Android开发中ListView自定义adapter的封装
【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脚本之家。
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