Android 构建一个可复用的自定义BaseAdapter
本节引言:
如题,本节给大家带来的是构建一个可复用的自定义BaseAdapter,我们每每涉及到ListView GridView等其他的Adapter控件,都需要自己另外写一个BaseAdapter类,这样显得非常麻烦, 又比如,我们想在一个界面显示两个ListView的话,我们也是需要些两个BaseAdapter... 这,程序员都是喜欢偷懒的哈,这节我们就来写一个可复用的自定义BaseAdapter类~
1.我们一点点开始改:
首先我们把上节写的自定义BaseAdapter贴下,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:
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;
}
@SuppressWarnings("unchecked")
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;
}
/**
* 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
}
}
本节小结:
本节给大家介绍了如何来实现一个可供复用的BaseAdapter,当然大家可以在这个的基础上根据 自己的需求进行修改,比如通过异步设置网络图片等~改代码是参考鸿洋大神的视频写的: 视频链接:Android-打造万能适配器 另外,实际编写中遇到一些问题,非常感谢Berial(B神)的耐心点拨~ ありがとうございます~
更多建议: