/**
* loadding...
* ① import { LoadingController } from 'ionic-angular';
* ② constructor(public loadingCtrl: LoadingController) {}
* ③ presentLoading() {this.loadingCtrl.create({content: '',duration: 1000,dismissOnPageChange: true}).present();}
* ④ 调用 this.presentLoading()
*/
presentLoading() {
this.loadingCtrl.create({
content: '',
duration: 1000,
dismissOnPageChange: true
}).present();
}