Question

我尝试以下方式，但我在iv.setImageBitmap（bm）获得Null Pointer Exception。我尝试使用网格视图和布局Inflater设置带有文本的图像。我也进行了debuging过程，但我仍然无法获得解决方案。请检查以下代码。

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

您不应该在适配器中执行URLConnection，这将尝试执行多重连接，因为每次在适配器中显示该视图时都会调用getView（）。而是在一个单独的类中处理连接。

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;

你必须使用viewHolder类型的对象，当convertView不为null时，你的iv imageView为null。所以你在null对象上使用setImageBitmap（）。试试我的代码。

HTH。

如何在gridview中使用低于它的文本设置图像？

2 个答案: