Nativescript-Vue Shadow Directive Plugin

This repo is a port to Nativescript-Vue of @JoshDSommer's NativeScript Angular Shadow Directive project. As such, a good portion of the code is inspired by it, but many changes were made to fit into how Vue does Directives.

Installation

From the command prompt go to your app's root folder and execute:

npm install nativescript-vue-shadow

Demo

How to use it

This is a Vue directive to make your life easier when it comes to using native shadows with Nativescript-Vue.

Shadows are a very important part of Material design specification. It brings up the concept of elevation, which implies in the natural human way of perceiving objects raising up from the surface.

With this directive, you won't have to worry about all the aspects regarding shadowing on Android and on iOS. On the other hand, if you care about some of the details, you will still be able to provide certain extra attributes and they will superseed the default ones.

However, running this on Android you will require the SDK to be greater or equal than 21 (Android 5.0 Lollipop or later), otherwise shadows will simply not be shown. There should be no problem running this on any version of iOS.

Import the Directive into main.js

import NSVueShadow from 'nativescript-vue-shadow'
Vue.use(NSVueShadow)

Use in your view or component

Simple attribute for v-shadow:

<Label v-shadow="2"></Label>

You can property bind it in your template tag. This can be a string, number or object ( AndroidData | IOSData ):

<Label v-shadow="myCustomData"></Label>

Then in your script tag you can do something like this where we bind to the object:

import { AndroidData, ShapeEnum } from "nativescript-vue-shadow";
// ...
export default class MyComponent extends Vue {
  private myCustomData: AndroidData = {
    elevation: 6,
    bgcolor: "#ff1744",
    shape: ShapeEnum.OVAL
  };
  // ...
}

You can also provide details directly in your markup by using the v-shadow directive with an explicit object ( AndroidData | IOSData ):

<Label v-shadow="{ elevation: elevation, shape: shape.RECTANGLE, bgcolor: '#006968', cornerRadius: 15 }"></Label>

There are a couple of platform specific attributes you might want to use to customize your view. Bear in mind some of them clash with CSS styles applied to the same views. When it happens, the default behaviour on Android is the original HTML/CSS styles are lost in favor of the ones provided by this directive. On iOS, on the other hand, HTML/CSS pre-existent styles are regarded, consequently the shadow might not be applied.

The tip is avoid applying things like background color and border radius to the same view you intend to apply this directive (Note: this is now supported).

List of attributes

The table below list and describes all possible attributes as well as show which platform supports each one of them:

Attribute	Type	Default	Platform	Description
elevation	number | string		both	Determines the elevation of the view from the surface. It does all shadow related calculations. You might want to have a look at this enum of standard material design elevations. FYI, it's calculated in DIPs (or DPs, density independent pixels) on Android, or PTs (points) on iOS.
pressedElevation	number | string		Android	Determines the view's elevation when on pressed state.
shape	string => 'RECTANGLE' | 'OVAL' | 'RING' | 'LINE'	'RECTANGLE'	Android	Determines the shape of the view and overrides its format styles.
bgcolor	string (#RGB)		Android	Determines view's background color and overrides its previous background. If not set, the previous background is used. NOTE: setting the background to transparent is known to cause issues on Android (the shadow may overlap the background)
cornerRadius	number		Android	Determines view's corner radius (CSS border-radius) and overrides its previous style. If this is not set, the view's CSS border-radius are used. FYI, it's calculated in DIPs (or DPs, density independent pixels).
translationZ	number		Android	Determines an extra distance (in DIP) to the surface.
pressedTranslationZ	number		Android	Determines an extra distance (in DIP) to the surface when the view is in the pressed state.
forcePressAnimation	boolean	false	Android	By default, if a view has a StateAnimator, it is overwritten by an animator that raises the View on press. Setting this to true will always define this new animator, essentially making any clickable View work as a button.
maskToBounds	boolean	false	iOS	Determines whether the shadow will be limited to the view margins.
shadowColor	string (#RGB)		iOS	Determines shadow color. Shadow won't be applied if the view already has background.
shadowOffset	number		iOS	Determines the distance in points (only on Y axis) of the shadow. Negative value shows the shadow above the view.
shadowOpacity	number		iOS	From 0 to 1. Determines the opacity level of the shadow.
shadowRadius	number		iOS	Determines the blurring effect in points of the shadow. The higher the more blurred.
useShadowPath	boolean	true	iOS	Determines whether to use shadowPath to render the shadow. Setting this to false negatively impacts performance.
rasterize	boolean	false	iOS	Determines whether the view should be rasterized. Activating this will increase memory usage, as rasterized views are stored in memory, but will massively improve performance.

Pre-defined elevations

If you want to be consistent with the Material Design specification but you're sick of trying to memorize which elevation your view should have. We've put together a list of pre-defined elevations:

• SWITCH: 1
• CARD_RESTING: 2
• RAISED_BUTTON_RESTING: 2
• SEARCH_BAR_RESTING: 2
• REFRESH_INDICADOR: 3
• SEARCH_BAR_SCROLLED: 3
• APPBAR: 4
• FAB_RESTING: 6
• SNACKBAR: 6
• BOTTOM_NAVIGATION_BAR: 8
• MENU: 8
• CARD_PICKED_UP: 8,
• RAISED_BUTTON_PRESSED: 8
• SUBMENU_LEVEL1: 9
• SUBMENU_LEVEL2: 10
• SUBMENU_LEVEL3: 11
• SUBMENU_LEVEL4: 12
• SUBMENU_LEVEL5: 13
• FAB_PRESSED: 12
• NAV_DRAWER: 16
• RIGHT_DRAWER: 16
• MODAL_BOTTOM_SHEET: 16
• DIALOG: 24
• PICKER: 24

If you don't even want to check it out every time you have to shadow an element, just import the Elevation enum and enjoy :)

Component

import { Elevation } from "nativescript-vue-shadow";

export default class MyComponent extends Vue {
  // ...
  private elevation: number = Elevation.SNACKBAR;
  // ...
}

Override Android default StateListAnimator

Android buttons are split into three categories: floating, raised and flat. Different from labels and other ui elements, each button category has its own state animator. So, when buttons are tapped, Android does affect their elevation (and z translation) in a way that Angular is not notified. At the end of tap animation, buttons get back to resting defaults (i.e. raised button's elevation at 2dp and translationZ at 0) overriding the shadow stablished by this plugin.

This plugin replaces the default StateListAnimator with one that gets back to the values you provide for elevation and translationZ.

Feel free to fill submit a PR if you want the flexibility of defining your own StateListAnimator. The motivation so far was simply put this plugin to work with buttons without changing the original state once they are clicked.

It's also possible to set this StateListAnimator to any View, making it behave like a button.

Plugin Development Work Flow

• Clone repository to your machine.
• Run npm install in base directory of project
• Change to Demo directory and then run npm install
• Run and deploy to your device or emulator with npm run serve:android or npm run serve:ios. (use debug:android or debug:ios to attach to devtools)

Changelog

• 0.1.0 Initial implementation

License

MIT License