B4J Tutorial [BANanoVuetifyAD3] Improving Perceived Performance on 7.29+

Mashiane · Jan 19, 2022

Hi there

I'm not going to kid you. Before BVAD3 shows the first page, it takes a lot of time to build and show the app e.g. calling all those .Initialize subs in each of the route pages, loading layouts, calling bindstates, checking all SubExists and all that etc etc.

Perceived performance measures how fast a user thinks your mobile app is.

So lets change this about BVAD3.

1. In Main > AppStart, add this code

B4X:

BANano.Header.OnDOMContentLoaded = BANanoShared.DOMContentLoaded

Document: DOMContentLoaded event - Web APIs | MDN

The DOMContentLoaded event fires when the HTML document has been completely parsed, and all deferred scripts (<script defer src="…"> and <script type="module">) have downloaded and executed. It doesn't wait for other things like images, subframes, and async scripts to finish loading.

developer.mozilla.org

2. In each of your route pages, ensure that at least this code exists..

B4X:

Sub beforeEnter(boTo As Map, boFrom As Map, boNext As BANanoObject)   'ignoreDeadCode
    'show a loader
    vuetify.Loading(True)
    'continue navigating to this page
    vuetify.NavigateToNext(boNext, "")
End Sub

Sub mounted   'ignoreDeadCode
    'hide the loader
    vuetify.Loading(False)
End Sub

Vue Router

The official Router for Vue.js

router.vuejs.org

This has the effect of showing this loader before each page is shown, from the onset your browser page opens until your StartPage i.e root / is shown.

That's it!!

NB: Any code being BANanoShared.AddLoader, BANAnoShared.ShowLoader, BANanoShared.HideLoader SHOULD BE REMOVED!

To understand what happens, here is the snippet.

B4X:

'code for DOMContentLoaded
Sub DOMContentLoaded As String
    Dim str As String = $"var body = document.getElementById("body");
    var loader1 = document.createElement("div");
    loader1.setAttribute("id", "loader-1")
    loader1.style.cssText = 'display:block;position:fixed;width:100%;height:100%;z-index:999999';
    var loader = document.createElement("div");
    loader.setAttribute("id", "loader")
    loader1.appendChild(loader);
    body.appendChild(loader1);"$
    Return str
End Sub

Sub ShowLoader
    Dim lEL As BANanoElement
    lEL.Initialize("#loader-1")
    Dim mStyle As Map = CreateMap()
    mStyle.Put("display", "block")
    lEL.SetStyle(BANano.ToJson(mStyle))
End Sub

Sub HideLoader
    Dim lEL As BANanoElement
    lEL.Initialize("#loader-1")
    Dim mStyle As Map = CreateMap()
    mStyle.Put("display", "none")
    lEL.SetStyle(BANano.ToJson(mStyle))
End Sub

And you will need this css. This can be saved in a file.

B4X:

/*Loader 1- Spinning */

#loader-1 #loader{
    position: relative;
    left: 50%;
    top: 50%;
    height: 20vw;
    width: 20vw;
    margin: -10vw 0 0 -10vw;
    border: 3px solid transparent;
    border-top-color: #3498db;
    border-bottom-color: #3498db;
    border-radius: 50%;
    z-index: 2;
    -webkit-animation: spin 2s linear infinite;
    -moz-animation: spin 2s linear infinite;
    -o-animation: spin 2s linear infinite;
    animation: spin 2s linear infinite;
}
#loader-1 #loader:before{
    content: "";
    position: absolute;
    top:2%;
    bottom: 2%;
    left: 2%;
    right: 2%;
    border: 3px solid transparent;
    z-index: 2;
    border-top-color: #db213a;
    border-radius: 50%;
    -webkit-animation: spin 3s linear infinite;
    -moz-animation: spin 3s linear infinite;
    -o-animation: spin 3s linear infinite;
    animation: spin 3s linear infinite;
}
#loader-1 #loader:after{
    content: "";
    position: absolute;
    top:5%;
    bottom: 5%;
    left: 5%;
    right: 5%;
    border: 3px solid transparent;
    border-top-color: #dec52d;
    z-index: 2;
    border-radius: 50%;
    -webkit-animation: spin 1.5s linear infinite;
    -moz-animation: spin 1.5s linear infinite;
    -o-animation: spin 1.5s linear infinite;
    animation: spin 1.5s linear infinite;
}
/*Keyframes for spin animation */
@-webkit-keyframes spin {
    0%   {
        -webkit-transform: rotate(0deg);  /* Chrome, Opera 15+, Safari 3.1+ */
        -ms-transform: rotate(0deg);  /* IE 9 */
        transform: rotate(0deg);  /* Firefox 16+, IE 10+, Opera */
    }
    50% {
        -webkit-transform: rotate(360deg);  /* Chrome, Opera 15+, Safari 3.1+ */
        -ms-transform: rotate(360deg);  /* IE 9 */
        transform: rotate(180deg);  /* Firefox 16+, IE 10+, Opera */
    }
    100% {
        -webkit-transform: rotate(360deg);  /* Chrome, Opera 15+, Safari 3.1+ */
        -ms-transform: rotate(360deg);  /* IE 9 */
        transform: rotate(360deg);  /* Firefox 16+, IE 10+, Opera */
    }
}

@-moz-keyframes spin {
    0%   {
        -webkit-transform: rotate(0deg);  /* Chrome, Opera 15+, Safari 3.1+ */
        -ms-transform: rotate(0deg);  /* IE 9 */
        transform: rotate(0deg);  /* Firefox 16+, IE 10+, Opera */
    }
    50% {
        -webkit-transform: rotate(360deg);  /* Chrome, Opera 15+, Safari 3.1+ */
        -ms-transform: rotate(360deg);  /* IE 9 */
        transform: rotate(180deg);  /* Firefox 16+, IE 10+, Opera */
    }
    100% {
        -webkit-transform: rotate(360deg);  /* Chrome, Opera 15+, Safari 3.1+ */
        -ms-transform: rotate(360deg);  /* IE 9 */
        transform: rotate(360deg);  /* Firefox 16+, IE 10+, Opera */
    }
}
@-o-keyframes spin {
    0%   {
        -webkit-transform: rotate(0deg);  /* Chrome, Opera 15+, Safari 3.1+ */
        -ms-transform: rotate(0deg);  /* IE 9 */
        transform: rotate(0deg);  /* Firefox 16+, IE 10+, Opera */
    }
    50% {
        -webkit-transform: rotate(360deg);  /* Chrome, Opera 15+, Safari 3.1+ */
        -ms-transform: rotate(360deg);  /* IE 9 */
        transform: rotate(180deg);  /* Firefox 16+, IE 10+, Opera */
    }
    100% {
        -webkit-transform: rotate(360deg);  /* Chrome, Opera 15+, Safari 3.1+ */
        -ms-transform: rotate(360deg);  /* IE 9 */
        transform: rotate(360deg);  /* Firefox 16+, IE 10+, Opera */
    }
}
@keyframes spin {
    0%   {
        -webkit-transform: rotate(0deg);  /* Chrome, Opera 15+, Safari 3.1+ */
        -ms-transform: rotate(0deg);  /* IE 9 */
        transform: rotate(0deg);  /* Firefox 16+, IE 10+, Opera */
    }
    50% {
        -webkit-transform: rotate(360deg);  /* Chrome, Opera 15+, Safari 3.1+ */
        -ms-transform: rotate(360deg);  /* IE 9 */
        transform: rotate(180deg);  /* Firefox 16+, IE 10+, Opera */
    }
    100% {
        -webkit-transform: rotate(360deg);  /* Chrome, Opera 15+, Safari 3.1+ */
        -ms-transform: rotate(360deg);  /* IE 9 */
        transform: rotate(360deg);  /* Firefox 16+, IE 10+, Opera */
    }
}

Have fun!

B4J Tutorial [BANanoVuetifyAD3] Improving Perceived Performance on 7.29+

Document: DOMContentLoaded event - Web APIs | MDN

Vue Router

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