通常在BaseAdapter.getView中会使用ViewHolder方式来缓存界面中的组件,以便提高性能.那我们可以定义一个DataViewHolder类
public class DataViewHolder { HashMap<Integer,View> mapView = new HashMap<Integer,View>(); HashMap<String,Object> mapData = new HashMap<String,Object>(); public void setView(int key,View v){ this.mapView.put(key, v); } @SuppressWarnings("unchecked") public <T> T getView(int key){ return (T)this.mapView.get(key); } @SuppressWarnings("unchecked") public <T> T getView(Class<T> clazz, int key){ return (T)this.mapView.get(key); } public void setData(String key, Object value){ mapData.put(key, value); } @SuppressWarnings("unchecked") public <T> T getData(String key){ return (T)mapData.get(key); } @SuppressWarnings("unchecked") public <T> T getData(Class<T> clazz, String key){ return (T)mapData.get(key); } }对界面组件入手时,我们需要一个方法来提供一组界面组件的ID号,便于在BaseAdapter.getView方法中获取该组件实例.
public int[] getFindViewByIDs() { return new int[]{ R.id.ItemText, R.id.ItemImage }; }在实现BaseAdapter.getView方法时,通常需要获取布局资源,那么我们提供一个方法
public View getLayout(int position, DataViewHolder vh) { return inflater.inflate(R.layout.gv_content, null); }以便在BaseAdapter.getView方法中调用,我们来实现BaseAdapter.getView方法
public View getView(int position, View convertView, ViewGroup parent) { DataViewHolder vh; if(convertView == null){ vh = new DataViewHolder(); convertView = this.getLayout(position,vh); //获取布局资源 if(convertView == null) return null; int[] idAry = this.getFindViewByIDs(); //获取界面组件 if(idAry == null)idAry = new int[]{}; for(int id : idAry){ vh.setView(id, convertView.findViewById(id)); //资源id作为key,缓存界面中的组件 } convertView.setTag(vh); } else vh = (DataViewHolder)convertView.getTag(); this.renderData(position, vh); //继承类中的方法,完成数据到界面组件的赋值 return convertView; }
public void renderData(int position, DataViewHolder vh) { HashMap<String,String> map = (HashMap<String,String>)this.getItem(position); vh.getView(TextView.class, R.id.ItemText).setText(map.get("title")); ImageView imgView = vh.getView(R.id.ItemImage); imgView.setImageURI(...); }
public abstract class DataAdapter<TItem> extends BaseAdapter { protected LayoutInflater inflater=null; protected Context mContext; private List<TItem> lst; public DataAdapter(Context c, List<TItem> lst){ this.mContext = c; this.lst = lst; this.inflater=LayoutInflater.from(c); } @Override public int getCount() { return lst.size(); } public void insert(TItem data){ lst.add(0, data); this.notifyDataSetChanged(); } public void append(TItem data){ lst.add(data); this.notifyDataSetChanged(); } public void replace(TItem data){ int idx = this.lst.indexOf(data); this.replace(idx, data); } public void replace(int index, TItem data){ if(index<0)return; if(index> lst.size()-1)return; lst.set(index, data); this.notifyDataSetChanged(); } public List<TItem> getItems(){ return lst; } @Override public Object getItem(int position) { return lst.get(position); } public TItem getItemT(int position) { return lst.get(position); } @Override public long getItemId(int position) { return position; } public void removeItem(int position){ if(lst.size()<=0)return; if(position<0)return; if(position>lst.size()-1)return; lst.remove(position); this.notifyDataSetChanged(); } public void clear(){ lst.clear(); this.notifyDataSetChanged(); } public abstract int[] getFindViewByIDs(); public abstract View getLayout(int position, DataViewHolder vh); public final View getResourceView(int id){ return inflater.inflate(id, null); } @Override public View getView(int position, View convertView, ViewGroup parent) { DataViewHolder vh; if(convertView == null){ vh = new DataViewHolder(); convertView = this.getLayout(position,vh); if(convertView == null) return null; int[] idAry = this.getFindViewByIDs(); if(idAry == null)idAry = new int[]{}; for(int id : idAry){ vh.setView(id, convertView.findViewById(id)); } convertView.setTag(vh); } else vh = (DataViewHolder)convertView.getTag(); this.renderData(position, vh); return convertView; } public abstract void renderData(int position, DataViewHolder vh); }
实际使用,如何使用DataAdapter类呢?我们还是要继承来实现.
public class T1Activity extends Activity { protected void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.activity_t1); HashMap<String,String> map1 = new HashMap<String,String>(); map1.put("title","xxx"); map1.put("url","xxx"); ... List<HashMap<String,String>> al = new ArrayList<HashMap<String,String>>(); al.add(map1); //添加数据 al.add(map2); //添加数据 ... PrgmAdapter adapter = new PrgmAdapter(T1Activity.this, al); //实例化数据适配器 GridView gridview=(GridView)findViewById(R.id.gridView1); gridview.setAdapter(adapter); } //实际使用要继承来实现.现在我们不需要关心getView方法了(除非有特殊需求),只需要提供布局资源,组件资源号,并在renderData中完成赋值就OK了. private class PrgmAdapter extends DataAdapter<HashMap<String,String>>{ public PrgmAdapter(Context c, List<HashMap<String,String>> lst){ super(c,lst); } @Override public int[] getFindViewByIDs() { return new int[]{ R.id.ItemText, R.id.ItemImage }; } @Override public View getLayout(int position, DataViewHolder vh) { return this.getResourceView(R.layout.gv_content); } @Override public void renderData(int position, DataViewHolder vh) { HashMap<String,String> map = this.getItemT(position); vh.getView(TextView.class, R.id.ItemText).setText(map.get("title")); ImageView imgView = vh.getView(R.id.ItemImage); ... } } }
class StrAdapter extends DataAdapter<String>{}完全可以再进行调整,比如设置资源ID提供一个方法,在getView中使用.目前就可以基本使用满足通用性.
贴图:(都是使用上面定义的适配器)