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The selected background color of the item list is unexpectedly reused after scrolling through the list on tablets

In my view of the list on tablets, I am trying to select the selected list item in order to preserve its state when, but, unfortunately, I see some strange behavior. For some reason, whenever I scroll through the list until the selected item is not displayed, and then scroll back to the point where the selected IS item is selected, the background color is unexpectedly reused. I believe that something needs to be used in the getView method, but I'm not sure what to do with this method. What needs to be done to prevent background color reuse?

Adapter class

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 Class

 public class FragmentVictoriaLine extends ListFragment { private VictoriaListAdapter mAdapter; public FragmentVictoriaLine() { } /** * Whether or not the activity is in two-pane mode, ie 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); } }

data class

 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; } }
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1 answer

When you scroll through a list, the items / views in the ListView will be reused to optimize memory. Therefore, when you set the selected state to a list item, you will see that you are viewing the selected state in several list items. The best way to prevent this is to save state in the Data Model and set the state in the getView the Adapter function.

Here is what you can do -

  @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); --- ---

And in the adapter -

 @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")); }

Hope this helps!

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Source: https://habr.com/ru/post/1232047/

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