NativeScript: Accessing native Android API - nativescript

Question

There is still something i don't get in accessing native Platform stuff with nativescript. Here is a simple snippet where i try to access a native gui element and add it to a page:
var PagesModule = require('ui/page');
var Application = require('application');
var StackLayout = require('ui/layouts/stack-layout').StackLayout;
exports.createPage = function createPage(args) {
var page = new PagesModule.Page;
page.actionBarHidden = true;
page.backgroundColor = '#F5F5F5';
page.backgroundSpanUnderStatusBar = false;
var textView = new android.widget.TextView(Application.android.currentContext);
var stackLayout = new StackLayout();
stackLayout.addChild(textView);
page.content = stackLayout;
return page;
}
I think i am missing something in the understanding of how nativescript interacts with the native platform.

Answer 1

The reason it is failing is because only "view" or "view" descendants can be assigned to "view" child or children.
You are creating a direct android component; but it isn't part of the NS framework, so the framework doesn't know what to do with it. When you create a visual component you descend your component from a view (or another view descendant). The NS version of the code should be:
var PagesModule = require('ui/page');
var Application = require('application');
var StackLayout = require('ui/layouts/stack-layout').StackLayout;
vat TextView = require('ui/text-view').TextView;
exports.createPage = function createPage(args) {
var page = new PagesModule.Page;
page.actionBarHidden = true;
page.backgroundColor = '#F5F5F5';
page.backgroundSpanUnderStatusBar = false;
var textView = new TextView();
var stackLayout = new StackLayout();
stackLayout.addChild(textView);
page.content = stackLayout;
return page;
}
If you are actually wanting to create your own component I would recommend you look at the UI/Switch it is probably the simplest example; but in a nutshell you need to subclass the view, on Android use the function _createUI to actually create the native component, and so in simplest terms it would be:
var View = require('ui/core/view').View;
function MyTextView() {
View.apply(this, arguments);
}
__extends(MyTextView, View);
Object.defineProperty(MyTextView.prototype, "android", {
get: function () {
return this._android;
},
enumerable: true,
configurable: true
});
MyTextView.prototype._createUI = function () {
this._android = new android.widget.TextView(Application.android.currentContext);
};
Then you can use new MyTextView() instead of the built in new TextView() function in the first code sample.
Please note with this component, because we haven't defined any additional helper function, to set and get the text you would have to do things like
var x = page.GetViewById('myTextId').android.setText("Some Value");
and to access the native underlying control and its android properties.
Please note I have a whole blog article on some of this at http://fluentreports.com/blog/?p=167 (And many other articles on the site about NS)