Question

如何判断 一个窗口是否为活动窗口

Answer 1

某些情况下，需判断当前ViewController是否正在显示

Answer 2

// 各种浏览器兼容
var hidden, state, visibilityChange;
if (typeof document.hidden !== "undefined") {
hidden = "hidden";
visibilityChange = "visibilitychange";
state = "visibilityState";
} else if (typeof document.mozHidden !== "undefined") {
hidden = "mozHidden";
visibilityChange = "mozvisibilitychange";
state = "mozVisibilityState";
} else if (typeof document.msHidden !== "undefined") {
hidden = "msHidden";
visibilityChange = "msvisibilitychange";
state = "msVisibilityState";
} else if (typeof document.webkitHidden !== "undefined") {
hidden = "webkitHidden";
visibilityChange = "webkitvisibilitychange";
state = "webkitVisibilityState";
}

// 添加监听器，在title里显示状态变化
document.addEventListener(visibilityChange, function() {
document.title = document[state];
}, false);

// 初始化
document.title = document[state];