maybe because of the bitmap config (although it
> >> should work just fine in 565.)
>
> >> What I don't understand however is why you refuse to use the drawing
> >> cache API that already exists for this purpose? Using this API will
> >> not necessarily force another redraw of the view. With the drawing
> >> cache, the cache is automatically redrawn whenever the view changes.
> >> Your approach however doubles the workload on *every* frame.
>
> >> On Thu, Jun 23, 2011 at 4:23 PM,rukiman<ruksh...@optushome.com.au> wrote:
> >> > I am trying to understand which this code which works perfectly for
> >> > capturing almost any view except if there is a ScrollView in the
> >> > framelayout, in this case there is a slight issue with the top and
> >> > bottom areas where scrollview fades its contents. There is some
> >> > corruption occurring.
>
> >> > public class FrameLayoutWithOfflineBitmap extends FrameLayout {
>
> >> > private Bitmap mOfflineBitmap;
> >> > private Canvas mOfflineCanvas;
>
> >> > public FrameLayoutWithOfflineBitmap(Context context) {
> >> > super(context);
> >> > }
>
> >> > @Override
> >> > public void onSizeChanged(int w, int h, int oldw, int oldh) {
> >> > // just in case we already had the bitmap allocated before
> >> > if(mOfflineBitmap != null) {
> >> > mOfflineBitmap.recycle();
> >> > }
> >> > mOfflineBitmap = Bitmap.createBitmap(w, h,
> >> > Bitmap.Config.RGB_565);
> >> > mOfflineCanvas = new Canvas();
> >> > mOfflineCanvas.setBitmap(mOfflineBitmap);
> >> > }
>
> >> > @Override
> >> > public void dispatchDraw(Canvas canvas) {
> >> > // draw to our offline bitmap
> >> > super.dispatchDraw(mOfflineCanvas);
> >> > // now draw our offline bitmap to the system canvas
> >> > canvas.drawBitmap(mOfflineBitmap, 0, 0, null);
> >> > }
>
> >> > public Bitmap getScreenSnapshot() {
> >> > return mOfflineBitmap;
> >> > }
> >> > }
>
> >> > I understand there are other ways to capture the view such as using
> >> > the View's drawing cache, but I am not interested in this method. Can
> >> > someone explain to me what is going on here and if there is way to
> >> > address this issue? Basically I am trying to get access to a snapshot
> >> > of a view as quick as possible. My idea is that the view is already
> >> > drawn onto the screen, we should be able to get access to this without
> >> > having to force another redundant redraw of the view.
>
> >> > I am also very keen to understand the flaw with the above code in
> >> > terms of the scrollview. Thanks.
>
> >> > --
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>
> >> --
> >> Romain Guy
> >> Android framework engineer
> >> romain...@android.com
>
> >> Note: please don't send private questions to me, as I don't have time
> >> to provide private support. All such questions should be posted on
> >> public forums, where I and others can see and answer them
>
> > --
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>
> --
> Romain Guy
> Android framework engineer
> romain...@android.com
>
> Note: please don't send private questions to me, as I don't have time
> to provide private support. All such questions should be posted on
> public forums, where I and others can see and answer them
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