如何在Android中的ListView中的imageview中设置图像？

Question

我有一个列表视图，其中包括2 textview和1 imageview。现在，imageview中的图像将在特定条件下设置，否则它应该留空而不显示图像。

问题是图像没有进入正确的行。说，例如图像应该显示在第3行，但它显示在第4行。并且，在某些情况下，每行将具有相同的图像。

有人遇到过这样的问题吗？我对这背后的原因无能为力。任何人都可以指出问题吗？

---

private static class VilleAdapter extends BaseAdapter { 
    private LayoutInflater mInflater = null; 

    // private Context context = null; 

    public VilleAdapter(Context context) { 
     // Cache the LayoutInflate to avoid asking for a new one each time. 
     mInflater = LayoutInflater.from(context); 
    } 

    /** 
    * The number of items in the list is determined by the number of 
    * speeches in our array. 
    * 
    * @see android.widget.ListAdapter#getCount() 
    */ 
    public int getCount() { 
     // return BabbleMainListParse.getNumOfBabbles(); 
     return VilleMainListParse.getVilleCount(); 
    } 

    /** 
    * Since the data comes from an array, just returning the index is 
    * sufficent to get at the data. If we were using a more complex data 
    * structure, we would return whatever object represents one row in the 
    * list. 
    * 
    * @see android.widget.ListAdapter#getItem(int) 
    */ 
    public Object getItem(int position) { 
     return position; 
    } 

    /** 
    * Use the array index as a unique id. 
    * 
    * @see android.widget.ListAdapter#getItemId(int) 
    */ 
    public long getItemId(int position) { 
     return position; 
    } 

    /** 
    * Make a view to hold each row. 
    * 
    * @see android.widget.ListAdapter#getView(int, android.view.View, 
    *  android.view.ViewGroup) 
    */ 
    public View getView(int position, View convertView, ViewGroup parent) 
    { 
     // A ViewHolder keeps references to children views to avoid 
     // unneccessary calls 
     // to findViewById() on each row. 
     ViewHolder holder; 

     // When convertView is not null, we can reuse it directly, there is 
     // no need 
     // to reinflate it. We only inflate a new View when the convertView 
     // supplied 
     // by ListView is null. 
     if (convertView == null) 
     { 
      convertView = mInflater.inflate(R.layout.villerow, parent,false); 

      // Creates a ViewHolder and store references to the two children 
      // views 
      // we want to bind data to. 
      holder = new ViewHolder(); 
      holder.txtVilleListTitle = (TextView) convertView.findViewById(R.id.txtVilleListTitle); 
      holder.txtVilleDescription = (TextView) convertView.findViewById(R.id.txtVilleDescription); 
      holder.imgvillepwd = (ImageView) convertView.findViewById(R.id.imgvillepwd); 

      convertView.setTag(holder); 
     } 
     else 
     { 
      // Get the ViewHolder back to get fast access to the TextView 
      holder = (ViewHolder) convertView.getTag(); 
     } 

     // Bind the data efficiently with the holder. 
     holder.txtVilleListTitle.setText(VilleMainListParse.getMsgTitle(position)); 

     if(VilleMainListParse.getMsgDesc(position).length() > 30) 
     { 
      String temp = VilleMainListParse.getMsgDesc(position).substring(0, 30); 
      temp = temp +"....."; 
      holder.txtVilleDescription.setText(temp); 
     } 
     else 
      holder.txtVilleDescription.setText(VilleMainListParse.getMsgDesc(position)); 

     if(!VilleMainListParse.getPwd(position).equals("")) 
     { 
      if(VilleMainListParse.getUnlock(position)) 
      { 
       holder.imgvillepwd.setBackgroundResource(R.drawable.lock); 
      } 
      else if(!VilleMainListParse.getUnlock(position)) 
      { 
       holder.imgvillepwd.setBackgroundResource(R.drawable.lock_open); 
      } 
     } 

     return convertView; 
    } 

    static class ViewHolder 
    { 
     TextView txtVilleListTitle; 
     TextView txtVilleDescription; 
     ImageView imgvillepwd; 
    } 
} 

上面的代码仅是适配器的。当登录按钮被点击时，最初有一个登录屏幕，数据从互联网上载入，然后这个列表视图被载入这个数据。该数据在最初加载正确。

有人可以让我知道这个代码有什么问题吗？

Answer 1

由于您正在重复使用相同的视图，因此您应该清除不应显示的图像。否则，先前的图片将显示在那里。所以我建议以下修复：

if(!VilleMainListParse.getPwd(position).equals("")) 
{ 
    if(VilleMainListParse.getUnlock(position)) 
    { 
     holder.imgvillepwd.setBackgroundResource(R.drawable.lock); 
    } 
    else if(!VilleMainListParse.getUnlock(position)) 
    { 
     holder.imgvillepwd.setBackgroundResource(R.drawable.lock_open); 
    } 
} 
else 
    holder.imgvillepwd.setBackgroundDrawable(null); 

Answer 2

您也可以考虑使用setImageResource/setImageBitmap方法而不是setBackgroundXxx。