Adapter优化（三）万能适配器

一、概述
实现万能适配器，基于通用ViewHolder。
链接：http://blog.youkuaiyun.com/qq_27993003/article/details/51447283

二、设想
Adapter要通用，首先要抽象的是：数据（抽象成List），getCount()、getItemId()、getItem()可以直接在抽象类实现，然后是重要的getView()方法…

分析getView()方法：

    @Override
    public View getView(int position, View convertView, ViewGroup parent) {
        ViewHolder viewHolder = ViewHolder.getViewHolder(context, parent, R.layout.item_1,
                position, convertView);
        viewHolder.setText(R.id.itemTitle, datas.get(position).getTitle())
                .setText(R.id.itemContent, datas.get(position).getContent());
        return viewHolder.getConvertView();
    }

第一行：特殊的在R.layout.item_1，设计：把这个layoutId通过构造器传进来
第二行：两个参数都是特性的，用抽象方法convert()封装
第三行：直接抽象类实现

新的getView()方法设计：

    @Override
    public View getView(int position, View convertView, ViewGroup parent) {
        ViewHolder viewHolder = ViewHolder.getViewHolder(context, parent, mItemLayoutId,
                position, convertView);
        convertViewHolder(viewHolder, getItem(position));
        return viewHolder.getConvertView();
    }


    public abstract void convertViewHolder(ViewHolder viewHolder, T item);

三、代码实现

通用接口：

package com.example.barbara.commonadapterexample;

import android.content.Context;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.BaseAdapter;

import java.util.List;

/**
 * 万能Adapter
 * @param <T>
 */
public abstract class CommonAdapter<T> extends BaseAdapter {
    private Context context;
    private List mDatas;
    private LayoutInflater mLayoutInflater;
    private int mItemLayoutId;

    public CommonAdapter(Context mcontext, List<T> mDatas, int mItemLayoutId) {
        mLayoutInflater = LayoutInflater.from(mcontext);
        this.context = mcontext;
        this.mDatas = mDatas;
        this.mItemLayoutId = mItemLayoutId;
    }

    @Override
    public int getCount() {
        return (mDatas==null)?-1:mDatas.size();
    }

    @Override
    public T getItem(int position) {
        return (mDatas==null)?null:(T) mDatas.get(position);
    }

    @Override
    public long getItemId(int position) {
        return position;
    }

    @Override
    public View getView(int position, View convertView, ViewGroup parent) {
        ViewHolder viewHolder = ViewHolder.getViewHolder(context, parent, mItemLayoutId,
                position, convertView);
        convertViewHolder(viewHolder, getItem(position));
        return viewHolder.getConvertView();
    }


    public abstract void convertViewHolder(ViewHolder viewHolder, T item);
}

MainActivity调用：

//直接匿名内部类，重写一个方法就OK！
        listView.setAdapter(new CommonAdapter<ItemBean>(this, list, R.layout.item_1){
            @Override
            public void convertViewHolder(ViewHolder viewHolder, ItemBean item) {
                viewHolder.setText(R.id.itemTitle, item.getTitle())
                        .setText(R.id.itemContent, item.getContent());

            }
        });