使用ViewHolder的Android列表视图

Question

我有个问题.点击后我试图在列表视图中更改图标.它可以正常工作,虽然不会仅修改点击的图标,但也不会修改那些未显示的图标.例如,如果我单击列表视图的第一项中的图标,则第五个图标也会更改.对于以下所有项目(列表视图的每五个项目)重复此行为.这是我的getView方法:

   public class AlphabeticalAdapter extends ArrayAdapter<String>
   {
       int layoutResourceId; 
       private final Context context;
       private List<String> data;
       private ProgressDialog mProgressDialog;
       private ImageView downloadImageButton;


       public AlphabeticalAdapter(Context context, int resource, List<String> data){
           super(context, resource, data);
           this.layoutResourceId = resource;
           this.context = context;
           this.data = data;    
       }

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

          // View rowView = convertView;
           final ViewHolder viewHolder;

           if (convertView == null) {

               LayoutInflater inflater = (LayoutInflater) context
                        .getSystemService(Context.LAYOUT_INFLATER_SERVICE);


               convertView  = inflater.inflate(R.layout.catalogslist_single_row, parent, false);

           viewHolder = new ViewHolder();

           viewHolder.catlogTitle=(TextView)convertView.findViewById(R.id.txtTitle);
           viewHolder.icon=(ImageView)convertView.findViewById(R.id.imageView2); 
           viewHolder.downloadImageButton=(ImageView)convertView.findViewById(R.id.downloadImageButton);

           //downloadImageButton = (ImageView)rowView.findViewById(R.id.downloadImageButton);

           viewHolder.position = position;


           viewHolder.downloadImageButton.setOnClickListener(new OnClickListener() {
               @Override  
               public void onClick(View v) {
                     System.out.println("DOWNLOAD PRESSED");

                     viewHolder.downloadImageButton = (ImageView)v.findViewById(R.id.downloadImageButton);
                     viewHolder.downloadImageButton.setImageResource(R.drawable.icon_ok);
                     viewHolder.downloadImageButton.setTag("downloaded");
                     //rowView.setTag("downloaded");


                 }
             });



           convertView.setTag(viewHolder);

           }

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

           viewHolder.catlogTitle.setText(data.get(position));
           viewHolder.catlogTitle.setTypeface(regularDin);
           viewHolder.icon.setImageResource(R.drawable.cata);


           if(viewHolder.downloadImageButton.getTag() == "downloaded"){
             downloadImageButton = (ImageView)convertView.findViewById(R.id.downloadImageButton);
             downloadImageButton.setImageResource(R.drawable.icon_ok);
           }
           else{
               downloadImageButton = (ImageView)convertView.findViewById(R.id.downloadImageButton);
                 downloadImageButton.setImageResource(R.drawable.icon_download);
           }


           viewHolder.position = position;

        return convertView;

       } //close getView 

...

这是我的ViewHolder类:

      static class ViewHolder{
       ImageView downloadImageButton;
       TextView catlogTitle;
       ImageView icon;
       int position;
   }

Answer 1

在下面更改您的代码.我想你错过了.

public class AlphabeticalAdapter extends ArrayAdapter<String> {
    int layoutResourceId;
    private final Context context;
    private List<String> data;
    private List<String> tags;
    private ProgressDialog mProgressDialog;
    private ImageView downloadImageButton;

    public AlphabeticalAdapter(Context context, int resource, List<String> data) {
        super(context, resource, data);
        this.layoutResourceId = resource;
        this.context = context;
        this.data = data;
        tags = new ArrayList<String>();
        int size = data.size();
        for (int i = 0; i < size; i++) {
            tags.add("tag");
        }
    }

    static class ViewHolder {
        ImageView downloadImageButton;
        TextView catlogTitle;
        ImageView icon;
        int position;
    }

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

        // View rowView = convertView;
        final ViewHolder viewHolder;

        if (convertView == null) {
            LayoutInflater inflater = (LayoutInflater) context
                    .getSystemService(Context.LAYOUT_INFLATER_SERVICE);
            // convertView = inflater.inflate(R.layout.catalogslist_single_row,
            // parent, false);
            viewHolder = new ViewHolder();
            viewHolder.position = position;
            viewHolder.downloadImageButton
                    .setOnClickListener(new OnClickListener() {
                        @Override
                        public void onClick(View v) {
                            System.out.println("DOWNLOAD PRESSED");
                            viewHolder.downloadImageButton.setTag("downloaded");
                            tags.add(position, "downloaded");
                        }
                    });
            convertView.setTag(viewHolder);
        } else {
            viewHolder = (ViewHolder) convertView.getTag();
        }

        viewHolder.catlogTitle.setText(data.get(position));
        viewHolder.catlogTitle.setTypeface(regularDin);
        viewHolder.icon.setImageResource(R.drawable.cata);

        if (tags.get(position) == "downloaded") {
            downloadImageButton.setImageResource(R.drawable.icon_ok);
        } else {
            downloadImageButton.setImageResource(R.drawable.icon_download);
        }

        viewHolder.position = position;
        return convertView;
    } // close getView
}

Answer 2

有许多convertViews许多排在同一时间看到你的ListView(系统会重复使用它).所以你实际上有5个convertView,因此你有5个ImageView图标.问题是您使用这些ImageView的标签来存储"已下载"的信息.这是5状态,这就是为什么你在列表中滚动时看到每下载第五行的原因.

我想你现在看到它不会起作用.您需要为每个项目存储下载的状态,因此您必须更改底层,List<String>以便List<ListItem>在哪里ListItem可以存储实际行的下载状态.

之后,您所要做的就是更新convertView's ImageView(in getView())以显示正确的图标.