Titanium manual dimension calculation

app.js

var win = Ti.UI.createWindow({
    layout: 'vertical',
    backgroundColor: '#000'
});

var view = Ti.UI.createView({
	backgroundColor: '39c',
	//height: '70%',
	layout: 'vertical'
});

view.sizeCalculated = {};

var b1 = Ti.UI.createButton({
	height: 100,
	top: 0,
	title: 'Set fixed'
});

b1.addEventListener('click', function() {
	
	Ti.API.info('Setting fixed value ...');
	
	//set view's value
	view.height = 500;
	
	//calculate view's value
	view.sizeCalculated.height = 500;
});

var b2 = Ti.UI.createButton({
	height: 100,
	top: 0,
	title: 'Set percentage'
});

b2.addEventListener('click', function() {
	
	Ti.API.info('Setting percentage value ...');
	
	view.height = '50%';
	//calculation
	var percentageNumber = +view.height.slice(0, view.height.length - 1) / 100;
	
	view.sizeCalculated.height = Math.floor(view.parentElement.size.height * percentageNumber);
});

var b3 = Ti.UI.createButton({
	height: 100,
	top: 0,
	title: 'Set auto'
});

b3.addEventListener('click', function() {
	
	Ti.API.info('Setting auto value ...');
	
	view.height = 'auto';

	//calculation
	var viewHeight = 0;
	for (var i = 0; i < view.children.length; ++i) {
	    viewHeight += view.children[i].size.height;
	}
	
	view.sizeCalculated.height = viewHeight;
	
});

var b4 = Ti.UI.createButton({
	height: 100,
	top: 0,
	title: 'Get calculated'
});

b4.addEventListener('click', function() {
	Ti.alert('TiCalc: ' + view.size.height);
	Ti.alert('MyCalc: ' + view.sizeCalculated.height);
});

 
view.add(b1);
view.add(b2);
view.add(b3);
view.add(b4);

win.add(view);

view.parentElement = win;
 
win.open();