使用改造库时，变量未反映分配的值：Android

Question

I am trying to get the photo of the day from bing using this url

http://www.bing.com/HPImageArchive.aspx?format=js&idx=0&n=1&mkt=en-US

I am having trouble saving the value of the url which i am getting through retrofit library. This is my code:

MainActivity.class

package com.gadgetsaint.downloadmanagerexample;
import android.Manifest;
import android.app.DownloadManager;
import android.support.v4.app.NotificationCompat;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.util.Log;
import android.view.View;
import android.widget.TextView;
import android.widget.Toast;
import org.greenrobot.eventbus.EventBus;
import org.greenrobot.eventbus.Subscribe;
import org.greenrobot.eventbus.ThreadMode;
import java.util.ArrayList;
import retrofit.Call;
import retrofit.Callback; 
import retrofit.Response;
import retrofit.Retrofit;

public class MainActivity extends AppCompatActivity {
private DownloadManager downloadManager;
private long refid;
private Uri Download_Uri;
String url,name;

ArrayList<Long> list = new ArrayList<>();
ApiInterface apiService;
TextView  btnSingle ;


@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);

    apiService=ApiClient.getClient().create(ApiInterface.class);

    downloadManager = (DownloadManager) getSystemService(Context.DOWNLOAD_SERVICE);
    getImageUrl();
    registerReceiver(onComplete,
            new IntentFilter(DownloadManager.ACTION_DOWNLOAD_COMPLETE));

    //url is showing null value even after assigning the data obtained through json .

    Download_Uri = Uri.parse(url);
    btnSingle = (TextView) findViewById(R.id.single);
    btnSingle.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View view) {


            list.clear();

            DownloadManager.Request request = new DownloadManager.Request(Download_Uri);
            request.setAllowedNetworkTypes(DownloadManager.Request.NETWORK_WIFI | DownloadManager.Request.NETWORK_MOBILE);
            request.setAllowedOverRoaming(false);
            request.setTitle("Abhishek Adhikari's file  Downloading " + name + ".png");
            request.setDescription("Downloading " + name + ".jpg");
            request.setVisibleInDownloadsUi(true);
            request.setDestinationInExternalPublicDir(Environment.getExternalStorageState(), "/adhikariabhishek/"  + "/" + name + ".jpg");


            refid = downloadManager.enqueue(request);


            Log.e("OUT", "" + refid);

            list.add(refid);

        }
    });




 //   TextView btnMultiple = (TextView) findViewById(R.id.multiple);


    if(!isStoragePermissionGranted())
    {


    }


   /* btnMultiple.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View view) {



            list.clear();

            for(int i = 0; i < 2; i++)
            {
                DownloadManager.Request request = new DownloadManager.Request(Download_Uri);
                request.setAllowedNetworkTypes(DownloadManager.Request.NETWORK_WIFI | DownloadManager.Request.NETWORK_MOBILE);
                request.setAllowedOverRoaming(false);
                request.setTitle("GadgetSaint Downloading " + "Sample_" + i + ".png");
                request.setDescription("Downloading " + "Sample_" + i + ".png");
                request.setVisibleInDownloadsUi(true);
                request.setDestinationInExternalPublicDir(Environment.DIRECTORY_DOWNLOADS, "/GadgetSaint/"  + "/" + "Sample_" + i + ".png");

                refid = downloadManager.enqueue(request);


                Log.e("OUTNM", "" + refid);

                list.add(refid);

            }


        }
    });

   */




}

public  boolean isStoragePermissionGranted() {
    if (Build.VERSION.SDK_INT >= 23) {
        if (checkSelfPermission(android.Manifest.permission.WRITE_EXTERNAL_STORAGE)
                == PackageManager.PERMISSION_GRANTED) {
            return true;
        } else {

            ActivityCompat.requestPermissions(this, new String[]{Manifest.permission.WRITE_EXTERNAL_STORAGE}, 1);
            return false;
        }
    }
    else { //permission is automatically granted on sdk<23 upon installation
        return true;
    }
}





BroadcastReceiver onComplete = new BroadcastReceiver() {

    public void onReceive(Context ctxt, Intent intent) {




        long referenceId = intent.getLongExtra(DownloadManager.EXTRA_DOWNLOAD_ID, -1);


        Log.e("IN", "" + referenceId);

        list.remove(referenceId);


        if (list.isEmpty())
        {


            Log.e("INSIDE", "" + referenceId);
            NotificationCompat.Builder mBuilder =
                    new NotificationCompat.Builder(MainActivity.this)
                            .setSmallIcon(R.mipmap.ic_launcher)
                            .setContentTitle("FileDownloader")
                            .setContentText("All Download completed");


            NotificationManager notificationManager = (NotificationManager) getSystemService(Context.NOTIFICATION_SERVICE);
            notificationManager.notify(455, mBuilder.build());


        }

    }
};




@Override
protected void onDestroy() {


    super.onDestroy();

   unregisterReceiver(onComplete);



}


@Override
public void onRequestPermissionsResult(int requestCode, String[] permissions, int[] grantResults) {
    super.onRequestPermissionsResult(requestCode, permissions, grantResults);
    if(grantResults[0]== PackageManager.PERMISSION_GRANTED){


        // permission granted

    }
}


private void getImageUrl() {
    Call<ImageModel> call = apiService.getImageDetails("js","0","1","en-US");
    call.enqueue(new Callback<ImageModel>() {
        @Override
        public void onResponse(Response<ImageModel> response, Retrofit retrofit) {
            try {
                Toast.makeText(MainActivity.this, "inside onresponse()", Toast.LENGTH_SHORT).show();

                url=response.body().getImages().get(0).getUrl().toString();

                //Here variable "url" is showing the data obtained through json
                // but not reflecting changes back in "oncreate" method when used with variable "Download_uri"
                Toast.makeText(MainActivity.this, url, Toast.LENGTH_SHORT).show();

            } catch (Exception e) {
                e.printStackTrace();
            }

        }

        @Override
        public void onFailure(Throwable t) {
            Toast.makeText(MainActivity.this, "Cannot download the image", Toast.LENGTH_SHORT).show();
        }
    });


}

@Subscribe(sticky = true,threadMode = ThreadMode.MAIN)
public void onMessage(String url){

    Toast.makeText(MainActivity.this, "inside Eventbus : "+url+" ", Toast.LENGTH_SHORT).show();

}

@Override
public void onStart() {
    super.onStart();
    EventBus.getDefault().register(this);
}

@Override
public void onStop() {
    EventBus.getDefault().unregister(this);
    super.onStop();
}

}

ApiInterface.class

 package com.gadgetsaint.downloadmanagerexample;


  import retrofit.Call;
  import retrofit.http.GET;
  import retrofit.http.Query;

   public interface ApiInterface {
       @GET("HPImageArchive.aspx")
       Call<ImageModel> getImageDetails(@Query("format") String format, 
       @Query("idx") String idx, @Query("n") String n, @Query("mkt") String 
      mkt);


   }

ApiClient.class

package com.gadgetsaint.downloadmanagerexample;


import retrofit.GsonConverterFactory;
import retrofit.Retrofit;


public class ApiClient {

public static final String BASE_URL = "http://www.bing.com/";
private static Retrofit retrofit = null;


public static Retrofit getClient() {
    if (retrofit==null) {

         retrofit = new Retrofit.Builder()
                .baseUrl(BASE_URL)
                .addConverterFactory(GsonConverterFactory.create())
                .build();
    }
    return retrofit;
  }
}

ImageModel.class

package com.gadgetsaint.downloadmanagerexample;

 import java.util.List;


 public class ImageModel {


/**
 * images : [{"startdate":"20170920","fullstartdate":"201709200700","enddate":"20170921","url":"/az/hprichbg/rb/RotenbergVineyards_EN-US11270850012_1920x1080.jpg","urlbase":"/az/hprichbg/rb/RotenbergVineyards_EN-US11270850012","copyright":"Vineyards at Rotenberg in Baden-Württemberg, Germany (© Werner Dieterich/plainpicture)","copyrightlink":"http://www.bing.com/search?q=rotenberg+stuttgart&form=hpcapt&filters=HpDate:%2220170920_0700%22","quiz":"/search?q=Bing+homepage+quiz&filters=WQOskey:%22HPQuiz_20170920_RotenbergVineyards%22&FORM=HPQUIZ","wp":true,"hsh":"0b5b6af9429a1f1e53c494ee482c73bc","drk":1,"top":1,"bot":1,"hs":[]}]
 * tooltips : {"loading":"Loading...","previous":"Previous image","next":"Next image","walle":"This image is not available to download as wallpaper.","walls":"Download this image. Use of this image is restricted to wallpaper only."}
 */

private TooltipsBean tooltips;
private List<ImagesBean> images;

public TooltipsBean getTooltips() {
    return tooltips;
}

public void setTooltips(TooltipsBean tooltips) {
    this.tooltips = tooltips;
}

public List<ImagesBean> getImages() {
    return images;
}

public void setImages(List<ImagesBean> images) {
    this.images = images;
}

public static class TooltipsBean {
    /**
     * loading : Loading...
     * previous : Previous image
     * next : Next image
     * walle : This image is not available to download as wallpaper.
     * walls : Download this image. Use of this image is restricted to wallpaper only.
     */

    private String loading;
    private String previous;
    private String next;
    private String walle;
    private String walls;


    public String getLoading() {
        return loading;
    }

    public void setLoading(String loading) {
        this.loading = loading;
    }

    public String getPrevious() {
        return previous;
    }

    public void setPrevious(String previous) {
        this.previous = previous;
    }

    public String getNext() {
        return next;
    }

    public void setNext(String next) {
        this.next = next;
    }

    public String getWalle() {
        return walle;
    }

    public void setWalle(String walle) {
        this.walle = walle;
    }

    public String getWalls() {
        return walls;
    }

    public void setWalls(String walls) {
        this.walls = walls;
    }
}

public static class ImagesBean {
    /**
     * startdate : 20170920
     * fullstartdate : 201709200700
     * enddate : 20170921
     * url : /az/hprichbg/rb/RotenbergVineyards_EN-US11270850012_1920x1080.jpg
     * urlbase : /az/hprichbg/rb/RotenbergVineyards_EN-US11270850012
     * copyright : Vineyards at Rotenberg in Baden-Württemberg, Germany (© Werner Dieterich/plainpicture)
     * copyrightlink : http://www.bing.com/search?q=rotenberg+stuttgart&form=hpcapt&filters=HpDate:%2220170920_0700%22
     * quiz : /search?q=Bing+homepage+quiz&filters=WQOskey:%22HPQuiz_20170920_RotenbergVineyards%22&FORM=HPQUIZ
     * wp : true
     * hsh : 0b5b6af9429a1f1e53c494ee482c73bc
     * drk : 1
     * top : 1
     * bot : 1
     * hs : []
     */

    private String startdate;
    private String fullstartdate;
    private String enddate;
    private String url;
    private String urlbase;
    private String copyright;
    private String copyrightlink;
    private String quiz;
    private boolean wp;
    private String hsh;
    private int drk;
    private int top;
    private int bot;
    private List<?> hs;

    public String getStartdate() {
        return startdate;
    }

    public void setStartdate(String startdate) {
        this.startdate = startdate;
    }

    public String getFullstartdate() {
        return fullstartdate;
    }

    public void setFullstartdate(String fullstartdate) {
        this.fullstartdate = fullstartdate;
    }

    public String getEnddate() {
        return enddate;
    }

    public void setEnddate(String enddate) {
        this.enddate = enddate;
    }

    public String getUrl() {
        return url;
    }

    public void setUrl(String url) {
        this.url = url;
    }

    public String getUrlbase() {
        return urlbase;
    }

    public void setUrlbase(String urlbase) {
        this.urlbase = urlbase;
    }

    public String getCopyright() {
        return copyright;
    }

    public void setCopyright(String copyright) {
        this.copyright = copyright;
    }

    public String getCopyrightlink() {
        return copyrightlink;
    }

    public void setCopyrightlink(String copyrightlink) {
        this.copyrightlink = copyrightlink;
    }

    public String getQuiz() {
        return quiz;
    }

    public void setQuiz(String quiz) {
        this.quiz = quiz;
    }

    public boolean isWp() {
        return wp;
    }

    public void setWp(boolean wp) {
        this.wp = wp;
    }

    public String getHsh() {
        return hsh;
    }

    public void setHsh(String hsh) {
        this.hsh = hsh;
    }

    public int getDrk() {
        return drk;
    }

    public void setDrk(int drk) {
        this.drk = drk;
    }

    public int getTop() {
        return top;
    }

    public void setTop(int top) {
        this.top = top;
    }

    public int getBot() {
        return bot;
    }

    public void setBot(int bot) {
        this.bot = bot;
    }

    public List<?> getHs() {
        return hs;
    }

    public void setHs(List<?> hs) {
        this.hs = hs;
    }
  }
}

activity_main.xml

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
     android:id="@+id/activity_main"
     android:layout_width="match_parent"
      android:layout_height="match_parent"
     android:paddingBottom="@dimen/activity_vertical_margin"
      android:paddingLeft="@dimen/activity_horizontal_margin"
      android:paddingRight="@dimen/activity_horizontal_margin"
      android:paddingTop="@dimen/activity_vertical_margin"
      tools:context="com.gadgetsaint.downloadmanagerexample.MainActivity">

      <TextView
            android:id="@+id/single"
            android:textSize="20sp"
            android:textStyle="bold"
            android:textColor="#fff"
            android:padding="20dp"
            android:background="#ce3910"
            android:layout_centerInParent="true"
             android:layout_width="wrap_content"
           android:layout_height="wrap_content"
            android:text="Download single file" />

         </RelativeLayout>

There is some trouble with the getImageUrl() method in MainActivity.class. Help me out guys!!

Answer 1

Replace your getImageUrl() like this

private String getImageUrl() {
String imurl;
Call<ImageModel> call = apiService.getImageDetails("js","0","1","en-US");
call.enqueue(new Callback<ImageModel>() {
    @Override
    public void onResponse(Response<ImageModel> response, Retrofit retrofit) {
        try {
            Toast.makeText(MainActivity.this, "inside onresponse()", Toast.LENGTH_SHORT).show();

            imurl=response.body().getImages().get(0).getUrl().toString();

            //Here variable "url" is showing the data obtained through json
            // but not reflecting changes back in "oncreate" method when used with variable "Download_uri"
            Toast.makeText(MainActivity.this, url, Toast.LENGTH_SHORT).show();

        } catch (Exception e) {
            e.printStackTrace();
        }

    }

    @Override
    public void onFailure(Throwable t) {
        Toast.makeText(MainActivity.this, "Cannot download the image", Toast.LENGTH_SHORT).show();
    }
});

return imurl;
}

and in oncreate change,

Download_Uri = Uri.parse(url);

by this

Download_Uri = Uri.parse(getImageUrl());