提高大型ListView适配器的平滑滚动，有时会出现卡顿。

Question

我正在尝试找出是什么原因导致我的列表视图在滚动时有时会抖动，有时特别严重，尤其是当应用程序首次启动时。

我所有的条件都是必需的，除非有些东西我不知道（很可能）。我没有在单独的线程上运行某些任务，因为它们依赖于我从后端接收到的数据（我同时编写了前端和后端代码，因此后端建议也是受欢迎的）。产品处于测试阶段，但确实需要使其更加流畅。我正在压缩图片，它们有点长，但这不是问题，因为当我从设备上传图片时，我还包括图像的宽度和高度，并将其发送到后端。加载列表时，这些尺寸会返回。

我想知道的一件事是，计算/转换特定设备屏幕的尺寸是否会导致轻微的延迟。不确定该任务需要多少资源，但如果没有它（不知道尺寸），每行将从平面开始，然后扩展到实际图片大小，这将导致列表跳动，因此我也无法在后台运行该计算。

基本上，滚动并不糟糕，但我需要以某种方式改进它。

这是我的适配器：

public class VListAdapter extends BaseAdapter {

    ViewHolder viewHolder;
    private boolean isItFromProfile;

    /**
     * fields For number formating, ex. 1000
     * would return 1k in the format method
     */
    private static final NavigableMap<Long, String> suffixes = new TreeMap<>();

    static {
        suffixes.put(1_000L, "k");
        suffixes.put(1_000_000L, "M");
        suffixes.put(1_000_000_000L, "G");
        suffixes.put(1_000_000_000_000L, "T");
        suffixes.put(1_000_000_000_000_000L, "P");
        suffixes.put(1_000_000_000_000_000_000L, "E");
    }

    private Context mContext;
    private LayoutInflater mInflater;
    private ArrayList<Post> mDataSource;
    private static double lat;
    private static double lon;

    public VListAdapter(Context context, ArrayList<Post> items) {
        mContext = context;
        mDataSource = items;
        //mInflater = (LayoutInflater) mContext.getSystemService(Context.LAYOUT_INFLATER_SERVICE);
        isItFromProfile = false;
        mInflater = LayoutInflater.from(context);
    }

    public VListAdapter() {

    }

    public VListAdapter(Context baseContext, ArrayList<Post> posts, boolean b) {
        mContext = baseContext;
        mDataSource = posts;
        //mInflater = (LayoutInflater) mContext.getSystemService(Context.LAYOUT_INFLATER_SERVICE);
        isItFromProfile = b;
        mInflater = LayoutInflater.from(baseContext);
    }


    public void addElement(Post post) {
        mDataSource.add(0, post);
        this.notifyDataSetChanged();
    }

    @Override
    public int getCount() {
        return mDataSource.size();
    }

    @Override
    public Object getItem(int position) {
        return mDataSource.get(position);
    }

    @Override
    public long getItemId(int position) {
        return position;
    }


    @Override
    public View getView(final int position, View convertView, ViewGroup parent) {
        int limit = Math.min(position + 4, getCount());
        for (int i = position; i < limit; i++) {
            Glide.with(mContext).load(((Post) getItem(i)).getFilename().toString()).preload();
        }


//        StrictMode.setThreadPolicy(new StrictMode.ThreadPolicy.Builder().detectDiskReads()
//                .detectDiskWrites().detectNetwork()
//                .penaltyLog().build());



        View rowView = convertView;

        if (rowView == null) {
            viewHolder = new ViewHolder();
            rowView = mInflater.inflate(R.layout.mylist, parent, false);

            viewHolder.titleTextView = (TextView) rowView.findViewById(R.id.usernameinlist);
            viewHolder.timeago = (TextView) rowView.findViewById(R.id.timeago);
            //viewHolder.sharebutton = (ImageView) rowView.findViewById(R.id.sharebutton);
            viewHolder.likesTextView = (TextView) rowView.findViewById(R.id.likestext);
            viewHolder.viewcount = (TextView) rowView.findViewById(R.id.viewcount);
            viewHolder.distance = (TextView) rowView.findViewById(R.id.distance);
            viewHolder.footprints = (TextView) rowView.findViewById(R.id.footprintcount);
            viewHolder.postText = (TextView) rowView.findViewById(R.id.posttext);
            viewHolder.profilePic = (ImageView) rowView.findViewById(R.id.profilethumb);
            viewHolder.caption = (TextView) rowView.findViewById(R.id.captiontext);
            viewHolder.moremenu = (ImageView) rowView.findViewById(R.id.dots);
            viewHolder.likesPic = (ImageView) rowView.findViewById(R.id.likeimage);
            viewHolder.mapitPic = (ImageView) rowView.findViewById(R.id.mapimage);
            viewHolder.playbutton = (ImageView) rowView.findViewById(R.id.playbutton);
            viewHolder.videoThumb = (ImageView) rowView.findViewById(R.id.videothumb);
            viewHolder.listphoto = (ImageView) rowView.findViewById(R.id.listphoto);
            viewHolder.rainbow = (ImageView) rowView.findViewById(R.id.rainbow);
            rowView.setTag(viewHolder);

        } else {
            viewHolder = (ViewHolder) rowView.getTag();
        }


        final Post post = (Post) getItem(position);
        int color = Color.parseColor("#dddddd");
        viewHolder.likesPic.setColorFilter(color);
        viewHolder.mapitPic.setColorFilter(color);
        viewHolder.moremenu.setColorFilter(color);


        if (Hawk.count() == 0)
            initHawkWithDataFromServer();

        if (isItFromProfile) {
            viewHolder.profilePic.setVisibility(View.GONE);
            viewHolder.titleTextView.setVisibility(View.GONE);
            viewHolder.distance.setVisibility(View.GONE);
        }

        viewHolder.titleTextView.setText(post.getUsername());
        PrettyTime prettyTime = new PrettyTime();
        DateTime dateTime = new DateTime(post.getUploadDate().get$date());
        viewHolder.timeago.setText(prettyTime.format(dateTime.toDate()));
        viewHolder.likesTextView.setText(String.valueOf(format(post.getLikes())));
        viewHolder.footprints.setText(String.valueOf(format(post.getLocation().size() - 1)));

        //don't display 0 if there are no likes, just show heart icon
        if (viewHolder.likesTextView.getText().equals("0"))
            viewHolder.likesTextView.setVisibility(View.GONE);
        else
            viewHolder.likesTextView.setVisibility(View.VISIBLE);



        //don't display 0 if there are no footprints
        if (viewHolder.footprints.getText().equals("0"))
            viewHolder.footprints.setVisibility(View.GONE);
        else
            viewHolder.footprints.setVisibility(View.VISIBLE);

        double[] loc = post.getLocation().get(0);
        viewHolder.distance.setText("~" + PostListFragment.distance(loc[0], loc[1], 'M') + " Miles");
        if (post.getViews() != null)
            viewHolder.viewcount.setText(format(post.getViews()) + (post.getViews() == 1 ? " View" : " Views"));

        String profilePictureS3Url = "https://s3-us-west-2.amazonaws.com/moleheadphotos/" + post.getUsername()
                + ".jpg";

        String filename = post.getS3link();
        final String videoThumbURL = "https://s3-us-west-2.amazonaws.com/moleheadphotos/" + filename;


        Glide.with(mContext).load(profilePictureS3Url).asBitmap().centerCrop().into(new BitmapImageViewTarget(viewHolder.profilePic) {
            @Override
            protected void setResource(Bitmap resource) {
                RoundedBitmapDrawable circularBitmapDrawable =
                        RoundedBitmapDrawableFactory.create(mContext.getResources(), resource);
                circularBitmapDrawable.setCircular(true);
                viewHolder.profilePic.setImageDrawable(circularBitmapDrawable);
            }
        });

        int height = ((Post) getItem(position)).getHeight();
        int width = ((Post) getItem(position)).getWidth();

        if (height != 0 && width != 0) {
            ViewGroup.LayoutParams params = viewHolder.listphoto.getLayoutParams();
            Resources r = mContext.getResources();
            height = (int) getHeight(height, width);
            params.height = height;
            params.width = ViewGroup.LayoutParams.MATCH_PARENT;
            viewHolder.listphoto.setLayoutParams(params);

        } else {
            ViewGroup.LayoutParams params = viewHolder.listphoto.getLayoutParams();
            params.height = ViewGroup.LayoutParams.WRAP_CONTENT;
            params.width = ViewGroup.LayoutParams.MATCH_PARENT;
            viewHolder.listphoto.setLayoutParams(params);
        }

        if (post.getType() == null) {
            Glide.clear(viewHolder.listphoto);
            viewHolder.listphoto.setVisibility(View.GONE);
            //Glide.clear(viewHolder.listphoto);
            viewHolder.videoThumb.setVisibility(View.VISIBLE);
            viewHolder.rainbow.setVisibility(View.VISIBLE);
            Glide.with(mContext).load(videoThumbURL).fitCenter()
                    .diskCacheStrategy(DiskCacheStrategy.ALL).dontAnimate().into(viewHolder.videoThumb);
            viewHolder.playbutton.setVisibility(View.VISIBLE);

        }

        if (post.getType() != null) {
            if (post.getType().equals("video")) {
                viewHolder.playbutton.setVisibility(View.VISIBLE);
                Glide.clear(viewHolder.listphoto);
                viewHolder.listphoto.setVisibility(View.GONE);
                Glide.clear(viewHolder.postText);
                viewHolder.postText.setVisibility(View.GONE);
                viewHolder.videoThumb.setVisibility(View.VISIBLE);
                viewHolder.rainbow.setVisibility(View.VISIBLE);

                Glide.with(mContext).load(videoThumbURL).fitCenter()
                        .diskCacheStrategy(DiskCacheStrategy.ALL).dontAnimate().into(viewHolder.videoThumb);

            }

            if (post.getType().equals("image")) {
                Glide.clear(viewHolder.videoThumb);
                viewHolder.videoThumb.setVisibility(View.GONE);
                viewHolder.rainbow.setVisibility(View.GONE);
                Glide.clear(viewHolder.playbutton);
                viewHolder.playbutton.setVisibility(View.GONE);
                Glide.clear(viewHolder.postText);
                viewHolder.postText.setVisibility(View.GONE);
                viewHolder.listphoto.setVisibility(View.VISIBLE);
                viewHolder.listphoto.setBottom(0);

                Glide.with(mContext).load(post.getFilename().toString())
                        .diskCacheStrategy(DiskCacheStrategy.ALL).dontAnimate()
                        .into(viewHolder.listphoto);
            }

            if (post.getType().equals("text")) {
                Glide.clear(viewHolder.videoThumb);
                viewHolder.videoThumb.setVisibility(View.GONE);
                viewHolder.rainbow.setVisibility(View.GONE);
                Glide.clear(viewHolder.playbutton);
                viewHolder.playbutton.setVisibility(View.GONE);
                Glide.clear(viewHolder.listphoto);
                viewHolder.listphoto.setVisibility(View.GONE);
                viewHolder.postText.setVisibility(View.VISIBLE);
                viewHolder.postText.setText(post.getText());
            }

        }

        if (Hawk.contains("liked" + post.getId().get$oid())) {
            viewHolder.likesPic.clearColorFilter();
            Glide.with(mContext).load(R.drawable.heartroundorange).into(viewHolder.likesPic);
            ((ImageView) viewHolder.likesPic).setColorFilter(Color.parseColor("#ff3a6f"));
        } else {

            Glide.with(mContext).load(R.drawable.heartroundgray).diskCacheStrategy(DiskCacheStrategy.ALL)
                    .into(viewHolder.likesPic);
        }


        if (Hawk.contains("mapped" + post.getId().get$oid())) {
            viewHolder.mapitPic.clearColorFilter();
            ((ImageView) viewHolder.mapitPic).setImageResource(R.drawable.dropmaincolororange);
            ((ImageView) viewHolder.mapitPic).setColorFilter(Color.parseColor("#444444"));
        } else {
            Glide.with(mContext).load(R.drawable.dropdarkgray).diskCacheStrategy(DiskCacheStrategy.ALL)
                    .into(viewHolder.mapitPic);
        }


        if (!Hawk.contains("mapped" + post.getId().get$oid())) {
            viewHolder.mapitPic.setOnClickListener(new View.OnClickListener() {
                @Override
                public void onClick(View view) {
                    Hawk.put("mapped" + post.getId().get$oid(), 1);
                    ((ImageView) viewHolder.mapitPic).setImageResource(R.drawable.dropmaincolororange);
                    viewHolder.footprints.setText(String.valueOf(post.getLocation().size() + 1));
                    post.getLocation().add(new double[]{PostListFragment.lon, PostListFragment.lat});
                    notifyDataSetChanged();
                    Thread t = new Thread(new Runnable() {
                        @Override
                        public void run() {
                            postMappedToServer(post.getId().get$oid());
                        }
                    });
                    t.start();
                    TastyToast.makeText(mContext, "Post dropped off here.", TastyToast.LENGTH_SHORT, TastyToast.CONFUSING);
                }
            });
        } else {
            viewHolder.mapitPic.setClickable(false);
        }

        if (!Hawk.contains("liked" + post.getId().get$oid())) {
            viewHolder.likesPic.setOnClickListener(new View.OnClickListener() {

                @Override
                public void onClick(View v) {
                    Hawk.put("liked" + post.getId().get$oid(), 1);
                    viewHolder.likesPic.setClickable(false);
                    ((ImageView) viewHolder.likesPic).setImageResource(R.drawable.heartroundorange);
                    viewHolder.likesTextView.setText(String.valueOf(post.getLikes() + 1));
                    post.setLikes(post.getLikes() + 1);
                    notifyDataSetChanged();
                    Thread t = new Thread(new Runnable() {
                        @Override
                        public void run() {
                            postLikeToServer(post);
                        }
                    });
                    t.start();
                }
            });
        } else {
            viewHolder.likesPic.setClickable(false);
        }


        if (post.getType() == null || post.getType().equals("video"))
            viewHolder.videoThumb.setOnClickListener(new View.OnClickListener() {
                @Override
                public void onClick(View view) {

                    if (VListAdapter.this.mContext instanceof ProfileFeed) {
                        ((ProfileFeed) VListAdapter.this.mContext).closeActivity();
                    }

                    Intent broadcast = new Intent();
                    broadcast.setAction("com.molehead.openout.POST");

                    broadcast.putExtra("postId", post.getFilename().toString());
                    broadcast.putExtra("hawkId", post.getId().get$oid());
                    broadcast.putExtra("s3link", post.getS3link());
                    broadcast.putExtra("username", post.getUsername());

                    if (Hawk.contains("liked" + post.getId().get$oid()))
                        broadcast.putExtra("liked", "yes");
                    else
                        broadcast.putExtra("liked", "no");

                    broadcast.putExtra("likecount", post.getLikes().toString());

                    App.post = post;
                    LocalBroadcastManager.getInstance(mContext.getApplicationContext()).sendBroadcast(broadcast);
                }
            });

        viewHolder.moremenu.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                PopupMenu popup = new PopupMenu(mContext.getApplicationContext(), viewHolder.moremenu, Gravity.CENTER);
                //Inflating the Popup using xml file
                popup.getMenuInflater().inflate(R.menu.menu_main, popup.getMenu());

                //registering popup with OnMenuItemClickListener
                popup.setOnMenuItemClickListener(new PopupMenu.OnMenuItemClickListener() {
                    public boolean onMenuItemClick(MenuItem item) {
                        switch (item.getItemId()) {
                            case R.id.action_share:
                                String postId = post.getId().get$oid();
                                Intent sharingIntent = new Intent(android.content.Intent.ACTION_SEND);
                                sharingIntent.setType("text/plain");
                                String shareBody = postId + ".jpg"; //https://openout.herokuapp.com/posts/" + postId;
                                String shareSub = "Shared via Molehead";
                                sharingIntent.putExtra(android.content.Intent.EXTRA_SUBJECT, shareSub);
                                sharingIntent.putExtra(android.content.Intent.EXTRA_TEXT, shareBody);
                                sharingIntent.setFlags(Intent.FLAG_ACTIVITY_NEW_TASK);
                                Intent new_intent = Intent.createChooser(sharingIntent, "Share");
                                new_intent.setFlags(Intent.FLAG_ACTIVITY_NEW_TASK);
                                mContext.getApplicationContext().startActivity(new_intent);
                                break;
                        }
                        return true;
                    }
                });

                popup.show();
            }
        });
        return rowView;
    }


    private void initHawkWithDataFromServer() {
        SharedPreferences settings = mContext.getApplicationContext().getSharedPreferences("userinfo", 0);
        String username = settings.getString("username", "ok");
        String password = settings.getString("password", "ok");


        LoginService loginService =
                ServiceGenerator.createService(LoginService.class, username, password);
        final Call<List<Post>> call = loginService.getLikes(username);
        Log.i("lonlat", String.valueOf(lon) + " and  " + String.valueOf(lat));


        call.enqueue(new Callback<List<Post>>() {
            @Override
            public void onResponse(Call<List<Post>> call, Response<List<Post>> response) {

                ArrayList<Post> posts = new ArrayList<>();
                posts = (ArrayList<Post>) response.body();
                if (!posts.isEmpty())
                    for (Post p : posts) {
                        Hawk.put("liked" + p.getId().get$oid(), 1);
                    }
            }

            @Override
            public void onFailure(Call<List<Post>> call, Throwable t) {
            }
        });
    }


    private void postMappedToServer(String oid) {
        SharedPreferences settings = mContext.getSharedPreferences("userinfo", 0);
        String username = settings.getString("username", "ok");
        String password = settings.getString("password", "ok");
        LoginService loginService =
                ServiceGenerator.createService(LoginService.class, username, password);

        Log.i("postlistfraglat", String.valueOf(PostListFragment.lat));
        Call<ResponseBody> call = loginService.addLocation(oid, PostListFragment.lon, PostListFragment.lat);

        call.enqueue(new Callback<ResponseBody>() {
            @Override
            public void onResponse(Call<ResponseBody> call, Response<ResponseBody> response) {
                if (response.isSuccessful())
                    Log.i("mapped", "success");
            }

            @Override
            public void onFailure(Call<ResponseBody> call, Throwable t) {

            }
        });
    }


    public void postLikeToServer(Post post) {

        SharedPreferences settings = mContext.getSharedPreferences("userinfo", 0);
        String username = settings.getString("username", "ok");
        String password = settings.getString("password", "ok");

        LoginService loginService =
                ServiceGenerator.createService(LoginService.class, username, password);

        Call<ResponseBody> call = loginService.like(post, 1, username);


        call.enqueue(new Callback<ResponseBody>() {
            @Override
            public void onResponse(Call<ResponseBody> call, Response<ResponseBody> response) {

                if (response.isSuccessful()) {
                    try {
                        Log.i("call", response.body().string());
                    } catch (IOException e) {
                        e.printStackTrace();
                    }
                }
            }

            @Override
            public void onFailure(Call<ResponseBody> call, Throwable t) {
                Log.i("MFEED", "like request failed");
            }
        });
    }


    public static String format(long value) {
        //Long.MIN_VALUE == -Long.MIN_VALUE so we need an adjustment here
        if (value == Long.MIN_VALUE) return format(Long.MIN_VALUE + 1);
        if (value < 0) return "-" + format(-value);
        if (value < 1000) return Long.toString(value); //deal with easy case

        Map.Entry<Long, String> e = suffixes.floorEntry(value);
        Long divideBy = e.getKey();
        String suffix = e.getValue();

        long truncated = value / (divideBy / 10); //the number part of the output times 10
        boolean hasDecimal = truncated < 100 && (truncated / 10d) != (truncated / 10);

        return hasDecimal ? (truncated / 10d) + suffix : (truncated / 10) + suffix;
    }


    static class ViewHolder {
        private TextView titleTextView;
        private TextView timeago;
        private TextView likesTextView;
        private TextView viewcount;
        private TextView distance;
        private TextView footprints;
        private ImageView profilePic;
        private ImageView moremenu;
        private ImageView likesPic;
        private ImageView mapitPic;
        private ImageView rainbow;
        //private ImageView sharebutton;
        private TextView caption;
        private ImageView listphoto;
        private ImageView videoThumb;
        private ImageView playbutton;
        private TextView postText;
        private Post post;

    }


    private float getHeight(float height, float width) {
        WindowManager wm = (WindowManager) mContext.getSystemService(Context.WINDOW_SERVICE);
        Display display = wm.getDefaultDisplay();
        Point size = new Point();
        display.getSize(size);
        return (height * size.x / width);

    }
}

- franklinexpress

---

我建议你使用RecyclerView。 - Ganesh Katikar

RecyclerView是专门为此目的而制作的。Recycler View - jack jay

据我所知，当您编写if条件时，应该同时编写else条件。还有一件非常重要的事情是，在解析或从服务器获取数据时，每个条件都应该存储在其他变量（布尔值）中。 - Mavya Soni

@GaneshKatikar 是的，但是如果将它转换为RecyclerView，我几乎要从头开始了，对吧？ - franklinexpress

这个适配器存在一些严重的问题。你在适配器里做了太多的事情。你处理了点击和服务端调用。这违反了单一职责原则。你应该只使用数据来显示屏幕上的数据。 - Leandro Borges Ferreira

Answer 1

由于您的适配器中有很多代码，因此不可能指出具体问题。但是有一件事是确定的——在这种情况下切换到RecyclerView并不能帮助您。

适配器不应包含业务逻辑——它们只应将输入对象“适配”到底层视图中。在您的情况下，似乎适配器执行计算、生成新线程、执行网络请求等操作。

您需要重构代码，使适配器类似于以下内容：

public class PostsListAdapter extends ArrayAdapter<Post> {


    private Context mContext;

    public PostsListAdapter(Context context, int resource) {
        super(context, resource);
        mContext = context;
    }

    public void bindPosts(List<Post> posts) {
        clear();
        addAll(posts);
        notifyDataSetChanged();
    }


    @NonNull
    @Override
    public View getView(int position, View convertView, ViewGroup parent) {
        if (convertView == null) {
            // assign new View to convertView
            // create new ViewHolder
            // set ViewHolder as tag of convertView
            // set listeners
        } else {
            // get a reference to existing ViewHolder
        }

        // populate ViewHolder's elements with data from getItem(position)
        // kick off asynchronous loading of images
        // NOTE: no calculations allowed here - just simple bidding of data to Views

        return convertView;
    }

}

您的代码需要按照一定的结构进行编写，这样可以确保在绑定新数据到 ListView 之前执行涉及计算和数据转换的业务逻辑，并且传递给 bindPosts() 方法的 Post 对象已经包含了上述计算和转换的结果。

适配器只是将最终数据从 Posts 转换为 Views，没有其他作用。

如果您现在时间紧迫，只需要让它“正常工作”，那么我建议先删除生成新线程并进行网络请求的逻辑。看看是否能提高性能。

- Vasiliy

---

你读过https://developer.android.com/training/displaying-bitmaps/index.html的培训文档序列吗？使用缓存对我的图像GridView滚动平滑度产生了巨大的影响。 - Gary99

他有很多命令来调整视图，比如setVisible、setLayout等，基于数据。因此使用recycle-view将帮助他使代码更好，并且性能会稍微提高一点。 - Võ Quang Hòa

@VõQuangHòa，我在OP的代码中看到的两个最“性能贪婪”的部分是线程和网络相关逻辑。使用RecyclerView而不是带有ViewHolder模式的ListView不能保证更快（惊讶吧），即使在这种情况下它确实更快，由于线程和网络逻辑的性能低效，因此这种改变带来的性能提升将与之相比微不足道，因此无法察觉。OP应该从适配器中重构出网络和线程。 - Vasiliy

@Vasiliy 我同意，"性能贪婪"的主要原因是过多的线程和网络相关逻辑。 - Võ Quang Hòa

谢谢大家，是的，你们说得对，我正在将一些逻辑从适配器中移除。 - franklinexpress

Answer 2

• Change your implementation to RecyclerView which is more efficient in terms of scrapping views or recycling.

• We can also enable optimizations if the items are static and will not change for significantly smoother scrolling:

  recyclerView.setHasFixedSize(true);
  

• Create an intent service and register BroadcastReceiver as data return callback or error callback when api request, business rule, data modification completed. Use synchronous call to execute initHawkWithDataFromServer() in advance and after getting result from api continue modifying or applying business logic. After that create new adapter or update existing adapter data set.

• Move all the below data calculation or data value formatting logic from adapter's getView() to above intent service.

  You can add more getter and setter to existing Post pojo.

  DateTime dateTime = new DateTime(post.getUploadDate().get$date()); 
  viewHolder.timeago.setText(prettyTime.format(dateTime.toDate()));
  viewHolder.likesTextView.setText(String.valueOf(format(post.getLikes())));
  viewHolder.footprints.setText(String.valueOf(format(post.getLocation().size)) - 1)));
  
  Post{
      //Your existing property
      @Expose(serialize = false, deserialize = false)
      //equals neither serialize nor deserialize or
      private DateTime uploadedDateTime;
      //etc. prettyTime.format, String.valueOf
  }
  

• Removes unnecessary reflection:

  GsonBuilder builder = new GsonBuilder();
  builder.excludeFieldsWithoutExposeAnnotation();
  Gson gson = builder.create();
  new  Retrofit.Builder().addConverterFactory(GsonConverterFactory.create(gson)).build();
  

  and it to your retrofit Service creation class. You can also use transient(private transient DateTime uploadedDateTime;)

• Remove public void addElement(Post post) { mDataSource.add(0, post); this.notifyDataSetChanged();} and whenever you need to notify if a single or more items inserted, deleted etc. Use the below:

  notifyItemChanged(int)
  notifyItemInserted(int)
  notifyItemRemoved(int)
  notifyItemRangeChanged(int, int)
  notifyItemRangeInserted(int, int)
  notifyItemRangeRemoved(int, int)
  

我们可以从活动或片段中使用这些内容：

//Add a new contact
items.add(0, new Post("Barney"));
//Notify the adapter that an item was inserted at position 0
adapter.notifyItemInserted(0);

以上方法更加有效。每次我们想要向RecyclerView中添加或删除项目时，都需要明确告知适配器事件。与ListView适配器不同，RecyclerView适配器不应依赖于notifyDataSetChanged()，因为应使用更精细的操作。更多细节请参见API文档。

另外，如果您打算更新现有列表，请在进行任何更改之前获取当前项目数。例如，应调用适配器上的getItemCount()来记录将要更改的第一个索引。

// record this value before making any changes to the existing list
int curSize = adapter.getItemCount(); // replace this line with wherever you get new records
ArrayList<Post> newItems = Post.createPostsList(20);
// update the existing list
items.addAll(newItems);
// curSize should represent the first element that got added
// newItems.size() represents the itemCount
adapter.notifyItemRangeInserted(curSize, newItems.size());

比较大型更改

在支持库v24.2.0中新增了一个DiffUtil类，帮助计算旧列表和新列表之间的差异。详情请见

• Don't preload images via glide if your image sizes are different. Try creating your own. Also try looking at.

• Create color as the class member

  int color = Color.parseColor("#dddddd");
  

• Write View.GONE or View.VISIBLE in Post pojo itself, which will be executed in background thread from Retrofit if IntentService. Try api return boolean in json instead "0" as String.

• Move all below to IntentService //don't display 0 if there are no likes, just show heart icon if (viewHolder.likesTextView.getText().equals("0")) viewHolder.likesTextView.setVisibility(View.GONE); else viewHolder.likesTextView.setVisibility(View.VISIBLE);

  //don't display 0 if there are no footprints
  if (viewHolder.footprints.getText().equals("0"))
      viewHolder.footprints.setVisibility(View.GONE);
  else
      viewHolder.footprints.setVisibility(View.VISIBLE);
  
  double[] loc = post.getLocation().get(0);
  viewHolder.distance.setText("~" + PostListFragment.distance(loc[0], loc[1], 'M') + " Miles");
  

• All String concatenation also in Post or IntnetService like:

  String profilePictureS3Url = "https://s3-us-west-2.amazonaws.com/moleheadphotos/" + post.getUsername() + ".jpg";
  

你可以提前创建颜色过滤器，只需一次即可。从列表视图中删除滚动条，因为它需要计算高度以显示滚动条。

- Anurag Singh

Answer 3

太多需要改进的地方。以下是一些例子。

我看到这个：

if (Hawk.count() == 0)
        initHawkWithDataFromServer();

我相信在列表出现期间，方法initHawkWithDataFromServer将会被多次调用。

当activity创建时，这个调用只能执行一次。

Glide.with(mContext).load(videoThumbURL).fitCenter()

但是在此之前，您应该重构您的代码，将逻辑移动到另一个类中。尝试删除一些代码，比如这样的代码（它应该使用一些布局属性来完成）。

ViewGroup.LayoutParams params = viewHolder.listphoto.getLayoutParams();
        Resources r = mContext.getResources();
        height = (int) getHeight(height, width);
        params.height = height;
        params.width = ViewGroup.LayoutParams.MATCH_PARENT;
        viewHolder.listphoto.setLayoutParams(params);

- Võ Quang Hòa

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Hawk.count()只应调用一次，在第一次调用之后，数据将保存在设备上，因此在第二次调用时count将不等于0。 - franklinexpress

@franklinexpress 这不正确。我可以看到函数异步调用了 Web API，所以那里的条件是不够的。它将根据网络连接（慢或快）被调用一次或多次。我建议您在该函数内部放置一些 Log.i(...) 来查看其工作方式。 - Võ Quang Hòa