慕课网ListViewCommonAdapter万能适配器代码摘要

1.ViewHolder类中代码  主要三个方法加上构造方法

        主要三个方法:get(),getView(),getConvertView();

public class ViewHolder {
    SparseArray<View> mView;//这是一种<以int做键,object做值>的更高效的Map
    int mPosition;
    View mConvertView;
    public ViewHolder(Context context, int position, ViewGroup parent, int layoutId){
        this.mPosition=position;
        this.mView=new SparseArray<>();
        mConvertView=LayoutInflater.from(context).inflate(layoutId,null);
        mConvertView.setTag(this);

    }
    public static ViewHolder get(Context context, View convertView, ViewGroup parent, int layoutId,int position){

        if (convertView==null){

            return new ViewHolder(context,position,parent,layoutId);

        }else {
            ViewHolder holder= (ViewHolder) convertView.getTag();
            holder.mPosition=position;
            return holder;
        }
    }


    public <T extends View> T getView(int viewId){
        View view=mView.get(viewId);
        if (view==null){
            view=mConvertView.findViewById(viewId);
            mView.put(viewId,view);
        }
        return (T)view;
    }

   public View getConvertView(){

       return mConvertView;
   }
    //辅助:将convert方法继续简化,可以为常用的textView,imageView 等添加同类方法
    public ViewHolder setText(int viewId,String text){
        TextView tv=getView(viewId);
        tv.setText(text);
        return this;
    }
    //使用getPosition结合List<Integer>可以配合点击事件保存选中Item项
    public int getPosition() {
        return mPosition;
    }


}

2.CommonAdapter 抽象类类中的代码

    重点解析:通过提供抽象convert()方法分解出getView()方法中的不易复用的代码功能

public abstract class CommonAdapter<T> extends BaseAdapter{

    Context context;
    List<T> mDatas;
    int mlayoutId;

    public CommonAdapter(List<T> mDatas, Context context,int layoutId) {

        this.mDatas = mDatas;
        this.context = context;
        this.mlayoutId=layoutId;
    }

    @Override
    public int getCount() {
        return mDatas.size();
    }

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

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

    @Override
    public  View getView(int position, View convertView, ViewGroup parent){
        ViewHolder viewHolder=ViewHolder.get(context,convertView,parent,mlayoutId,       position);

        convert(viewHolder,this.getItem(position));
        return viewHolder.getConvertView();
    }
    public abstract void convert(ViewHolder holder,T t);
}

3.不考虑ListView点击事件等后续情况可以在Activity中使用匿名内部类的方式创建适配器对象,代码如下:

 list.setAdapter(new CommonAdapter<Bean>(beanList,this,R.layout.list_item) {
    @Override
    public void convert(ViewHolder viewHolder, final Bean bean) {
        viewHolder.setText(R.id.id_title,bean.getTitle())
                .setText(R.id.id_desc,bean.getDesc())
                .setText(R.id.id_time,bean.getTime())
                .setText(R.id.id_phone,bean.getPhone());//使用链式编程简化代码
   //配合CheckBox使用,解决convertView复用后CheckBox的选中问题
   //这种写法实在bean中有isChecked属性来保存CheckBox的选中状态的请况下
        final CheckBox cb=viewHolder.getView(R.id.id_check);
        cb.setChecked(bean.getChecked());

        cb.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                bean.setChecked(cb.isChecked());
            }
        });
    }
});

4.考虑的ListView的点击事件等等情况,不适合用匿名内部类的时候就用外部类,也很方便:

public class YouAdapter extends CommonAdapter<Bean>{

    List<Integer> mPos=new ArrayList<>();//定义一个集合来保存选中项

    public YouAdapter( List<Bean> mDatas,Context context,int layoutId) {
       super(mDatas,context,layoutId);
    }



    //现在YouAdapter里只有一个方法,建议使用匿名内部类的写法简化
    @Override
    public void convert(final ViewHolder viewHolder, final Bean bean) {
        ((TextView)viewHolder.getView(R.id.id_title)).setText(bean.getTitle());
        ((TextView)viewHolder.getView(R.id.id_desc)).setText(bean.getDesc());
        ((TextView)viewHolder.getView(R.id.id_time)).setText(bean.getTime());
        ((TextView)viewHolder.getView(R.id.id_phone)).setText(bean.getPhone());


     final CheckBox cb=viewHolder.getView(R.id.id_check);
           //  cb.setChecked(bean.getChecked());
//
//        cb.setOnClickListener(new View.OnClickListener() {
//            @Override
//            public void onClick(View v) {
//                  bean.setChecked(cb.isChecked());

//            }
//        });
        //或者在bean中没有isCheck的属性来保存是否选中,可以定义一个List<Integer>集合来保存所选中Item
            cb.setChecked(false);
        if (mPos.contains(viewHolder.getPosition())){
            cb.setChecked(true);
        }
        cb.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {

                if (cb.isChecked()) {
                    mPos.add(viewHolder.getPosition());
                }else{
                    mPos.remove((Integer) viewHolder.getPosition());
                }
            }
        });
    }
}