Label Widget

You are here: Creating a Label Using a Constructor: voltmx.ui.Label

The Label widget is used to display static text on a form. It can be used as a form label or an area header with various text alignments and styles.

Following are the key concepts of Label widget:

Naming widgets: Label widget is used to provide static names to other widgets. For instance, consider a login form that has Employee details as the title of the form.
Providing Information: Label widget is used to provide static data. For instance, consider the following employee details form providing employee details such as Employee ID, Name, and Designation.
Tool Tip: Using Label widget, you can display a message on hovering the mouse pointer over a widget. It is very helpful for a new user to know more about various functionalities.
Text Copyable: Label widget enables you to copy a text and paste it elsewhere.

Widgets are normally added to your application using Volt MX Iris, but can also be added from code. For general information on using widgets in Volt MX Iris, see Designing an Application in the Iris User Guide.

For general information on the Label widget see the Label topic in the Volt MX Iris User Guide.

This widget supports drag and drop of text for iOS 11 on iPad.

The Label widget capabilities can be broadly categorized into the following:

Layout
Animations
Data Management
User Input Handling
3D Touch
UI Appearance
Enabling RTL
Miscellaneous
Configurations Common To All Widgets

Layout

Events	Description
doLayout	Invoked for every widget when the widget position and dimensions are computed.

Properties	Description
anchorPoint	Specifies the anchor point of the widget bounds rectangle using the widget's coordinate space.
bottom	Determines the bottom edge of the widget and is measured from the bottom bounds of the parent container.
centerX	Determines the center of a widget measured from the left bounds of the parent container.
centerY	Determines the center of a widget measured from the top bounds of the parent container.
contentAlignment	Specifies the alignment of the text for a widget with respect to its boundaries.
left	Determines the lower left corner edge of the widget and is measured from the left bounds of the parent container.
maxHeight	Specifies the maximum height of the widget and is applicable only when the height property is not specified.
maxWidth	Specifies the maximum width of the widget and is applicable only when the width property is not specified.
minHeight	Specifies the minimum height of the widget and is applicable only when the height property is not specified.
minWidth	Specifies the minimum width of the widget and is applicable only when the width property is not specified.
padding	Defines the space between the content of the widget and the widget boundaries.
paddingInPixel	Indicates if the padding is to be applied in pixels or in percentage.
top	Determines the top edge of the widget and measured from the top bounds of the parent container.
width	Determines the width of the widget and is measured along the x-axis.
zIndex	Specifies the stack order of a widget.

Animations

Methods	Description
animate	Applies an animation to the widget.

Properties	Description
transform	Contains an animation transformation that can be used to animate the widget.
widgetSwipeMove	Used to enable and configure the left or right swipe actions for a widget.

Data Management

Methods	Description
clone	When this method is used on a container widget, then all the widgets inside the container are cloned.

Properties	Description
breakStrategy	Specifies the method to perform line breaks on paragraphs of Label text.
fontMetrics	Enables apps to obtain information about the metrics of a Label widget's text.
hyphenationFrequency	Sets the periodicity in which words break in a Label text.
pasteboardType	Enables an application to share data within the application or with another application using system-wide or application-specific pasteboards.
text	Specifies a general or descriptive text for a Label widget.
textCopyable	Enables you to copy a text from a Label widget when the widget is enabled state.
textStyle	Enables apps to get and set values that control the appearance of the Label widget's text.
textTruncatePosition	Enables the appearance of ellipses at a particular position (start, middle, and end of the line) if the text gets truncated due to the maxNumberOfLines property.
toolTip	Specifies the hint text when the cursor hovers over a widget, without clicking it.
wrapping	When the content of the label reaches the boundaries, it starts wrapping.

3D Touch

Methods	Description
registerForPeekandPop	Registers a widget to enable 3D Touch peek and pop gestures.
setOnPeek	Sets and overrides the existing onPeekCallback for the widget.
setOnPop	Overrides the existing onPopCallback for the widget.
unregisterForPeekandPop	Unregisters a widget from 3D Touch peek and pop gestures.

User Input Handling

Events	Description
onScrollWidgetPosition	This event callback is invoked by the platform when the widget location position gets changed on scrolling.
onTouchEnd	An event callback is invoked by the platform when the user touch is released from the touch surface.
onTouchMove	An event callback is invoked by the platform when the touch moves on the touch surface continuously until movement ends.
onTouchStart	An event callback is invoked by the platform when the user touches the touch surface.

Methods	Description
addGestureRecognizer	Allows you to set a gesture recognizer for a specified gesture for a specified widget.
removeGestureRecognizer	Allows you to remove the specified gesture recognizer for the specified widget.
setGestureRecognizer	Allows you to set a gesture recognizer for a specified gesture for a specified widget.

UI Appearance

Properties	Description
backgroundColor	Specifies the background color of the widget in hex format.
backgroundColorMultiStepGradient	Specifies the multi-step gradient color for the background of the widget.
backgroundColorTwoStepGradient	Specifies the two-step gradient color for the background of the widget.
backgroundImage	Sets the image for the background of the widget.
borderColor	Specifies the border color of the widget.
borderColorGradient	Specifies the multi-step gradient color for the border of the widget.
borderStyle	Specifies the border style for the widget.
borderWidth	Specifies the width of the border for the widget in pixels.
cornerRadius	Specifies the radius of the border for the widget.
disabledStateSkinProperties	Specifies the skin properties that define the look and feel of the widget, when the widget is disabled or blocked.
focusStateSkinProperties	Specifies the skin properties that define the look and feel of the widget, when the widget is in focus.
fontColor	Specifies the font color of the widget.
fontFamily	Specifies the font family for the font of the widget.
fontSize	Specifies the font size for the widget in percentage (%) units.
fontStyle	Specifies the font style for the widget.
fontWeight	Specifies the weight for the font of the widget.
hoverStateSkinProperties	Specifies the skin properties that define the look and feel of the widget, when the cursor hovers on the widget.
pressedStateSkinProperties	Specifies the skin properties that define the look and feel of the widget, when the widget is pressed or clicked.
shadowColor	Specifies the color for the shadow of the widget.
shadowOffset	This property specifies the current coordinates of the shadow region in the widget.
shadowRadius	Specifies the radius for the blur value of the shadow.
textShadowColor	Specifies the color for the text shadow of the widget.
textShadowOffset	This property specifies the current coordinates of the text shadow region in the widget.
textShadowRadius	Specifies the radius for the blur value of the text shadow.
blur	You can enable or disable a blur-effect for a widget
clipView	Defines a shape to clip the widget view.
hoverSkin	Specifies the look and feel of a widget when the cursor hovers on the widget.
opacity	Specifies the opacity of the widget.
renderAsAnchor	Most of the Mobile Web browsers do not offer a very good user experience when the entire segment is made clickable.
shadowDepth	Defines the depth of the shadow effect applied to the Label Widget.
shadowType	Sets a type of the shadow effect to apply to the Label Widget.

Enabling RTL

Properties	Description
retainContentAlignment	Helps to retain the content alignment of the widget while applying RTL.
retainFlexPositionProperties	Helps to retain the left, right and padding properties while applying RTL.
retainFlowHorizontalAlignment	Enables you to change the horizontal flow of the widget from left to right.

Miscellaneous

Properties	Description
cursorType	Specifies the type of the mouse pointer used.
maxNumberOfLines	Defines the maximum number of lines of text allowed in a Label Widget.
newUnderlineBehaviour	Underlines the text in Label widget for iOS platform.

Methods	Description
getBadge	Enables you to read the badge value (if any) attached to the specified widget.
setBadge	Enables you to set the badge value to the given widget at the upper, right corner of the widget.

Configurations Common To All Widgets

Methods	Description
blur	Enables you to make the widget look unfocused.
convertPointFromWidget	Allows you to convert the coordinate system from a widget to a point (receiver's coordinate system).
convertPointToWidget	Allows you to convert the coordinate system from a point (receiver's coordinate system) to a widget.
removeFromParent	Allows you to remove a child widget from a parent widget.
setEnabled	Specifies the widget that must be enabled or disabled.
setFocus	Specifies the widget on which there must be focus.
setVisibility	Sets the visibility of the widget.

Properties	Description
accessibilityConfig	Enables you to control accessibility behavior and alternative text for the widget.
enable	Allows you to make a widget visible but not actionable.
enableCache	Enables you to improve the performance of Positional Dimension Animations.
id	id is a unique identifier of Image consisting of alpha numeric characters.
info	A custom JSObject with the key value pairs that a developer can use to store the context with the widget.
isVisible	Controls the visibility of a widget on the Form.
parent	Helps you access the parent of the widget.

When do I use a Label Widget?

You can use a Label widget in the following scenarios:

To identify or name a neighboring widget.
To provide instructions to the user on the usage of a feature or a widget. For example, if you want to inform a user to select one of the options from a CheckBoxGroup, you can place a Label before the CheckBoxGroup widget with the text "Choose one of the following".

Creating a Label Using a Constructor: voltmx.ui.Label

var lbl1 = new voltmx.ui.Label(basicConf, layoutConf, pspConf);

basicConf is an object with basic properties.
layoutConf is an object with layout properties.
pspConf is an object with platform specific properties.

Note: The configuration properties should be passed only in the respective configuration objects otherwise they are ignored.

Example

//Defining the properties for a label with id:"label"
var lblBasic = {
    id: "label",
    skin: "lblSkn",
    text: "Hello world",
    isVisible: true
};
var lblLayout = {
    containerWeight: 100,
    padding: [5, 5, 5, 5],
    margin: [5, 5, 5, 5],
    hExpand: true,
    vExpand: false
};
var lblLayout = {
    renderAsAnchor: true,
    wrapping: constants.WIDGET_TEXT_WORD_WRAP
};
//Creating the label.
var lbl = new voltmx.ui.Label(lblBasic, lblLayout, lblLayout);

//Reading the id of the label.
alert("Label id::" + lbl.id);

Customizing a Label's Appearance

You can customize the appearance of the Label widget using the following properties:

contentAlignment: Specifies the alignment of the content within widget boundaries.
margin: Defines the space around a widget.
padding: Defines the space between the content of the widget and the widget boundaries.
skin: Specifies the skin.
fontMetrics. Controls the label's characteristics that govern the Label's appearance such as the top, bottom, ascent, descent, and point size of the text.
textStyle. Defines properties such as the line spacing, letter spacing, strikethrough, base line, and line height of a Label's text.

Changing the Text Size through the Larger Text option in iOS

You can now change the text size of Label widget through the Larger Text option from Settings -> General -> Accessibility -> Larger Text in iOS.

To support this feature, you must implement the 'dynamicTypeList' dictionary in the voltmx.application.setApplicationBehaviors function as follows:

voltmx.application.setApplicationBehaviors({
    dynamicTypeList: {
        enableChangeTextSizeFromAccessibility: true,
        fontTextStyle: constants.FONT_TEXT_STYLE_BODY
    }
});

Input Parameters

enableChangeTextSizeFromAccessibility (BOOL): If set to true, you can change the text size through the Larger Text option from Settings -> General -> Accessibility -> Larger Text in iOS. Otherwise, the text size will not be changed.
fontTextStyle: This is the font style applied on the Label widget. If you pass only the enableChangeTextSizeFromAccessibility key-value pair in the dictionary and don’t send the fontTextStyle key-value pair, the default value for fontTextStyle will be constants.FONT_TEXT_STYLE_BODY. The values for fontTextStyle are as follows:
- constants.FONT_TEXT_STYLE_BODY
- constants.FONT_TEXT_STYLE_HEADLINE
- constants.FONT_TEXT_STYLE_SUBHEADLINE
- constants.FONT_TEXT_STYLE_FOOTNOTE
- constants.FONT_TEXT_STYLE_CAPTION1
- constants.FONT_TEXT_STYLE_CAPTION2
- constants.FONT_TEXT_STYLE_TITLE1 (available in iOS 9.0 and later)
- constants.FONT_TEXT_STYLE_TITLE2 (available in iOS 9.0 and later)
- constants.FONT_TEXT_STYLE_TITLE3 (available in iOS 9.0 and later)
- constants.FONT_TEXT_STYLE_CALLOUT (available in iOS 9.0 and later)
- constants.FONT_TEXT_STYLE_LARGETITLE (available in iOS 11.0 and later)

Platform Availability

iOS

Limitations

If you enable this feature, the font size and font family from the respective skin is not respected.
This feature is available only in iOS.

Font Metrics and Text Style

To gain finer control over the appearance of the text in a Label widget, your app can use the fontMetrics and textStyle properties. Both the fontMetrics and textStyle properties contain JavaScript objects that hold the font information.

A font's metrics and text style as defined for Android and iOS as shown in the following diagrams.

Android:

iOS:

The fontMetrics property is contains an object that encapsulates about how to render a particular font. Specifically, it controls the following properties of the Label's text.

Property	Platform Availability
top	Android
bottom	Android
ascent	Android, iOS
descent	Android, iOS
leading	Android, iOS
pointSize	iOS
capHeight	iOS
xHeight	iOS
lineHeight	Android, iOS

The fontMetrics property is read-only. The following example shows how an app can read the fontMetrics property.

var fontMatricesObject = form.label.fontMetrics;  
voltmx.print ("ascent :" + fontMatricesObject.ascent);  
voltmx.print ("descent:" + fontMatricesObject.descent);

The textStyle property enables your app to set or get the following text properties of a Label widget. It contains a JavaScript object of key/value pairs. The keys are shown in the following table.

Property	Platform Availability
lineSpacing	Android, iOS
letterSpacing	Android, iOS
strikeThrough	Android, iOS
strikeThroughStyle	iOS
baseLine	iOS
minLineHeight	iOS
maxLineHeight	iOS

The textStyle property is read/write. The following code provides an example of how an app might use the textStyle property.

//Writing values to the textStyle property.
form.label.textStyle = {
    "lineSpacing": 10,
    "letterSpacing": 10,
    "strikeThrough": true,
    "strikeThroughStyle": constants.TEXTSTYLE_STRIKETHROUGH_STYLE_THICK,
    "baseline": 0.5
};
//Reading values from the textStyle property.
var textStyleInfo = form.label.textStyle;

Important Considerations

Label has the following considerations:

If the text in the Label is occupying more space than the allocated height of the Label widget, the Label is stretched vertically to accommodate the full text (infinite wrapping) and does not stretch in the horizontal direction.
If you place a Label in the Form and do not enter a text, when rendered, the height and width occupied by the Label depends on the following:
- If the Expand property is false, the Label occupies zero height and width.
- If the Expand property is true, the Label occupies the width and height as determined by the Expand property.