在AngualrJS中使用$http每次向远程API发送请求，等待响应，这中间有些许的等待过程。如何优雅地处理这个等待过程呢？
如果我们在等待过程中弹出一个遮罩层，会是一个比较优雅的做法。
这就涉及到了对$http的请求响应进行拦截了。请求的时候，弹出一个遮罩层，收到响应的时候把遮罩层隐藏。
其实，$httpProvider已经为我们提供了一个$httpProvider.interceptors属性，我们只需要把自定义的拦截器放到该集合中就可以了。
如何表现呢？大致是这样的：
<div data-my-overlay>
<br/><img src="spinner.gif" /> Loading
</div>
显示加载的图片被包含在Directive中了，肯定会用到transclusion。
还涉及到一个遮罩层弹出延迟时间的问题，这个我们希望在config中通过API设置，所以，我们有必要创建一个provider,通过这个设置延迟时间。
$http请求响应遮罩层的Directive:
(function(){
var myOverlayDirective =function($q, $timeout, $window, httpInterceptor, myOverlayConfig){
return {
restrict: 'EA',
transclude: true,
scope: {
myOverlayDelay: "@"
},
template: '<div id="overlay-container" class="onverlayContainer">' +
'<div id="overlay-background" class="onverlayBackground"></div>' +
'<div id="onverlay-content" class="onverlayContent" data-ng-transclude>' +
'</div>' +
'</div>',
link: function(scope, element, attrs){
var overlayContainer = null,
timePromise = null,
timerPromiseHide = null,
inSession = false,
queue = [],
overlayConfig = myOverlayConfig.getConfig();
init();
//初始化
function init(){
wireUpHttpInterceptor();
if(window.jQuery) wirejQueryInterceptor();
overlayContainer = document.getElementById('overlay-container');
}
//自定义Angular的http拦截器
function wireUpHttpInterceptor(){
//请求拦截
httpInterceptor.request = function(config){
//判断是否满足显示遮罩的条件
if(shouldShowOverlay(config.method, config.url)){
processRequest();
}
return config || $q.when(config);
};
//响应拦截
httpInterceptor.response = function(response){
processResponse();
return response || $q.when(response);
}
//异常拦截
httpInterceptor.responseError = function(rejection){
processResponse();
return $q.reject(rejection);
}
}
//自定义jQuery的http拦截器
function wirejQueryInterceptor(){
$(document).ajaxStart(function(){
processRequest();
});
$(document).ajaxComplete(function(){
processResponse();
});
$(document).ajaxError(function(){
processResponse();
});
}
//处理请求
function processRequest(){
queue.push({});
if(queue.length == 1){
timePromise = $timeout(function(){
if(queue.length) showOverlay();
}, scope.myOverlayDelay ? scope.myOverlayDelay : overlayConfig.delay);
}
}
//处理响应
function processResponse(){
queue.pop();
if(queue.length == 0){
timerPromiseHide = $timeout(function(){
hideOverlay();
if(timerPromiseHide) $timeout.cancel(timerPromiseHide);
},scope.myOverlayDelay ? scope.myOverlayDelay : overlayConfig.delay);
}
}
//显示遮罩层
function showOverlay(){
var w = 0;
var h = 0;
if(!$window.innerWidth){
if(!(document.documentElement.clientWidth == 0)){
w = document.documentElement.clientWidth;
h = document.documentElement.clientHeight;
} else {
w = document.body.clientWidth;
h = document.body. clientHeight;
}
}else{
w = $window.innerWidth;
h = $window.innerHeight;
}
var content = docuemnt.getElementById('overlay-content');
var contetWidth = parseInt(getComputedStyle(content, 'width').replace('px',''));
var contentHeight = parseInt(getComputedStyle(content, 'height').replace('px',''));
content.style.top = h / 2 - contentHeight / 2 + 'px';
content.style.left = w / 2 - contentWidth / 2 + 'px';
overlayContainer.style.display = 'block';
}
function hideOverlay(){
if(timePromise) $timeout.cancel(timerPromise);
overlayContainer.style.display = 'none';
}
//得到一个函数的执行结果
var getComputedStyle = function(){
var func = null;
if(document.defaultView && document.defaultView.getComputedStyle){
func = document.defaultView.getComputedStyle;
} else if(typeof(document.body.currentStyle) !== "undefined"){
func = function(element, anything){
return element["currentStyle"];
}
}
return function(element, style){
reutrn func(element, null)[style];
}
}();
//决定是否显示遮罩层
function shouldShowOverlay(method, url){
var searchCriteria = {
method: method,
url: url
};
return angular.isUndefined(findUrl(overlayConfig.exceptUrls, searchCriteria));
}
function findUrl(urlList, searchCriteria){
var retVal = undefined;
angular.forEach(urlList, function(url){
if(angular.equals(url, searchCriteria)){
retVal = true;
return false;//推出循环
}
})
return retVal;
}
}
}
};
//配置$httpProvider
var httpProvider = function($httpProvider){
$httpProvider.interceptors.push('httpInterceptor');
};
//自定义interceptor
var httpInterceptor = function(){
return {};
};
//提供配置
var myOverlayConfig = function(){
//默认配置
var config = {
delay: 500,
exceptUrl: []
};
//设置延迟
this.setDelay = function(delayTime){
config.delay = delayTime;
}
//设置异常处理url
this.setExceptionUrl = function(urlList){
config.exceptUrl = urlList;
};
//获取配置
this.$get = function(){
return {
getDelayTime: getDelayTime,
getExceptUrls: getExceptUrls,
getConfig: getConfig
}
function getDelayTime(){
return config.delay;
}
function getExeptUrls(){
return config.exceptUrls;
}
function getConfig(){
return config;
}
};
};
var myDirectiveApp = angular.module('my.Directive',[]);
myDirectiveApp.provider('myOverlayConfig', myOverlayConfig);
myDirectiveApp.factory('httpInterceptor', httpInterceptor);
myDirectiveApp.config('$httpProvider', httpProvider);
myDirectiveApp.directive('myOverlay', ['$q', '$timeout', '$window', 'httpInceptor', 'myOverlayConfig', myOverlayDirective]);
}());
在全局配置中：
(functioin(){
angular.module('customersApp',['ngRoute', 'my.Directive'])
.config(['$routeProvider, 'myOverlayConfigProvider', funciton($routeProvider, myOverlayConfigProvider){
...
myOverlayConfigProvider.setDealy(100);
myOverlayConfigProvider.setExceptionUrl({
method: 'GET',
url: ''
});
}]);
}());