ListView适配器的写法

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初级

优点:复用convertView
缺点:每次调用getview()都会去findview,是耗费资源的操作

public class MyAdapter extends BaseAdapter {    protected List<Bean> mList;    protected Context mContext;    LayoutInflater mInflater;    public MyAdapter(Context context, List<Bean> list) {        this.mList = list;        this.mContext = context;        mInflater=LayoutInflater.from(context);    }    @Override    public int getCount() {        return mList.size();    }    @Override    public Object getItem(int position) {        return mList.get(position);    }    @Override    public long getItemId(int position) {        return position;    }    public View getView(int position, View convertView, ViewGroup parent) {        /*----------视图操作--------------*/        View itemview = null;        if (convertView == null) {            //初始化布局            itemview = mInflater.inflate(R.layout.item, parent, false);        } else {            //复用convertView            itemview = convertView;        }         /*-------------- 查找控件 --------------*/        TextView title = (TextView) itemview.findViewById(R.id.tv_title);        TextView desc = (TextView) itemview.findViewById(R.id.tv_desc);        /*-------------- 数据绑定 --------------*/        Bean bean = mList.get(position);        title.setText(bean.tilte);        desc.setText(bean.desc);        return itemview;    }}

简化写法

    public View getView(int position, View convertView, ViewGroup parent) {        /*----------视图操作--------------*/        if (convertView == null) {            //convertView为空,            convertView = mInflater.inflate(R.layout.item, parent, false);        }        /*-------------- 查找控件 --------------*/        TextView title = (TextView) convertView.findViewById(R.id.tv_title);        TextView desc = (TextView) convertView.findViewById(R.id.tv_desc);        /*-------------- 数据绑定 --------------*/        Bean bean = mList.get(position);        title.setText(bean.tilte);        desc.setText(bean.desc);        return convertView;    }

中级

优点:利用ViewHolder存储找到的控件,避免多次findViewById
缺点:代码量大

public View getView(int position, View convertView, ViewGroup parent) {    ViewHolder holder = null;    /*----------视图操作--------------*/    if (convertView == null) {        //解析布局文件        convertView = mInflater.inflate(R.layout.item, parent, false);        //创建对象        holder = new ViewHolder();        //设置标记        convertView.setTag(holder);        /*-----------findview ,并存储到holder--------*/         holder.title = (TextView) convertView.findViewById(R.id.tv_title);        holder.desc = (TextView) convertView.findViewById(R.id.tv_desc);    } else {        //根据标记,取出holder        holder = (ViewHolder) convertView.getTag();    }    /*-------------- 赋值 --------------*/    Bean bean = mList.get(position);    holder.title.setText(bean.tilte);    holder.desc.setText(bean.desc);    return convertView;}//存放控件,避免多次findViewByIdclass ViewHolder{    TextView title;    TextView desc ;}

高级

holder可通用,减少代码量

public View getView(int position, View convertView, ViewGroup parent) {        HolderView holderView = null;        /*--------------视图操作--------------------*/        if (convertView == null) {            //创建一个holder            holderView = new HolderView(mContext, R.layout.item, position, parent);        } else {            //取出holder            holderView = (HolderView) convertView.getTag();            //更新条目位置            holderView.mPosition=position;        }        /*--------------数据绑定--------------------*/        //数据        Bean bean = mList.get(position);        //设置数据        holderView.setText(R.id.tv_commond, bean.commond)                .setText(R.id.tv_title, bean.tilte)                .setText(R.id.tv_desc, bean.desc)                .setText(R.id.tv_time, bean.time);        return holderView.mItemView;}

class HolderView {    //条目视图    View mItemView;    //条目位置    int mPosition;    //实质上是存储<Integer,Object>的HashMap,效率高于HashMap    SparseArray<View> mArrays;    public HolderView(Context context,int layoutId,int position,ViewGroup parent) {        LayoutInflater inflater=LayoutInflater.from(context);        //初始化布局        this.mItemView =inflater.inflate(layoutId, parent, false);        //创建容器        mArrays = new SparseArray<>();        //记录条目位置        mPosition = position;        //标记        this.mItemView.setTag(this);    }    /**     * 获取控件     */    public <T extends View> T getView(int viewId) {        //根据id从容器取出控件        View view = mArrays.get(viewId);        if (view == null) {            //findview            view = mItemView.findViewById(viewId);            //缓存            mArrays.put(viewId, view);        }        return (T) view;    }    /**     * 设置文本     */    public HolderView setText(int viewId, String string) {        TextView textView = getView(viewId);        textView.setText(string);        return this;    }    //以后如果有ImageView,Button等空间,可以自行增加方法,进行数据绑定}

超级

封装通用Adapter
封装通用Holder

public abstract class CommonAdapter<T> extends BaseAdapter {    protected List<T> mList;    protected Context mContext;    /**     * 布局文件id     */    protected int mLayoutId;    public CommonAdapter(Context context, int layoutId, List<T> list) {        this.mList = list;        this.mLayoutId = layoutId;        this.mContext = context;    }    @Override    public int getCount() {        return mList.size();    }    @Override    public Object getItem(int position) {        return mList.get(position);    }    @Override    public long getItemId(int position) {        return position;    }    @Override    public View getView(int position, View convertView, ViewGroup parent) {        //找到holder        BaseViewHolder holder = BaseViewHolder.get(mContext, mLayoutId, position, convertView, parent);        T bean = mList.get(position);        bindData(bean, holder);        return holder.getItemView();    }    /**     * 数据和控件进行绑定     *     * @param bean     * @param holder     */    protected abstract void bindData(T bean, BaseViewHolder holder);}

public class BaseViewHolder {    /**     * 泛型为<Integer,Object>的HashMap,效率比普通的HashMap高一些     * 存储子控件     */    private SparseArray<View> mArrays;    /**     * 条目位置     */    private int mPosition;    /**     * 条目视图View     */    private View mItemView;    /**     * 获取条目位置     */    public int getPosition() {        return mPosition;    }    /**     * 获取条目视图     */    public View getItemView() {        return mItemView;    }    //构造方法私有,禁止外部创建对象    //内部创建对象时:进行初始化布局等操作    private BaseViewHolder(Context context, int resId, int position, ViewGroup parent) {        //创建容器        this.mArrays = new SparseArray<>();        //记录item位置        this.mPosition = position;        //初始化布局        this.mItemView = LayoutInflater.from(context).inflate(resId, parent, false);        //标记Holder        this.mItemView.setTag(this);    }    /**     * 获取Holder     *     * @param context     上下文     * @param layoutId    布局id     * @param position    条目的位置     * @param convertView 复用的视图,convert(转换的)     * @param parent      父view     * @return     */    public static BaseViewHolder get(Context context, int layoutId,                                     int position, View convertView, ViewGroup parent) {        if (convertView == null) {            //返回一个新创建的Holder            return new BaseViewHolder(context, layoutId, position, parent);        } else {            //返回一个从标记中取出Holder            BaseViewHolder baseHolder = (BaseViewHolder) convertView.getTag();            //更新条目位置            baseHolder.mPosition = position;            return baseHolder;        }    }    /**     * 根据控件Id找到控件     *     * @param viewId 控件Id     * @param <T>     * @return     */    public <T extends View> T getView(int viewId) {        //从容器中取出控件        View view = mArrays.get(viewId);        //控件为空        if (view == null) {            //findview            view = mItemView.findViewById(viewId);            //缓存            mArrays.put(viewId, view);        }        return (T) view;    }    /**     * 设置文本     *     * @param viewId 控件Id     * @param text   文本内容     * @return     */    public BaseViewHolder setText(int viewId, String text) {        TextView textView = getView(viewId);        textView.setText(text);        return this;    }   //更多方法,根据条目id和数据自行创建... }

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