Ionic http.get error

hi ,

I got an error at http.get request ionic typescript that in below.

please help me .

how can I fix this issue.

import {RequestOptions ,Http} from ‘@angular/http’;

import ‘rxjs/add/operator/map’;

import ‘rxjs/add/operator/timeout’;

constructor(public navCtrl: NavController,

private _http: Http,

) {

.map(res => res.json()).subscribe(data => {
let response = data;

                // work with your response data here!

            err => {                      // communication error with server or timeout
                console.log('  encountered an error');


result :

TypeError: Cannot read property ‘get’ of undefined
at Object. (http://localhost:8100/build/main.js:2382:23)
at fire (http://localhost:8100/build/vendor.js:148633:30)
at Object.fireWith (http://localhost:8100/build/vendor.js:148743:7)
at [as resolve] (http://localhost:8100/build/vendor.js:148750:10)
at Object. (http://localhost:8100/build/vendor.js:119535:26)
at http://localhost:8100/build/vendor.js:148312:12

private _http: HttpClient,