Question

我想使用自定义arrayadapter显示列表，问题是我的第一个和最后一个项目相同实际上我的ArrayList中有四个项目但是第四个项目没有显示，而是它显示第一个项目，有时反之亦然。我的代码，我是一个完整的初学者，所以不知道在这里发布需要哪些代码。

Place.java（列表项的自定义类）

/** Image resource ID for the Place */
private int mImageResourceId;
/**Description ID for the Place */
private  int mDescriptionId;
/**Name ID for the Place */
private  int mNameId;

/**
 * Create a new Word object.
 *
 * @param imageResourceId is the image resource ID for the image of place
 * @param nameId is the string resource Id for the name of place
 * @param descriptionId is the  string resource ID for the description associated with this place
 */
public Place(int imageResourceId, int nameId, int descriptionId) {
    mImageResourceId = imageResourceId;
    mNameId= nameId;
    mDescriptionId =descriptionId;
}

public int getImageResourceId (){return mImageResourceId;}

public int getDescriptionId(){return mDescriptionId;}

public  int getNameId() {return mNameId;}}

PlaceAdapter.java（自定义Adapterfor my lsit）

public class PlaceAdapter extends ArrayAdapter<Place> {


public PlaceAdapter(Context context, ArrayList<Place> place) {
    super(context, 0, place);
}

@NonNull
@Override
public View getView(int position, @Nullable View convertView, @NonNull ViewGroup parent) {
    View listItemView = convertView;
    if (listItemView == null) {
        listItemView = LayoutInflater.from(getContext()).inflate(
                R.layout.list_item, parent, false);

        Place currentPlace = getItem(position);

        TextView name = (TextView) listItemView.findViewById(R.id.name);
        name.setText(currentPlace.getNameId());

        TextView description = (TextView) listItemView.findViewById(R.id.description);
        description.setText(currentPlace.getDescriptionId());

        ImageView image = (ImageView) listItemView.findViewById(R.id.image);
        image.setImageResource(currentPlace.getImageResourceId());

    }
    return listItemView;
}
}

HistoricFragment.java（片段包含listView）

public class HistoricFragment extends Fragment {

public HistoricFragment() {
    // Required empty public constructor
}

@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
                         Bundle savedInstanceState) {
    // Inflate the layout for this fragment
    View rootView = inflater.inflate(R.layout.place_list, container, false);

    // Create a list of Place
    final ArrayList<Place> place = new ArrayList<Place>();
    place.add(new Place(R.drawable.badshahi_mosque, R.string.badshahi_name,
            R.string.badshahi_description));
    place.add(new Place(R.drawable.lahore_fort, R.string.fort_name,
            R.string.fort_description));
    place.add(new Place(R.drawable.sheesh_mahal_lahore_fort, R.string.mahal_name,
            R.string.mahal_description));
    place.add(new Place(R.drawable.wazir_mosque, R.string.wazir_khan_name,
            R.string.wazir_mosque_description));

    // Create an {@link PlaceAdapter}, whose data source is a list of {@link Place}s. The
    // adapter knows how to create list items for each item in the list.
    PlaceAdapter adapter = new PlaceAdapter(getActivity(), place);

    // Find the {@link ListView} object in the view hierarchy of the {@link Activity}.
    // There should be a {@link ListView} with the view ID called list, which is declared in the
    // place_list.xml layout file.
    ListView listView = (ListView) rootView.findViewById(R.id.list);

    // Make the {@link ListView} use the {@link PlaceAdapter} we created above, so that the
    // {@link ListView} will display list items for each {@link Place} in the list.
    listView.setAdapter(adapter);

    return  rootView;
}
}

Answer 1

    @Override
    public View getView(int position, @Nullable View convertView, @NonNull ViewGroup parent) {
        View listItemView = convertView;
        if (listItemView == null) {
            listItemView = LayoutInflater.from(getContext()).inflate(
                R.layout.list_item, parent, false);
        }
        Place currentPlace = getItem(position);

        TextView name = (TextView) listItemView.findViewById(R.id.name);
        name.setText(currentPlace.getNameId());

        TextView description = (TextView) listItemView.findViewById(R.id.description);
        description.setText(currentPlace.getDescriptionId());

        ImageView image = (ImageView) listItemView.findViewById(R.id.image);
        image.setImageResource(currentPlace.getImageResourceId());
        return listItemView;
}

这将解决问题。但您可以谷歌并使用更有效的Viewholder模式。

Answer 2

像这样更改你的代码

public class PlaceAdapter extends ArrayAdapter<Place> {


    public PlaceAdapter(Context context, ArrayList<Place> place) {
        super(context, 0, place);
    }

    @NonNull
    @Override
    public View getView(int position, @Nullable View convertView, @NonNull ViewGroup parent) {
        ViewHolder holder;
        View listItemView;
        if (convertView == null) {
            listItemView = LayoutInflater.from(getContext()).inflate(
                    R.layout.list_item, parent, false);

            holder = new ViewHolder();
            holder.name = (TextView) listItemView.findViewById(R.id.name);
            holder.description = (TextView) listItemView.findViewById(R.id.description);
            holder.image = (ImageView) listItemView.findViewById(R.id.image);

            convertView.setTag(holder);
        }

        holder = (ViewHolder) convertView.getTag();

        Place currentPlace = getItem(position);
        holder.name.setText(currentPlace.getNameId());
        holder.description.setText(currentPlace.getDescriptionId());
        holder.image.setImageResource(currentPlace.getImageResourceId());
        return convertView;
    }

    public static class ViewHolder {
        TextView name;
        TextView description;
        ImageView image;
    }

}

listView的第一项和最后一项是相同的

2 个答案: