I am working on a chat application for BlackBerry that leverages ListView to display chat messages. I have different kinds of messages and therefore I use multiple ListItemComponents, but what's more important, I use property: stickToEdgePolicy: ListViewStickToEdgePolicy.End to ensure that the scroll is positioned at the end when new chat messages arrive.
Everything is working fine, but sometimes the content of ListView starts shaking by few pixels up and down and that lasts infinitely. This is usually happening when a user is scrolling the view by swipe gestures and reaches the bottom. Also, this may happen if a new message has arrived. However, this never happens consistently! Also, worth to mention this happens with equal probability on square screen and rectangle screen devices.
While researching this, I found that the height of the view is affecting this jittering effect by making it less or more likely to happen, but none of the height values made it completely gone.
My question is addresed to the experienced BB10 developers, who practically saw this issue and know how to this fix.
The layout is pretty straightforward:
Container {
ChatTitle {
// this is just another Container with chat title Label
}
ListView {
id: chatEntries
stickToEdgePolicy: ListViewStickToEdgePolicy.End
topMargin: ui.sdu(1)
bottomMargin: ui.sdu(1)
...
listItemComponents: [
...
]
}
...
// few controls below the ListView, e.g. TextArea, Buttons.
}
Appreciate any help, thanks!
Related
This question is regarding QML, QtQuick 1.1, Qt 4.8.6
I have seen source code of an embedded application, in which all the screens are loaded at start. For Example,
//Main.qml
Rectangle{ //Base Container
width:640
height:480
MainScreen{ id: main_screen} //Individual screen files are given here
SettingScreen1 { id:screen1}
SettingScreen2 { id:screen2}
HelpScreen1 {id: help_screen1}
...
...
...
}
and in the respective screen document, when a mouse area is clicked the Value of Z of the individual document is changed to make it appear front
//MainScreen.qml
Rectangle{
width: 640
height:480
z:1
//some buttons
//Mousearea for next button
onClicked: {screen1.z = 10}
//Mousearea for back button
onClicked: {screen1.z = 0}
}
My question is,
1. As from main.qml all the children are created at once and only their visibility of stack order is changed. Is this a good method?
2. When so many children are loaded at beginning what happens if I have like 200 screens. What is the effect in CPU load at start and while operation.
Is there any other method for screen transitions?
Other than component loader. I don`t want to use that feature
How this code is converted and showed in display as an object?
I will be very happy is least you can give hints in comments.
Thanks!!
To your questions:
1): Bad Idea. Using the z-index needs the engine to determine that the lower items are hidden completely. You should help the enigne if you are sure about this (which would be the case here) by setting the visibility to false. Then however, you would not need to use the z-index at all. Don't use the z-index. Don't!
However this won't solve that you might have 200 possibly complex views in your memory.
The Loader you mentioned is already a better start.
You can use it in combination with the visibility to preload pages that are likely to be shown soon, and unload them once you are sure they are not shown anytime soon (within the next one or two clicks)
2): The effect is: Long time of unresponsivenes until everything is loaded. The documentation sais: Show a splash-screen if you want to do something like this. In order to show the splash-screen, show it, then use a Loader to load all the other stuff... But in general: Don't do it, if not absolutly necessary. Load dynamically. Never use the z-index to hide screens completely. Load only what needs to be loaded... I feel repetitive...
I have items that can be dropped only to a small DropArea (called AcceptDropZone). This works fine.
Now I want the following behavior : if items are dropped elsewhere, they go back to their starting position when the user releases the mouse. To do this, I have added another DropArea (called RejectDropZone) in the background, that fills the entire window of the application.
The problem is that RejectDropZone consumes the onDropped event even when the items are dropped over AcceptDropZone. As RejectDropZone is in the background of the QML stack, I was expecting AcceptDropZone to get the event first, as for MouseArea components.
Is this a bug or a valid behaviour of overlapping DropAreas? How can I get the result I am looking for?
Thanks for your help;
Regards
For those who may be interested, here is the solution to my problem:
https://forum.qt.io/topic/71036/droparea-overlapping/6
Regards
I've created a rather simple Flex application using Flex Builder 4, which connects to a webcam on the user's PC. To do so, Flash is presenting the user with the infamous privacy warning.
Now, the problem is that user can't click on the panel, as it seems unresponsive to any user interaction.
Some more details:
Firefox 3.6.12 on Mac/OSX, Snow Leopard.
Adobe Flash Plugin 10.1.85.3 / 10.1 r85
The Flex app is working fine in its own window/tab but the problem shows up as soon as the html page with the Flex app is embedded into the iframe of another page.
If I artificially put an Alert box before connecting the camera, the user is able to interact with the Flex application but as soon as the Privacy panel is shown, the Flex app stops interacting.
The app works fine under Chrome and Safari but I have not tried this under Windows.
I've read that there are problems with CSS positioning so I removed any CSS style impacting the Flex app.
Before I change my strategy and get rid of the iframe (which will cost me quite some effort) I'd be happy to know whether others have experienced the same problem and if there are workarounds.
Thanks.
I had the same issue for weeks now. I found what may be the problem. It has something to do with the css alignment. try to remove the text-align:center; from the div flash is in and it will work again. Somehow the active areas from the security panel don´t shift with the display image…
In my application, this problem is apparently caused by an element containing the flash having the css margin: 0 auto. This leads to the left edge of the flash object sometimes being reported as a decimal, e.g. $('.flash').position().left --> 450.5px. Whenever it's not a whole number, the security panel failed to react to clicks.
The fix described in https://bugs.adobe.com/jira/browse/FP-4183 and linked to by Christiano almost works. However, it failed whenever the browser was resized to be so small that the left margin disappeared.
Here's what fixed the issue for me:
function registerMozillaFlashFix() {
if ($.browser.mozilla) {
$(window).resize(function() {
$(".flash").each(function(ii, e) {
var $e = $(e);
$e.css('margin-left', $e.position().left % 1 === 0 ? '0' : '0.5px');
});
});
}
}
Then just call window.resize() once your flash has been set up.
If a SWF file or even a component within it has scrollbars, wouldn't it make sense that if the user is hovered over that area (it's in focus) and uses the mouse wheel, that this movement would automatically translate to the scrollbar moving.
Any ideas how this is done, the events or classes used for this? I'm open to outside components or classes too. I haven't started yet, but I'll do an item renderer because it's easy to give it scrollbar.
Here's some code which will let you deal with mouse wheel scrolling, it's pretty easy to deal with:
objectToBeHoveringOver.addEventListener(MouseEvent.MOUSE_WHEEL, scrollObject);
function scrollObject(event:MouseEvent):void
{
trace(event.delta);
}
The event.delta part will be a number that's either positive or negative, depending on which way you scrolled the wheel. You can use this to move your object up and down. Hope this helps.
debu
Sort of a complicated scenario - just curious if anyone else could come up with something:
I have a Text control and when I scroll it and stop the scroll with the cursor over some text that has a url, the cursor doesn't revert to a hand, and also flash player starts acting as if a selection is being made from the last cursor position. So IOW a bonafide bug in flash as far as I can determine.
The above probably wasn't completely clear so let me elaborate. If you grab a scrollbar thumb and start moving it up and down, you don't actually have to keep the mouse pointer on the thumb while doing so. When you stop the scroll, the mouse pointer could be outside the browser window, inside your flash application, but not currently on the scroll bar thumb, or wherever. The previously mentioned bug occurs when you stop the scroll with the mouse pointer positioned over text with an html anchor (a hyperlink). At that point the cursor enters into some state of limbo, and doesn't show the url hand pointer, and furthermore acts as if some text selection is taking place from the last cursor position prior to the scroll.
So the question would be, what sort of event could I simulate in code to jolt flash out of this erroneous state it is in. And furthermore in what event could I perform this simulated event (given that for example there is no AS3 event to signal the end of a scroll.)
To be clear, the Text control in question is on a canvas, and that canvas (call it A) is on another canvas which actually owns the scrollbar, and scrolling takes place by changing the scrollRect of canvas A.
I have run into this exact same problem with the TextArea in Flex 4: Scroll (textarea content is large than it's container) and release the mouse when over a link, and the cursor doesn't act right.
I think it's a bug, try submitting it to the Adobe Bug and Issue Management System. I will vote for it :).
Are you using Flex 3 or 4? If you're in Flex 4, I can make some suggestions. As a base, I would examine the TextArea and related source code in the Flex 3 SDK and figure out what events are being dispatched from links and whatnot. If you can eliminate the possibility that it's a Flash TextField (which TextArea uses), then it's a Flex bug. Try dispatching events that they're dispatching within the TextArea, from the things that are dispatching it (Event.CHANGE is all I can see taking a quick glance).
Good luck!
This is really in response to viatropos.
I was just able to duplicate the bug using the code example from the end of the Text documentation page in Flex 3.5 reference.
Just replace their htmlText in that example with a huge block of htmlText containing anchors tags (<a>...</a>). Then make the browser window small. Then click some arbitrary area of the htmlText with the mouse (That step is important.) Then scroll using the thumb. Stop the scroll with the cursor directly over one of the hyperlinks you created and release the mouse. The entire block of htmlText is selected and highlighted and the mouse pointer will not revert to a hand. (Well it will after you click somewhere else.)
As far as reporting this to adobe through their bug tracking system, I guess if I want to wait several months for it to be fixed. I reported another genuine bug over a year ago that was never fixed.
But examining their source code as you suggested - probably my best bet.