In my project, I add several views to a vertical extended LinearLayout (named MyLinearLayout) circularly, but after the loop, the method onSizeChanged finally executes, and it executes only once.
Why?
Related
I made an andorid application using the "activity" component. I used it for a while, but over time I found that one page was not enough for me. I needed to add tabLayout, viewPager2 and three fragments.
I needed to migrate the functionality from mainActivity to the firstFragment.
I encountered a problem with events during the XML migration. In the activity I called android: onClick = "myOnClicFunction". But is that not possible?
I know that this has been discussed several times here in several threads. However, I would like to ask how to proceed correctly.
Here in the thread Android Fragment onClick button Method is the advice "even if you are in the fragment, put the onClick functions into activity" there is another similar advice to, "if you insist to make it in a fragment"
But what is right? Should the onclick function be correct in the activity or in the fragment?
I don't want to put the source code here, because I don't know which procedure is correct at all.
I am creating a program that is for testing students. An example is displayed and a response is pending.
The first tab has a lot of buttons + saves the result to an xml files.
The second tab will contain statistics. From saved files displays how many calculations were correct, wrong, average response time, etc ...
In Activity I had functions like getQuestion(), evaluateQuestion(), saveToXml() and events zeroWasPressed(), oneWasPressed(), twoWasPressed(), threeWasPressed() ...
Where should I put all these functions when I change the application from Activity to Fragment?
on click function listener should be placed in corresponding fragment, where the button is added in fragment layout.
events zeroWasPressed(), oneWasPressed(), twoWasPressed(), threeWasPressed() ... should be placed inside corresponding fragment where those buttons were added in layout.
getQuestion(), evaluateQuestion(), saveToXml() , this function can be placed in your activity or some other custom classes, that would appropriate according to architecture viewpoint.
I am trying to execute a SequentialTransition, but between the animations, I need to execute some commands.
My problem is that it is always executing the last commands passed on the node. Is there any way to fix this?
Where is "is ignored" is the code that I need to be executed in the first animation, then where this "is executed" is the code that I need to be executed in the second animation.
Thanks
private void startAnimation(){
vb_adv.setPrefWidth(197);
ap_services.toBack();// Is ignored
vb_adv.toFront();// Is ignored
ScaleTransition expandAdvertising = new ScaleTransition(Duration.millis(2000), vb_adv);
expandAdvertising.setToX(2);
expandAdvertising.setCycleCount(2);
expandAdvertising.setAutoReverse(true);
ap_services.setPrefWidth(124);
ap_services.toFront();//is executed
ScaleTransition expandService = new ScaleTransition(Duration.millis(2000), ap_services);
expandService.setDelay(Duration.seconds(3));
expandService.setToX(3.7);
expandService.setCycleCount(2);
expandService.setAutoReverse(true);
SequentialTransition sequence = new SequentialTransition(expandAdvertising, expandService);
sequence.play();
}
In the code as you currently have it, you move ap_services to the back of the z-order, and vb_adv to the front:
ap_services.toBack();
vb_adv.toFront();
Then you create and set up you ScaleTransition. Note that doing this part takes essentially no time; all you are doing is configuring the animation which will run later.
The next thing you do is to move ap_services to the front:
ap_services.toFront();
Note that this will happen essentially immediately after the previous calls to toFront() and toBack(), and of course this negates the effect of those calls. So your initial calls are actually executed (not "ignored"), but you immediately do something which undoes their effect.
What you really want is to execute ap_services.toFront() after the ScaleTransition finishes. You can do this by putting that call in an onFinished() handler:
// ap_services.toFront();
expandAdvertising.setOnFinished(e -> ap_services.toFront());
I use a custom class (Configuration) derived from QGraphicsItem and I add its objects to a QGraphicsScene, which is then displayed in a QGraphicsView. Usual stuff. What Im doing exactly is drawing a tree, in multiple steps, one level a step, each node beeing my custom QGraphicsItem.
Here a screenshot. The tree happens to be sequential in the simple case.
I first draw the root node. The signal that triggers that is fired after the user entered a string.
void MainWindow::drawRootSlot(ConfigTreeBuilder & builder)//this is a slot
{
c_scene->clear(); //the clear cause headache. i'll expain
Configuration* conf = new Configuration(builder.getNodesX(), builder.getNodesY(),builder.getNodesConfig());
//code
c_scene->addItem(conf);
//code
}
Each subsequent Configuration is draw inside another slot.
void MainWindow::configTreeSlot(ConfigTreeBuilder & builder) //SLOT!!!
{
while(builder.chooseNextNode()) {
Configuration* conf = new Configuration(builder.getNodesX(), builder.getNodesY(), builder.getNodesConfig());
//code, while loop
QGraphicsLineItem *edge = c_scene->addLine(QLineF(*(parentsPoint), conf->getLeftOrigin()));
edge->setZValue(-1); //below the Configuration item
c_scene->addItem(conf);
}
}
All works fine when done for the first time. When I enter a new string, resetting the tree, dark magic happens. What I expected to it do is: call drawRootSlot(), deleting the whole tree (c_scene->clear()), draw a new root node. And, if I put a debugger breakpoint inside drawRootSlot() this is exactly what happens! But when I run it (without breakpoints), what I get is this:
The previous tree got mangled, but not deleted. The scene gets indeed cleared of its items (printed that) but the view does not reflect that. But again, when I put a breakpoint inside drawRootSlot() thhe view and the scene are in sync.
I tried to delete the scene object, and instaciate a new one instead of calling c_scene->clear(), to guarantee it empty. Then the changes are reflected on the view (the first time drawing always works).
So, I have no idea what to deduce from these symptoms. It works as expected with a breakpoint or with a freshh QGraphicsScene object. It does not when just using c_scene->clear(). One couldsay I just messed up the parent-object/child-object relation, but clear() does remove items from the view... I tried calling it right after c_scene->addItem().
What is this sorrcery? One that makes me believe I'm not actually stupid?
EDIT: Whats interesting and may be a hint to the real problem, is that when c_scene->clear() is called, the edges of the tree, which are normal QGraphicsLineItems, are indeed deleted in all cases (breakpoint or not). Something to do with them not beeing custom?
Ok, calling QGraphicsView::viewport().update() after QGraphicsScene::clear() solved my problems.
But does anyone have an explanaition to the behavior described above?
EDIT: Upon doing doing something else I stumbled upon the actual core of the problem: I messed up the boundingRect() of my GraphicItems, so it was below the visble item, touching only its lower edge (which got deleted, as seen on the screenshot). So now no calls to any update() methods are neccesary.
I think when you call this fitInView() for the graphicsview it cleans up the view from any artifacts that remain from a previous scene.
You can clear both scene and Graphics View
scene->clear();
ui->graphicsView->items().clear();
graphicsView = name of your graphics view
This code will delete both scene and graphics view
I'm trying to allow items from a QListWidget to be dragged to a "Trash" (A subclassed widget which accepts drops and does nothing with them).
I know that if I setDropAction(Qt.MoveAction), the items I am removing from the source will be automatically deleted. This works correctly.
My problem is that I also need to trigger an action that updates other widgets who depend upon the contents of the source.
It seems to me that the dropEvent happens before any items are actually removed from the source. I'm having a terrible time trying to figure out this problem. I've thought of two possible solutions:
Find a way to embed the references to the actual QListWidgetItems that are being dragged in the event's QMimeData. This would allow me to do the deletions by hand, before I trigger updates.
Figure out how to wait until the source has been automatically cleared, but I can't find any signals that fire when items are removed from a list automatically.
Aha!
The key I was missing was the mimeData method. This method is called when a drag is started, and in it I am passed a list of all files being dragged.
I first built the meta object to be returned, then I deleted the files being dragged from the list, and called the refresh action that I needed.
Here's an example:
def mimeData(self, items):
m = QMimeData()
m.setUrls([QUrl(i.url) for i in items])
# Clean up the list:
[self.files.takeItem(self.files.indexFromItem(i).row()) for i in items]
self._update_meta()
return m
I have a flex app that takes data from a back end database then displays the content in one of 3 views.
These views are all in a viewstack which is instantiated in main.mxml
The method to get the data (remote object)is also in main.mxml.
The views rely on the data so how can I go about making sure that the data is loaded first before any of the views in viewstack are created / initialised to stop me having null reference errors?
When you get the data, you should have a callback function defined to receive that data (callback function is the function you put into addEventListener). You just need to call the function to create your viewstack after all your callbacks have been called.
The way I would do it is create an class field called numCallbacks. Increment this variable everytime one of your callbacks is called. Right after you increment it, check if numCallbacks == the number of callbacks you have. If true, create your view stack.