自定义一个可复用的BaseAdapter

1.我们一点点开始改：

首先我们自定义BaseAdapter，等下我们就要对他进行升级改造

/**

 * Created by Jay on 2015/9/21 0021.

 */

public class MyAdapter extends BaseAdapter {

    private Context mContext;

    private LinkedList<Data> mData;

    public MyAdapter() {

    }

    public MyAdapter(LinkedList<Data> mData, Context mContext) {

        this.mData = mData;

        this.mContext = mContext;

    }

    @Override

    public int getCount() {

        return mData.size();

    }

    @Override

    public Object getItem(int position) {

        return null;

    }

    @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 = LayoutInflater.from(mContext).inflate(R.layout.item_list, parent, false);

            holder = new ViewHolder();

            holder.img_icon = (ImageView) convertView.findViewById(R.id.img_icon);

            holder.txt_content = (TextView) convertView.findViewById(R.id.txt_content);

            convertView.setTag(holder);

        } else {

            holder = (ViewHolder) convertView.getTag();

        }

        holder.img_icon.setImageResource(mData.get(position).getImgId());

        holder.txt_content.setText(mData.get(position).getContent());

        return convertView;

    }

    //添加一个元素

    public void add(Data data) {

        if (mData == null) {

            mData = new LinkedList<>();

        }

        mData.add(data);

        notifyDataSetChanged();

    }

    //往特定位置，添加一个元素

    public void add(int position,Data data){

        if (mData == null) {

            mData = new LinkedList<>();

        }

        mData.add(position, data);

        notifyDataSetChanged();

    }

    public void remove(Data data) {

        if(mData != null) {

            mData.remove(data);

        }

        notifyDataSetChanged();

    }

    public void remove(int position) {

        if(mData != null) {

            mData.remove(position);

        }

        notifyDataSetChanged();

    }

    public void clear() {

        if(mData != null) {

            mData.clear();

        }

        notifyDataSetChanged();

    }

    private class ViewHolder {

        ImageView img_icon;

        TextView txt_content;

    }

}

升级1：将Entity设置成泛型

好的，毕竟我们传递过来的Entitiy实体类可能千奇百怪，比如有Person，Book，Wether等，所以我们将Entity设置成泛型，修改后的代码如下：

<pre>

public class MyAdapter<T> extends BaseAdapter {

    private Context mContext;

    private LinkedList<T> mData;

    public MyAdapter() {

    }

    public MyAdapter(LinkedList<T> mData, Context mContext) {

        this.mData = mData;

        this.mContext = mContext;

    }

    @Override

    public int getCount() {

        return mData.size();

    }

    @Override

    public Object getItem(int position) {

        return null;

    }

    @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 = LayoutInflater.from(mContext).inflate(R.layout.item_list, parent, false);

            holder = new ViewHolder();

            holder.img_icon = (ImageView) convertView.findViewById(R.id.img_icon);

            holder.txt_content = (TextView) convertView.findViewById(R.id.txt_content);

            convertView.setTag(holder);

        } else {

            holder = (ViewHolder) convertView.getTag();

        }

        holder.img_icon.setImageResource(mData.get(position).getImgId());

        holder.txt_content.setText(mData.get(position).getContent());

        return convertView;

    }

    //添加一个元素

    public void add(T data) {

        if (mData == null) {

            mData = new LinkedList<>();

        }

        mData.add(data);

        notifyDataSetChanged();

    }

    //往特定位置，添加一个元素

    public void add(int position,T data){

        if (mData == null) {

            mData = new LinkedList<>();

        }

        mData.add(position, data);

        notifyDataSetChanged();

    }

    public void remove(T data) {

        if(mData != null) {

            mData.remove(data);

        }

        notifyDataSetChanged();

    }

    public void remove(int position) {

        if(mData != null) {

            mData.remove(position);

        }

        notifyDataSetChanged();

    }

    public void clear() {

        if(mData != null) {

            mData.clear();

        }

        notifyDataSetChanged();

    }

    private class ViewHolder {

        ImageView img_icon;

        TextView txt_content;

    }

}

好的，上面我们做的事仅仅是将Data类型换成了泛型T！

升级2：ViewHolder类的升级改造：

我们先来看看前面我们的ViewHolder干了什么？答：findViewById，设置控件状态；下面我们想在完成这个基础上，将getView()方法大部分的逻辑写到ViewHolder类里，这个ViewHolder要做的事：

定义一个查找控件的方法，我们的思路是通过暴露公共的方法，调用方法时传递过来控件id，以及设置的内容，比如TextView设置文本： public ViewHolder setText(int id, CharSequence text){文本设置}

将convertView复用部分搬到这里，那就需要传递一个context对象了，我们把需要获取的部分都写到构造方法中！

写一堆设置方法(public)，比如设置文字大小颜色，图片背景等！

好的，接下来我们就来一步步改造我们的ViewHolder类

1）相关参数与构造方法：

public static class ViewHolder {

    private SparseArray<View> mViews;   //存储ListView 的 item中的View

    private View item;                  //存放convertView

    private int position;               //游标

    private Context context;            //Context上下文

    //构造方法，完成相关初始化

    private ViewHolder(Context context, ViewGroup parent, int layoutRes) {

        mViews = new SparseArray<>();

        this.context = context;

        View convertView = LayoutInflater.from(context).inflate(layoutRes, parent,false);

        convertView.setTag(this);

        item = convertView;

    }

    ImageView img_icon;

    TextView txt_content;

}

2）绑定ViewHolder与Item

在上面的基础上我们再添加一个绑定的方法

//绑定ViewHolder与item

public static ViewHolder bind(Context context, View convertView, ViewGroup parent,

                              int layoutRes, int position) {

    ViewHolder holder;

    if(convertView == null) {

        holder = new ViewHolder(context, parent, layoutRes);

    } else {

        holder = (ViewHolder) convertView.getTag();

        holder.item = convertView;

    }

    holder.position = position;

    return holder;

}

3）根据id获取集合中保存的控件

public <T extends View> T getView(int id) {

    T t = (T) mViews.get(id);

    if(t == null) {

        t = (T) item.findViewById(id);

        mViews.put(id, t);

    }

    return t;

}

4) 接着我们再定义一堆暴露出来的方法

/**

 * 获取当前条目

 */

public View getItemView() {

    return item;

}

/**

 * 获取条目位置

 */

public int getItemPosition() {

    return position;

}

/**

 * 设置文字

 */

public ViewHolder setText(int id, CharSequence text) {

    View view = getView(id);

    if(view instanceof TextView) {

        ((TextView) view).setText(text);

    }

    return this;

}

/**

 * 设置图片

 */

public ViewHolder setImageResource(int id, int drawableRes) {

    View view = getView(id);

    if(view instanceof ImageView) {

        ((ImageView) view).setImageResource(drawableRes);

    } else {

        view.setBackgroundResource(drawableRes);

    }

    return this;

}

/**

 * 设置点击监听

 */

public ViewHolder setOnClickListener(int id, View.OnClickListener listener) {

    getView(id).setOnClickListener(listener);

    return this;

}

/**

 * 设置可见

 */

public ViewHolder setVisibility(int id, int visible) {

    getView(id).setVisibility(visible);

    return this;

}

/**

 * 设置标签

 */

public ViewHolder setTag(int id, Object obj) {

    getView(id).setTag(obj);

    return this;

}

//其他方法可自行扩展

好的，ViewHolder的改造升级完成~

升级3：定义一个抽象方法，完成ViewHolder与Data数据集的绑定

public abstract void bindView(ViewHolder holder, T obj);

我们创建新的BaseAdapter的时候，实现这个方法就好，另外，别忘了把我们自定义的BaseAdapter改成abstact抽象的！

升级4：修改getView()部分的内容

@Override

public View getView(int position, View convertView, ViewGroup parent) {

    ViewHolder holder = ViewHolder.bind(parent.getContext(), convertView, parent, mLayoutRes

            , position);

    bindView(holder,getItem(position));

    return holder.getItemView();

}

2.升级完毕，我们写代码来体验下：

我们要实现的效果图：

就是上面有两个列表，布局不一样，但是我只使用一个BaseAdapter类来完成上述效果！

关键代码如下：

MainActivity.java：

public class MainActivity extends AppCompatActivity {

    private Context mContext;

    private ListView list_book;

    private ListView list_app;

    private MyAdapter<App> myAdapter1 = null;

    private MyAdapter<Book> myAdapter2 = null;

    private List<App> mData1 = null;

    private List<Book> mData2 = null;

    @Override

    protected void onCreate(Bundle savedInstanceState) {

        super.onCreate(savedInstanceState);

        setContentView(R.layout.activity_main);

        mContext = MainActivity.this;

        init();

    }

    private void init() {

        list_book = (ListView) findViewById(R.id.list_book);

        list_app = (ListView) findViewById(R.id.list_app);

        //数据初始化

        mData1 = new ArrayList<App>();

        mData1.add(new App(R.mipmap.iv_icon_baidu,"百度"));

        mData1.add(new App(R.mipmap.iv_icon_douban,"豆瓣"));

        mData1.add(new App(R.mipmap.iv_icon_zhifubao,"支付宝"));

        mData2 = new ArrayList<Book>();

        mData2.add(new Book("《第一行代码Android》","郭霖"));

        mData2.add(new Book("《Android群英传》","徐宜生"));

        mData2.add(new Book("《Android开发艺术探索》","任玉刚"));

        //Adapter初始化

        myAdapter1 = new MyAdapter<App>((ArrayList)mData1,R.layout.item_one) {

            @Override

            public void bindView(ViewHolder holder, App obj) {

                holder.setImageResource(R.id.img_icon,obj.getaIcon());

                holder.setText(R.id.txt_aname,obj.getaName());

            }

        };

        myAdapter2 = new MyAdapter<Book>((ArrayList)mData2,R.layout.item_two) {

            @Override

            public void bindView(ViewHolder holder, Book obj) {

                holder.setText(R.id.txt_bname,obj.getbName());

                holder.setText(R.id.txt_bauthor,obj.getbAuthor());

            }

        };

        //ListView设置下Adapter：

        list_book.setAdapter(myAdapter2);

        list_app.setAdapter(myAdapter1);

    }

}

我们写的可复用的BaseAdapter的使用就如上面所述~

3.代码示例下载：

ListViewDemo4.zip

贴下最后写好的MyAdapter类吧，可根据自己的需求进行扩展：

MyAdapter.java：

/**

 * Created by Jay on 2015/9/22 0022.

 */

public abstract class MyAdapter<T> extends BaseAdapter {

    private ArrayList<T> mData;

    private int mLayoutRes;           //布局id

    public MyAdapter() {

    }

    public MyAdapter(ArrayList<T> mData, int mLayoutRes) {

        this.mData = mData;

        this.mLayoutRes = mLayoutRes;

    }

    @Override

    public int getCount() {

        return mData != null ? mData.size() : 0;

    }

    @Override

    public T getItem(int position) {

        return mData.get(position);

    }

    @Override

    public long getItemId(int position) {

        return position;

    }

    @Override

    public View getView(int position, View convertView, ViewGroup parent) {

        ViewHolder holder = ViewHolder.bind(parent.getContext(), convertView, parent, mLayoutRes

                , position);

        bindView(holder, getItem(position));

        return holder.getItemView();

    }

    public abstract void bindView(ViewHolder holder, T obj);

    //添加一个元素

    public void add(T data) {

        if (mData == null) {

            mData = new ArrayList<>();

        }

        mData.add(data);

        notifyDataSetChanged();

    }

    //往特定位置，添加一个元素

    public void add(int position, T data) {

        if (mData == null) {

            mData = new ArrayList<>();

        }

        mData.add(position, data);

        notifyDataSetChanged();

    }

    public void remove(T data) {

        if (mData != null) {

            mData.remove(data);

        }

        notifyDataSetChanged();

    }

    public void remove(int position) {

        if (mData != null) {

            mData.remove(position);

        }

        notifyDataSetChanged();

    }

    public void clear() {

        if (mData != null) {

            mData.clear();

        }

        notifyDataSetChanged();

    }

    public static class ViewHolder {

        private SparseArray<View> mViews;   //存储ListView 的 item中的View

        private View item;                  //存放convertView

        private int position;               //游标

        private Context context;            //Context上下文

        //构造方法，完成相关初始化

        private ViewHolder(Context context, ViewGroup parent, int layoutRes) {

            mViews = new SparseArray<>();

            this.context = context;

            View convertView = LayoutInflater.from(context).inflate(layoutRes, parent, false);

            convertView.setTag(this);

            item = convertView;}//绑定ViewHolder与itempublicstaticViewHolder bind(Context context,View convertView,ViewGroup parent,int layoutRes,int position){ViewHolder holder;if(convertView ==null){

                holder =newViewHolder(context, parent, layoutRes);}else{

                holder =(ViewHolder) convertView.getTag();

                holder.item = convertView;}

            holder.position = position;return holder;}@SuppressWarnings("unchecked")public<T extendsView> T getView(int id){

            T t =(T) mViews.get(id);if(t ==null){

                t =(T) item.findViewById(id);

                mViews.put(id, t);}return t;}/**

         * 获取当前条目

         */publicView getItemView(){return item;}/**

         * 获取条目位置

         */publicint getItemPosition(){return position;}/**

         * 设置文字

         */publicViewHolder setText(int id,CharSequence text){View view = getView(id);if(view instanceofTextView){((TextView) view).setText(text);}returnthis;}/**

         * 设置图片

         */publicViewHolder setImageResource(int id,int drawableRes){View view = getView(id);if(view instanceofImageView){((ImageView) view).setImageResource(drawableRes);}else{

                view.setBackgroundResource(drawableRes);}returnthis;}/**

         * 设置点击监听

         */publicViewHolder setOnClickListener(int id,View.OnClickListener listener){

            getView(id).setOnClickListener(listener);returnthis;}/**

         * 设置可见

         */publicViewHolder setVisibility(int id,int visible){

            getView(id).setVisibility(visible);returnthis;}/**

         * 设置标签

         */publicViewHolder setTag(int id,Object obj){

            getView(id).setTag(obj);returnthis;}//其他方法可自行扩展}}

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