UIWebView not evaluating java script using method stringByEvaluatingJavaScriptFromString:

Question

I am having trouble evaluating youtube api javascript commands from a UIWebView

The commands are evaluating correctly in Safari and Firefox

the webview is initialized with options

allowsInlineMediaPlayback = YES;
mediaPlaybackRequiresUserAction = NO;

The Html I am loading is:

<div id="player"></div>

<script>
    var tag = document.createElement('script');
    //playerVars: { 'autoplay': 0, 'modestbranding': 1, 'rel': 0, 'showinfo': 0, 'iv_load_policy': 3, 'controls': 1, 'playsinline':1 },
    var configuration = {
        playerVars: {
            'playsinline':1,
            'showinfo': 0,
            'modestbranding': 1
        },
        events: {
            'onReady': onPlayerReady,
            'onStateChange': onPlayerStateChange
        }
    };

tag.src = "https://www.youtube.com/iframe_api";
var firstScriptTag = document.getElementsByTagName('script')[0];
firstScriptTag.parentNode.insertBefore(tag, firstScriptTag);

function setup(key, value) {
    configuration[key] = value;
}

function configurePlayer(key, value) {
    configuration.playerVars[key] = value;
}
// area for the code injection
setup('videoId', 'cDhlx60nTCU');
setup('startingTime', 10);
setup('autoPlay' , true);
setup('width', 400);
setup('height', 200);
configurePlayer('controls', true);


var player;
function onYouTubeIframeAPIReady() {
    player = new YT.Player('player', configuration);
}

function onPlayerReady(event) {
    if (configuration['autoPlay']) {
        if (configuration['startingTime']) {
            player.playVideoAt(configuration['startingTime']);
        } else {
            event.target.playVideo();
        }
    }
}

function onPlayerStateChange(event) {
    if (event.data == YT.PlayerState.PLAYING) {
        // Do something...
    }
}

function stopVideo() {
    player.stopVideo();
    return "OK";
}
</script>
Printing description of html:
<div id="player"></div>

<script>
    var tag = document.createElement('script');
    //playerVars: { 'autoplay': 0, 'modestbranding': 1, 'rel': 0, 'showinfo': 0, 'iv_load_policy': 3, 'controls': 1, 'playsinline':1 },
    var configuration = {
        playerVars: {
            'playsinline':1,
            'showinfo': 0,
            'modestbranding': 1
        },
        events: {
            'onReady': onPlayerReady,
            'onStateChange': onPlayerStateChange
        }
    };

tag.src = "https://www.youtube.com/iframe_api";
var firstScriptTag = document.getElementsByTagName('script')[0];
firstScriptTag.parentNode.insertBefore(tag, firstScriptTag);

function setup(key, value) {
    configuration[key] = value;
}

function configurePlayer(key, value) {
    configuration.playerVars[key] = value;
}
// area for the code injection
setup('videoId', 'cDhlx60nTCU');
setup('startingTime', 0);
setup('autoPlay' , true);
setup('width', 320);
setup('height', 288);
configurePlayer('controls', true);


var player;
function onYouTubeIframeAPIReady() {
    player = new YT.Player('player', configuration);
}

function onPlayerReady(event) {
    if (configuration['autoPlay']) {
        if (configuration['startingTime']) {
            player.playVideoAt(configuration['startingTime']);
        } else {
            event.target.playVideo();
        }
    }
}

function onPlayerStateChange(event) {
    if (event.data == YT.PlayerState.PLAYING) {
        // Do something...
    }
}

function stopVideo() {
    player.stopVideo();
    return "OK";
}
</script>

I am loading the webview page with this

-(void)viewDidAppear:(BOOL)animated
{
    [self.webview loadHTMLString:html baseURL:[NSURL URLWithString:@"html"]];
}

after the webview delegate calls webViewDidFinishLoad

I tried calling methods on the player with this syntax

-(void)pause
{
    [self.webview stringByEvaluatingJavaScriptFromString:@"player.pauseVideo();"];
}

Are there possibly any flags that are interfering with the java script evaluation?

Answer 1

Change this line:

[webView loadHTMLString:embedHTML baseURL:[NSURL URLWithString:@"html"]];

to this:

[webView loadHTMLString:embedHTML baseURL:[NSURL URLWithString:@"about:blank"]];

I've noticed that stringByEvaluatingJavaScriptFromString won't work when you don't use a valid URL (you'll see that this also happens when you use NULL as the value. I just tested your code with both versions, and found that the version with about:blank will correctly evaluate JavaScript, whereas the version with html as the NSURL value will not.