On Mon, Apr 18, 2016 at 4:43 PM, Alberto Mardegan < [email protected]> wrote:
> On 18/04/2016 13:57, Omer Akram wrote: > > While working on a pet project[1] for the Phone, an issue that I faced > > was stuttering scrolling in listviews. QML tips page[2] suggested to use > > Flickable+Column+Repeater combination to have smooth scrolling, that > > worked and is currently what I have implemented in my app but I always > > thought that was not the perfect solution. > > > > With some knowledge of how Android ListView works and its mechanism of > > recycling ListView items, I wrote a hack[3] to achieve something similar > > in QML. > [...] > > You are trying to reinvent the QML ListView :-) > The QML ListView recycles the delegates, and this behaviour is partially > configurable via the cacheBuffer property: > > http://doc.qt.io/qt-5/qml-qtquick-listview.html#cacheBuffer-prop My initial implementation was indeed using ListView and with a higher(random) cacheBuffer, it was smooth but I had that itch of experimenting and producing an optimized version of ListView. Plus I have seen quite a few apps in the store have scrolling issues. > > > Now, this means that when scrolling a listview, occasionally the > delegates need to be either created (the first time they are used) or > reused (which causes a reassignment of their properties based on the > model data). > Both these operations can be expensive, that's why someone gave the tip > of using a Column+Repeater when the number of delegates is low and > doesn't change, so that the whole list is created only once and > scrolling will be smooth. > Well, I think re-using already created elements and updating their properties is potentially much less resource hungry than creating a new element, though I don't have stats to prove that but my experimental ListView scrolls smooth, as I would expect it to. > > If now you found that this tip doesn't work well for you (typically > because of high memory consumption if the model has many items), it > means that you should go back to using a ListView. :-) > > Ciao, > Alberto > > -- > Mailing list: https://launchpad.net/~ubuntu-phone > Post to : [email protected] > Unsubscribe : https://launchpad.net/~ubuntu-phone > More help : https://help.launchpad.net/ListHelp >
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