listview<一> 自定义适配器
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【正文】
【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
1 <RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android" 2 xmlns:tools="http://schemas.android.com/tools" 3 android:layout_width="match_parent" 4 android:layout_height="match_parent" 5 android:padding="10dp"> 6 7 <TextView 8 android:id="@+id/titleTv" 9 android:layout_width="wrap_content"10 android:layout_height="wrap_content"11 android:singleLine="true"12 android:text="Android新技能"13 android:textColor="#444"14 android:textSize="16sp" />15 16 <TextView17 android:id="@+id/descTv"18 android:layout_width="match_parent"19 android:layout_height="wrap_content"20 android:layout_below="@+id/titleTv"21 android:layout_marginTop="10dp"22 android:maxLines="2"23 android:minLines="1"24 android:text="Android为ListView和GridView打造万能适配器"25 android:textColor="#898989"26 android:textSize="16sp" />27 28 <TextView29 android:id="@+id/timeTv"30 android:paddingTop="3dp"31 android:layout_width="wrap_content"32 android:layout_height="wrap_content"33 android:layout_below="@+id/descTv"34 android:layout_marginTop="10dp"35 android:text="2015-05-04"36 android:textColor="#898989"37 android:textSize="12sp" />38 39 <TextView40 android:padding="2dp"41 android:id="@+id/phoneTv"42 android:gravity="center"43 android:layout_width="wrap_content"44 android:layout_height="wrap_content"45 android:layout_below="@+id/descTv"46 android:layout_marginTop="10dp"47 android:background="#2ED667"48 android:drawableLeft="@mipmap/phone"49 android:drawablePadding="5dp"50 android:text="10086"51 android:textColor="#ffffff"52 android:textSize="12sp"53 android:layout_alignParentRight="true" />54 55 56 </RelativeLayout>
其对应的布局效果如下:
(3)Bean.java:ListView的数据集
1 package com.smyhvae.baseadapter.entities; 2 3 /** 4 * Created by smyhvae on 2015/5/4. 5 */ 6 public class Bean { 7 private String title; 8 private String desc; 9 private String time;10 private String phone;11 12 public Bean() {13 }14 15 public Bean(String title, String desc, String time, String phone) {16 this.title = title;17 18 this.desc = desc;19 this.time = time;20 this.phone = phone;21 }22 23 public String getTitle() {24 return title;25 }26 27 public void setTitle(String title) {28 this.title = title;29 }30 31 public String getDesc() {32 return desc;33 }34 35 public void setDesc(String desc) {36 this.desc = desc;37 }38 39 public String getTime() {40 return time;41 }42 43 public void setTime(String time) {44 this.time = time;45 }46 47 public String getPhone() {48 return phone;49 }50 51 public void setPhone(String phone) {52 this.phone = phone;53 }54 }
(4)MyAdapter.java:自定义适配器,继承自BaseAdapter
1 package com.smyhvae.baseadapter; 2 3 import android.content.Context; 4 import android.view.LayoutInflater; 5 import android.view.View; 6 import android.view.ViewGroup; 7 import android.widget.BaseAdapter; 8 import android.widget.TextView; 9 10 import com.smyhvae.baseadapter.entities.Bean;11 12 import java.util.List;13 14 /**15 * Created by smyhvae on 2015/5/4.16 */17 public class MyAdapter extends BaseAdapter {18 private LayoutInflater mInflater;19 private List<Bean> mDatas;20 21 //MyAdapter需要一个Context,通过Context获得Layout.inflater,然后通过inflater加载item的布局22 public MyAdapter(Context context, List<Bean> datas) {23 24 mInflater = LayoutInflater.from(context);25 mDatas = datas;26 }27 28 //返回数据集的长度29 @Override30 public int getCount() {31 return mDatas.size();32 }33 34 @Override35 public Object getItem(int position) {36 return mDatas.get(position);37 }38 39 @Override40 public long getItemId(int position) {41 return position;42 }43 44 //这个方法才是重点,我们要为它编写一个ViewHolder45 @Override46 public View getView(int position, View convertView, ViewGroup parent) {47 ViewHolder holder = null;48 if (convertView == null) {49 convertView = mInflater.inflate(R.layout.item_listview, parent, false); //加载布局50 holder = new ViewHolder();51 52 holder.titleTv = (TextView) convertView.findViewById(R.id.titleTv);53 holder.descTv = (TextView) convertView.findViewById(R.id.descTv);54 holder.timeTv = (TextView) convertView.findViewById(R.id.timeTv);55 holder.phoneTv = (TextView) convertView.findViewById(R.id.phoneTv);56 57 convertView.setTag(holder);58 } 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holder59 holder = (ViewHolder) convertView.getTag();60 }61 62 Bean bean = mDatas.get(position);63 holder.titleTv.setText(bean.getTitle());64 holder.descTv.setText(bean.getDesc());65 holder.timeTv.setText(bean.getTime());66 holder.phoneTv.setText(bean.getPhone());67 68 return convertView;69 }70 71 //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72 private class ViewHolder {73 TextView titleTv;74 TextView descTv;75 TextView timeTv;76 TextView phoneTv;77 }78 79 }
(5)MainActivity.java:
1 package com.smyhvae.baseadapter; 2 3 import android.app.Activity; 4 import android.os.Bundle; 5 import android.view.Menu; 6 import android.view.MenuItem; 7 import android.widget.ListView; 8 9 import com.smyhvae.baseadapter.entities.Bean;10 11 import java.util.ArrayList;12 import java.util.List;13 14 public class MainActivity extends Activity {15 16 private ListView listView;17 private List<Bean> mDatas;18 private MyAdapter mAdapter;19 20 @Override21 protected void onCreate(Bundle savedInstanceState) {22 super.onCreate(savedInstanceState);23 setContentView(R.layout.activity_main);24 25 initView();26 initData();27 28 }29 30 //方法:初始化View31 private void initView() {32 listView = (ListView) findViewById(R.id.listView);33 }34 35 //方法;初始化Data36 private void initData() {37 mDatas = new ArrayList<Bean>();38 39 //将数据装到集合中去40 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");41 mDatas.add(bean);42 43 bean = new Bean("Android新技能2", "Android为ListView和GridView打造万能适配器", "2015-05-04", "10086");44 mDatas.add(bean);45 46 bean = new Bean("Android新技能3", "Android为ListView和GridView打造万能适配器", "2015-05-04", "10086");47 mDatas.add(bean);48 49 bean = new Bean("Android新技能4", "Android为ListView和GridView打造万能适配器", "2015-05-04", "10086");50 mDatas.add(bean);51 52 //为数据绑定适配器53 mAdapter = new MyAdapter(this,mDatas);54 55 listView.setAdapter(mAdapter);56 }57 58 }
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)
1 <RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android" 2 xmlns:tools="http://schemas.android.com/tools" 3 android:layout_width="match_parent" 4 android:layout_height="match_parent" 5 android:padding="10dp"> 6 7 <TextView 8 android:id="@+id/titleTv" 9 android:layout_width="wrap_content"10 android:layout_height="wrap_content"11 android:singleLine="true"12 android:text="Android新技能"13 android:textColor="#444"14 android:textSize="16sp" />15 16 <TextView17 android:id="@+id/descTv"18 android:layout_width="match_parent"19 android:layout_height="wrap_content"20 android:layout_below="@+id/titleTv"21 android:layout_marginTop="10dp"22 android:maxLines="2"23 android:minLines="1"24 android:text="Android为ListView和GridView打造万能适配器"25 android:textColor="#898989"26 android:textSize="16sp" />27 28 <TextView29 android:id="@+id/timeTv"30 android:paddingTop="3dp"31 android:layout_width="wrap_content"32 android:layout_height="wrap_content"33 android:layout_below="@+id/descTv"34 android:layout_marginTop="10dp"35 android:text="2015-05-04"36 android:textColor="#898989"37 android:textSize="12sp" />38 39 <TextView40 android:padding="2dp"41 android:id="@+id/phoneTv"42 android:gravity="center"43 android:layout_width="wrap_content"44 android:layout_height="wrap_content"45 android:layout_below="@+id/descTv"46 android:layout_marginTop="10dp"47 android:background="#2ED667"48 android:drawableLeft="@mipmap/phone"49 android:drawablePadding="5dp"50 android:text="10086"51 android:textColor="#ffffff"52 android:textSize="12sp"53 android:layout_alignParentRight="true" />54 55 56 </RelativeLayout>
其对应的布局效果如下:
(3)Bean.java:数据集
1 package com.smyhvae.baseadapter.entities; 2 3 /** 4 * Created by smyhvae on 2015/5/4. 5 */ 6 public class Bean { 7 private String title; 8 private String desc; 9 private String time;10 private String phone;11 12 public Bean() {13 }14 15 public Bean(String title, String desc, String time, String phone) {16 this.title = title;17 18 this.desc = desc;19 this.time = time;20 this.phone = phone;21 }22 23 public String getTitle() {24 return title;25 }26 27 public void setTitle(String title) {28 this.title = title;29 }30 31 public String getDesc() {32 return desc;33 }34 35 public void setDesc(String desc) {36 this.desc = desc;37 }38 39 public String getTime() {40 return time;41 }42 43 public void setTime(String time) {44 this.time = time;45 }46 47 public String getPhone() {48 return phone;49 }50 51 public void setPhone(String phone) {52 this.phone = phone;53 }54 }
(4)【可复用的代码】ViewHolder.java:
1 package com.smyhvae.baseadapter.utils; 2 3 import android.content.Context; 4 import android.util.SparseArray; 5 import android.view.LayoutInflater; 6 import android.view.View; 7 import android.view.ViewGroup; 8 9 /**10 * Created by smyhvae on 2015/5/4.11 */12 public class ViewHolder {13 14 private SparseArray<View> mViews;15 private int mPosition;16 private View mConvertView;17 18 public ViewHolder(Context context, ViewGroup parent, int layoutId, int position) {19 this.mPosition = position;20 this.mViews = new SparseArray<View>();21 22 mConvertView = LayoutInflater.from(context).inflate(layoutId, parent, false);23 24 mConvertView.setTag(this);25 26 }27 28 public static ViewHolder get(Context context, View convertView, ViewGroup parent, int layoutId, int position) {29 if (convertView == null) {30 return new ViewHolder(context, parent, layoutId, position);31 } else {32 ViewHolder holder = (ViewHolder) convertView.getTag();33 holder.mPosition = position; //即使ViewHolder是复用的,但是position记得更新一下34 return holder;35 }36 }37 38 /*39 通过viewId获取控件40 */41 //使用的是泛型T,返回的是View的子类42 public <T extends View> T getView(int viewId) {43 View view = mViews.get(viewId);44 45 if (view == null) {46 view = mConvertView.findViewById(viewId);47 mViews.put(viewId, view);48 }49 50 return (T) view;51 }52 53 public View getConvertView() {54 return mConvertView;55 }56 57 }
(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
1 package com.smyhvae.baseadapter.utils; 2 3 import android.content.Context; 4 import android.view.LayoutInflater; 5 import android.view.View; 6 import android.view.ViewGroup; 7 import android.widget.BaseAdapter; 8 9 import java.util.List;10 11 /**12 * Created by smyhvae on 2015/5/4.13 * 通用的ListView的BaseAdapter,所有的ListView的自定义adapter都可以继承这个类哦14 */15 public abstract class ListViewAdapter<T> extends BaseAdapter {16 17 //为了让子类访问,于是将属性设置为protected18 protected Context mContext;19 protected List<T> mDatas;20 protected LayoutInflater mInflater;21 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22 23 public ListViewAdapter(Context context, List<T> datas, int layoutId) {24 this.mContext = context;25 mInflater = LayoutInflater.from(context);26 this.mDatas = datas;27 this.layoutId = layoutId;28 }29 30 @Override31 public int getCount() {32 return mDatas.size();33 }34 35 @Override36 public T getItem(int position) {37 return mDatas.get(position);38 }39 40 @Override41 public long getItemId(int position) {42 return position;43 }44 45 @Override46 public View getView(int position, View convertView, ViewGroup parent) {47 //初始化ViewHolder,使用通用的ViewHolder,一行代码就搞定ViewHolder的初始化咯48 ViewHolder holder = ViewHolder.get(mContext, convertView, parent, layoutId, position);//layoutId就是单个item的布局49 50 convert(holder, getItem(position));51 return holder.getConvertView(); //这一行的代码要注意了52 }53 54 //将convert方法公布出去55 public abstract void convert(ViewHolder holder, T t);56 57 }
(6)ListViewAdapterWithViewHolder.java:继承自ListViewAdapter
1 package com.smyhvae.baseadapter; 2 3 import android.content.Context; 4 import android.widget.TextView; 5 6 import com.smyhvae.baseadapter.entities.Bean; 7 import com.smyhvae.baseadapter.utils.ListViewAdapter; 8 import com.smyhvae.baseadapter.utils.ViewHolder; 9 10 import java.util.List;11 12 /**13 * Created by smyhvae on 2015/5/4.14 */15 public class ListViewAdapterWithViewHolder extends ListViewAdapter<Bean> {16 17 //MyAdapter需要一个Context,通过Context获得Layout.inflater,然后通过inflater加载item的布局18 public ListViewAdapterWithViewHolder(Context context, List<Bean> datas) {19 super(context, datas, R.layout.item_listview);20 }21 22 @Override23 public void convert(ViewHolder holder, Bean bean) {24 25 ((TextView) holder.getView(R.id.titleTv)).setText(bean.getTitle());26 ((TextView) holder.getView(R.id.descTv)).setText(bean.getDesc());27 ((TextView) holder.getView(R.id.timeTv)).setText(bean.getTime());28 ((TextView) holder.getView(R.id.phoneTv)).setText(bean.getPhone());29 30 /*31 TextView tv = holder.getView(R.id.titleTv);32 tv.setText(...);33 34 ImageView view = getView(viewId);35 Imageloader.getInstance().loadImag(view.url);36 */37 }38 }
(7)MainActivity.java:
1 package com.smyhvae.baseadapter; 2 3 import android.app.Activity; 4 import android.os.Bundle; 5 import android.widget.ListView; 6 7 import com.smyhvae.baseadapter.entities.Bean; 8 9 import java.util.ArrayList;10 import java.util.List;11 12 public class MainActivity extends Activity {13 14 private ListView listView;15 private List<Bean> mDatas;16 17 private ListViewAdapterWithViewHolder listViewAdapterWithViewHolder;18 19 @Override20 protected void onCreate(Bundle savedInstanceState) {21 super.onCreate(savedInstanceState);22 setContentView(R.layout.activity_main);23 24 initView();25 initData();26 }27 28 29 //方法:初始化View30 private void initView() {31 listView = (ListView) findViewById(R.id.listView);32 }33 34 //方法;初始化Data35 private void initData() {36 mDatas = new ArrayList<Bean>();37 38 //将数据装到集合中去39 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");40 mDatas.add(bean);41 42 bean = new Bean("Android新技能2", "Android为ListView和GridView打造万能适配器", "2015-05-04", "10086");43 mDatas.add(bean);44 45 bean = new Bean("Android新技能3", "Android为ListView和GridView打造万能适配器", "2015-05-04", "10086");46 mDatas.add(bean);47 48 bean = new Bean("Android新技能4", "Android为ListView和GridView打造万能适配器", "2015-05-04", "10086");49 mDatas.add(bean);50 51 //为数据绑定适配器52 listViewAdapterWithViewHolder = new ListViewAdapterWithViewHolder(this, mDatas);53 54 listView.setAdapter(listViewAdapterWithViewHolder);55 56 }57 }
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"
办法二: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。
本文转自:http://www.cnblogs.com/smyhvae/p/4477079.html
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