android:ViewHolder模式

[java] 

 

        ViewHolder holder = null;
        if(convertView == null){
                convertView = mInflater.inflate(R.layout.xxx null);
                holder = new ViewHolder();
                holder.tvXXX = (TextView)findViewById(R.id.xxx);
                //...一連串的findViewById
        }
        else{
                holder = (ViewHolder) convertView.getTag();
        }



        private static class ViewHolder{
                TextView tvXXX;
                //很多view的定義
        }

這麼寫一次還行，但問題是總有很多很多的ViewAdapter要這麼寫，每次都repeat,repeat,repeat  累啊。      所以，有這麼一種簡潔的寫法分享給大家，先宣告，從國外網站上看的，不是自己原創的，但確實很喜歡這個簡潔的設計。

ViewHolder這麼寫（只提供一個靜態方法，其實可以加一個私有建構函式防止外部例項化），程式碼很簡單，看過就明白了

 

public class ViewHolder {
    // I added a generic return type to reduce the casting noise in client code
    @SuppressWarnings("unchecked")
    public static <T extends View> T get(View view, int id) {
        SparseArray<View> viewHolder = (SparseArray<View>) view.getTag();
        if (viewHolder == null) {
            viewHolder = new SparseArray<View>();
            view.setTag(viewHolder);
        }
        View childView = viewHolder.get(id);
        if (childView == null) {
            childView = view.findViewById(id);
            viewHolder.put(id, childView);
        }
        return (T) childView;
    }
}

在getView裡這樣

 

 

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

    if (convertView == null) {
        convertView = LayoutInflater.from(context)
          .inflate(R.layout.banana_phone, parent, false);
    }

    ImageView bananaView = ViewHolder.get(convertView, R.id.banana);
    TextView phoneView = ViewHolder.get(convertView, R.id.phone);

    BananaPhone bananaPhone = getItem(position);
    phoneView.setText(bananaPhone.getPhone());
    bananaView.setImageResource(bananaPhone.getBanana());

    return convertView;
}