Binding data in Xamarin Forms - xamarin.forms

I have an enumerable datasource that I want to bind to a some control in Xamarin Forms.
I want the layout to look something like -
ColA | ColB | ColC | ColD
3 4 1 6
15 25 62 26
Just a standard table with a header.
I have tried the ListView but it doesn't support headers. I've tried TableLayout but it doesn't support binding to a datasource.
Have I missed something or is there some other control I should use.

Yeah theres no control out of the box for it, here's a one way to hack it:
Create a grid that has a row for your header (4 columns), the next row has a listview with a viewcell for your items, then you use a viewcell template, and in your template you have the grid with 4 columns ,and 4 labes ( 1 each column) just like the header, now the trick here is how will you bind 4 values in 1 viewcell, my sugestions is having a object like 'Something' that has Prop1, Prop2, Prop3, Prop4 , and now you bind label1 to Prop1, label2 to Prop2 and so one,
So when you create your datasource it will be something like:
var list = List<Something>();
list.Add(new Something() { Prop1 = 3, Prop2 = 4, Prop3 = 1, Prop4 = 6});
list.Add(new Something() { Prop1 = 15, Prop2 = 25, Prop3 = 62, Prop4 = 26});
this should accomplish what you need..

As Stephane Delcroix mentioned in this other StackOverflow question:-
"Horizontal ListView Xamarin.Forms"
The ListView does not natively support horizontal orientation, so you couldn't use this as your are ideally wanting to bind to an IEnumerable datasource.
There is another hack method mentioned in the following post:-
"How to adjust size of Horizontal ListView in Xamarin.Forms?"
that suggests to use Rotation to get around this, although this will more than likely be quite cumbersome and problematic in cases as rotation will apply outside a normal View bounds, unless it is a square dimension.
That would allow you to use your bindable datasource however by using the ItemTemplate property of the ListView and creating your DataTemplate with other control bindings specified in it.
It is however not ideal with the rotation hack, and personally I wouldn't even consider it.
The best method, at present, would be to do as Rui is mentioning, creating some kind of Grid of equal columns and do your formatting within.
You could also achieve this with a StackLayout specifying a specific WidthRequest for each of the child Views and then do your formatting from within each child View.
Should you need to display more than 4 columns, or more information than would fit on a typical device screen width, then you may want to put a ScrollView as the parent of this Grid or StackLayout, so you can view everything with better spacing rather than cramming everything in.
As a final alternative - you could write your own custom-renderer to support a horizontal ListView with a bindable datasource.

<Grid x:Name="dgvEmp">
<Grid.RowDefinitions>
</Grid.RowDefinitions>
<Grid.ColumnDefinitions>
</Grid.ColumnDefinitions>
</Grid>
List<Employee> lstEmp;
public Gridbasic()
{
InitializeComponent();
lstEmp= new List<Employee>()
{
new Employee()
{
EmpId=1,EmpName="Test1",EmpSalary=12345
},
new Employee()
{
EmpId=2,
EmpName="Test2",
EmpSalary=12345
},
new Employee()
{
EmpId=3,
EmpName="Test3",
EmpSalary=12334
}
};
dgvEmp.Children.Add(new Label() {Text="EmpName" }, 0, 0);
dgvEmp.Children.Add(new Label() { Text = "EmpSal" }, 1, 0);
for(int i=0,j = 1; i <lstEmp.Count; i++)
{
Label lbl = new Label()
{
Text = lstEmp[i].EmpName
};
Label llblEmpSal = new Label()
{
Text = lstEmp[i].EmpSalary.ToString()
};
dgvEmp.Children.Add(lbl, 0, j);
dgvEmp.Children.Add(llblEmpSal, 1, j);
j++;
}
}

Related

Xamarin Forms Collection View Extra Padding

I"m trying out the Xamarin Forms Collection View. It appears to have some extra padding around each item in the list. I can't see how to remove it.
Here is a picture of my view. The view has an aqua background. The 2 column grid in the template has labels set to red.
And here is the XAML/C#
<CollectionView
x:Name="BodyView"
SelectionMode="Single"
HorizontalOptions="FillAndExpand"
BackgroundColor="Aqua"
Grid.Row="2" />
BodyView.ItemTemplate = new DataTemplate(() =>
{
var converter = (IValueConverter) Application.Current.Resources["GridCellConverter"];
Grid grid = new Grid( );
grid.RowDefinitions.Add(new RowDefinition { Height = GridLength.Auto });
foreach (var col in _gridColumns)
{
grid.ColumnDefinitions.Add(new ColumnDefinition { Width = new GridLength(1, GridUnitType.Star) });
var content = new Label();
content.Style = (Style)Application.Current.Resources["GridCellLabel"];
content.BackgroundColor = Color.Red;
Binding binding = new Binding("CellData", BindingMode.OneWay, converter, col.PageFieldId);
content.SetBinding(Label.TextProperty, binding);
grid.Children.Add(content, grid.ColumnDefinitions.Count - 1, 0);
}
return grid;
});
I zeroed everything I could find to zero.
I tried setting a negative margin on the grid but it won't move left.
Is there any way to remove the padding?
What you are looking for is the Grid's Row and Column Spacing!
Grid grid = new Grid( ){ ColumnSpacing= "0", RowSpacing="0" };
Also, this needs to be removed:
grid.Margin = new Thickness(-20, 0, 0, 0);
A quick question though are you using it in UWP?
Also since you are using CollectionView why not use a single item in DataTemplate that goes into a GridItemsLayout?
More information here: https://learn.microsoft.com/en-us/xamarin/xamarin-forms/user-interface/collectionview/layout#vertical-grid

Finding QGridLayout elements in Qt

I created labels and added them to the layout. How to get the elements from the layout? I tried to use method children(), but it gives empty list... Is there a way to get them? Some sample code below.
QGridLayout* layout = new QGridLayout();
QLabel* test = new QLabel();
test->setPixmap(m_staticStorage->getFirstImg());
test->setScaledContents(true);
QLabel* test2 = new QLabel();
test2->setMaximumSize(50,50);
test2->setPixmap(m_staticStorage->getSecondImg());
tes2->setScaledContents(true);
layout->addWidget(worker, 0, 0);
layout->addWidget(farmer, 0, 1);
ui->verticalLayout->addLayout(layout);
//layout->children() ->>>> empty
This will iterate over any QLayout subclass to find the items which have been added so far:
for (int i=0; i < layout->count(); ++i) {
QLayoutItem *item = layout->itemAt(i);
if (!item || !item->widget())
continue;
QLabel *label = qobject_cast<QLabel*>(item->widget());
if (label) {
// .... do stuff with label
}
}
One can also iterate in a similar fashion over each row or column of a QGridLayout using QGridLayout::columnCount() or QGridLayout::rowCount() and then QGridLayout::itemAtPosition() to get the actual QLayoutItem.
If you need to uniquely identify the QLabel after finding it, you could for example give each label a unique objectName or do a setProperty() on them with a unique ID when creating them.
QLabel *test1 = new QLabel(this);
test1->setObjectName(QStringLiteral("test1"));
....
if (label) {
if (!label->objectName().compare(QLatin1String("test1")))
// this is "test1" label
}
QLabel *test1 = new QLabel(this);
test1->setProperty("id", 1);
....
if (label) {
if (label->property("id").toInt() == 1)
// this is "test1" label
}
Better to use the function QObject::findChild
Qt is returning all children of a given Type and Objectname. You can decide to get only direct children or also all recursively.
this->findChild<QLabel*>(QString(), Qt::FindDirectChildrenOnly);
This will return all direct children of this (where this is your parent widget, not your layout) with any name and of type QLabel*
Your approach do not work because the layout do not take the ownership of the labels:
From Layout Management:
Tips for Using Layouts
When you use a layout, you do not need to pass a parent when
constructing the child widgets. The layout will automatically
reparent the widgets (using QWidget::setParent()) so that they are
children of the widget on which the layout is installed.
Note: Widgets in a layout are children of the widget on which the
layout is installed, not of the layout itself. Widgets can only have
other widgets as parent, not layouts.
You can nest layouts using addLayout() on a layout; the inner layout
then becomes a child of the layout it is inserted into.
BTW: Don't forget to set a parent for your layout
QGridLayout* layout = new QGridLayout(this);
and for your labels too
QLabel* test2 = new QLabel(this);

Flex : SpriteVisualElement can not add as a child Spark Label?

var s : SpriteVisualElement = new SpriteVisualElement();
s.graphics.beginFill( 0xFFFF00 );
s.graphics.drawRect( 0, 0, 100, 20 );
s.graphics.endFill();
s.width = 100;
s.height = 20;
this.addElement( s ) ;
var l : Label = new Label();
l.text = "text";
l.width = s.width;
l.height = s.height;
s.addChild( l );
The follow code seems not to working ( Flex 4.5 ).
What could cause this issue, and how to fix it ?
It's not being displayed because you're not adding Label (which is a UIComponent and works with the component lifecycle) to another UIComponent that will actually instantiate it properly. Your SpriteVisualElement is not made to have UIComponents within it, it's made to have sprites which can draw itself. Label is waiting for 'invalidateDisplayList' to be called so that it can draw itself.
Either do a force draw or use a UIComponent as the container for Label.
The Spark Label is not a container; and therefore does not have an addElement method. I assume you're getting a compile error because of this [but you didn't tell us what your problem was].
You can wrap the label up in a container, such as a Group or SkinnableContainer and use your extra visual element as a child of the same group.
Or you could try the addChild method of the Label. It's odd to try to add Children to a component, such as Label, that is not intended as a container, though.

Styling UITextField

I've been playing around with different methods of determining at runtime the width of a "label" so that I can resize the "label" because I don't want it to truncate. I've finally found an easy solution through UITextField which allows me to set the .autoSize which is great! However, now I'm trying to "style" (simply adjust font and font size) of the UITextField but it seems that I have to do it manually with '.htmlText' (which I'll gladly accept if that is the ONLY way).
I'm using the .text to set the value of the label.
My test case involves a HBox (I'm actually using a Grid but they should be the same and I've done testing on both):
I style the HBox and the style carries through to the UITextField. I don't believe this will work for me because I have other components inside that I need to style differently.
I've tried: UITextFormat and TextFormat (I see that the .htmlText being updated accordingly but the output doesn't update. Then I noticed that whenever I called hbox.addChild(myUITextField) it would override the .htmlText
I've tried setting the style with myUITextField.setStyle("fontSize", 20) before and/or after the call to addChild neither of which made an impact on the display as per what I noted above.
Changes are being made but they seem to be overrided when I add it to the display.
So what do I need to do in order to style the UITextField aside from manually setting it along with my contents in .htmlText? Solutions not using UITextField is fine as long as there is some easy way of not truncating the text.
EDIT: I want to just do textField.setStyle('fontSize', 20) and expect that every time I change the text, I wouldn't need to use HTML to go with it (so I can just do textField.text = 'something else' and expect that it will still have a font size of 20). This is what I meant by not using .htmlText (sorry if I wasn't clear before).
2nd EDIT: I guess I should present the whole issue and maybe that'll clarify what I did wrong or couldn't achieve.
My intent is to have a Grid and add text into it. I do not want it to wrap or scroll so I add it to the next row in the Grid when the current row's children total width exceeds some number. In order to add it to the next row, I need to be able to calculate the width of the text. I would like to be able to style that text individually based on cases and there might be other components (like a TextInput). Essentially what I'm trying to accomplish is "Fill in the Blank".
I've included code to show what I'm currently doing and it works somewhat. It might be un-related to the original issue of styling but I can't figure out how to adjust the distance between each UITextField but aside from that this fits what I would like to accomplish. Relevant to the question is: I would like to change the way I style each UITextField (currently setting .htmlText) into something a bit straightforward though like I previously mentioned I'll gladly accept using .htmlText if that's the only solution.
So I have a Grid with x Rows in it and in each row, I have exactly one GridItem. Based on the input, I add UITextField and TextInput into the GridItem going on to the next GridItem when necessary. If you have a better way of doing so then that would be better but I guess what I really want is to find a different way of styling.
Also another problem, I'm not sure of the exact way to add a TextField into the display. I tried:
var t : TextField = new TextField();
t.text = "I'm a TextField";
hBox.addChild(t); // doesn't work
//this.addChild(t); // doesn't work either
But I get the following error:
TypeError: Error #1034: Type Coercion failed: cannot convert flash.text::TextField#172c8f9 to mx.core.IUIComponent.
Here's what I have that's working.
private function styleQuestionString(str : String) : String {
return '<FONT leading="1" face="verdana" size="20">' + str + '</FONT>';
}
private function loadQuestion(str : String) : void {
/* Split the string */
var tmp : Array = str.split("_");
/* Track the current width of the GridItem */
var curWidth : int = 0;
/* Display components that we will add */
var txtField : UITextField = null;
var txtInput : TextInput = null;
/* Track the current GridItem */
var curGridItem : GridItem = null;
/* Track the GridItem we can use */
var gridItemAC : ArrayCollection = new ArrayCollection();
var i : int = 0;
/* Grab the first GridItem from each GridRow of Grid */
var tmpChildArray : Array = questionGrid.getChildren();
for (i = 0; i < tmpChildArray.length; i++) {
gridItemAC.addItem((tmpChildArray[i] as GridRow).getChildAt(0));
}
curGridItem = gridItemAC[0];
gridItemAC.removeItemAt(0);
/* Used to set the tab index of the TextInput */
var txtInputCounter : int = 1;
var txtFieldFormat : UITextFormat = new UITextFormat(this.systemManager);
txtFieldFormat.leading = "1";
//var txtFieldFormat : TextFormat = new TextFormat();
//txtFieldFormat.size = 20;
/* Proper Order
txtField = new UITextField();
txtField.text = tmp[curItem];
txtField.autoSize = TextFieldAutoSize.LEFT;
txtField.setTextFormat(txtFieldFormat);
*/
var txtLineMetrics : TextLineMetrics = null;
var tmpArray : Array = null;
curGridItem.setStyle("leading", "1");
var displayObj : DisplayObject = null;
for (var curItem : int= 0; curItem < tmp.length; curItem++) {
/* Using UITextField because it can be auto-sized! */
/** CORRECT BLOCK (ver 1)
txtField = new UITextField();
txtField.text = tmp[curItem];
txtField.autoSize = TextFieldAutoSize.LEFT;
txtField.setTextFormat(txtFieldFormat);
***/
tmpArray = (tmp[curItem] as String).split(" ");
for (i = 0; i < tmpArray.length; i++) {
if (tmpArray[i] as String != "") {
txtField = new UITextField();
txtField.htmlText = styleQuestionString(tmpArray[i] as String);
//txtField.setTextFormat(txtFieldFormat); // No impact on output
txtLineMetrics = curGridItem.measureHTMLText(txtField.htmlText);
curWidth += txtLineMetrics.width + 2;
if (curWidth >= 670) {
curGridItem = gridItemAC[0];
curGridItem.setStyle("leading", "1");
if (gridItemAC.length != 1) {
gridItemAC.removeItemAt(0);
}
// TODO Configure the proper gap distance
curWidth = txtLineMetrics.width + 2;
}
displayObj = curGridItem.addChild(txtField);
}
}
//txtField.setColor(0xFF0000); // WORKS
if (curItem != tmp.length - 1) {
txtInput = new TextInput();
txtInput.tabIndex = txtInputCounter;
txtInput.setStyle("fontSize", 12);
txtInputCounter++;
txtInput.setStyle("textAlign", "center");
txtInput.width = TEXT_INPUT_WIDTH;
curWidth += TEXT_INPUT_WIDTH;
if (curWidth >= 670) {
curGridItem = gridItemAC[0];
if (gridItemAC.length != 1) {
gridItemAC.removeItemAt(0);
}
// TODO Decide if we need to add a buffer
curWidth = TEXT_INPUT_WIDTH + 2;
}
curGridItem.addChild(txtInput);
txtInputAC.addItem(txtInput);
/* Adds event listener so that we can perform dragging into the TextInput */
txtInput.addEventListener(DragEvent.DRAG_ENTER, dragEnterHandler);
txtInput.addEventListener(DragEvent.DRAG_DROP, dragDropHandler);
txtInput.addEventListener(DragEvent.DRAG_EXIT, dragExitHandler);
}
/* Add event so that this label can be dragged */
//txtField.addEventListener(MouseEvent.MOUSE_MOVE, dragThisLabel(event, txtField.text));
}
}
After about 8 hours of searching for a solution to what would seem to be such a simple issue I FINALLY stumbled on your posts here... Thankyou!!!
I have been stumbling around trying to get TextField to work and had no Joy, Label was fine, but limited formatting, and I need to be able to use embedded fonts and rotate. After reading the above this finally worked for me:
var myFormat:TextFormat = new TextFormat();
myFormat.align = "center";
myFormat.font = "myFont";
myFormat.size = 14;
myFormat.color = 0xFFFFFF;
var newTxt:UITextField = new UITextField();
newTxt.text = "HELLO";
addChild(newTxt);
newTxt.validateNow();
newTxt.setTextFormat(myFormat);
The order of addChild before the final 2 steps was critical! (myFont is an embedded font I am using).
One again... a thousand thankyou's...
John
EDIT BASED ON THE ASKERS FEEDBACK:
I didn't realize you wanted to just apply one style to the whole textfield, I thought you wanted to style individual parts. This is even simpler for you, won't give you any trouble at all :)
var textFormat: TextFormat = new TextFormat("Arial", 12, 0xFF0000);
myText.setTextFormat(textFormat);
Be aware that this sets the style to the text that is in the TextField, not necessarily future text you put in. So have your text in the field before you call setTextFormat, and set it again every time you change it just to be sure it stays.
It's probably best if you use a normal TextField as opposed to the component. If you still want the component you may need to call textArea.validateNow() to get it to update with the new style (not 100% sure on that one though) Adobe components are notoriously bad, and should be avoided. :(
To see all available options on the TextFormat object see here
END EDIT ---------
This is easy enough to just do with CSS in a normal old TextField.
var myCSS: String = "Have some CSS here, probably from a loaded file";
var myHTML: String = "Have your HTML text here, and have it use the CSS styles";
// assuming your textfield's name is myText
var styleSheet: StyleSheet = new StyleSheet();
styleSheet.parseCSS(myCSS);
myText.autoSize = TextFieldAutoSize.LEFT;
myText.styleSheet = styleSheet;
myText.htmlText = myHTML;
Supported HTML tags can be found here
Supported CSS can be found here
The reason you have a problem adding Textfield to containers is that it doesn't implement the IUIComponent interface. You need to use UITextField if you want to add it. However, that's presenting me with my own styling issues that brought me to this question.
A few things I know:
TextField is styled using the TextFormat definition, and applying it to the textfield. As Bryan said, order matters.
setStyle does nothing on IUITextField, and the TextFormat method doesn't seem to work the same as in normal TextFields. (Edit #2: Ahah. You need to override the "validateNow" function on UITextFields to use the setTextFormat function)
To autosize a TextArea, you need to do something like this (inheriting from TextArea):
import mx.core.mx_internal;
use namespace mx_internal;
...
super.mx_internal::getTextField().autoSize = TextFieldAutoSize.LEFT;
this.height = super.mx_internal::getTextField().height;
Found this code on, I think, on StackOverflow a while back. Apologies to the original author. But the idea is that you need to access the "mx_internal" raw textfield.
Text and TextArea have wrapping options. (Label does not). So if you set the explicit width of a Text object, you might be able to size using the measuredHeight option and avoid truncation.
(edit: That was #4, but stackoverflow parsed it into a 1...)

Flex: Custom Item Renderer For Combobox controls truncates text

I've implemented a custom item renderer that I'm using with a combobox on a flex project I'm working on. It displays and icon and some text for each item. The only problem is that when the text is long the width of the menu is not being adjusted properly and the text is being truncated when displayed. I've tried tweaking all of the obvious properties to alleviate this problem but have not had any success. Does anyone know how to make the combobox menu width scale appropriately to whatever data it's rendering?
My custom item renderer implementation is:
<?xml version="1.0" encoding="utf-8"?>
<mx:HBox xmlns:mx="http://www.adobe.com/2006/mxml"
styleName="plain" horizontalScrollPolicy="off">
<mx:Image source="{data.icon}" />
<mx:Label text="{data.label}" fontSize="11" fontWeight="bold" truncateToFit="false"/>
</mx:HBox>
And my combobox uses it like so:
<mx:ComboBox id="quicklinksMenu" change="quicklinkHandler(quicklinksMenu.selectedItem.data);" click="event.stopImmediatePropagation();" itemRenderer="renderers.QuickLinkItemRenderer" width="100%"/>
EDIT:
I should clarify on thing: I can set the dropdownWidth property on the combobox to some arbitrarily large value - this will make everything fit, but it will be too wide. Since the data being displayed in this combobox is generic, I want it to automatically size itself to the largest element in the dataprovider (the flex documentation says it will do this, but I have the feeling my custom item renderer is somehow breaking that behavior)
Just a random thought (no clue if this will help):
Try setting the parent HBox and the Label's widths to 100%. That's generally fixed any problems I've run into that were similar.
Have you tried using the calculatePreferredSizeFromData() method?
protected override function calculatePreferredSizeFromData(count:int):Object
This answer is probably too late, but I had a very similar problem with the DataGrid's column widths.
After much noodling, I decided to pre-render my text in a private TextField, get the width of the rendered text from that, and explicitly set the width of the column on all of the appropriate resize type events. A little hack-y but works well enough if you haven't got a lot of changing data.
You would need to do two things:
for the text, use mx.controls.Text (that supports text wrapping) instead of mx.controls.Label
set comboBox's dropdownFactory.variableRowHeight=true -- this dropdownFactory is normally a subclass of List, and the itemRenderer you are setting on ComboBox is what will be used to render each item in the list
And, do not explicitly set comboBox.dropdownWidth -- let the default value of comboBox.width be used as dropdown width.
If you look at the measure method of mx.controls.ComboBase, you'll see that the the comboBox calculates it's measuredMinWidth as a sum of the width of the text and the width of the comboBox button.
// Text fields have 4 pixels of white space added to each side
// by the player, so fudge this amount.
// If we don't have any data, measure a single space char for defaults
if (collection && collection.length > 0)
{
var prefSize:Object = calculatePreferredSizeFromData(collection.length);
var bm:EdgeMetrics = borderMetrics;
var textWidth:Number = prefSize.width + bm.left + bm.right + 8;
var textHeight:Number = prefSize.height + bm.top + bm.bottom
+ UITextField.TEXT_HEIGHT_PADDING;
measuredMinWidth = measuredWidth = textWidth + buttonWidth;
measuredMinHeight = measuredHeight = Math.max(textHeight, buttonHeight);
}
The calculatePreferredSizeFromData method mentioned by #defmeta (implemented in mx.controls.ComboBox) assumes that the data renderer is just a text field, and uses flash.text.lineMetrics to calculate the text width from label field in the data object. If you want to add an additional visual element to the item renderer and have the ComboBox take it's size into account when calculating it's own size, you will have to extend the mx.controls.ComboBox class and override the calculatePreferredSizeFromData method like so:
override protected function calculatePreferredSizeFromData(count:int):Object
{
var prefSize:Object = super.calculatePrefferedSizeFromData(count);
var maxW:Number = 0;
var maxH:Number = 0;
var bookmark:CursorBookmark = iterator ? iterator.bookmark : null;
var more:Boolean = iterator != null;
for ( var i:int = 0 ; i < count ; i++)
{
var data:Object;
if (more) data = iterator ? iterator.current : null;
else data = null;
if(data)
{
var imgH:Number;
var imgW:Number;
//calculate the image height and width using the data object here
maxH = Math.max(maxH, prefSize.height + imgH);
maxW = Math.max(maxW, prefSize.width + imgW);
}
if(iterator) iterator.moveNext();
}
if(iterator) iterator.seek(bookmark, 0);
return {width: maxW, height: maxH};
}
If possible store the image dimensions in the data object and use those values as imgH and imgW, that will make sizing much easier.
EDIT:
If you are adding elements to the render besides an image, like a label, you will also have to calculate their size as well when you iterate through the data elements and take those dimensions into account when calculating maxH and maxW.

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