Famo.us how to make a scrollview be filled from bo

问题:

Assuming I've a scrollview with direction 1 (vertical). While populating the scrollView, the items do appear and are aligned from top to bottom.

I would like to know if there is a way to reverse this ordering i.e. to make the scrollView be populated from the bottom to the top. A good example of usage is a message list. You want the last message to always appear on the bottom of the list. By default, the message would be aligned on top, which is not convenient.

[EDIT] I just found we can easily set our own transform according to an offset overriding the outputFrom function callback. For example the following will invert the scroll content:

scrollview.outputFrom(function(offset)
{
       return  Transform.translate(0, -offset)
});

回答1:

Did it like you suggested, it works just fine while rotating all by 180˚. Example: http://jsfiddle.net/tamtamchik/LA49a/3/

Famous.loaded(function () {
    var Engine = Famous.Core.Engine;
    var Surface = Famous.Core.Surface;
    var Scrollview = Famous.Views.Scrollview;
    var Timer = Famous.Utilities.Timer;
    var Transform = Famous.Core.Transform;
    var StateModifier = Famous.Modifiers.StateModifier;
    var ContainerSurface = Famous.Surfaces.ContainerSurface;

    var mainContext = Engine.createContext();

    var scrollview = new Scrollview();
    var surfaces = [];
    var i = 0;
    var surfaceHeight = 50;

    scrollview.sequenceFrom(surfaces);

    Timer.setInterval(function () {
        var container = new ContainerSurface({
            size: [undefined, surfaceHeight]
        });

        var temp = new Surface({
            content: "Surface: " + (i + 1),
            size: [undefined, surfaceHeight],
            properties: {
                backgroundColor: "hsl(" + (i * 360 / 40) + ", 100%, 50%)",
                lineHeight: "50px",
                textAlign: "center"
            }
        });

        var surfaceRotate = new StateModifier({
            transform: Transform.rotateZ(Math.PI)
        });

        var surfacePush = new StateModifier({
            transform: Transform.translate(window.innerWidth, surfaceHeight)
        });

        container.add(surfacePush).add(surfaceRotate).add(temp);
        container.pipe(scrollview);
        temp.pipe(scrollview);
        surfaces.unshift(container);
        i++;
    }, 400);

    var rotate = new StateModifier({
        transform: Transform.rotateZ(Math.PI)
    });

    var push = new StateModifier({
        transform: Transform.translate(window.innerWidth, window.innerHeight)
    });

    mainContext.add(push).add(rotate).add(scrollview);
});

回答2:

Well as famo.us documentation says: "Scrollview will lay out a collection of renderables sequentially in the specified direction", so it will order the surfaces in the order you provide.

My advice is to add the surfaces to a list and then just add them to the ScrollView in reverse.

回答3:

What you are looking for is unshift(). You can view the following code run at codefamo.us

var Engine = require('famous/core/Engine');
var Surface = require('famous/core/Surface');
var StateModifier = require('famous/modifiers/StateModifier');
var Transform = require('famous/core/Transform');
var Easing = require('famous/transitions/Easing');
var Scrollview = require('famous/views/Scrollview');

var mainContext = Engine.createContext();
var items = [];
var scroll = new Scrollview();
mainContext.add(scroll);
var counter=0;
scroll.sequenceFrom(items);

function addOne() {
    setTimeout(function() {
        var surface = new Surface({
            size: [100, 100],
            content: 'surf: '+counter++,
            properties: {
                textAlign: 'center',
                lineHeight: '20px'
            }
        });
        items.unshift(surface);

        if (counter<10) 
        addOne();
    },2000);
}
addOne();