Wie kann ich meinen ArrayAdapter dem ViewHolder-Muster folgen lassen?

Hier ist mein ArrayAdapter. Ich möchte dies effizienter machen, indem ich dem ViewHolder-Muster folge:

http://developer.android.com/resources/samples/ApiDemos/src/com/example/android/apis/view/List14.html

aber ich bin mir nicht sicher, wie ich das erreichen soll.

UPDATE: ViewHolder-Muster

private class QuoteAdapter extends ArrayAdapter { private ArrayList items; // used to keep selected position in ListView private int selectedPos = -1; // init value for not-selected public QuoteAdapter(Context context, int textViewResourceId, ArrayList items) { super(context, textViewResourceId, items); this.items = items; } public void setSelectedPosition(int pos) { selectedPos = pos; // inform the view of this change notifyDataSetChanged(); } @Override public View getView(int position, View convertView, ViewGroup parent) { View v = convertView; ViewHolder holder; // to reference the child views for later actions if (v == null) { LayoutInflater vi = (LayoutInflater)getSystemService(Context.LAYOUT_INFLATER_SERVICE); v = vi.inflate(R.layout.mainrow, null); // cache view fields into the holder holder = new ViewHolder(); holder.nameText = (TextView) v.findViewById(R.id.nameText); holder.priceText = (TextView) v.findViewById(R.id.priceText); holder.changeText = (TextView) v.findViewById(R.id.changeText); // associate the holder with the view for later lookup v.setTag(holder); } else { // view already exists, get the holder instance from the view holder = (ViewHolder)v.getTag(); } // change the row color based on selected state if (selectedPos == position) { v.setBackgroundResource(R.drawable.stocks_selected_gradient); holder.nameText.setTextColor(Color.WHITE); holder.priceText.setTextColor(Color.WHITE); holder.changeText.setTextColor(Color.WHITE); } else { v.setBackgroundResource(R.drawable.stocks_gradient); holder.nameText.setTextAppearance(getApplicationContext(), R.style.BlueText); holder.priceText.setTextAppearance(getApplicationContext(), R.style.BlueText); holder.changeText.setTextAppearance(getApplicationContext(), R.style.BlueText); } Quote q = items.get(position); if (q != null) { if (holder.nameText != null) { holder.nameText.setText(q.getSymbol()); } if (holder.priceText != null) { holder.priceText.setText(q.getLastTradePriceOnly()); } if (holder.changeText != null) { try { float floatedChange = Float.valueOf(q.getChange()); if (floatedChange < 0) { if (selectedPos != position) holder.changeText.setTextAppearance(getApplicationContext(), R.style.RedText); // red } else { if (selectedPos != position) holder.changeText.setTextAppearance(getApplicationContext(), R.style.GreenText); // green } } catch (NumberFormatException e) { System.out.println("not a number"); } catch (NullPointerException e) { System.out.println("null number"); } holder.changeText.setText(q.getChange() + " (" + q.getPercentChange() + ")"); } } return v; } } 

Der ViewHolder ist im Grunde eine statische classninstanz, die Sie beim Erstellen mit einer Ansicht verknüpfen und die untergeordneten Ansichten zur Laufzeit zwischenspeichern. Wenn die Ansicht bereits vorhanden ist, rufen findViewById die Halterinstanz ab und verwenden Sie ihre Felder, anstatt findViewById .

In Ihrem Fall:

 @Override public View getView(int position, View convertView, ViewGroup parent) { View v = convertView; ViewHolder holder; // to reference the child views for later actions if (v == null) { LayoutInflater vi = (LayoutInflater) getSystemService(Context.LAYOUT_INFLATER_SERVICE); v = vi.inflate(R.layout.mainrow, null); // cache view fields into the holder holder = new ViewHolder(); holder.nameText = (TextView) v.findViewById(R.id.nameText); holder.priceText = (TextView) v.findViewById(R.id.priceText); holder.changeText = (TextView) v.findViewById(R.id.changeText); // associate the holder with the view for later lookup v.setTag(holder); } else { // view already exists, get the holder instance from the view holder = (ViewHolder) v.getTag(); } // no local variables with findViewById here // use holder.nameText where you were // using the local variable nameText before return v; } // somewhere else in your class definition static class ViewHolder { TextView nameText; TextView priceText; TextView changeText; } 

Einschränkung: Ich habe nicht versucht, dies zu kompilieren, also nimm es mit einem Körnchen Salz.