AngularJS Why I changed the value of the variable in the controller, DOM has not changed

' Use strict 'App.controller (function($scope) {    =null;         function () {        wx.chooseimage ({            sourcetype: [],                success:function(res) {                      =1}})        ;

< p ng-click= "chooseimage ()">{{aaaa}}</p>

After clicking on the page AAAA value will not change to 1

Because Wx.chooseimage this method is the API, not in the angular context, does not call the Apply method.

$apply method Usage Scenario: AngularJS external Controllers (DOM events, external callback functions such as jQuery UI space, and so on) must call $apply after the AngularJS function is called. In this case, you need to command AngularJS to refresh itself (model, view, etc.), $apply is used to do this thing.

before I saw my colleague write a $timeout (function () {}) is good, is also curious. Originally angular in the $timeout method has encapsulated the Apply method.

I mainly read these two articles:

Talk about angular about $watch, $apply and how $digest works

"AngularJS"----$apply and $watch

AngularJS Why I changed the value of the variable in the controller, DOM has not changed