模版方法模式

作用

把都需要實現的上放到抽象父類中,具體細節交給子類實現;
實現了代碼的複用;

Demo

以常用的listview的adapter舉例

//把通用操作抽取到抽象父類中
public abstract class MyBaseAdapter<T> extends BaseAdapter {
    Context mContext;
    List<T> mDatas;
    LayoutInflater mLayoutInflater;
    public MyBaseAdapter(Context context, List<T> datas) {
        mContext = context;
        mDatas = datas;
        mLayoutInflater=LayoutInflater.from(context);
    }

    @Override
    public int getCount() {
        return mDatas!=null?mDatas.size():0;
    }
    @Override
    public T getItem(int position) {
        return mDatas!=null?mDatas.get(position):null;
    }
    @Override
    public long getItemId(int position) {
        return position;
    }
    @Override
    public abstract View getView(int position, View convertView, ViewGroup parent);

    //datas相關
    public void setDatas(List<T> datas){
        mDatas=datas;
        notifyDataSetChanged();
    }
    public void clearDatas(){
        mDatas=null;
        notifyDataSetChanged();
    }
    public void appendDatas(List<T> datas){
        if (mDatas==null)mDatas=new ArrayList<>();
        mDatas.addAll(datas);
    }
    public void appendDatas(T data){
        if (mDatas==null)mDatas=new ArrayList<>();
        mDatas.add(data);
    }
}

public abstract class CommonAdapter<T,H> extends MyBaseAdapter<T> {

    public CommonAdapter(Context context, List<T> datas) {
        super(context, datas);
    }

    @Override
    public View getView(int position, View convertView, ViewGroup parent) {
        T data = mDatas.get(position);
        H holder=null;
        if (convertView==null){
            convertView=createConvertView(mLayoutInflater,position,parent,getItemViewType(position));
            holder=createViewHolder(convertView,data,position);
            convertView.setTag(holder);
        }else{
            holder= (H) convertView.getTag();
        }
        bindDatas(holder,data,position);
        return convertView;
    }

    public abstract View createConvertView(LayoutInflater layoutInflater, int position, ViewGroup parent, int itemViewType);
    public abstract H createViewHolder(View convertView, T data, int position);
    protected abstract void bindDatas(H holder, T data, int position);
}

//細節由子類實現
public class CommonAdapterDEMO extends CommonAdapter<String, CommonAdapterDEMO.Holder > {
    public CommonAdapterDEMO(Context context, List datas) {
        super(context, datas);
    }

    @Override
    public View createConvertView(LayoutInflater layoutInflater, int position, ViewGroup parent, int itemViewType) {
        View layout = layoutInflater.inflate(android.R.layout.simple_list_item_1, parent, false);
        return layout;
    }

    @Override
    public Holder createViewHolder(View convertView, String data, int position) {
        return new Holder(convertView);
    }

    @Override
    protected void bindDatas(Holder holder, String data, int position) {
        holder.tv.setText(data);
    }

    class Holder {
        TextView tv;
        public Holder(View view) {
            tv= (TextView) view.findViewById(android.R.id.text1);
        }
    }
}