Re: [android-developers] Re: How to detect if a view is on screen
Hello Ed, Thanks for your answer but I'm not sure a ListView will work (though I will look at the video). Isn't a ListView limited to Vertical scrolling? (at least the javadoc says so) Kind Regards, Marc 2011/9/6 Ed edscha...@gmail.com Hi Marc, Have a look at ListView. It's probably done most of the hardwork for you if you just write your own adapter. Just make sure you get your getView correct. Watch a couple of Romain Guy's videos from Google I/O e.g. http://www.youtube.com/watch?v=wDBM6wVEO70 Should help get you started in the right direction. Cheers, Ed -- You received this message because you are subscribed to the Google Groups Android Developers group. To post to this group, send email to android-developers@googlegroups.com To unsubscribe from this group, send email to android-developers+unsubscr...@googlegroups.com For more options, visit this group at http://groups.google.com/group/android-developers?hl=en -- You received this message because you are subscribed to the Google Groups Android Developers group. To post to this group, send email to android-developers@googlegroups.com To unsubscribe from this group, send email to android-developers+unsubscr...@googlegroups.com For more options, visit this group at http://groups.google.com/group/android-developers?hl=en
[android-developers] Re: How to detect if a view is on screen
I would have said use ScrollView, but that too is limited to vertical scrolling. So now I have to ask: do you really HAVE to have the scrolling done horizontally? You might be in for a harder time if you insist on this. On Sep 5, 11:29 pm, Marc Van Daele marc.van.dael...@gmail.com wrote: Hello Ed, Thanks for your answer but I'm not sure a ListView will work (though I will look at the video). Isn't a ListView limited to Vertical scrolling? (at least the javadoc says so) Kind Regards, Marc 2011/9/6 Ed edscha...@gmail.com Hi Marc, Have a look at ListView. It's probably done most of the hardwork for you if you just write your own adapter. Just make sure you get your getView correct. Watch a couple of Romain Guy's videos from Google I/O e.g. http://www.youtube.com/watch?v=wDBM6wVEO70 Should help get you started in the right direction. Cheers, Ed -- You received this message because you are subscribed to the Google Groups Android Developers group. To post to this group, send email to android-developers@googlegroups.com To unsubscribe from this group, send email to android-developers+unsubscr...@googlegroups.com For more options, visit this group at http://groups.google.com/group/android-developers?hl=en -- You received this message because you are subscribed to the Google Groups Android Developers group. To post to this group, send email to android-developers@googlegroups.com To unsubscribe from this group, send email to android-developers+unsubscr...@googlegroups.com For more options, visit this group at http://groups.google.com/group/android-developers?hl=en
[android-developers] Re: How to detect if a view is on screen
Hah, I should have thought of this name! 'HorizontalScrollView' has been supported since API level 3, and it sounds like just what you want. On Sep 5, 11:39 pm, Indicator Veritatis mej1...@yahoo.com wrote: I would have said use ScrollView, but that too is limited to vertical scrolling. So now I have to ask: do you really HAVE to have the scrolling done horizontally? You might be in for a harder time if you insist on this. On Sep 5, 11:29 pm, Marc Van Daele marc.van.dael...@gmail.com wrote: Hello Ed, Thanks for your answer but I'm not sure a ListView will work (though I will look at the video). Isn't a ListView limited to Vertical scrolling? (at least the javadoc says so) Kind Regards, Marc 2011/9/6 Ed edscha...@gmail.com Hi Marc, Have a look at ListView. It's probably done most of the hardwork for you if you just write your own adapter. Just make sure you get your getView correct. Watch a couple of Romain Guy's videos from Google I/O e.g. http://www.youtube.com/watch?v=wDBM6wVEO70 Should help get you started in the right direction. Cheers, Ed -- You received this message because you are subscribed to the Google Groups Android Developers group. To post to this group, send email to android-developers@googlegroups.com To unsubscribe from this group, send email to android-developers+unsubscr...@googlegroups.com For more options, visit this group at http://groups.google.com/group/android-developers?hl=en -- You received this message because you are subscribed to the Google Groups Android Developers group. To post to this group, send email to android-developers@googlegroups.com To unsubscribe from this group, send email to android-developers+unsubscr...@googlegroups.com For more options, visit this group at http://groups.google.com/group/android-developers?hl=en
Re: [android-developers] Re: How to detect if a view is on screen
In fact, I'm using HorizontalScrollView already
but I'm worried about memory consumption (I'm coming from the embedded
software world)
Inside the HorizontalScrollView I have a LinearLayout containing a list of
my own Views
(actually a ViewGroup displaying a movie poster but also information on the
actors, description, icons for parental rating etc).
Whenever my View is first loaded (first dispatchDraw call), I load the
Bitmap for the movie poster.
But right now, I never unload this bitmap so I'm worried about memory usage.
Hence I want to release the Bitmap when the View is not on screen.
I don't think HorizontalScrollView as such (nor ListView) provides support
for this (please correct me if I'm wrong)
I looked a bit in the source code of HorizontalScrollView and noticed that
it has a private :-( method isOffScreen(..).
Based on that code I now do something like (in the parents dispatchDraw)
ViewGroup scroller = (ViewGroup)
getChildAt(0);//HorizontalScrollView
ViewGroup layout = (ViewGroup) scroller.getChildAt(0);//LinearLayout
for (int i = 0; i layout.getChildCount(); i++)
{
View child = layout.getChildAt(i);
//check if an asset/event is visible
if(isOffScreenHorizontal(scroller, child))
{
//call unload method
}
}
with isOffScreenHorizontal
private boolean isOffScreenHorizontal(ViewGroup parent, View child)
{
Rect mTempRect = new Rect();
child.getDrawingRect(mTempRect);
parent.offsetDescendantRectToMyCoords(child, mTempRect);
return !((mTempRect.right) = parent.getScrollX()
(mTempRect.left) = (parent.getScrollX() +
parent.getWidth()));
}
Can you give feedback on this approach?
TIA,
Marc
2011/9/6 Indicator Veritatis mej1...@yahoo.com
Hah, I should have thought of this name! 'HorizontalScrollView' has
been supported since API level 3, and it sounds like just what you
want.
On Sep 5, 11:39 pm, Indicator Veritatis mej1...@yahoo.com wrote:
I would have said use ScrollView, but that too is limited to
vertical scrolling. So now I have to ask: do you really HAVE to have
the scrolling done horizontally? You might be in for a harder time if
you insist on this.
On Sep 5, 11:29 pm, Marc Van Daele marc.van.dael...@gmail.com wrote:
Hello Ed,
Thanks for your answer but I'm not sure a ListView will work (though I
will
look at the video).
Isn't a ListView limited to Vertical scrolling? (at least the javadoc
says
so)
Kind Regards,
Marc
2011/9/6 Ed edscha...@gmail.com
Hi Marc,
Have a look at ListView. It's probably done most of the hardwork for
you if
you just write your own adapter. Just make sure you get your getView
correct.
Watch a couple of Romain Guy's videos from Google I/O e.g.
http://www.youtube.com/watch?v=wDBM6wVEO70
Should help get you started in the right direction.
Cheers,
Ed
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[android-developers] Re: How to detect if a view is on screen
I didn't see my question (see below) appear in the group yet so I'm resending. Sorry if it appears twice. Marc 2011/9/3 vdaele marc.van.dael...@gmail.com Hello, Suppose I have a horizontal scrollable list of say 100 movie posters (each in its own View) of which only 4 Views fit on the screen at the same time. When I've scrolled through the complete list once, I will have 100 Bitmaps in memory of which only 4 are visible. To save memory, I want to release the Bitmaps of those Views that are off-screen. Is there an easy way to know whether a View is effectively visible or should I compute this myself? (I've looked at the onVisibilityChanged listener but this seems to serve a different purpose) Thanks for your help, Marc -- You received this message because you are subscribed to the Google Groups Android Developers group. To post to this group, send email to android-developers@googlegroups.com To unsubscribe from this group, send email to android-developers+unsubscr...@googlegroups.com For more options, visit this group at http://groups.google.com/group/android-developers?hl=en
[android-developers] Re: How to detect if a view is on screen
Hi Marc, Have a look at ListView. It's probably done most of the hardwork for you if you just write your own adapter. Just make sure you get your getView correct. Watch a couple of Romain Guy's videos from Google I/O e.g. http://www.youtube.com/watch?v=wDBM6wVEO70 Should help get you started in the right direction. Cheers, Ed -- You received this message because you are subscribed to the Google Groups Android Developers group. To post to this group, send email to android-developers@googlegroups.com To unsubscribe from this group, send email to android-developers+unsubscr...@googlegroups.com For more options, visit this group at http://groups.google.com/group/android-developers?hl=en
