如何在GridView中設置文字下方的圖像？

Question

我按以下方式嘗試，但是在iv.setImageBitmap（bm）上出現了空指針異常。 我嘗試使用網格視圖和Layout Inflater設置帶有文本的圖像。我也進行了調試過程，但仍然無法解決問題，請檢查以下代碼。

public class CategoryAdapter extends BaseAdapter {
private Context mContext;
public static final int ACTIVITY_CREATE = 10;
int id=-1;
public CategoryAdapter(Context c) {
        mContext = c;
 }
public int getCount() {
    return CategorylogoActivity.logoarray.length;
}

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

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

public View getView(int position, View convertView, ViewGroup parent) {
       Bitmap bm=null;
       ImageView iv = null ;
       TextView tv=null;
       View v;
                    if(convertView==null){

                        @SuppressWarnings("static-access")
                        LayoutInflater li = (LayoutInflater)mContext.getSystemService(mContext.LAYOUT_INFLATER_SERVICE);  

                        v = li.inflate(R.layout.category_icon, null);
                        tv= (TextView)v.findViewById(R.id.icon_text);

                        iv = (ImageView)v.findViewById(R.id.icon_image);


                    }
                    else
                    {
                        v = convertView;
                    }
                        try {
                            URL aURL = new URL(CategorylogoActivity.logoarray[position]);
                            URLConnection conn = aURL.openConnection();
                            conn.connect();
                            InputStream is = conn.getInputStream();
                            // Buffered is always good for a performance plus. 
                            BufferedInputStream bis = new BufferedInputStream(is);
                            // Decode url-data to a bitmap. 
                            bm = BitmapFactory.decodeStream(bis);

                            bis.close();
                            is.close();
                        } catch (MalformedURLException e) {

                            e.printStackTrace();
                        } catch (IOException e) {

                            e.printStackTrace();
                        }
                     iv.setImageBitmap(bm);
                    tv.setText(CategorylogoActivity.namearray[0]);

                    return v;

Answer 1

您不應該在適配器中執行URLConnection，這將嘗試進行多重連接，因為每次在適配器中顯示該視圖時都會調用getView（）。 而是在單獨的類中處理連接。

Answer 2

static class viewHolder {
       ImageView iv = null ;
       TextView tv=null;
}


public View getView(int position, View convertView, ViewGroup parent) {
       Bitmap bm=null;
       viewHolder vh;
       View v;
                    if(convertView==null){
                        vh = new viewHolder();
                        @SuppressWarnings("static-access")
                        LayoutInflater li = (LayoutInflater)mContext.getSystemService(mContext.LAYOUT_INFLATER_SERVICE);  


                        v = li.inflate(R.layout.category_icon, null);
                        vh.tv= (TextView)v.findViewById(R.id.icon_text);

                        vh.iv = (ImageView)v.findViewById(R.id.icon_image);

                        v.setTag(vh);
                    }
                    else
                    {
                        vh = (viewHolder)convertView.getTag();
                        v = convertView;
                    }
                        try {
                            URL aURL = new URL(CategorylogoActivity.logoarray[position]);
                            URLConnection conn = aURL.openConnection();
                            conn.connect();
                            InputStream is = conn.getInputStream();
                            // Buffered is always good for a performance plus. 
                            BufferedInputStream bis = new BufferedInputStream(is);
                            // Decode url-data to a bitmap. 
                            bm = BitmapFactory.decodeStream(bis);

                            bis.close();
                            is.close();
                        } catch (MalformedURLException e) {

                            e.printStackTrace();
                        } catch (IOException e) {

                            e.printStackTrace();
                        }
                     vh.iv.setImageBitmap(bm);
                    vh.tv.setText(CategorylogoActivity.namearray[0]);

                    return v;

您必須使用viewHolder類型的對象，當convertView不為null時，您的iv imageView為null。 因此您在空對象上使用setImageBitmap（）。 試試我的代碼。

HTH。