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NativeScript Core

Segmented Bar

Using a SegementedBar inside JavaScript project gives you a simple way to define a collection of tabbed views. The SegmentedBar’s selectedIndexChange property notifies you for every changes of the component’s selectedIndex.

The specific SegmentedBar properties are:

  • items
  • selectedIndex
  • selectedIndexChange
const segmentedBarModule = require("tns-core-modules/ui/segmented-bar");
import { SegmentedBar, SegmentedBarItem, SelectedIndexChangedEventData } from "tns-core-modules/ui/segmented-bar";

Basics

The example shows how to create SegmentedBar component via XML and handle selectedIndex change.

<SegmentedBar row="0"  class="m-5" selectedIndex="{{ sbSelectedIndex }}">
    <SegmentedBar.items>
        <SegmentedBarItem title="Item 1" />
        <SegmentedBarItem title="Item 2" />
        <SegmentedBarItem title="Item 3" />
    </SegmentedBar.items>
</SegmentedBar>
function onNavigatingTo(args) {
    const page = args.object;
    // set up the SegmentedBar selected index
    const vm = new observableModule.Observable();
    vm.set("prop", 0);
    vm.set("sbSelectedIndex", 0);
    // handle selected index change
    vm.on(observableModule.Observable.propertyChangeEvent, (propertyChangeData) => {
        if (propertyChangeData.propertyName === "sbSelectedIndex") {
            vm.set("prop", propertyChangeData.value);
        }
    });
    page.bindingContext = vm;
}

exports.onNavigatingTo = onNavigatingTo;
export function onNavigatingTo(args) {
    const page: Page = <Page>args.object;
    // set up the SegmentedBar selected index
    const vm = new Observable();
    vm.set("prop", 0);
    vm.set("sbSelectedIndex", 0);
    // handle selected index change
    vm.on(Observable.propertyChangeEvent, (propertyChangeData: PropertyChangeData) => {
        if (propertyChangeData.propertyName === "sbSelectedIndex") {
            vm.set("prop", propertyChangeData.value);
        }
    });
    page.bindingContext = vm;
}

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Code Behind

In the following example is shown, how to create SegmentedBar via Code-behind

<StackLayout id="stackLayoutId">
    <Label text="{{ 'Result(index): ' + sbResult}}" textWrap="true" />

</StackLayout>
function onPageLoaded(args) {
    const page = args.object;
    const vm = new observableModule.Observable();
    const stackLayout = page.getViewById("stackLayoutId");

    vm.set("sbResult", 0);
    // creating new SegmentedBar and binding the selectedIndex property
    const options = {
        sourceProperty: "sbindex",
        targetProperty: "selectedIndex"
    };
    const segmentedBar = new segmentedBarModule.SegmentedBar();
    const items = [];
    const item1 = new segmentedBarModule.SegmentedBarItem();
    item1.title = "Item1";
    items.push(item1);
    const item2 = new segmentedBarModule.SegmentedBarItem();
    item2.title = "Item2";
    items.push(item2);
    const item3 = new segmentedBarModule.SegmentedBarItem();
    item3.title = "Item3";
    items.push(item3);
    segmentedBar.items = items;

    segmentedBar.bind(options, vm);
    // setting SegmentedBar selected index to 0
    vm.set("sbindex", 0);

    segmentedBar.on("selectedIndexChange", (args) => {
        vm.set("sbResult", args.object.selectedIndex);
    });

    stackLayout.insertChild(segmentedBar, 0);

    page.bindingContext = vm;
}

exports.onPageLoaded = onPageLoaded;
export function onPageLoaded(args) {
    const page: Page = <Page>args.object;
    const vm = new Observable();
    const stackLayout: StackLayout = <StackLayout>page.getViewById("stackLayoutId");

    vm.set("sbResult", 0);
    // creating new SegmentedBar and binding the selectedIndex property
    const options = {
        sourceProperty: "sbindex",
        targetProperty: "selectedIndex"
    };
    const segmentedBar = new SegmentedBar();
    const items = [];
    const item1 = new SegmentedBarItem();
    item1.title = "Item1";
    items.push(item1);
    const item2 = new SegmentedBarItem();
    item2.title = "Item2";
    items.push(item2);
    const item3 = new SegmentedBarItem();
    item3.title = "Item3";
    items.push(item3);
    segmentedBar.items = items;

    segmentedBar.bind(options, vm);
    // setting SegmentedBar selected index to 0
    vm.set("sbindex", 0);

    segmentedBar.on("selectedIndexChange", (sbargs: SelectedIndexChangedEventData) => {
        vm.set("sbResult", (<SegmentedBar>sbargs.object).selectedIndex);
    });

    stackLayout.insertChild(segmentedBar, 0);

    page.bindingContext = vm;
}

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Views

Example showing how to handle the SegmentedBar index change event and changing the displayed Layouts.

<SegmentedBar row="0" loaded="sbLoaded" class="m-5" selectedIndex="{{ sbSelectedIndex }}">
    <SegmentedBar.items>
        <SegmentedBarItem title="Item 1" />
        <SegmentedBarItem title="Item 2" />
        <SegmentedBarItem title="Item 3" />
    </SegmentedBar.items>
</SegmentedBar>
<GridLayout row="1" rows="*" visibility="{{ visibility1 ? 'visible' : 'collapsed' }}" backgroundColor="white">
    <Label text="{{ 'The new selectedIndex is: ' + prop }}" class="m-15 h3 p-5 text-center"/>
</GridLayout>

<GridLayout row="1" rows="*" visibility="{{ visibility2 ? 'visible' : 'collapsed' }}" backgroundColor="green">
    <Label text="{{ 'The new selectedIndex is: ' + prop }}" class="m-15 h3 p-5 text-center" color="white"/>
</GridLayout>

<GridLayout row="1" rows="*" visibility="{{ visibility3 ? 'visible' : 'collapsed' }}" backgroundColor="red">
    <Label text="{{ 'The new selectedIndex is: ' + prop }}" class="m-15 h3 p-5 text-center" color="white"/>
</GridLayout>
function onNavigatingTo(args) {
    const page = args.object;
    // set up the SelectedBar selected index
    const vm = new observableModule.Observable();
    vm.set("prop", 0);
    vm.set("sbSelectedIndex", 0);
    vm.set("visibility1", true);
    vm.set("visibility2", false);
    vm.set("visibility3", false);

    page.bindingContext = vm;
}

function sbLoaded(args) {
    // handle selected index change
    const segmentedBarComponent = args.object;
    segmentedBarComponent.on("selectedIndexChange", (sbargs) => {
        const page = sbargs.object.page;
        const vm = page.bindingContext;
        const selectedIndex = sbargs.object.selectedIndex;
        vm.set("prop", selectedIndex);
        switch (selectedIndex) {
            case 0:
                vm.set("visibility1", true);
                vm.set("visibility2", false);
                vm.set("visibility3", false);
                break;
            case 1:
                vm.set("visibility1", false);
                vm.set("visibility2", true);
                vm.set("visibility3", false);
                break;
            case 2:
                vm.set("visibility1", false);
                vm.set("visibility2", false);
                vm.set("visibility3", true);
                break;
            default:
                break;
        }
    });
}

exports.onNavigatingTo = onNavigatingTo;
exports.sbLoaded = sbLoaded;
export function onNavigatingTo(args) {
    const page: Page = <Page>args.object;
    // set up the SelectedBar selected index
    const vm = new Observable();
    vm.set("prop", 0);
    vm.set("sbSelectedIndex", 0);
    vm.set("visibility1", true);
    vm.set("visibility2", false);
    vm.set("visibility3", false);

    page.bindingContext = vm;
}

export function sbLoaded(args) {
    // handle selected index change
    const segmentedBarComponent: SegmentedBar = <SegmentedBar>args.object;
    segmentedBarComponent.on("selectedIndexChange", (sbargs: SelectedIndexChangedEventData) => {
        const page = (<SegmentedBar>sbargs.object).page;
        const vm = page.bindingContext;
        const selectedIndex = (<SegmentedBar>sbargs.object).selectedIndex;
        vm.set("prop", selectedIndex);
        switch (selectedIndex) {
            case 0:
                vm.set("visibility1", true);
                vm.set("visibility2", false);
                vm.set("visibility3", false);
                break;
            case 1:
                vm.set("visibility1", false);
                vm.set("visibility2", true);
                vm.set("visibility3", false);
                break;
            case 2:
                vm.set("visibility1", false);
                vm.set("visibility2", false);
                vm.set("visibility3", true);
                break;
            default:
                break;
        }
    });
}

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API Reference for the SegementedBar Class

Native Component

Android iOS
android.widget.TabHost UISegmentedControl