angular - Nativescript-ui Radlistview Null ポインタ エラー

Question

Radlistview がソース配列をレンダリングしない。どこが間違っているのかを理解するのを手伝ってください.これは私にヌルポインタ例外を与えています. 以下のセクションにコードを含めました。

srtdetails.component.html

<GridLayout tkExampleTitle tkToggleNavButton>
    <RadListView [items]="source">
        <template tkListItemTemplate let-item="item">
            <ScrollView>
                <StackLayout orientation="vertical">

                <GridLayout class="srtgrid border" rows="auto" columns=" *, *, *">

                <Label class="srtlabel " row="0" col="0" textWrap="true" [text]="item.requestid" ></Label>

                <Label class="srtlabel  " row="1" col="1" textWrap="true" [text]="item.requestedon" ></Label>

                <Label class="srtlabel " row="2" col="2" textWrap="true" [text]="item.requesttype" ></Label>

               </GridLayout>
            </StackLayout>              
          </ScrollView>               
        </template>
    </RadListView>
</GridLayout> 

strdetails.component.ts

import { Component, ElementRef, OnInit, ViewChild } from "@angular/core";
...

@Component({
  selector: "vp-srt-list",
  moduleId: module.id,
  templateUrl: './srtdetails.component.html',
  styleUrls: ["./srtdetails.component.css"],
  providers: [LoginService,NativeScriptUIListViewModule]
})

export class SrtListComponent implements OnInit{

public source: Array<any>;

constructor( private router: Router,
   private LoginService: LoginService,
   private routerExtensions: RouterExtensions){}
  ngOnInit(){
  this.source = this.LoadSrt();

}

 LoadSrt(): Array<any>{
    if (getConnectionType() === connectionType.none) {
        alert("Oops!! looks like your device is not connected to the internet ");
        return;
      }     
        this.LoginService.getAssociatedRequest()
            .subscribe((response: Array<any>) => {
          //let data = JSON.stringify(response)
          this.source = response; 
          console.log ("Response: " +this.source);
          return this.source;

        },          
        (error) => { console.log("Error happened", error.message)},
        () => { console.log("srt is completed")
        return this.source;
       }
    );         
  }

}

login.service.ts

  getAssociatedRequest(){
let headers = new Headers();
    return this.http.get(
     BackendService.requestUrl
  )
    .map((response) => { 

            return response.json(); 
              //  console.log("JSON BODY: ",JSON.stringify(body));
              }
                )

    .catch(this.handleErrors);
  }