Effectively if you are interested in handling pinch you would just override:
protected boolean pinch(float scale) and return true after handling the pinch operation. We did this to support our new
(where you can see a working sample of pinch), the image viewer allows you to inspect, zoom and pan into an image. It also allows swiping between images if you have a set of images (using an image list model).
Now to simulate the pinching we needed a simpler solution than just building for the device, which is why we added right click dragging. Now when you drag using the right mouse button (or by pressing 2 fingers on a Mac laptop and dragging together) you will get a pinch effect. We do this by hardcoding the second finger at position 0,0. So effectively if you drag towards the top left corner you will be zooming out (fingers closer together) and by dragging away you will be zooming in.
Here is a simple example of using the ImageViewer:
This leads me to one of the more important aspects here: image locking.
Once of the big performance improvements we got in swiping was through image locking, unfortunately this is so unclear in our current docs that when Nokia forked LWUIT they actually removed the usage of EncodedImage instead of fixing a minor locking bug.
To understand locking we first need to understand EncodedImage. EncodedImage stores the data of the image in RAM (png or JPEG data) which is normally pretty small, unlike the full decoded image which can take up to width X height X 4. When a user tries to draw an encoded image we check a WeakReference cache and if the image is cached then we show it otherwise w
e load the image, cache it then draw.
Naturally loading the image is more expensive so we want the images that are showing to stay in cache (otherwise GC will thrash a lot).
That’s where lock() kicks in, we automatically invoke image loading when necessary but when lock() is active we keep a hard reference to the actual native image so it won’t get GC’d.
Internally we invoke this automatically for bg images, icons etc. which results in a huge performance boost. However, if you use a complex renderer or custom drawing UI you should lock() your images where possible!
You might have noticed from the code above that the list model is now generified, the same is also true now for the list renderer and list. We are working on modernizing as much of our code as we can while maintaining backwards compatibility.
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This is one of missing APIs,what I am waiting for. Great!!
i have dynamic list in ImageViewer( images from url)
i want to swipe images not on touch only but in pressing button too (swiping left and right)
how can i do it
there is a code sample within the JavaDocs that covers just that use case: [https://www.codenameone.com…](https://www.codenameone.com/javadoc/com/codename1/components/ImageViewer.html)
It’s also included in the developer guide section of the ImageViewer:
thank you …
i use setSelectedIndex method in ImageList
int myNewIndex=myImageViewer.getImageList().getSelectedIndex()(+1 or -1); to swiping left and right
i have ImageViewer the image size 800X400
when i run my app on small device the image looks like attached image (there’s a space on top and bottom of image )
any idea please
Images default to “scale to fit” in the image viewer.
ok how i can change it
You can change the zoom level, but are you trying to show a static image or allow the user to change that? If the former then image viewer is the wrong component to use.
dynamic list in ImageViewer( images from url) i show it as slider
So if you have multiple images in the viewer and flip between them zooming in will be a mistake.
This can create an image whose edges are wider than the screen so when you try to swipe you will really pan within the image…
You can replicate that behavior by zooming in with pinch and trying to swipe to see what I mean.
i have list of images not multi-images and i have Image Viewer
if you understand what i mean , is any way to create slider images without space on top and bottom of image in small device
thanks a lot
If I understand correctly you want to do something similar to the phone picture gallery where you swipe between the photos you took.
If you look at that native OS UI you will notice space above or on the sides to keep the aspect ratio of the image in place as you swipe. If you are speaking of a different UI/UX I’ll need a reference.