【引入】

我们一般编写listView的时候顺序是这样的：

•需要展示的数据集List<T>

•为这个数据集编写一个ListView

•为这个ListView编写一个Adapter，一般继承自BaseAdapter

•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<T>:ListView --> Adapter extends BaseAdapter --> ViewHolder

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：

•抽取ViewHolder，作为公共的类。

•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:

<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android" xmlns:tools="http://schemas.android.com/tools" android:layout_width="match_parent" android:layout_height="match_parent"> <ListView android:id="@+id/listView" android:layout_width="match_parent" android:layout_height="match_parent"></ListView> </RelativeLayout>

(2)item_listview.xml:单个item的布局文件

<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android" xmlns:tools="http://schemas.android.com/tools" android:layout_width="match_parent" android:layout_height="match_parent" android:padding="10dp"> <TextView android:id="@+id/titleTv" android:layout_width="wrap_content" android:layout_height="wrap_content" android:singleLine="true" android:text="Android新技能" android:textColor="#444" android:textSize="16sp" /> <TextView android:id="@+id/descTv" android:layout_width="match_parent" android:layout_height="wrap_content" android:layout_below="@+id/titleTv" android:layout_marginTop="10dp" android:maxLines="2" android:minLines="1" android:text="Android为ListView和GridView打造万能适配器" android:textColor="#898989" android:textSize="16sp" /> <TextView android:id="@+id/timeTv" android:paddingTop="3dp" android:layout_width="wrap_content" android:layout_height="wrap_content" android:layout_below="@+id/descTv" android:layout_marginTop="10dp" android:text="2015-05-04" android:textColor="#898989" android:textSize="12sp" /> <TextView android:padding="2dp" android:id="@+id/phoneTv" android:gravity="center" android:layout_width="wrap_content" android:layout_height="wrap_content" android:layout_below="@+id/descTv" android:layout_marginTop="10dp" android:background="#2ED667" android:drawableLeft="@mipmap/phone" android:drawablePadding="5dp" android:text="10086" android:textColor="#ffffff" android:textSize="12sp" android:layout_alignParentRight="true" /> </RelativeLayout>

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<Bean> 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<Bean> 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<Bean> 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<Bean>(); //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:

<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android" xmlns:tools="http://schemas.android.com/tools" android:layout_width="match_parent" android:layout_height="match_parent"> <ListView android:id="@+id/listView" android:layout_width="match_parent" android:layout_height="match_parent"></ListView> </RelativeLayout>

（2）item_listview.xml.xml:（ListView中单个item的布局）

<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android" xmlns:tools="http://schemas.android.com/tools" android:layout_width="match_parent" android:layout_height="match_parent" android:padding="10dp"> <TextView android:id="@+id/titleTv" android:layout_width="wrap_content" android:layout_height="wrap_content" android:singleLine="true" android:text="Android新技能" android:textColor="#444" android:textSize="16sp" /> <TextView android:id="@+id/descTv" android:layout_width="match_parent" android:layout_height="wrap_content" android:layout_below="@+id/titleTv" android:layout_marginTop="10dp" android:maxLines="2" android:minLines="1" android:text="Android为ListView和GridView打造万能适配器" android:textColor="#898989" android:textSize="16sp" /> <TextView android:id="@+id/timeTv" android:paddingTop="3dp" android:layout_width="wrap_content" android:layout_height="wrap_content" android:layout_below="@+id/descTv" android:layout_marginTop="10dp" android:text="2015-05-04" android:textColor="#898989" android:textSize="12sp" /> <TextView android:padding="2dp" android:id="@+id/phoneTv" android:gravity="center" android:layout_width="wrap_content" android:layout_height="wrap_content" android:layout_below="@+id/descTv" android:layout_marginTop="10dp" android:background="#2ED667" android:drawableLeft="@mipmap/phone" android:drawablePadding="5dp" android:text="10086" android:textColor="#ffffff" android:textSize="12sp" android:layout_alignParentRight="true" /> </RelativeLayout>

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<View> mViews; private int mPosition; private View mConvertView; public ViewHolder(Context context, ViewGroup parent, int layoutId, int position) { this.mPosition = position; this.mViews = new SparseArray<View>(); 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 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; } }

（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 ListViewAdapter<T> extends BaseAdapter { //为了让子类访问，于是将属性设置为protected protected Context mContext; protected List<T> 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<T> 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<Bean> { //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<Bean> 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<Bean> 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<Bean>(); //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查字典教程网。