Android 万能适配器

传统写法：

一个ListView对应一个Adapter对应一个ViewHolder。

MyAdapter

public class MyAdapter extends BaseAdapter {    private LayoutInflater mInflater;    private List<Bean> mdatas = new ArrayList<>();    MyAdapter(Context context, List<Bean> mDatas) {        mInflater = LayoutInflater.from(context);        this.mdatas = mdatas;    }    @Override    public int getCount() {        return mdatas.size();    }    @Override    public Object 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 holder = null;        if (convertView == null) {            convertView = mInflater.inflate(R.layout.item_listview, parent, false);            holder = new ViewHolder();            holder.mTitle = (TextView) convertView.findViewById(R.id.id_title);            holder.mDesc = (TextView) convertView.findViewById(R.id.id_desc);            holder.mTime = (TextView) convertView.findViewById(R.id.id_time);            holder.mPhone = (TextView) convertView.findViewById(R.id.id_phone);            convertView.setTag(holder);        } else {            holder = (ViewHolder) convertView.getTag();        }        Bean bean = mdatas.get(position);        holder.mTitle.setText(bean.getTitle());        holder.mDesc.setText(bean.getDesc());        holder.mTime.setText(bean.getTime());        holder.mPhone.setText(bean.getPhone());        return convertView;    }    private class ViewHolder {        TextView mTitle;        TextView mDesc;        TextView mTime;        TextView mPhone;    }}

MainActivity

public class MainActivity extends Activity {    private ListView mListView;    private List<Bean> mDatas;    private MyAdapter mAdapter;    @Override    protected void onCreate(Bundle savedInstanceState) {        super.onCreate(savedInstanceState);        setContentView(R.layout.activity_commonadapter);        initDatas();        initView();    }    private void initView() {        mListView = (ListView) findViewById(R.id.id_listview);        mListView.setAdapter(mAdapter);    }    private void initDatas() {        mDatas = new ArrayList<Bean>();        Bean bean = new Bean("Android新技能Get 1", "打造万能的ListView和GridView适配器", "2016-11-06", "10086");        mDatas.add(bean);        bean = new Bean("Android新技能Get 2", "打造万能的ListView和GridView适配器", "2016-11-06", "10086");        mDatas.add(bean);        bean = new Bean("Android新技能Get 3", "打造万能的ListView和GridView适配器", "2016-11-06", "10086");        mDatas.add(bean);        bean = new Bean("Android新技能Get 4", "打造万能的ListView和GridView适配器", "2016-11-06", "10086");        mDatas.add(bean);        bean = new Bean("Android新技能Get 5", "打造万能的ListView和GridView适配器", "2016-11-06", "10086");        mDatas.add(bean);        bean = new Bean("Android新技能Get 6", "打造万能的ListView和GridView适配器", "2016-11-06", "10086");        mDatas.add(bean);        bean = new Bean("Android新技能Get 7", "打造万能的ListView和GridView适配器", "2016-11-06", "10086");        mDatas.add(bean);        bean = new Bean("Android新技能Get 8", "打造万能的ListView和GridView适配器", "2016-11-06", "10086");        mDatas.add(bean);        bean = new Bean("Android新技能Get 9", "打造万能的ListView和GridView适配器", "2016-11-06", "10086");        mDatas.add(bean);        mAdapter = new MyAdapter(this, mDatas);    }}

但是如果项目中有许多的ListView，就需要些很多的adapter和viewholder。

共通ViewHolder:

public class ViewHolder {    // 比map更有效率，key固定为Integer    private SparseArray<View> mViews;    private int mPosition;    private View mConvertView;    public ViewHolder(Context mContext, ViewGroup parent, int layoutId, int position) {        this.mPosition = position;        this.mViews = new SparseArray<>();        this.mConvertView = LayoutInflater.from(mContext).inflate(layoutId, parent, false);        this.mConvertView.setTag(this);    }    public static ViewHolder get(Context mContext, View convertView, ViewGroup parent, int layoutId, int position) {        if (convertView == null) {            return new ViewHolder(mContext, parent, layoutId, position);        } else {            ViewHolder holder = (ViewHolder) convertView.getTag();            holder.mPosition = position;            return holder;        }    }    /**     * 通过ViewId获取控件     *     * @param viewId     * @param <T>     * @return     */    public <T extends View> T getView(int viewId) {        View view = mViews.get(viewId);        if (view == null) {            view = mConvertView.findViewById(viewId);            mViews.put(viewId, view);        }        return (T) view;    }    public View getConvertView() {        return mConvertView;    }    public ViewHolder setText(int viewId, String context) {        TextView tv = getView(viewId);        tv.setText(context);        return this;    }    public ViewHolder setImageResource(int viewId, int resId) {        ImageView tv = getView(viewId);        tv.setImageResource(resId);        return this;    }    public int getPosition() {        return mPosition;    }}

任意的Adapter可以通过这个共通的ViewHolder获取布局，如果当前convertView没有tag就新建一个，如果已经存在，就直接返回，这一点和传统的写法是一样的。

而当前的布局中所有的控件，都可以通过getView获取，如果是第一次调用会往view里面加数据，如果不是第一次，就可以直接从views里面直接读取view。

共通的Adapter:

Adapter中有很多代码是可以提取出来的，例如getItem（）getCount（）等等。

public abstract class CommonAdapter<T> extends BaseAdapter {    protected Context mContext;    protected List<T> mDatas;    protected LayoutInflater mInflater;    protected int layoutId;    public CommonAdapter(Context mContext, List<T> mDatas, int layoutId) {        this.mContext = mContext;        this.mDatas = mDatas;        this.mInflater = LayoutInflater.from(mContext);        this.layoutId = 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(mContext, convertView, parent, layoutId, position);        convert(viewHolder, getItem(position));        return viewHolder.getConvertView();    }    public abstract void convert(ViewHolder viewHolder, T t);}

convert方法用来自定义数据源和控件之间的联系。

自定义adapter：

public class MyAdapterWithCommonViewHolder extends CommonAdapter<Bean> {    public MyAdapterWithCommonViewHolder(Context mContext, List<Bean> mDatas) {        super(mContext, mDatas, R.layout.item_listview);    }    @Override    public void convert(final 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());    }}

这样代码就会变得非常的简洁，如果列表中有出了textview以外的空间，也可以去共通的ViewHolder类中添加对应的方法。