当我滚动GridView时图像发生变化 [英] Image change when i scroll gridview

问题描述

GridView从URL加载图像.当我滚动gridview时，会有更多的图像机会，如何解决它...我尝试了imageAdapter.notifyDataSetChanged()，gridView.invalidateViews()..我没有找到解决此问题的方法.

GridView load images from URL. When i scrolls gridview, more image chance, how to do fix it... I have tried imageAdapter.notifyDataSetChanged(), gridView.invalidateViews().. I have not found a solution to this problem.

public class ImageAdapter extends BaseAdapter{

    private Context mContext;
    private LayoutInflater mInflater;   
    private ArrayList<NodeFood> listImage = new ArrayList<NodeFood>();

    public ImageAdapter(Context c, ArrayList<NodeFood> listImage){
        this.mContext = c;
        this.listImage = listImage;
    }

    public class ViewHolder{
        ImageView imageView;
        ProgressBar progress;
    }

    public int getCount() {
        return listImage.size();
    }

    public Object getItem(int arg0) {
        return arg0;
    }

    public long getItemId(int arg0) {
        return arg0;
    }

    public View getView(int arg0, View arg1, ViewGroup arg2) {
        final ViewHolder holder;
        if(arg1 == null){
            holder  = new ViewHolder();
            mInflater = LayoutInflater.from(mContext);
            arg1    =   mInflater.inflate(R.layout.layout_item_grid, null);
            holder.imageView = (ImageView)arg1.findViewById(R.id.imageItemGrid);
            holder.progress = (ProgressBar)arg1.findViewById(R.id.progressBar);
            holder.progress.getIndeterminateDrawable().setColorFilter(0xFFFF0000,android.graphics.PorterDuff.Mode.MULTIPLY);
            arg1.setTag(holder);
        }else{
            holder = (ViewHolder)arg1.getTag();
        }
        holder.imageView.setTag(arg0);
        holder.progress.setTag(arg0);
        NodeFood a = this.listImage.get(arg0);
        String URL = a.getSRC();
        task_LoadIMG bb = new task_LoadIMG(URL,holder);
        bb.execute();
        return arg1;
    }   

    public class task_LoadIMG extends AsyncTask<Void,Void,Bitmap>{
        private String url;
        private ViewHolder holder;
        public task_LoadIMG(String url, ViewHolder holder){
            this.url = url;
            this.holder = holder;
        }
        @Override
        protected Bitmap doInBackground(Void... arg0) {
            try{
                URL aURL = new URL(this.url);
                URLConnection connect = aURL.openConnection();
                connect.connect();

                InputStream is = connect.getInputStream();
                BufferedInputStream bis = new BufferedInputStream(is);
                Bitmap bm = BitmapFactory.decodeStream(bis);
                bis.close();
                is.close();
                return bm;
            }catch(IOException e){
                return null;
            }
        }

        @Override
        protected void onPostExecute(Bitmap result) {
            holder.progress.setVisibility(View.GONE);
            holder.imageView.setImageBitmap(result);
            holder.imageView.setScaleType(ScaleType.CENTER_CROP);
        }
    }
}

推荐答案

问题是您的AsyncTask加载图像所需的时间比显示该图像所需的时间长.下载完成后，该单元就来去去并已被回收用于下一张图像.

The problem is that your AsyncTask is taking longer to load an image than that image is being displayed for. Once it's finished downloaded, that cell has come and gone and has been recycled for the next image.

要解决此问题，请将单元格图像的URL存储在单元格的tag属性中.然后，检查并确保AsyncTask完成时单元格URL相同.如果不一致，则此单元已被回收，您应该放弃更新.这是一些代码:

To work around this, store the URL of the cell's image in the cell's tag property. Then, check to make sure that the cell URL is the same when the AsyncTask completes. If it's not the same, then the cell has been recycled in the meantime and you should discard the update. Here's some code:

public View getView(int arg0, View arg1, ViewGroup arg2) {
    final ViewHolder holder;
    if(arg1 == null){
        holder  = new ViewHolder();
        mInflater = LayoutInflater.from(mContext);
        arg1    =   mInflater.inflate(R.layout.layout_item_grid, null);
        holder.imageView = (ImageView)arg1.findViewById(R.id.imageItemGrid);
        holder.progress = (ProgressBar)arg1.findViewById(R.id.progressBar);
        holder.progress.getIndeterminateDrawable().setColorFilter(0xFFFF0000,android.graphics.PorterDuff.Mode.MULTIPLY);
        arg1.setTag(holder);
    }else{
        holder = (ViewHolder)arg1.getTag();
    }
    NodeFood a = this.listImage.get(arg0);
    String URL = a.getSRC();
    holder.imageView.setTag(URL);
    task_LoadIMG bb = new task_LoadIMG(URL,holder);
    bb.execute();
    return arg1;
}   

public class task_LoadIMG extends AsyncTask<Void,Void,Bitmap>{
    private String url;
    private ViewHolder holder;
    public task_LoadIMG(String url, ViewHolder holder){
        this.url = url;
        this.holder = holder;
    }
    @Override
    protected Bitmap doInBackground(Void... arg0) {
        try{
            URL aURL = new URL(this.url);
            URLConnection connect = aURL.openConnection();
            connect.connect();

            InputStream is = connect.getInputStream();
            BufferedInputStream bis = new BufferedInputStream(is);
            Bitmap bm = BitmapFactory.decodeStream(bis);
            bis.close();
            is.close();
            return bm;
        }catch(IOException e){
            return null;
        }
    }

    @Override
    protected void onPostExecute(Bitmap result) {
        if (url.equals(holder.imageView.getTag()) {
            holder.progress.setVisibility(View.GONE);
            holder.imageView.setImageBitmap(result);
            holder.imageView.setScaleType(ScaleType.CENTER_CROP);
        } else {
            // View was updated in the meantime, ignore the image
        }
    }
}

您还可以考虑在单元回收后立即取消AsyncTask，以节省带宽/CPU周期.留给读者练习.

You might also consider canceling the AsyncTask as soon as the cell is recycled to save bandwidth/CPU cycles. That's left as an exercise for the reader.

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