java - 在平板电脑上滚动列表后意外重用了选定的列表项背景颜色

Question

对于我在平板电脑上的 ListView ，我试图让我选择的列表项选择在选择时保持其状态，但不幸的是我看到了一些奇怪的行为。出于某种原因，每当我将列表滚动到所选项目不可见的位置，然后滚动回到所选项目可见的位置时，背景颜色意外地被重新使用。我相信 getView 方法中需要包含某些内容，但我不确定如何使用此方法。为了防止背景色被重复使用，必须做什么？

适配器类

public class VictoriaListAdapter extends BaseAdapter {

    private List<Victoria> mData;
    private LayoutInflater mInflater;

    public VictoriaListAdapter (List<Victoria> data, Context context) {
        mData = data;
        mData = new ArrayList(mData);
        mInflater = (LayoutInflater) context.getSystemService(Context.LAYOUT_INFLATER_SERVICE);
    }

    @Override
    public int getCount() {
        return mData.size();
    }

    @Override
    public String getItem(int position) {
        return mData.get(position).getStation();
    }

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

    @Override
    public View getView(int position, View convertView, ViewGroup parent) {

        ViewHolder holder;

        if (convertView == null) {
            convertView = mInflater.inflate(R.layout.list_item_dualline, parent, false);
            holder = new ViewHolder();

            holder.title = (TextView) convertView.findViewById(R.id.item_station);
            holder.description = (TextView) convertView.findViewById(R.id.item_zone);

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

        holder.title.setText(mData.get(position).getStation());
        holder.description.setText(mData.get(position).getZone());

        return convertView;
    }

    /**
     * View holder
     */
    static class ViewHolder {
        private TextView title;
        private TextView description;
    }
}

fragment 类

public class FragmentVictoriaLine extends ListFragment {

    private VictoriaListAdapter mAdapter;

    public FragmentVictoriaLine() {
    }

    /**
     * Whether or not the activity is in two-pane mode, i.e. running on a tablet
     * device.
     */
    public boolean mTwoPane;

    public static FragmentVictoriaLine newInstance() {
        return new FragmentVictoriaLine();
    }

    @Nullable
    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
        View view = inflater.inflate(R.layout.fragment_victoria_line, container, false);
        initialize();
        return view;
    }

    List<Victoria> list = new ArrayList<>();
    private void initialize() {
        String[] items = getActivity().getResources().getStringArray(R.array.victoria_stations);
        String[] itemDescriptions = getActivity().getResources().getStringArray(R.array.victoria_zones);
        for (int n = 0; n < items.length; n++){
            Victoria victoria = new Victoria();
            victoria.setID();
            victoria.setStation(items[n]);
            victoria.setZone(itemDescriptions[n]);
            list.add(victoria);
        }

        mAdapter = new VictoriaListAdapter(list, getActivity());
        setListAdapter(mAdapter);
    }

    @Override
    public void onActivityCreated(Bundle savedInstanceState) {
        View v = getView();

        mTwoPane = getActivity().findViewById(R.id.detail_container) != null;

        assert v != null;
        ListView lv = (ListView)v.findViewById(android.R.id.list);
        lv.setOnItemClickListener(new AdapterView.OnItemClickListener() {
            private Victoria selectedMain;
            private View selectedView;

            @Override
            public void onItemClick(AdapterView<?> parent, View view, int position, long id) {
                VictoriaListAdapter adapter = (VictoriaListAdapter) parent.getAdapter();
                String station = adapter.getItem(position);

                if (mTwoPane) {
                    setItemNormal();
                    View rowView = view;
                    setItemSelected(rowView);

                    Fragment newFragment;
                    if (station.equals(view.getResources().getString(R.string.bho))) {
                        newFragment = new FragmentVictoriaBHO();
                    } else if (station.equals(view.getResources().getString(R.string.brx))) {
                        newFragment = new FragmentVictoriaBRX();
                    } else if (station.equals(view.getResources().getString(R.string.eus))) {
                        newFragment = new FragmentVictoriaEUS();
                    } else if (station.equals(view.getResources().getString(R.string.fpk))) {
                        newFragment = new FragmentVictoriaFPK();
                    } else if (station.equals(view.getResources().getString(R.string.green_park))) {
                        newFragment = new FragmentVictoriaGreenPark();
                    } else if (station.equals(view.getResources().getString(R.string.hhy))) {
                        newFragment = new FragmentVictoriaHHY();
                    } else if (station.equals(view.getResources().getString(R.string.kxsp))) {
                        newFragment = new FragmentVictoriaKXSP();
                    } else {
                        newFragment = new FragmentVictoriaBHO();
                    }
                    VictoriaLineActivity activity = (VictoriaLineActivity) view.getContext();
                    FragmentTransaction transaction = activity.getSupportFragmentManager().beginTransaction();
                    transaction.setCustomAnimations(R.anim.fade_out, R.anim.fade_in);
                    transaction.replace(R.id.detail_container, newFragment);
                    transaction.commit();
                } else {
                    Intent intent;
                    if (station.equals(view.getResources().getString(R.string.bho))) {
                        intent = new Intent(getActivity(), VictoriaBHOActivity.class);
                    } else if (station.equals(view.getResources().getString(R.string.brx))) {
                        intent = new Intent(getActivity(), VictoriaBRXActivity.class);
                    } else if (station.equals(view.getResources().getString(R.string.eus))) {
                        intent = new Intent(getActivity(), VictoriaEUSActivity.class);
                    } else if (station.equals(view.getResources().getString(R.string.fpk))) {
                        intent = new Intent(getActivity(), VictoriaFPKActivity.class);
                    } else if (station.equals(view.getResources().getString(R.string.green_park))) {
                        intent = new Intent(getActivity(), VictoriaGreenParkActivity.class);
                    } else if (station.equals(view.getResources().getString(R.string.hhy))) {
                        intent = new Intent(getActivity(), VictoriaHHYActivity.class);
                    } else if (station.equals(view.getResources().getString(R.string.kxsp))) {
                        intent = new Intent(getActivity(), VictoriaKXSPActivity.class);
                    } else {
                        intent = new Intent(getActivity(), VictoriaBHOActivity.class);
                    }
                    startActivity(intent);
                }
            }

            public void setItemSelected(View view) {
                View rowView = view;
                view.setBackgroundColor(Color.parseColor("#868F98"));

                TextView tv0 = (TextView) rowView.findViewById(R.id.item_station);
                tv0.setTextColor(Color.WHITE);

                TextView tv1 = (TextView) rowView.findViewById(R.id.item_zone);
                tv1.setTextColor(Color.WHITE);
            }

            public void setItemNormal() {
                for (int i = 0; i < getListView().getChildCount(); i++) {
                    View v = getListView().getChildAt(i);
                    v.setBackgroundColor(Color.TRANSPARENT);

                    TextView tv0 = ((TextView) v.findViewById(R.id.item_station));
                    tv0.setTextColor(Color.WHITE);

                    TextView tv1 = ((TextView) v.findViewById(R.id.item_zone));
                    tv1.setTextColor(Color.parseColor("#B5B5B5"));
                }
            }
        });

        super.onActivityCreated(savedInstanceState);
    }
}

数据类

public class Victoria {
    public Victoria(){}

    private String station;
    private String zone;
    private boolean selected;

    public String getStation(){
        return station;
    }

    public void setStation(String item){
        this.station = item;
    }

    public String getZone(){
        return zone;
    }

    public void setZone(String zone){
        this.zone = zone;
    }

    private int _id;
    public void getID(int _id){
        this._id = _id;
    }

    public int setID(){
        return _id;
    }

    public boolean isSelected() {
        return selected;
    }

    public void setSelected(boolean selected) {
        this.selected = selected;
    }
}

Answer 1

当您滚动列表时，ListView 中的项/ View 将被重用以优化内存。因此，当您将选定状态设置为列表项时，您将看到该选定状态滚动浏览时在多个列表项中。防止这种情况的最佳方法是在您的数据模型中保留状态并在适配器的getView函数中设置状态。

这是你可以做的 -

 @Override
 public void onItemClick(AdapterView<?> parent, View view, int position,long id) {
   VictoriaListAdapter adapter = (VictoriaListAdapter) parent.getAdapter();

   //reverse the selected state in data model
   for (int i = 0; i < adapter.getCount(); i++) {
     Victoria victoria = (Victoria)adapter.getItem(i);
     victoria.setSelected(i == position ? true : false);
   }
   Victoria victoria = (Victoria)adapter.getItem(position);

   ---
   ---

在适配器中 -

@Override
public Object getItem(int position) {
    //Return full object, coz we need to access other 
    //member variables too
    return mData.get(position);
}

@Override
public View getView(int position, View convertView, ViewGroup parent) {

    ViewHolder holder;

    if (convertView == null) {
        convertView = mInflater.inflate(R.layout.list_item_dualline, parent, false);
        holder = new ViewHolder();

        holder.title = (TextView) convertView.findViewById(R.id.item_station);
        holder.description = (TextView) convertView.findViewById(R.id.item_zone);

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

    Victoria victoria = (Victoria)getItem(position);
    holder.title.setText(victoria.getStation());
    holder.description.setText(victoria.getZone());
    if (victoria.isSelected()) {
        setItemSelected(convertView);
    } else {
        setItemNormal(convertView);
    }

    return convertView;
}

 public void setItemSelected(View view) {
    View rowView = view;
    view.setBackgroundColor(Color.parseColor("#868F98"));

    TextView tv0 = (TextView) rowView.findViewById(R.id.item_station);
    tv0.setTextColor(Color.WHITE);

    TextView tv1 = (TextView) rowView.findViewById(R.id.item_zone);
    tv1.setTextColor(Color.WHITE);
 }

public void setItemNormal(View v) {

    v.setBackgroundColor(Color.TRANSPARENT);

    TextView tv0 = ((TextView) v.findViewById(R.id.item_station));
    tv0.setTextColor(Color.WHITE);

    TextView tv1 = ((TextView) v.findViewById(R.id.item_zone));
    tv1.setTextColor(Color.parseColor("#B5B5B5"));

 }

希望对您有所帮助!