Android 毕加索导致OutOfMemory错误

我使用毕加索将图片加载到网格中，但是每次我向下或向上滚动以加载图片时，它都会填满堆，以至于在滚动2-3次后，内存就会耗尽。我做错了什么

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Json;
using System.Threading.Tasks;
using Android.App;
using Android.Support.V4.App;
using Android.Content;
using Android.OS;
using Android.Graphics;
using Android.Graphics.Drawables;
using Android.Runtime;
using Android.Util;
using Android.Views;
using Android.Widget;
using *******.Adapters;
using *******.Models;
using Newtonsoft.Json;
using Com.Squareup.Picasso;
using System.Net;
using System.IO;

namespace *******.Fragments {
    public class Gallery : Android.Support.V4.App.Fragment {
        private GridView gridView;
        private ISharedPreferences pref;
        private SessionManager session;
        private DeviceModel deviceModel;
        public static Activity activity;
        private ProgressDialog progressDialog;
        private string cookie;
        private string sensorId;
        private List<string> photos;
        private const string URL_DATA = "http://*******/appapi/getdata";

        public override void OnCreate(Bundle bundle) {
            base.OnCreate(bundle);

            activity = Activity;
            session = new SessionManager();
            pref = Activity.GetSharedPreferences("UserSession", FileCreationMode.Private);
            cookie = pref.GetString("PHPSESSID", string.Empty);
            sensorId = Arguments.GetString("id");
            photos = new List<string>();
        }

        public async override void OnStart() {
            base.OnStart();

            //          progressDialog = ProgressDialog.Show(activity, String.Empty, GetString(Resource.String.loading_text));
            //          progressDialog.Window.ClearFlags(WindowManagerFlags.DimBehind);

                        await GetSensorData();
                        await GetPhotoUrls();

            gridView.Adapter = new ImageAdapter(activity, photos);

            gridView.ItemClick += (object sender, AdapterView.ItemClickEventArgs e) => {
                Toast.MakeText(Activity, e.Position.ToString(), ToastLength.Short).Show();
            };

            //          progressDialog.Hide();
        }

        public override View OnCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
            View view = inflater.Inflate(Resource.Layout.Gallery, container, false);

            gridView = view.FindViewById<GridView>(Resource.Id.gridview);

            return view;
        }

        public async Task GetSensorData() {
            var jsonFetcher = new JsonFetcher();
            JsonValue jsonGalerry = await jsonFetcher.FetchSensorDataAsync(URL_DATA, sensorId, "DESC", "20", cookie);
            deviceModel = new DeviceModel();
            deviceModel = JsonConvert.DeserializeObject<DeviceModel>(jsonGalerry);
        }

        public async Task GetPhotoUrls() {
            foreach (var data in deviceModel.SensorData) {
                string url = "*******" + data.StringData;
                Console.WriteLine(url);
//              Bitmap photoBitmap = await new ImageDownloader().GetImageBitmapFromUrlAsync(url, Activity, 300, 300);
//              Drawable photoDrawable = new BitmapDrawable(Resources, photoBitmap);
                photos.Add(url);
            }
        }
    }

    public class ImageAdapter : BaseAdapter {
        Context context;
        List<string> photos;

        public ImageAdapter(Context context, List<string> photos) {
            this.context = context;
            this.photos = photos;
        }

        public override int Count {
            get { return photos.Count; }
        }

        public override Java.Lang.Object GetItem(int position) {
            return null;
        }

        public override long GetItemId(int position) {
            return 0;
        }

        // create a new ImageView for each item referenced by the Adapter
        public override View GetView(int position, View convertView, ViewGroup parent) {
            ImageView imageView;
            if (convertView == null) {  // if it's not recycled, initialize some attributes
                imageView = new ImageView(context);
//              imageView.LayoutParameters = new GridView.LayoutParams (500, 500);
//              imageView.SetScaleType (ImageView.ScaleType.CenterCrop);
                //              imageView.SetPadding (8, 8, 8, 8);
            } else {
                imageView = (ImageView)convertView;
            }

            var imageDownloader = new ImageDownloader();
            imageDownloader.DownloadImage(photos[position], context, imageView);

            return imageView;
        }
    }
}

是的，这是正确的：如果你构建一个新的

毕加索

实例不止一个，它们中的每一个都将有一个单独的缓存，你的应用程序将很快耗尽内存

---

相反，我只构建一次实例（可能在

应用程序的
onCreate
中），然后使用
Picasso.setSingletonInstance
存储该实例供以后使用。从那时起，
Picasso.with
将始终返回您创建的实例。请注意，您必须在第一次调用
Picasso.with（）
之前执行此操作（否则，Picasso将在第一次调用时创建自己的实例，并且如果您稍后调用
SetSingleToInstance
，则会引发异常）。
看起来您每次都在调用Picasso builder，对吗？也许你应该重新构建一次为什么每次都要创建ImageDownloader？我还建议使用BaseAdapter的通用版本（BaseAdapter）。GetItemId始终返回0。一个更好的实现方法是返回位置本身。我还假设您的ConvertView始终是ImageView的新实例。这可以向我解释为什么你的内存不足。
    public void DownloadImage(string url, Context context, ImageView imageView) {
    var picasso = new Picasso.Builder(context).Downloader(new PhotoDownloader(context)).Build();
    picasso.Load(url).Into(imageView);
}

private class PhotoDownloader : UrlConnectionDownloader {
    private Context context;

    public PhotoDownloader(Context context) : base(context) {
        this.context = context;
    }

    protected override HttpURLConnection OpenConnection(Android.Net.Uri uri) {
        HttpURLConnection conn = base.OpenConnection(uri);
        ISharedPreferences pref = context.GetSharedPreferences("UserSession", FileCreationMode.Private);
        string cookie = pref.GetString("PHPSESSID", string.Empty);

        conn.SetRequestProperty("Cookie", "PHPSESSID=" + cookie);

        return conn;
    }
}