I am trying to move from an activity named MyNotes.java to one fragment named FragmentNotes.java. I found that the following codes should be used to perform the movement:
Fragment mFragmentNotes = new FragmentNotes ();
FragmentManager fragmentManager = getFragmentManager();
FragmentTransaction fragmentTransaction = fragmentManager.beginTransaction();
fragmentTransaction.replace(R.id.fragment_note_id, mFragmentNotes).addToBackStack(null);
fragmentTransaction.commit();
And I think R.id.fragment_note_id should be the id of the fragment's layout. (BTW, I am curious why I need to "replace" the id of the fragment's layout when I am simply moving back to the fragment.) However, the above codes do not work, making mFragmentNotes with a red line as follows:
How can I fix this problem?
I found that a mismatch of fragment types created the problem as described in here. I solved the problem by following the steps here. Hope this helps someone in the same situation that I was in.
Related
In my app, I'm using a Single Activity with multiple Fragments Architecture and I navigate between them using the Navigation Library. Within one of the fragments, I have multiple categories, each associated with an ID. When a category is clicked, I take the user to that respective category explainer screen with the code below.
val directions = MainNavGraphDirections.launchFragmentWithThisCategoryId(categoryId!!)
onRoute(AppRoute.Directions(directions))
The above code sends them to the explainer screen associated with the associated categoryId. All is well until this point, the right explainer screen gets launched based on the categoryId. Within this explainer screen, I have a deep-link with a tag chatbot://fragment/wizardintro that is supposed to let the main activity know the specific follow-up fragment to send the user to. I denote all the fragments that can receive this deep-link with the code below.
companion object{
const val DEEP_LINK = "chatbot://fragment/wizardintro"
}
In the MainActivity, I have a method that receives all the different deep linking intents and matches them to the tags that will launch the respective category fragment with the code below.
override fun onNewIntent(intent: Intent?) {
super.onNewIntent(intent)
intent?.data?.toString().also { deepLink ->
when (deepLink) {
IntroductionFragment.DEEP_LINK ->{
val categoryId = intent?.getLongExtra("categoryId", 0L)
val directions = MainNavGraphDirections.actionGlobalGoalWizard(categoryId)
navController.popBackStack()
navController.navigate(directions)
}
}
Now my problem arises when I try to retrieve this categoryId in the Main Activity and pass it to the next fragment. I don't get anything and only the default Long gets passed along. I think the function override fun onNewIntent(intent: Intent?) { } in the MainActivity recieve any intent. To be clear, these intents are sent from the explainer fragment which is technically a fragment that loads a json. Within the json there is a "route": {"type": "route", "url": "chatbot:///fragment/wizardintro"
In the MainActivity, the onNewIntent functions receive these intents unpacks them with this line intent?.data?.toString().also ...then in the when statement picks a fragment that has a matching chatbot:///fragment/wizardintro
I said all this to say that the main activity doesn't actually gets the categoryId, it simply picks launching the neccessary fragment without actually having anything associated with the categoryId
This makes me think that the first clicked categoryId doesn't actually get passed to the MainActivity. Although, to me, this seems like it shouldn't be this hard to pass objects/data from a fragment to an activity. What am I missing? What can I read to educate myself more on this?
Thanks for your time and responses!
Since we already got to the conclusion that MainActivity is not getting categoryId, you just need to pass that categoryId with the deep-link.
However, there is no need for any communication from Fragment to Activity.
You could achieve the same result through communication only between Fragment to Fragment, and Activity to Fragment.
What you want to do is to look more closely on deep-links and android navigation in the AndroidDocs, click here.
As you can tell, there are different ways to go around this, starting with arguments for each fragment. Assigning categoryId as an argument to the Fragment would help you use the navigationController and navigate to the new Fragment, while passing the categoryId to it.
Now, I am aware that you also wish to launch it with a deep-link; there's also a good explanation on here. According to the docs, you can place arguments in deep-links in the following manner...
Placeholders in the form of {placeholder_name} match one or more characters. For example, http://www.example.com/users/{id} matches http://www.example.com/users/4. The Navigation component attempts to parse the placeholder values into appropriate types by matching placeholder names to the defined arguments that are defined for the deep link destination. If no argument with the same name is defined, a default String type is used for the argument value.
The navigation is something amazing and capable, you just need to be aware of everything it can actually do. You can even bind it to a BottomNavBar, with extremely minimal amount of code.
Try going over the AndroidDocs about it, and it'll grow on you for sure.
Is there a way to clone a scene in JavaFX ?
I currently want to keep a reference of the previous scene but can't find a simple way of doing it (except passing in the previous scene as a parameter to every new class responsible for scene creation).
Heres what I was thinking of doing (this is a snipped of my view controller)
public void switchScene(Scene newScene){
previousScene = currentScene; // something which achieves this without aliasing
currentScene = newScene;
window.setScene(newScene);
}.
However as one can observe this leads to aliasing problems.
Any way to solve this problem ?
I've been trying to start with a simple app that retrieves data from a simple HTML page upon clicking a button and stumbled upon a rather helpful tutorial on QT-Project and have been trying to implement it for my own project.
Everything manages to compile until I try to actually try to implement the loadImage function (as found in the tutorial). (I actually had to initialize m_pImgCtrl as Filedownloader * m_pImgCtrl = new FileDownloader(imageUrl, this); and I'm not exactly sure how it's suppose to work without prior object declaration?)
From what I get, m_pImgCtrl isn't actually defined in the loadImage() function since it is initialized outside of the function? Or does the connect() function do something that I'm not too aware of?
Thanks for the help!
The tutorial doesn't tell you the whole story.
The code in section Usage is supposed to be part of a class MainWindow – the controller of your main window (see line 1 of tutorial's last snippet). This class contains a slot loadImaged() called when the NetworkReply has finished. It also has a member FileDownloader * m_pImgCtrl.
For instance, the second Usage snippet could be part of a slot MainWindow::buttonClicked() like
void MainWindow::buttonClicked()
{
QUrl imageUrl("http://qt.digia.com/Documents/1/QtLogo.png");
m_pImgCtrl = new FileDownloader(imageUrl, this);
connect(m_pImgCtrl, SIGNAL(downloaded()), SLOT(loadImage()));
}
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 am using Xcode 4.3 and am somewhat of a nubbie in Xcode although I have been a programmer for many years.
I have a UIView called First that contains a UITable that gets its contents from files in memory. I then create a subview UIView called Second that makes changes in the data files that should change the contents of the table in First. When I remove Second and return to First, not surprising, the table is not updated. The next time First is loaded from the start, the table reflects the changes that were made.
First contains the method viewDidLoad which is used to load an NSArray from data in files with the data needed by the table. I am able to call viewDidLoad from Second but unless the table is updated from the newly changed NSArray the table will appear as it did before the changes were made.
So my problem is how to call a table method from Second so that the table in First is updated when I remove Second and return to First. I have tried calling the table method that loads the data into the table but have been unsuccessful since I get compile errors. I need to know how to call the table function in a way that will result in the table being updated when I return to first.
At least part of my problem is I don't know how the table update is called since it is not called from viewDidLoad as I might have expected.
Sorry, it is a long winded description of the problem. Much of the rest of the program that I am writing is working and I have been dealing with this issue for several months. I return every few weeks and take another stab at it but no luck so far. I really would appreciate any help you can give that will improve my understanding and fix the problem.
Here is the code after the fix: first (superview) pertinent code
-(void)viewDidLoad {
NSFileManager * fm = [[NSFileManager alloc] init];
NSError* err = nil;
NSPredicate *fltr = [NSPredicate predicateWithFormat:#"self ENDSWITH '.dir'"];
NSArray *array = [fm contentsOfDirectoryAtPath: userFolder error:&err];
self.listData = [array filteredArrayUsingPredicate:fltr];
[self.tableView reloadData]; //This does the updating must make table an IBOutlet as
[super viewDidLoad]; //described in one of the comments by m. Othman
}
Here is the code after the fix: second (subview) pertinent code. This code located
in the method where changes are made that should effect the table display
UIView * start = [self.view superview]; //this line and next two call viewDidLoad in first
UIResponder * nextResponder = [start nextResponder];
[nextResponder viewDidLoad];
Have you read the UIViewController API reference? There are more options beyond -viewDidLoad for dealing with the (re)appearance of a view...
well, UITableView Delegates called just on the loading of the view or when you ask it to reload ..
so in your viewDidLoad or any method that should changes the content of the tableview , you need to write this line
[tableview reloadData];
I hope I understand your question!!