在Javascript中测试硬件支持，以获取iPhone 3GS的设备定位事件 [英] Testing hardware support in Javascript for device orientation events of the iPhone 3GS

问题描述

我正在尝试在Javascript中使用HTML5 deviceOrientation事件来在用户围绕他旋转iPhone时旋转图像。

I'm trying to use HTML5 deviceOrientation events in Javascript to rotate an image when the user rotate his iPhone around him.

我使用此代码来检测何时陀螺仪正在移动：

I use this code to detect when the gyroscope is moving :

window.addEventListener('deviceorientation', function (e) {
    alpha = e.alpha;
    beta = e.beta;
    gamma = e.gamma;            
}, true);

它在iPhone 4+和iPad 2上运行良好，但3GS上没有陀螺仪（和老款iPhone）。这就是我正在测试deviceOrientationSupport的原因：

It really works well on iPhone 4+ and iPad 2, but there's no gyroscope on the 3GS (and older iPhones). That's why I'm testing the deviceOrientationSupport like this :

if(window.DeviceOrientationEvent){ // gyroscope support
    alert('DeviceOrientationEvent support OK');
} else {
    alert('DeviceOrientationEvent support KO');
}

我在很多网站或论坛上看过这个代码，但我的问题是在IOS 5.0.1下使用我的iPhone 3GS，这个测试表明我：deviceOrientationSupport OK！

I've seen this code on many websites or forums, but my problem is that with my iPhone 3GS under IOS 5.0.1, this test indicates me : deviceOrientationSupport OK !

我认为只有Safari能够处理这些事件时才进行此测试： （

I think that this test check only if Safari is able to handle these events :(

所以我的问题是，是否可以添加测试以了解硬件是否可以触发定位事件？

谢谢！

推荐答案

遇到与上述相同的问题后，我也遇到了问题旧的iPad / iPhone甚至没有在addEventListener上调用该函数。

After having the same issue as above I also had problems with the older iPad/iPhones not even calling the function on addEventListener.

所以我发现以下对我来说效果更好，并且消除了任何不支持的设备通过的可能性（这是一个加载屏幕所以它确实需要一个间隔才能完成它的完整测试。所以不是每个人都有。）

So I found that the following worked a lot better for me and eliminated any chance of an unsupported device getting through (this was sat with a load screen so it did require an interval before completing its full test. So not for everyone).

var _i = null;
var _e = null;
var _c = 0;

var updateDegree = function(e){
    _e = e;
}

window.addEventListener('deviceorientation', updateDegree, false);

//  Check event support
_i = window.setInterval(function(){
    if(_e !== null && _e.alpha !== null){
        // Clear interval
        clearInterval(_i);
        // > Run app
    }else{
        _c++;
        if(_c === 10){
            // Clear interval
            clearInterval(_i);
            // > Redirect
        }
    }
}, 200);

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