原文出处：https://www.jianshu.com/p/243e4374e6c8 

为了方便管理，打算将GET和POST请求定义成一个公共方法来调用，另外调用的URL也可以定义到全局。
废话不多说，看代码~
1、首先定义一个service，我们命名为app.service.ts，放到app目录下即可。
里面还有一些其他有用的方法，大家可以参考，当然也可以自己添加啦~

import { LoadingController, AlertController, ToastController } from 'ionic-angular';
import { Injectable } from '@angular/core';
import {HttpClient, HttpParams} from "@angular/common/http";@Injectable()
export class AppGlobal {static BASE_URL='http://localhost:8088/ZTEMAS/';
}@Injectable()
export class AppService {constructor(public http: HttpClient, public loadingCtrl: LoadingController, private alertCtrl: AlertController, private toastCtrl: ToastController, ) { }GET(url: string, params: HttpParams, callback ?: (res: any, error: any) => void): void {this.http.get(url, {withCredentials: true,headers: {'content-type': 'application/x-www-form-urlencoded',},params: params}).subscribe(res => {callback && callback(res, null);}, error => {callback && callback(null, error);});}POST(url: string, params: HttpParams, callback ?: (res: any, error: any) => void): void {this.http.post(url, params,{withCredentials: true,headers: {'content-type': 'application/x-www-form-urlencoded;charset=UTF-8',}}).subscribe(res => {callback && callback(res, null);}, error => {callback && callback(null, error);});}alert(message, callback?) {if (callback) {let alert = this.alertCtrl.create({title: '提示',message: message,buttons: [{text: "确定",handler: data => {callback();}}]});alert.present();} else {let alert = this.alertCtrl.create({title: '提示',message: message,buttons: ["确定"]});alert.present();}}toast(message, callback?) {let toast = this.toastCtrl.create({message: message,duration: 2000,dismissOnPageChange: true,});toast.present();if (callback) {callback();}}setItem(key: string, obj: any) {try {var json = JSON.stringify(obj);window.localStorage[key] = json;}catch (e) {console.error("window.localStorage error:" + e);}}getItem(key: string, callback) {try {var json = window.localStorage[key];var obj = JSON.parse(json);callback(obj);}catch (e) {console.error("window.localStorage error:" + e);}}
}

2、在app.module.ts的prividers中加入此services

import { BrowserModule } from '@angular/platform-browser';
import { ErrorHandler, NgModule } from '@angular/core';
import { IonicApp, IonicErrorHandler, IonicModule } from 'ionic-angular';
import { SplashScreen } from '@ionic-native/splash-screen';
import { StatusBar } from '@ionic-native/status-bar';import { MyApp } from './app.component';
import {HttpClientModule} from "@angular/common/http";
import {IonicImageViewerModule} from "ionic-img-viewer";
import {AppService} from './app.service';@NgModule({declarations: [MyApp],imports: [BrowserModule,HttpClientModule,IonicImageViewerModule,IonicModule.forRoot(MyApp)],bootstrap: [IonicApp],entryComponents: [MyApp],providers: [StatusBar,SplashScreen,AppService,{provide: ErrorHandler, useClass: IonicErrorHandler}]
})
export class AppModule {}

3、在需要使用的页面的ts文件中加入引用，并直接调用即可。GET请求同理，请自行测试！

import {AppService} from "../../../app/app.service";
……constructor(public alertCtrl: AlertController,private http: HttpClient,private appService:AppService,public navCtrl: NavController, public navParams: NavParams) {}
……that.appService.POST(url,params,(res, error) => {if(res){let result=res['msg'];if(result=='Y'){this.appService.alert("流程已成功处理！");that.navCtrl.pop().then(() => {let msg="Y";this.navParams.get('callback')(msg);});}else{this.appService.alert("流程数据异常，请在电脑端处理！")}}if(error){console.log("PUT call in error");}})