About the flicker problem caused by using universalimageloader to load pictures and refresh data in recyclerview

About the RecyclerView Use in UniversalImageLoader Flicker problem caused by loading picture refresh data

Let's start with an effect picture :

This is what I'm using RecyclerView With the help of ItemTouchHelper A drag and drop effect with the help of . I call after successfully dragging notifyDatasetChanged When updating the data, the picture flashes .
Then I began to find solutions online . In the end, it didn't achieve the expected effect , But it is not to say that online methods are not good , Here it is , I'd like to summarize the following points :
1. If it's not used UIL Frame loading picture , It's the original imageView.setImage Load in the way of and call notifyDatasetChanged perhaps notifyItemRangeChanged(start,end) A flash occurs when the entire data is refreshed , It can be attributed to RecyclerView Own factors .
terms of settlement :
(1) Try to give each item Set up separate id, That is to say adapter Zhongyao setHasStableIds(true), And then in getItemId Return your item Of id. Google first recommends users to use this method , Set up id It will be solved later position Dislocation and many other inexplicable problems .
(2) close RecyclerView Default Item Animation effect .

((DefaultItemAnimator)recyclerView.getAnimator()).setSupportsChangeAnimations(false);

The above methods can well solve the flicker problem caused by their own factors .

2. use UIL The flicker produced by the frame .
First of all, this should be UIL Problems caused by your own loading mechanism .UIL There can be multi-level cache loading . Directly bind Viewholder In time Display Display of methods , Will be in holder When reusing, the process of multi-level loading is constantly called , Class I will talk about the transition from memory cache to disk cache . I haven't studied the whole loading process in detail , But there is no doubt that , And ordinary imageView.setImage Compared with the way , It's a lot more complicated . In fact, when I close the memory cache to load , Found that when refreshing data ,UIL The first thing to show is your default image in the configuration item , Then the real picture is displayed , Although the time is relatively short , But the transition moment is still relatively clear . Then I turned on the memory cache , Then I don't see the default picture , But blink . ad locum , I can venture to speculate that :
(1) The loading speed of memory cache is much faster than that of disk cache
(2) Blinking is actually a transition from the default image to the real image , It's just , The loading speed of memory cache is much faster than that of disk cache , As a result, the default pictures are directly displayed before they are finished , But after all, it is a transition , There is still a time difference , So there is a flicker .

So , To test my guess , The following method is specially written :

/** *  redefinition UIL How to display pictures <br> * UIL There can be multiple levels of caching ,（ Memory cache , Disk caching ）. *  Directly through display Method display picture , In general operation, it is completely OK Of . But if it comes to RecyclerView Full update of data , *  Such as {@link RecyclerView.Adapter#notifyDataSetChanged()} perhaps {@link android.support.v7.widget.RecyclerView.Adapter#notifyItemChanged(int)} *  And so on , It will flash . Online statements are very complicated , Some say it is RecyclerView Self contained item Animation effects and so on . Results the investigation found  *  yes UIL Caused by the mechanism of loading pictures by itself . This method can solve the problem of flicker . * @param view * @param imgUrl * @param option */
    public void showImage(ImageView view, String imgUrl, DisplayImageOptions option){
        // Make sure that the memory cache is configured in the current load configuration true
        Bitmap bmp= ImageLoader.getInstance().getMemoryCache().get(imgUrl);
        if(bmp!=null){
            view.setImageBitmap(bmp);
        }else{
            // Make sure that the disk cache is configured in the current loading configuration true
            File cache=ImageLoader.getInstance().getDiskCache().get(imgUrl);
            if(cache!=null){
                // Here, according to specific needs , You can define yourself Bitmap Compressed item of , However, there is generally no need to customize it again 
                //UIL The initial configuration of determines the compression result , The effect is better , direct decode That's it 
                view.setImageBitmap(BitmapFactory.decodeFile(cache.getAbsolutePath()));
            }else{
                // If the first two items are not , Prove that the image has not been cached , Honestly load it in the traditional way 
                ImageLoader.getInstance().displayImage(imgUrl,view, option);
            }
        }
    }

Now? , Let's see the effect :

perfect , No more flickering .