使用ViewHolder的Android列表視圖

Question

我有個問題。 點擊后我試圖在列表視圖中更改圖標。 它可以正常工作，雖然不會僅修改點擊的圖標，但也不會修改那些未顯示的圖標。 例如，如果我單擊列表視圖的第一項中的圖標，則第五個圖標也會更改。 對於以下所有項目（列表視圖的每五個項目）重復此行為。 這是我的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 

...

這是我的ViewHolder類：

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

Answer 1

在下面更改您的代碼。 我想你錯過了。

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

在ListView中，同一時間可以看到盡可能多的convertViews （系統重用它）。 所以你實際上有5個convertView ，因此你有5個ImageView的圖標。 問題是您使用這些ImageView的標簽來存儲“已下載”的信息。 這是5狀態，這就是為什么你在列表中滾動時看到每下載第五行的原因。

我想你現在看到它不會起作用。 您需要為每個項目存儲下載的狀態，因此您必須將基礎List<String>更改為List<ListItem> ，其中ListItem可以存儲實際行的下載狀態。

之后，您所要做的就是更新convertView的ImageView （在getView() ）以顯示正確的圖標。

Answer 3

你可以試試這個

public class CustomArrayAdapter extends ArrayAdapter {

// declare your custom list with type;
private List<YourModelClass> allData = new ArrayList<YourModelClass>();

public CustomArrayAdapter(@NonNull Context context, List<YourModelClass> allData) {
    super(context, R.layout.your_layout, allData); // add your_layout.xml
    this.allData = allData;
}

class ViewHolder {
    TextView name, phone; // declare your your_layout.xml view type
}

@NonNull
@Override
public View getView(int position, @Nullable View convertView, @NonNull ViewGroup parent) {
    LayoutInflater inflater = (LayoutInflater) getContext().getSystemService(Context.LAYOUT_INFLATER_SERVICE);
    ViewHolder holder = new ViewHolder();
    if (convertView == null) {

        convertView = inflater.inflate(R.layout.your_layout, parent, false); // inflate your_layout.xml

        //initialize your your_layout.xml view
        holder.name = convertView.findViewById(R.id.tv_item_name);
        holder.phone = convertView.findViewById(R.id.tv_item_phone);

        convertView.setTag(holder);
    } else {
        holder = (ViewHolder) convertView.getTag();
    }

    //set value into your_layout.xml
    holder.name.setText(allData.get(position).getName());
    holder.phone.setText(allData.get(position).getNumber());

    return convertView;
}

}

Answer 4

像這樣更改你的代碼。 在try塊之前使用convertView添加null檢查。

    final MenuItem   menuItem = getItem(position);
    View view = convertView;
    final ViewHolder viewHolder;

if (convertView == null) {

    LayoutInflater inflater;

        inflater = (LayoutInflater) getContext().getSystemService(Context.LAYOUT_INFLATER_SERVICE);
        view = inflater.inflate(R.layout.menu_item, parent, false);
        viewHolder = new ViewHolder();
//      viewHolder.half = (TextView) view.findViewById(R.id.half);
        viewHolder.name = (TextView) view.findViewById(R.id.name);
        viewHolder.description = (TextView) view.findViewById(R.id.description);
        viewHolder.price = (TextView) view.findViewById(R.id.price);
        viewHolder.add = (Button) view.findViewById(R.id.add);
        viewHolder.selectedView = view.findViewById(R.id.selectedView);
        viewHolder.remove = (Button) view.findViewById(R.id.remove);
        viewHolder.total = (TextView) view.findViewById(R.id.itemTotal);
        viewHolder.quantity = (TextView) view.findViewById(R.id.quantity);
        view.setTag(viewHolder);
}else{
    viewHolder= (ViewHolder)convertView.getTag(); 
}

Answer 5

public class AndroidListViewActivity extends ListActivity 
{
   private ListView listView;
   private String names[] = {
        "HV CAPACITOR",
        "LV CAPACITORCSS",

         };

private String desc[] = {
        "The Powerful Hypter Text Markup Language 5",
        "Cascading Style Sheets",

};


private Integer imageid[] = {
        R.drawable.hv_capacitor,
        R.drawable.lv_capacitor,

};

@Override
public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
   // setContentView(R.layout.capacitor_layout);
    // storing string resources into Array
    String[] product_name = getResources().getStringArray(R.array.product_name);
    // Binding Array to ListAdapter
    this.setListAdapter(new ArrayAdapter<String>(this, R.layout.list_item, R.id.label, product_name));

    ListView lv = getListView();

    // listening to single list item on click

    lv.setOnItemClickListener(new AdapterView.OnItemClickListener() {
        public void onItemClick(AdapterView<?> parent, View view,
                                int position, long id) {

            // selected item
            String product = ((TextView) view).getText().toString();

            // Launching new Activity on selecting single List Item
            Intent i = new Intent(getApplicationContext(), SingleListItem.class);
            // sending data to new activity
            i.putExtra("product", product);
            startActivity(i);

        }
    });


    CapacitorList capacitorList = new CapacitorList(this, names, desc, imageid);
    listView = (ListView) findViewById(R.id.listView);
    listView.setAdapter(capacitorList);

    listView.setOnItemClickListener(new AdapterView.OnItemClickListener() {

        // Launching new Activity on selecting single List Item
        Intent i = new Intent(getApplicationContext(), CapacitorList.class);
        // sending data to new activity

       // startActivity(i);

        @Override
        public void onItemClick(AdapterView<?> adapterView, View view, int i, long l) {
            Toast.makeText(getApplicationContext(), "You Clicked " + names[i], Toast.LENGTH_SHORT).show();
        }
    });

}

    @Override
    public boolean onCreateOptionsMenu (Menu menu){
        // Inflate the menu; this adds items to the action bar if it is present.
        getMenuInflater().inflate(R.menu.menu_main, menu);
        return true;
    }

    @Override
    public boolean onOptionsItemSelected (MenuItem item){
        // Handle action bar item clicks here. The action bar will
        // automatically handle clicks on the Home/Up button, so long
        // as you specify a parent activity in AndroidManifest.xml.
        int id = item.getItemId();

        //noinspection SimplifiableIfStatement
        if (id == R.id.action_settings) {
            return true;
        }

        return super.onOptionsItemSelected(item);


    }
}