【引入】
我们一般编写listView的时候顺序是这样的：
&＃8226;需要展示的数据集List
&＃8226;为这个数据集编写一个ListView
&＃8226;为这个ListView编写一个Adapter，一般继承自BaseAdapter
&＃8226;在BaseAdapter内部编写一个ViewHolder类，对应ListView里面的item控件，提高控件的查询效率
分析：
List
一般情况下，一个ListView对应一个Adapter类，对应一个ViewHolder类，那如果一个app中有20个ListView，我们岂不是要写20遍？所以的做法是：
&＃8226;抽取ViewHolder，作为公共的类。
&＃8226;将Adapter封装成CommonAdapter，作为公共的类。
一、传统方式编写适配器：
（1）activity_main.xml:
(2)item_listview.xml:单个item的布局文件
其对应的布局效果如下：
（3）Bean.java:ListView的数据集
package com.smyhvae.baseadapter.entities;
/**
* Created by smyhvae on 2015/5/4.
*/
public class Bean {
private String title;
private String desc;
private String time;
private String phone;
public Bean() {
}
public Bean(String title, String desc, String time, String phone) {
this.title = title;
this.desc = desc;
this.time = time;
this.phOne= phone;
}
public String getTitle() {
return title;
}
public void setTitle(String title) {
this.title = title;
}
public String getDesc() {
return desc;
}
public void setDesc(String desc) {
this.desc = desc;
}
public String getTime() {
return time;
}
public void setTime(String time) {
this.time = time;
}
public String getPhone() {
return phone;
}
public void setPhone(String phone) {
this.phOne= phone;
}
}
（4）MyAdapter.java:自定义适配器，继承自BaseAdapter
package com.smyhvae.baseadapter;
import android.content.Context;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.BaseAdapter;
import android.widget.TextView;
import com.smyhvae.baseadapter.entities.Bean;
import java.util.List;
/**
* Created by smyhvae on 2015/5/4.
*/
public class MyAdapter extends BaseAdapter {
private LayoutInflater mInflater;
private List mDatas;
//MyAdapter需要一个Context，通过Context获得Layout.inflater，然后通过inflater加载item的布局
public MyAdapter(Context context, List datas) {
mInflater = LayoutInflater.from(context);
mDatas = datas;
}
//返回数据集的长度
@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;
}
//这个方法才是重点，我们要为它编写一个ViewHolder
@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); //加载布局
holder = new ViewHolder();
holder.titleTv = (TextView) convertView.findViewById(R.id.titleTv);
holder.descTv = (TextView) convertView.findViewById(R.id.descTv);
holder.timeTv = (TextView) convertView.findViewById(R.id.timeTv);
holder.phOneTv= (TextView) convertView.findViewById(R.id.phoneTv);
convertView.setTag(holder);
} else { //else里面说明，convertView已经被复用了，说明convertView中已经设置过tag了，即holder
holder = (ViewHolder) convertView.getTag();
}
Bean bean = mDatas.get(position);
holder.titleTv.setText(bean.getTitle());
holder.descTv.setText(bean.getDesc());
holder.timeTv.setText(bean.getTime());
holder.phoneTv.setText(bean.getPhone());
return convertView;
}
//这个ViewHolder只能服务于当前这个特定的adapter，因为ViewHolder里会指定item的控件，不同的ListView，item可能不同，所以ViewHolder写成一个私有的类
private class ViewHolder {
TextView titleTv;
TextView descTv;
TextView timeTv;
TextView phoneTv;
}
}
(5)MainActivity.java:
package com.smyhvae.baseadapter;
import android.app.Activity;
import android.os.Bundle;
import android.view.Menu;
import android.view.MenuItem;
import android.widget.ListView;
import com.smyhvae.baseadapter.entities.Bean;
import java.util.ArrayList;
import java.util.List;
public class MainActivity extends Activity {
private ListView listView;
private List mDatas;
private MyAdapter mAdapter;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
initView();
initData();
}
//方法：初始化View
private void initView() {
listView = (ListView) findViewById(R.id.listView);
}
//方法；初始化Data
private void initData() {
mDatas = new ArrayList();
//将数据装到集合中去
Bean bean = new Bean("Android新技能1", "Android为ListView和GridView打造万能适配器", "2015-05-04", "10086");
mDatas.add(bean);
bean = new Bean("Android新技能2", "Android为ListView和GridView打造万能适配器", "2015-05-04", "10086");
mDatas.add(bean);
bean = new Bean("Android新技能3", "Android为ListView和GridView打造万能适配器", "2015-05-04", "10086");
mDatas.add(bean);
bean = new Bean("Android新技能4", "Android为ListView和GridView打造万能适配器", "2015-05-04", "10086");
mDatas.add(bean);
//为数据绑定适配器
mAdapter = new MyAdapter(this,mDatas);
listView.setAdapter(mAdapter);
}
}
运行效果如下：
【工程文件】
2015-05-04-BaseAdapter的传统写法.rar
二、ListView中自定义adapter的封装（万能的写法来编写适配器）：
完整版代码如下：
(1)activity_main.xml:
（2）item_listview.xml.xml:（ListView中单个item的布局）
其对应的布局效果如下：
（3）Bean.java:数据集
package com.smyhvae.baseadapter.entities;
/**
* Created by smyhvae on 2015/5/4.
*/
public class Bean {
private String title;
private String desc;
private String time;
private String phone;
public Bean() {
}
public Bean(String title, String desc, String time, String phone) {
this.title = title;
this.desc = desc;
this.time = time;
this.phOne= phone;
}
public String getTitle() {
return title;
}
public void setTitle(String title) {
this.title = title;
}
public String getDesc() {
return desc;
}
public void setDesc(String desc) {
this.desc = desc;
}
public String getTime() {
return time;
}
public void setTime(String time) {
this.time = time;
}
public String getPhone() {
return phone;
}
public void setPhone(String phone) {
this.phOne= phone;
}
}
（4）【可复用的代码】ViewHolder.java:
package com.smyhvae.baseadapter.utils;
import android.content.Context;
import android.util.SparseArray;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
/**
* Created by smyhvae on 2015/5/4.
*/
public class ViewHolder {
private SparseArray mViews;
private int mPosition;
private View mConvertView;
public ViewHolder(Context context, ViewGroup parent, int layoutId, int position) {
this.mPosition = position;
this.mViews = new SparseArray();
mCOnvertView= LayoutInflater.from(context).inflate(layoutId, parent, false);
mConvertView.setTag(this);
}
public static ViewHolder get(Context context, View convertView, ViewGroup parent, int layoutId, int position) {
if (cOnvertView== null) {
return new ViewHolder(context, parent, layoutId, position);
} else {
ViewHolder holder = (ViewHolder) convertView.getTag();
holder.mPosition = position; //即使ViewHolder是复用的，但是position记得更新一下
return holder;
}
}
/*
通过viewId获取控件
*/
//使用的是泛型T,返回的是View的子类
public 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;
}
}
（5）【可复用的代码】ListViewAdapter.java:自定义的通用适配器，继承自BaseAdapter。以后如果是自定义ListView的adapter，继承它就行了
package com.smyhvae.baseadapter.utils; import android.content.Context; import android.view.LayoutInflater; import android.view.View; import android.view.ViewGroup; import android.widget.BaseAdapter; import java.util.List; /** * Created by smyhvae on 2015/5/4. * 通用的ListView的BaseAdapter，所有的ListView的自定义adapter都可以继承这个类哦 */ public abstract class ListViewAdapterextends BaseAdapter { //为了让子类访问，于是将属性设置为protected protected Context mContext; protected List mDatas; protected LayoutInflater mInflater; private int layoutId; //不同的ListView的item布局肯能不同，所以要把布局单独提取出来 public ListViewAdapter(Context context, List datas, int layoutId) { this.mCOntext= context; mInflater = LayoutInflater.from(context); this.mDatas = datas; 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) { //初始化ViewHolder,使用通用的ViewHolder，一行代码就搞定ViewHolder的初始化咯 ViewHolder holder = ViewHolder.get(mContext, convertView, parent, layoutId, position);//layoutId就是单个item的布局 convert(holder, getItem(position)); return holder.getConvertView(); //这一行的代码要注意了 } //将convert方法公布出去 public abstract void convert(ViewHolder holder, T t); }
（6）ListViewAdapterWithViewHolder.java:继承自ListViewAdapter
package com.smyhvae.baseadapter; import android.content.Context; import android.widget.TextView; import com.smyhvae.baseadapter.entities.Bean; import com.smyhvae.baseadapter.utils.ListViewAdapter; import com.smyhvae.baseadapter.utils.ViewHolder; import java.util.List; /** * Created by smyhvae on 2015/5/4. */ public class ListViewAdapterWithViewHolder extends ListViewAdapter{ //MyAdapter需要一个Context，通过Context获得Layout.inflater，然后通过inflater加载item的布局 public ListViewAdapterWithViewHolder(Context context, List datas) { super(context, datas, R.layout.item_listview); } @Override public void convert(ViewHolder holder, Bean bean) { ((TextView) holder.getView(R.id.titleTv)).setText(bean.getTitle()); ((TextView) holder.getView(R.id.descTv)).setText(bean.getDesc()); ((TextView) holder.getView(R.id.timeTv)).setText(bean.getTime()); ((TextView) holder.getView(R.id.phoneTv)).setText(bean.getPhone()); /* TextView tv = holder.getView(R.id.titleTv); tv.setText(...); ImageView view = getView(viewId); Imageloader.getInstance().loadImag(view.url); */ } }
（7）MainActivity.java:
package com.smyhvae.baseadapter;
import android.app.Activity;
import android.os.Bundle;
import android.widget.ListView;
import com.smyhvae.baseadapter.entities.Bean;
import java.util.ArrayList;
import java.util.List;
public class MainActivity extends Activity {
private ListView listView;
private List mDatas;
private ListViewAdapterWithViewHolder listViewAdapterWithViewHolder;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
initView();
initData();
}
//方法：初始化View
private void initView() {
listView = (ListView) findViewById(R.id.listView);
}
//方法；初始化Data
private void initData() {
mDatas = new ArrayList();
//将数据装到集合中去
Bean bean = new Bean("Android新技能1", "Android为ListView和GridView打造万能适配器", "2015-05-04", "10086");
mDatas.add(bean);
bean = new Bean("Android新技能2", "Android为ListView和GridView打造万能适配器", "2015-05-04", "10086");
mDatas.add(bean);
bean = new Bean("Android新技能3", "Android为ListView和GridView打造万能适配器", "2015-05-04", "10086");
mDatas.add(bean);
bean = new Bean("Android新技能4", "Android为ListView和GridView打造万能适配器", "2015-05-04", "10086");
mDatas.add(bean);
//为数据绑定适配器
listViewAdapterWithViewHolder = new ListViewAdapterWithViewHolder(this, mDatas);
listView.setAdapter(listViewAdapterWithViewHolder);
}
}
运行效果：
这样的话，以后每写个ListView，就这么做：直接导入ViewHolder.java和ListViewAdapter，然后写一个自定义adapter继承自ListViewAdapter就行了。
【工程文件】2015-05-04-BaseAdapter的封装.rar
三、常见问题：
1、item控件抢占焦点：
假设item里有一个checkbox，那运行程序之后，发现只有checkBox能被点击，而item中的其他位置不能被点击(包括点击整个item也没有反应)，这是由于checkbox抢占了整个item的焦点。办法是:：
办法1：为该checkBox设置属性：android:focusable = "false"
办法2：为该item设置属性：android:descendantFocusability = "blocksDescendants"
不让这个item的焦点从上往下传。
2、ListView复用导致内容错乱。
以上就是本文的全部内容，希望对大家的学习有所帮助，也希望大家多多支持。
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