I'm trying to create my own BackBarButtonItem, but I'm having some problems.
My declaration:
var backButon = new UIBarButtonItem("Back",UIBarButtonItemStyle.Plain, null, null);
Exception:
Unhandled Exception: System.ArgumentNullException: Argument cannot be null.
Parameter name: target
What should I put in "target" and "action" parameters?
You shouldn't use that constructor, unless you want to use the target/action pattern, I suggest:
public UIBarButtonItem (string title, UIBarButtonItemStyle style, EventHandler handler)
which you use like:
var btn = new UIBarButtonItem ("Back", UIBarButtonItemStyle.Plain, delegate (object sender, EventArgs e) {
Console.WriteLine ("button clicked");
});
Related
I've attached the KeyDown event to a ListView in my Win 10 UWP app. I want to make VirtualKey.Enter have a special effect, but the event is not firing for this particular key. Neither does it for Space, Arrow up or down. This I guess because the listview already has defined a special behaviour for those keys.
I'd like to override some of those keys though, or at least trigger additional actions. Even attaching events to those key with modifiers (e.g. Shift+ArrowDown) would not work because the events still are not firing.
I read that for WPF that there is a PreviewKeyDown-event which one can attach to. I can't find that event for UWP though. Are there any other options?
Stephanie's answer is a good one and it works in the general case. However, as Nilzor observed it will not work in the case of a ListView for the Enter key. For some reason the ListView handles the KeyDown event in case Enter is pressed.
A better way to handle key events when dealing with a ListView, as the question asks, is this.
private void ListView_Loaded(object sender, RoutedEventArgs e)
{
(sender as ListView).AddHandler(UIElement.KeyDownEvent, new KeyEventHandler(ListView_KeyDown), true);
}
private void ListView_KeyDown(object sender, KeyRoutedEventArgs args)
{
if (args.Key == Windows.System.VirtualKey.Enter)
{
}
}
Notice the last argument in the AddHandler function. This specifies whether we want to handle events already handled by a previous element in the visual tree.
Of course don't forget to unsubscribe from the event when appropriate
Here is one way to do it : subscribe to the global Window.Current.CoreWindow.KeyDown event.
Then save the focus state of your listview and react accordingly.
Here is the code :
public sealed partial class MainPage : Page
{
bool hasFocus = false;
public MainPage()
{
this.InitializeComponent();
Window.Current.CoreWindow.KeyDown += CoreWindow_KeyDown;
}
private void CoreWindow_KeyDown(Windows.UI.Core.CoreWindow sender, Windows.UI.Core.KeyEventArgs args)
{
if(hasFocus)
{
Debug.Write("Key down on list");
}
}
private void myList_GotFocus(object sender, RoutedEventArgs e)
{
hasFocus = true;
}
private void myList_LostFocus(object sender, RoutedEventArgs e)
{
hasFocus = false;
}
You will also need to subscribe to the focus events in xaml, for your ListView :
<ListView .... GotFocus="myList_GotFocus" LostFocus="myList_LostFocus"/>
Corcus's solution doesn't work for me. What is working is handling PreviewKeyDown directly from XAML. Works well for SPACE or ENTER key:
XAML:
<ListView PreviewKeyDown="BookmarksListView_PreviewKeyDown">
Code behind:
private void BookmarksListView_PreviewKeyDown(object sender, KeyRoutedEventArgs e)
{
if (e.Key == Windows.System.VirtualKey.Enter)
{
// DO YOUR STUFF...
e.Handled = true;
}
}
You can use AddHandler method.
private void KeyEnterEventHandler(object sender, KeyRoutedEventArgs e)
{
if (e.OriginalKey == Windows.System.VirtualKey.Enter)
{
PlayFromListView();
}
}
private void LoadListView()
{
foreach (var music in playListStorageFile.PlayList)
{
ListViewItem item = new ListViewItem();
item.AddHandler(FrameworkElement.KeyDownEvent, new KeyEventHandler(KeyEnterEventHandler), true);
TextBlock mytext = new TextBlock();
mytext.Text = music.Nro.ToString() + " - " + music.Name;
mytext.Tag = music.Nro;
item.Content = mytext;
lvMusics.Items.Add(item);
}
}
https://learn.microsoft.com/en-us/uwp/api/windows.ui.xaml.uielement.addhandler?view=winrt-18362
1.Trying to display exception message in popup window. Exception message is not appearing.
2.Eg: When i click button a popup window (Second fxml file) is to load with proper exception message in the label
3.Popup window is appearing, But the Label is not loading (Bold one --> ExceptionLabel.setText("Please enter Proper file path")) it says null pointer exception.
4.I am not sure what i missing. Same declared in FX:ID and also in second fxml file linked the main controller. Thanks in advance.
#FXML
public Label ExceptionLabel;
Stage PopupWindow = new Stage();
public void Buttonhandle(ActionEvent event) throws IOException {
try {
if(ESBOutboundFile!=null && OutputFile!=null){
String Output = SBlogpaser.Logpaser(ESBInboundFile,ESBOutboundFile,OutputFile);
System.out.println(Output);
}else{
Window(PopupWindow);
**ExceptionLabel.setText("Please enter Proper file path");**
}
} catch (Exception ex) {
System.out.println(ex);
}
}
public void Window(Stage Popup) throws Exception {
this.Popup=Popup;
final FXMLLoader fxmlLoader = new FXMLLoader();
Parent root= fxmlLoader.load(getClass().getResource("POPUPWindow.fxml"));
Scene scene1 = new Scene(root);
Popup.setScene(scene1);
Popup.show();
}
If i keep the label in "OK" handle button it is getting displayed.
From where are you expecting ExceptionLabel to be instantiated?
Assuming you are pointing the fx:controller attribute of the root of your POPUPWindow.fxml file to the current class, it will just create a new instance of that class, and inject values into that instance. The field ExceptionLabel in the current instance won't be initialized.
You could probably just about make this work by setting the controller of the FXMLLoader to the current object, something like this:
public void window(Stage popup) throws Exception {
this.popup=popup; // why?
final FXMLLoader fxmlLoader = new FXMLLoader(getClass().getResource("POPUPWindow.fxml"));
fxmlLoader.setController(this);
Parent root= fxmlLoader.load();
Scene scene1 = new Scene(root);
popup.setScene(scene1);
popup.show();
}
and then remove the fx:controller attribute from POPUPWindow.fxml.
This seems like a really bad idea, though, because now the current object is acting as a controller for two different FXML files. This will be confusing at best, and under fairly reasonable conditions would produce weird results. It would be much better to write a different controller class for the popup:
public class PopupController {
private final String message ;
#FXML
private Label exceptionLabel ;
public PopupController(String message) {
this.message = message ;
}
public void initialize() {
exceptionLabel.setText(message);
}
}
and then use the window(...) method above, but with
fxmlLoader.setController(new PopupController("Please enter Proper file path"));
Obviously, if you're reusing the window(..) method, you might want to pass the message in as a parameter to that method.
Am not able to do INSERT UPDATE DELETE AND CLEAR operatopns on my ListView in WinForms
Here's my Code:
private void Form1_Load(object sender, EventArgs e)
{
ShowData();
}
private void ShowData()
{
SqlConnection con = new SqlConnection("User id=sa;password=sql#123;database=arvind;server=ASHOK-PC");
con.Open();
SqlCommand cmd = new SqlCommand("select * from Login_1",con);
DataTable dt = new DataTable();
SqlDataAdapter da = new SqlDataAdapter(cmd);
da.Fill(dt);
listView1.DataContext = dt.DefaultView;
}
I got error in DataContext as
System.Windows.Forms.ListView does not contain a definition for datacontext and no extension method accepting a first argument of type System.Windows.Forms.Listview could be found.
You appear to be trying to follow a code example made for WPF when you're using Windows Forms. The WinForms ListView indeed does not have such a property and in fact doesn;t support data-binding.
Do yourself a favour and use a DataGridView. Just assign the DataTable itself to the DataSource property. Binding the DefaultView is pointless.
I am trying to create a Waveform Control Panel to change the properties of its components. I attempted to apply the example in the Redhawk documentation for a Component Control Panel, but for some reason I get a java.lang.NullPointerException when running the plugin. The error occurs when I attempt to bind the text field to a component property, the exact line where the error occurred is in the comments of the code (at the very bottom).
public class TestControlPanel extends AbstractScaContentEditor<ScaWaveform> {
private ScaWaveform waveform;
private ScaComponent myComponent;
private Text propertyValueField;
private EMFDataBindingContext context;
/**
* {#inheritDoc}
*/
#Override
public void createPartControl(final Composite main) {
main.setLayout(new GridLayout(2, false));
Group controlGroup = new Group(main, SWT.SHADOW_ETCHED_OUT);
controlGroup.setLayoutData(GridDataFactory.fillDefaults().grab(true, true).create());
controlGroup.setText("Controls");
createControlGroup(controlGroup);
}
private void createControlGroup(Composite parent) {
parent.setLayout(new GridLayout(2, false));
EObject input = getInput();
if (input instanceof ScaWaveform) {
// make local copy of waveform
waveform = (ScaWaveform) input;
try {
waveform.refresh(null, RefreshDepth.FULL);
} catch (InterruptedException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
label = new Label(parent,SWT.None);
label.setText("Property Value:");
propertyValueField = new Text(parent, SWT.BORDER | SWT.FILL);
myComponent = waveform.getScaComponent("myComponent_1");
if(myComponent != null)
{
IObservableValue observable = SCAObservables.observeSimpleProperty(myComponent, "propertyId");
IObservableValue targetObservable = WidgetProperties.text(SWT.Modify).observeDelayed(5000,propertyValueField);
if(observable != null && targetObservable != null)
{
// ***** THE BELOW LINE CAUSES A java.lang.NullPointerException ERROR *****
context.bindValue(targetObservable, observable);
// ***** THE ABOVE LINE CAUSES A java.lang.NullPointerException ERROR *****
}
}
}
}
My original guess for the reason for this error was that one of the IObservableValue variables (e.g. targetObservable or observable) was null, which is why I check to make sure the values are not null before binding them. However, this didn't fix the problem and I still got the same error.
From what code I can see it seems as though your field varible "context" was never initialized.
Simply call the no argument constructor:
context = new EMFDataBindingContext();
It appears that the context variable is null. I see that you define "context" at the top of the class, but I didn't see where it has been set.
I have created an EntryElement in which the user enters a phone number.How can I add a button at the end of the element so that the user can press the button and make a call?
You need to create a new element that is a subclass of an EntryElement, override the get cell method and add to the accessoryView the button .
I know this doesn't exactly answer the question but I struggled for quite a while until I found the answer by #Janub which put me on the right track. Here is the code that I currently have working.
public class NextNumericCell : EntryElement
{
readonly EventHandler handler;
public NextNumericCell (string caption, string placeholder, string value, EventHandler onClick ) : base(caption,placeholder,value)
{
handler = onClick;
}
protected override UITextField CreateTextField (CGRect frame)
{
var textField = base.CreateTextField (frame);
var toolBar = new UIToolbar (new CGRect (0, 0, frame.Width, 35));
var spacerButton = new UIBarButtonItem (UIBarButtonSystemItem.FlexibleSpace);
var buttonTitle = ReturnKeyType == null ? "SetButtonTitle" : ReturnKeyType.ToString ();
var nextButton = new UIBarButtonItem (buttonTitle, UIBarButtonItemStyle.Plain, handler);
toolBar.Items = new UIBarButtonItem [] { spacerButton, nextButton };
textField.InputAccessoryView = toolBar;
return textField;
}
}