angular - 无法在纯cordova项目（无离子）角度8中读取null（单击）的属性'addEventListener'？

Question

在哪里添加点击事件监听器？我无法读取 null 的属性“addEventListener”。

export class BookConfirmComponent implements OnInit {
    constructor() {
        document.addEventListener("deviceready", onDeviceReady, false);
        function onDeviceReady() {
            console.log(""device is ready");    //this works
            document.getElementById("myBtn").addEventListener("click", function() {
            console.log("button is clicked");     //Cannot read property 'addEventListener' of null
            });
        }
    }
}

标签： angulartypescriptcordovaionic-framework