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：

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}}