图像缩略图未正确设置

Question

我正在尝试创建一个文件浏览器。除了我的图像缩略图加载太慢外，我实现了所有目标。所以我读到我必须转到asynctask，然后在post执行更新ui。在运行asynctask之前，我为所有文件提供了一个默认缩略图。在asynctask中我将position作为参数，因为我使用它们设置了标签。然后我使用该位置检查文件。如果那个图像或视频我为它创建一个位图。在post execute中，我创建了一个新的viewholder，并使用getTag（position）为它分配相同的标签。然后我使用setBitmapImage分配位图。问题：即使对于非图像/视频的文件，缩略图也在变化/闪烁。 到目前为止我尝试过的事情： 一个）updating of Image Thumbnails using AsyncTask for Android ListView not coming proper
B）Android ListView updating of Image Thumbnails using AsyncTask Causes View recycling

这是我的getView代码：

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


    File file=new File(String.valueOf(filenames[position]));
    if(file.isDirectory()){
        img=R.drawable.folder;
    }

    else{
        img=getImage(filenames[position]);
    }

    ViewHolder viewHolder = null;
    if (convertView == null) {
        LayoutInflater inflator = LayoutInflater.from(getContext());
        convertView = inflator.inflate(R.layout.list_item, null);
        viewHolder = new ViewHolder();
        viewHolder.tv = (TextView) convertView.findViewById(R.id.textView1);
        viewHolder.cb = (CheckBox) convertView.findViewById(R.id.checkBox1);
        viewHolder.iv= (ImageView)convertView.findViewById(R.id.imageView);
        viewHolder.cb.setOnCheckedChangeListener(new CompoundButton.OnCheckedChangeListener() {

            @Override
            public void onCheckedChanged(CompoundButton buttonView, boolean isChecked) {
                int getPosition = (Integer) buttonView.getTag();  // Here we get the position that we have set for the checkbox using setTag.
                myList.get(getPosition).setSelected(buttonView.isChecked()); // Set the value of checkbox to maintain its state.
            }
        });
        convertView.setTag(viewHolder);
        convertView.setTag(R.id.textView1, viewHolder.tv);
        convertView.setTag(R.id.checkBox1, viewHolder.cb);
        convertView.setTag(R.id.checkBox1, viewHolder.iv);
    }
    else {
        viewHolder = (ViewHolder) convertView.getTag();
    }
    viewHolder.iv.getLayoutParams().height = 80;
    viewHolder.iv.getLayoutParams().width = 80;
    viewHolder.cb.setTag(position);
    final ViewHolder ViewHolder= viewHolder;
    ViewHolder.iv.setImageResource(img);
    ViewHolder.tv.setText(myList.get(position).getName());
    ViewHolder.cb.setChecked(myList.get(position).isSelected());


    final View finalConvertView = convertView;
    class myTask extends AsyncTask<Integer,Void,Bitmap>{

        int pos;
        public myTask(int pos){
            this.pos=pos;
        }

        @Override
        protected Bitmap doInBackground(Integer... params) {
            Bitmap thumb=null;

            if((String.valueOf(filenames[pos])).contains(".jpeg")||String.valueOf(filenames[pos]).contains(".jpg")||String.valueOf(filenames[pos]).contains(".png")||String.valueOf(filenames[pos]).contains(".bmp")||String.valueOf(filenames[pos]).contains(".webp")||String.valueOf(filenames[pos]).contains(".gif")){
                thumb = ThumbnailUtils.extractThumbnail(BitmapFactory.decodeFile(String.valueOf(filenames[pos])), 64, 64);

            }
            else if((String.valueOf(filenames[pos])).contains(".mp4")||String.valueOf(filenames[pos]).contains(".mkv")||String.valueOf(filenames[pos]).contains(".webm")||String.valueOf(filenames[pos]).contains(".3gp")||String.valueOf(filenames[pos]).contains(".3gpp")){
                thumb=ThumbnailUtils.createVideoThumbnail(filenames[pos].getPath(), MediaStore.Video.Thumbnails.MINI_KIND);

            }
            return thumb;
        }
        @Override
        protected void onPostExecute(Bitmap thumb){
            if(isCancelled()){
                return;
            }
            ViewHolder v= (ViewHolder) finalConvertView.getTag(pos);

            if((String.valueOf(filenames[pos])).contains(".jpeg")||String.valueOf(filenames[pos]).contains(".jpg")||String.valueOf(filenames[pos]).contains(".png")||String.valueOf(filenames[pos]).contains(".bmp")||String.valueOf(filenames[pos]).contains(".webp")||String.valueOf(filenames[pos]).contains(".gif")){

                v.iv.setImageBitmap(thumb);
            }
            else if((String.valueOf(filenames[pos])).contains(".mp4")||String.valueOf(filenames[pos]).contains(".mkv")||String.valueOf(filenames[pos]).contains(".webm")||String.valueOf(filenames[pos]).contains(".3gp")||String.valueOf(filenames[pos]).contains(".3gpp")){

                v.iv.setImageBitmap(thumb);
            }


        }
    }

    myTask m=new myTask(position);
    m.execute();

   return convertView;



}

Answer 1

我终于找到了答案。

这是ListAdapter类：

class ListAdapter extends ArrayAdapter<Modal> {

    private final Context context;
    private int img;

    private List<Modal> myList;
    private File filenames[];
    private List<Integer> selectedItems=new ArrayList<Integer>();
    private CheckBox cb;
    public ListAdapter(Context context, List<Modal> list, File filenames[]) {
        super(context, R.layout.list_item, list);
        this.context = context;
        this.myList = list;
        this.filenames=filenames;
    }


    @Override
    public int getViewTypeCount() {

        if(getCount()>0){
            return getCount();
        }
        return 1;
    }

    @Override
    public int getItemViewType(int position) {

        return position;
    }

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


    static class ViewHolder {
        TextView tv;
        CheckBox cb;
        static ImageView iv;
    }

    public int getImage(File filename){
        if(String.valueOf(filename).contains(".rar")||String.valueOf(filename).contains(".zip")){
            return R.drawable.archive;
        }
        else if(String.valueOf(filename).contains(".doc")||String.valueOf(filename).contains(".docx")){
            return  R.drawable.doc;
        }
        else if(String.valueOf(filename).contains(".pdf")){
            return R.drawable.pdf;
        }
        else if(String.valueOf(filename).contains(".txt")){
            return R.drawable.txt;
        }
        else if(String.valueOf(filename).contains(".ppt")||String.valueOf(filename).contains(".pptx")){
            return R.drawable.ppt;
        }
        else if(String.valueOf(filename).contains(".xls")||String.valueOf(filename).contains(".xlsx")){
            return R.drawable.xls;
        }
        else if((String.valueOf(filename).contains(".jpeg")||String.valueOf(filename).contains(".jpg")||String.valueOf(filename).contains(".png")||String.valueOf(filename).contains(".bmp")||String.valueOf(filename).contains(".webp")||String.valueOf(filename).contains(".gif"))){
            return R.drawable.image;
        }
        else if((String.valueOf(filename).contains(".mp4")||String.valueOf(filename).contains(".mkv")||String.valueOf(filename).contains(".webm")||String.valueOf(filename).contains(".3gp")||String.valueOf(filename).contains(".3gpp"))||String.valueOf(filename).contains(".MOV")){
            return R.drawable.video;
        }
        else if((String.valueOf(filename).contains(".mp3")||String.valueOf(filename).contains(".wav")||String.valueOf(filename).contains(".wma")||String.valueOf(filename).contains(".MP2")||String.valueOf(filename).contains(".AAC")||String.valueOf(filename).contains(".AC3")||String.valueOf(filename).contains(".AU")||String.valueOf(filename).contains(".OGG")||String.valueOf(filename).contains(".FLAC"))){
            return R.drawable.music;
        }

        else {
            return R.drawable.unknown;
        }

    }


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




        File file=new File(String.valueOf(filenames[position]));
        if(file.isDirectory()){
            img=R.drawable.folder;
        }

        else{
            img=getImage(filenames[position]);
        }


        ViewHolder viewHolder = null;

        if (convertView == null) {
            LayoutInflater inflator = LayoutInflater.from(getContext());
            convertView = inflator.inflate(R.layout.list_item, null);
            viewHolder = new ViewHolder();
            viewHolder.tv = (TextView) convertView.findViewById(R.id.textView1);
            viewHolder.cb = (CheckBox) convertView.findViewById(R.id.checkBox1);
            viewHolder.iv= (ImageView)convertView.findViewById(imageView);
            viewHolder.cb.setOnCheckedChangeListener(new CompoundButton.OnCheckedChangeListener() {

                @Override
                public void onCheckedChanged(CompoundButton buttonView, boolean isChecked) {
                    int getPosition = (Integer) buttonView.getTag();  // Here we get the position that we have set for the checkbox using setTag.
                    myList.get(getPosition).setSelected(buttonView.isChecked()); // Set the value of checkbox to maintain its state.
                }
            });
            convertView.setTag(viewHolder);
            convertView.setTag(R.id.textView1, viewHolder.tv);
            convertView.setTag(R.id.checkBox1, viewHolder.cb);
            convertView.setTag(R.id.checkBox1, viewHolder.iv);
        }
        else {
            viewHolder = (ViewHolder) convertView.getTag();
        }

        viewHolder.iv.getLayoutParams().height = 150;
        viewHolder.iv.getLayoutParams().width = 150;
        viewHolder.cb.setTag(position);
        final ViewHolder ViewHolder= viewHolder;

        ViewHolder.tv.setText(myList.get(position).getName());
        ViewHolder.cb.setChecked(myList.get(position).isSelected());
        viewHolder.iv.setImageResource(img);


        Log.v("this","viewHolderMT: "+String.valueOf(viewHolder)+" position: "+position);
        myTask m=new myTask(position,viewHolder.iv);
        m.execute();

       return convertView;



    }
    class myTask extends AsyncTask<Integer,Bitmap,Bitmap>{



        int pos;
        ImageView iv;
        public myTask(int pos,ImageView iv){
            this.pos=pos;
            this.iv=iv;
            iv.setTag(pos);


        }

        @Override
        protected Bitmap doInBackground(Integer... params) {
            Bitmap thumb=null;


            if((String.valueOf(filenames[pos])).contains(".jpeg")||String.valueOf(filenames[pos]).contains(".jpg")||String.valueOf(filenames[pos]).contains(".png")||String.valueOf(filenames[pos]).contains(".bmp")||String.valueOf(filenames[pos]).contains(".webp")||String.valueOf(filenames[pos]).contains(".gif")){

                thumb = ThumbnailUtils.extractThumbnail(BitmapFactory.decodeFile(String.valueOf(filenames[pos])), 150, 150);

            }
            else if((String.valueOf(filenames[pos])).contains(".mp4")||String.valueOf(filenames[pos]).contains(".mkv")||String.valueOf(filenames[pos]).contains(".webm")||String.valueOf(filenames[pos]).contains(".3gp")||String.valueOf(filenames[pos]).contains(".3gpp")||String.valueOf(filenames[pos]).contains(".MOV")){
                thumb=ThumbnailUtils.createVideoThumbnail(filenames[pos].getPath(), MediaStore.Video.Thumbnails.MINI_KIND);


            }
            return thumb;
        }
        @Override
        protected void onProgressUpdate(Bitmap... thumb){


        }
        @Override
        protected void onPostExecute(Bitmap thumb){


            if(thumb!=null && (Integer)iv.getTag()==this.pos) {
                if ((String.valueOf(filenames[pos])).contains(".jpeg") || String.valueOf(filenames[pos]).contains(".jpg") || String.valueOf(filenames[pos]).contains(".png") || String.valueOf(filenames[pos]).contains(".bmp") || String.valueOf(filenames[pos]).contains(".webp") || String.valueOf(filenames[pos]).contains(".gif")) {

                    iv.setImageBitmap(thumb);

                }
                 else if ((String.valueOf(filenames[pos])).contains(".mp4") ||String.valueOf(filenames[pos]).contains(".MOV")|| String.valueOf(filenames[pos]).contains(".mkv") || String.valueOf(filenames[pos]).contains(".webm") || String.valueOf(filenames[pos]).contains(".3gp") || String.valueOf(filenames[pos]).contains(".3gpp")) {

                    iv.setImageBitmap(thumb);
                }


            }





        }
    }
}

我犯的错误：

• 在getview（）
之外移动AsyncTask
• 在async构造函数
中提供对imageView的引用
• 同时实现getItemViewType（）和getItemId（）函数
• 没有检查onPostExecute中的位置标记，因此图像在洗牌。

我花了一段时间才弄明白。希望它能帮助别人！