使用OKHttp将响应从doInBackground传递给onPostExecute异步方法

Question

我正在使用OKHttp 3.4.2，我想使用enqueue实现OKHttp异步网络调用。但我必须将数据返回到onPostExecute方法，我在doInBackground中将我的实例变量flower和容器声明为final并尝试但我的应用程序在进行网络调用时崩溃。

同步工作方式

package com.example.async;

import android.app.Activity;
import android.content.Context;
import android.graphics.Bitmap;
import android.graphics.BitmapFactory;
import android.os.AsyncTask;
import android.util.LruCache;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.ArrayAdapter;
import android.widget.ImageView;
import android.widget.TextView;

import com.example.async.model.Flower;

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

import okhttp3.OkHttpClient;
import okhttp3.Request;
import okhttp3.Response;

public class FlowerAdapter extends ArrayAdapter<Flower> {

    private Context context;
    private List<Flower> flowerList;
    private LruCache<Integer, Bitmap> imageCache;
    private OkHttpClient client = new OkHttpClient();

    public FlowerAdapter(Context context, int resource, List<Flower> objects) {
        super(context, resource, objects);
        this.context = context;
        this.flowerList = objects;
        final int maxMemory = (int) (Runtime.getRuntime().maxMemory() / 1024);
        final int cacheSize = maxMemory / 8;
        imageCache = new LruCache<>(cacheSize);
    }

    @Override
    public View getView(int position, View convertView, ViewGroup parent) {

        LayoutInflater inflater =
                (LayoutInflater) context.getSystemService(Activity.LAYOUT_INFLATER_SERVICE);
        View view = inflater.inflate(R.layout.item_flower, parent, false);
        Flower flower = flowerList.get(position);
        TextView tv = (TextView) view.findViewById(R.id.textView1);
        tv.setText(flower.getName());
        Bitmap bitmap = imageCache.get(flower.getProductId());
        if(bitmap != null) {
            ImageView image = (ImageView) view.findViewById(R.id.imageView1);
            image.setImageBitmap(flower.getBitmap());
        } else {
            FlowerAndView container = new FlowerAndView();
            container.flower = flower;
            container.view = view;
            ImageLoader loader = new ImageLoader();
            loader.execute(container);
        }
        return view;
    }

    class FlowerAndView {
        public Flower flower;
        public View view;
        public Bitmap bitmap;
    }

    private class ImageLoader extends AsyncTask<FlowerAndView, Void, FlowerAndView> {

        @Override
        protected FlowerAndView doInBackground(FlowerAndView... params) {
            FlowerAndView container = params[0];
            Flower flower = container.flower;
            try{
                String imageUrl = MainActivity.BASE_URL + flower.getPhoto();
                Request request = new Request.Builder().url(imageUrl).build();
                // below response need to be asynchronous using enqueue method
                Response response = client.newCall(request).execute();
                InputStream inputStream = response.body().byteStream();
                Bitmap bitmap = BitmapFactory.decodeStream(inputStream);
                flower.setBitmap(bitmap);
                inputStream.close();
                container.bitmap = bitmap;
                return container;
            } catch (Exception e) {
                e.printStackTrace();
            }
            return null;
        }

        @Override
        protected void onPostExecute(FlowerAndView result) {
            ImageView image = (ImageView) result.view.findViewById(R.id.imageView1);
            image.setImageBitmap(result.bitmap);
            imageCache.put(result.flower.getProductId(), result.bitmap);
        }
    }


}

异步方式无法正常工作 用异步入队方法替换了okhttp execute方法，并在doInBackground中将声明的变量替换为final

package com.example.async;

import android.app.Activity;
import android.content.Context;
import android.graphics.Bitmap;
import android.graphics.BitmapFactory;
import android.os.AsyncTask;
import android.util.LruCache;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.ArrayAdapter;
import android.widget.ImageView;
import android.widget.TextView;

import com.example.async.model.Flower;

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

import okhttp3.OkHttpClient;
import okhttp3.Request;
import okhttp3.Response;

public class FlowerAdapter extends ArrayAdapter<Flower> {

    private Context context;
    private List<Flower> flowerList;
    private LruCache<Integer, Bitmap> imageCache;
    private OkHttpClient client = new OkHttpClient();

    public FlowerAdapter(Context context, int resource, List<Flower> objects) {
        super(context, resource, objects);
        this.context = context;
        this.flowerList = objects;
        final int maxMemory = (int) (Runtime.getRuntime().maxMemory() / 1024);
        final int cacheSize = maxMemory / 8;
        imageCache = new LruCache<>(cacheSize);
    }

    @Override
    public View getView(int position, View convertView, ViewGroup parent) {

        LayoutInflater inflater =
                (LayoutInflater) context.getSystemService(Activity.LAYOUT_INFLATER_SERVICE);
        View view = inflater.inflate(R.layout.item_flower, parent, false);
        Flower flower = flowerList.get(position);
        TextView tv = (TextView) view.findViewById(R.id.textView1);
        tv.setText(flower.getName());
        Bitmap bitmap = imageCache.get(flower.getProductId());
        if(bitmap != null) {
            ImageView image = (ImageView) view.findViewById(R.id.imageView1);
            image.setImageBitmap(flower.getBitmap());
        } else {
            FlowerAndView container = new FlowerAndView();
            container.flower = flower;
            container.view = view;
            ImageLoader loader = new ImageLoader();
            loader.execute(container);
        }
        return view;
    }

    class FlowerAndView {
        public Flower flower;
        public View view;
        public Bitmap bitmap;
    }

    private class ImageLoader extends AsyncTask<FlowerAndView, Void, FlowerAndView> {

         @Override
        protected FlowerAndView doInBackground(FlowerAndView... params) {
            final FlowerAndView container = params[0];
            final Flower flower = container.flower;
            try{
                String imageUrl = MainActivity.PHOTOS_BASE_URL + flower.getPhoto();
                Request request = new Request.Builder().url(imageUrl).build();
                //Response response = client.newCall(request).execute();
                client.newCall(request).enqueue(new Callback() {
                    @Override
                    public void onFailure(Call call, IOException e) {
                        e.printStackTrace();
                    }

                    @Override
                    public void onResponse(Call call, Response response) throws IOException {
                        if(!response.isSuccessful()) {
                            throw new IOException("Unexpected code " + response);
                        } else {
                            InputStream inputStream = response.body().byteStream();
                            Bitmap bitmap = BitmapFactory.decodeStream(inputStream);
                            flower.setBitmap(bitmap);
                            inputStream.close();
                            // save the bitmap in the container
                            container.bitmap = bitmap;
                        }
                    }
                });
                return container;
            } catch (Exception e) {
                e.printStackTrace();
            }
            return null;
        }

        @Override
        protected void onPostExecute(FlowerAndView result) {
            ImageView image = (ImageView) result.view.findViewById(R.id.imageView1);
            image.setImageBitmap(result.bitmap);
            imageCache.put(result.flower.getProductId(), result.bitmap);
        }
    }


}