Q:

Load image after activity start

I'm a newbee in android development and i want to load image after i get image URL from my first Asynctask. I saw one tutorial for loading image when we click on  button , and i would like to replace images after activity start. 
this is my main activity
package kori.dev.kori.activity;

import android.app.ProgressDialog;
import android.content.res.Resources;
import android.graphics.Bitmap;
import android.graphics.BitmapFactory;
import android.graphics.Rect;
import android.os.AsyncTask;
import android.os.Bundle;
import android.support.design.widget.AppBarLayout;
import android.support.design.widget.CollapsingToolbarLayout;
import android.support.v7.app.AppCompatActivity;
import android.support.v7.widget.DefaultItemAnimator;
import android.support.v7.widget.GridLayoutManager;
import android.support.v7.widget.RecyclerView;

import android.support.v7.widget.Toolbar;
import android.util.Log;
import android.util.TypedValue;
import android.view.View;
import android.widget.Button;
import android.widget.ImageView;
import android.widget.TextView;
import android.widget.Toast;

import com.bumptech.glide.Glide;

import org.springframework.http.converter.json.MappingJackson2HttpMessageConverter;
import org.springframework.web.client.RestTemplate;

import java.io.InputStream;
import java.util.ArrayList;
import java.util.List;

import kori.dev.kori.R;
import kori.dev.kori.adapters.CardAdapter;
import kori.dev.kori.model.Card;
import kori.dev.kori.model.Carte;

/**
 * Created by Thefractus Bombatus on 13/12/2016.
 */

public class MainCard extends AppCompatActivity implements LoadImageTask.Listener{

    private RecyclerView recyclerView;
    private CardAdapter adapter;
    private List<Card> cardList;
    public static Carte[] carte;
    private ProgressDialog progressDialog ;
    private ImageView mImageView;

 @Override
    protected void onCreate(Bundle savedInstanceState) {

        loadtask();
        super.onCreate(savedInstanceState);

        setContentView(R.layout.main_card);
        Toolbar toolbar = (Toolbar) findViewById(R.id.toolbar);
        setSupportActionBar(toolbar);
        getSupportActionBar().setDisplayHomeAsUpEnabled(true);
        TextView sub_title = (TextView) findViewById(R.id.sub_title);
        String title_sub = getIntent().getStringExtra("name_cat") ;
        sub_title.setText(title_sub);

         mImageView = (ImageView) findViewById(R.id.test_img);
        Button btn_test = (Button) findViewById(R.id.btn_test);

        btn_test.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                Log.d("ooo",carte[0].getPhoto() );
                new LoadImageTask(MainCard.this).execute(carte[0].getPhoto());
            }
        });

    }

    public void onImageLoaded(Bitmap bitmap) {

        mImageView.setImageBitmap(bitmap);
    }

    public void onError() {
        Toast.makeText(this, "Error Loading Image !", Toast.LENGTH_SHORT).show();
    }

    /**
     * Initializing collapsing toolbar
     * Will show and hide the toolbar title on scroll
     */
    private void initCollapsingToolbar() {
        final CollapsingToolbarLayout collapsingToolbar =
                (CollapsingToolbarLayout) findViewById(R.id.collapsing_toolbar);
        collapsingToolbar.setTitle("dride");

        AppBarLayout appBarLayout = (AppBarLayout) findViewById(R.id.appbar);
        appBarLayout.setExpanded(true);

        // hiding & showing the title when toolbar expanded & collapsed
        appBarLayout.addOnOffsetChangedListener(new AppBarLayout.OnOffsetChangedListener() {
            boolean isShow = false;
            int scrollRange = -1;

            @Override
            public void onOffsetChanged(AppBarLayout appBarLayout, int verticalOffset) {
                if (scrollRange == -1) {
                    scrollRange = appBarLayout.getTotalScrollRange();
                }
                if (scrollRange + verticalOffset == 0) {
                    collapsingToolbar.setTitle(getString(R.string.app_name));
                    isShow = true;
                } else if (isShow) {
                    collapsingToolbar.setTitle(" ");
                    isShow = false;
                }
            }
        });
    }

    private void loadscren(Carte[] cartes){

        initCollapsingToolbar();

        recyclerView = (RecyclerView) findViewById(R.id.recycler_view);

        cardList = new ArrayList<>();
        adapter = new CardAdapter(this, cardList);

        RecyclerView.LayoutManager mLayoutManager = new GridLayoutManager(this, 2);
        recyclerView.setLayoutManager(mLayoutManager);
        recyclerView.addItemDecoration(new GridSpacingItemDecoration(2, dpToPx(10), true));
        recyclerView.setItemAnimator(new DefaultItemAnimator());
        recyclerView.setAdapter(adapter);
        try {
            Glide.with(this).load(R.drawable.carte_sport).into((ImageView) findViewById(R.id.backdrop));
        } catch (Exception e) {
            e.printStackTrace();
        }

        loadalbum(cartes);
    }

    private void loadalbum(Carte[] cartes){

         int[] covers = new int[]{

                R.drawable.album1,
                R.drawable.album2,
                R.drawable.album3,
                R.drawable.album4,
                R.drawable.album5,
                R.drawable.album6,
                R.drawable.album7,
                R.drawable.album8,
                R.drawable.album9,
                R.drawable.album10,
                R.drawable.album11};

        int i = 0;
        for(Carte c :cartes){
            Card a = new Card(c.getCarte(), c.getVendeur(), covers[i]);
            cardList.add(a);
            i++;
        }

        adapter.notifyDataSetChanged();
    }

    /**
     * Adding few albums for testing
     */
    private void loadtask() {

        new android.os.Handler().postDelayed(
                new Runnable() {
                    public void run() {
                        // On complete call either onLoginSuccess or onLoginFailed
                        new HttpRequestTaskCarte().execute();;

                    }
                }, 3000);

    }

    /**
     * RecyclerView item decoration - give equal margin around grid item
     */
    public class GridSpacingItemDecoration extends RecyclerView.ItemDecoration {

        private int spanCount;
        private int spacing;
        private boolean includeEdge;

        public GridSpacingItemDecoration(int spanCount, int spacing, boolean includeEdge) {
            this.spanCount = spanCount;
            this.spacing = spacing;
            this.includeEdge = includeEdge;
        }

        @Override
        public void getItemOffsets(Rect outRect, View view, RecyclerView parent, RecyclerView.State state) {
            int position = parent.getChildAdapterPosition(view); // item position
            int column = position % spanCount; // item column

            if (includeEdge) {
                outRect.left = spacing - column * spacing / spanCount; // spacing - column * ((1f / spanCount) * spacing)
                outRect.right = (column + 1) * spacing / spanCount; // (column + 1) * ((1f / spanCount) * spacing)

                if (position < spanCount) { // top edge
                    outRect.top = spacing;
                }
                outRect.bottom = spacing; // item bottom
            } else {
                outRect.left = column * spacing / spanCount; // column * ((1f / spanCount) * spacing)
                outRect.right = spacing - (column + 1) * spacing / spanCount; // spacing - (column + 1) * ((1f /    spanCount) * spacing)
                if (position >= spanCount) {
                    outRect.top = spacing; // item top
                }
            }
        }
    }

    /**
     * Converting dp to pixel
     */
    private int dpToPx(int dp) {
        Resources r = getResources();
        return Math.round(TypedValue.applyDimension(TypedValue.COMPLEX_UNIT_DIP, dp, r.getDisplayMetrics()));
    }

    private class DownloadImageTask extends AsyncTask<String, Void, Bitmap> {
        ImageView bmImage;

        public DownloadImageTask(ImageView bmImage) {
            this.bmImage = bmImage;
        }

        protected Bitmap doInBackground(String... urls) {
            String urldisplay = urls[0];
            Bitmap mIcon11 = null;
            try {
                InputStream in = new java.net.URL(urldisplay).openStream();
                mIcon11 = BitmapFactory.decodeStream(in);
            } catch (Exception e) {
                Log.e("Error", e.getMessage());
                e.printStackTrace();
            }
            return mIcon11;
        }

        protected void onPostExecute(Bitmap result) {
            bmImage.setImageBitmap(result);
        }
    }

    public  class HttpRequestTaskCarte extends AsyncTask<Void,Void,Carte[]> {

        @Override
        protected Carte[] doInBackground(Void... params) {
            try {
                final String url = "http://ayelive.xyz/website/testRest/RestController.php?carte=shopping";
                RestTemplate restTemplate = new RestTemplate();
                restTemplate.getMessageConverters().add(new MappingJackson2HttpMessageConverter());
                Carte[] greeting = restTemplate.getForObject(url, Carte[].class);
                return greeting;
            } catch (Exception e) {

                Toast.makeText(MainCard.this, "Error Loading  !", Toast.LENGTH_SHORT).show();
                //Log.e("MainActivity", e.getMessage(), e);
            }

            return null;
        }

        protected void onPreExecute(){

              progressDialog = new ProgressDialog(MainCard.this,
                    R.style.AppTheme_Dark_Dialog);
            progressDialog.setIndeterminate(true);
            progressDialog.setMessage("chargement des elements...");
            progressDialog.show();

        }

        @Override
        protected void onPostExecute(Carte[] greeting) {

            Carte[] greet =greeting;

            carte = greet ;

            Log.d("carte",greet[0].getPhoto());
            Log.d("carte",greet[1].getCarte());

            loadscren(greet);
            progressDialog.dismiss();

        }

    }
}

image task load
package kori.dev.kori.activity;

/**
 * Created by THEOPHRACTUS on 23/12/2016.
 */

import android.graphics.Bitmap;
import android.graphics.BitmapFactory;
import android.os.AsyncTask;
import android.util.Log;

import java.io.IOException;
import java.io.InputStream;
import java.net.URL;

public class LoadImageTask extends AsyncTask<String, Void, Bitmap> {

    public LoadImageTask(Listener listener) {

        mListener = listener;
    }

    public interface Listener{

        void onImageLoaded(Bitmap bitmap);
        void onError();
    }

    private Listener mListener;
    @Override
    protected Bitmap doInBackground(String... args) {

        try {
//Log.d("cat",args[0]);
            return BitmapFactory.decodeStream((InputStream)new URL(args[0]).getContent());

        } catch (IOException e) {
            e.printStackTrace();
        }
        return null;
    }

    @Override
    protected void onPostExecute(Bitmap bitmap) {

        if (bitmap != null) {

            mListener.onImageLoaded(bitmap);

        } else {

            mListener.onError();
        }
    }
}

and adapter
package kori.dev.kori.adapters;

import android.content.Context;
import android.content.Intent;
import android.support.v7.widget.PopupMenu;
import android.support.v7.widget.RecyclerView;
import android.view.LayoutInflater;
import android.view.MenuInflater;
import android.view.MenuItem;
import android.view.View;
import android.view.ViewGroup;
import android.widget.ImageView;
import android.widget.TextView;
import android.widget.Toast;

import com.bumptech.glide.Glide;

import java.util.List;

import kori.dev.kori.R;
import kori.dev.kori.activity.DetailActivity;
import kori.dev.kori.model.Card;

/**
 * Created by Thefractus Bombatus on 13/12/2016.
 */

public class CardAdapter extends RecyclerView.Adapter<CardAdapter.MyViewHolder> {

    private Context mContext;
    private List<Card> cardList;

    public class MyViewHolder extends RecyclerView.ViewHolder {
        public TextView title, count;
        public ImageView thumbnail, overflow;

        public MyViewHolder(View view) {
            super(view);
            title = (TextView) view.findViewById(R.id.title);
            count = (TextView) view.findViewById(R.id.count);
            thumbnail = (ImageView) view.findViewById(R.id.thumbnail);
            overflow = (ImageView) view.findViewById(R.id.overflow);
        }
    }

    public CardAdapter(Context mContext, List<Card> cardList) {
        this.mContext = mContext;
        this.cardList = cardList;
    }

    @Override
    public MyViewHolder onCreateViewHolder(ViewGroup parent, int viewType) {
        View itemView = LayoutInflater.from(parent.getContext())
                .inflate(R.layout.categorie_card, parent, false);

        return new MyViewHolder(itemView);
    }

    @Override
    public void onBindViewHolder(final MyViewHolder holder, int position) {
        Card card = cardList.get(position);
        holder.title.setText(card.getCatName());
        holder.count.setText(card.getEntrName() );

        // loading album cover using Glide library
        Glide.with(mContext).load(card.getThumbnail()).into(holder.thumbnail);

        holder.overflow.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                showPopupMenu(holder.overflow);
            }
        });
    }

    /**
     * Showing popup menu when tapping on 3 dots
     */
    private void showPopupMenu(View view) {
        // inflate menu
        PopupMenu popup = new PopupMenu(mContext, view);
        MenuInflater inflater = popup.getMenuInflater();
        inflater.inflate(R.menu.menu_categorie, popup.getMenu());
        popup.setOnMenuItemClickListener(new MyMenuItemClickListener());
        popup.show();
    }

    /**
     * Click listener for popup menu items
     */
    class MyMenuItemClickListener implements PopupMenu.OnMenuItemClickListener {

        public MyMenuItemClickListener() {
        }

        @Override
        public boolean onMenuItemClick(MenuItem menuItem) {
            switch (menuItem.getItemId()) {
                case R.id.action_add_favourite:
                    Toast.makeText(mContext, "Ajouter au panier", Toast.LENGTH_SHORT).show();
                    return true;
                case R.id.action_play_next:
                    Intent intent = new Intent(mContext, DetailActivity.class);
                    mContext.startActivity(intent);

                    return true;
                default:
            }
            return false;
        }
    }

    @Override
    public int getItemCount() {
        return cardList.size();
    }
}

PS : sorry for my english :) 

A:

You can use Glide Library to load your image and maintain the cache for that image.
for this you can visit for Glide SDK & Doc for implementation : 
Glide
Best Example

