Android開發中ListView自定義adapter的封裝

2019-12-12 05:20:38

字體：大中小

來源：轉載

供稿：網友

【引入】

我們一般編寫listView的時候順序是這樣的：
•需要展示的數據集List<T>
•為這個數據集編寫一個ListView
•為這個ListView編寫一個Adapter，一般繼承自BaseAdapter
•在BaseAdapter內部編寫一個ViewHolder類，對應ListView里面的item控件，提高控件的查詢效率

分析：

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

一般情況下，一個ListView對應一個Adapter類，對應一個ViewHolder類，那如果一個app中有20個ListView，我們豈不是要寫20遍？所以的做法是：
•抽取ViewHolder，作為公共的類。
•將Adapter封裝成CommonAdapter，作為公共的類。

一、傳統方式編寫適配器：

（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:單個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為ListView和GridView打造萬能適配器" 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>

其對應的布局效果如下：

（3）Bean.java:ListView的數據集

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:自定義適配器，繼承自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需要一個Context，通過Context獲得Layout.inflater，然后通過inflater加載item的布局 public MyAdapter(Context context, List<Bean> datas) { mInflater = LayoutInflater.from(context); mDatas = datas; } //返回數據集的長度 @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; } //這個方法才是重點，我們要為它編寫一個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); //加載布局  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里面說明，convertView已經被復用了，說明convertView中已經設置過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; } //這個ViewHolder只能服務于當前這個特定的adapter，因為ViewHolder里會指定item的控件，不同的ListView，item可能不同，所以ViewHolder寫成一個私有的類 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>(); //將數據裝到集合中去 Bean bean = new Bean("Android新技能1", "Android為ListView和GridView打造萬能適配器", "2015-05-04", "10086"); mDatas.add(bean); bean = new Bean("Android新技能2", "Android為ListView和GridView打造萬能適配器", "2015-05-04", "10086"); mDatas.add(bean); bean = new Bean("Android新技能3", "Android為ListView和GridView打造萬能適配器", "2015-05-04", "10086"); mDatas.add(bean); bean = new Bean("Android新技能4", "Android為ListView和GridView打造萬能適配器", "2015-05-04", "10086"); mDatas.add(bean); //為數據綁定適配器 mAdapter = new MyAdapter(this,mDatas); listView.setAdapter(mAdapter); }}

運行效果如下：

【工程文件】
2015-05-04-BaseAdapter的傳統寫法.rar

二、ListView中自定義adapter的封裝（萬能的寫法來編寫適配器）：
完整版代碼如下：

(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中單個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為ListView和GridView打造萬能適配器" 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>

其對應的布局效果如下：

（3）Bean.java:數據集

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）【可復用的代碼】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是復用的，但是position記得更新一下  return holder; } } /* 通過viewId獲取控件 */ //使用的是泛型T,返回的是View的子類 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）【可復用的代碼】ListViewAdapter.java:自定義的通用適配器，繼承自BaseAdapter。以后如果是自定義ListView的adapter，繼承它就行了

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的自定義adapter都可以繼承這個類哦 */public abstract class ListViewAdapter<T> extends BaseAdapter { //為了讓子類訪問，于是將屬性設置為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，所以要把布局單獨提取出來 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，一行代碼就搞定ViewHolder的初始化咯 ViewHolder holder = ViewHolder.get(mContext, convertView, parent, layoutId, position);//layoutId就是單個item的布局 convert(holder, getItem(position)); return holder.getConvertView(); //這一行的代碼要注意了 } //將convert方法公布出去 public abstract void convert(ViewHolder holder, T t);}

（6）ListViewAdapterWithViewHolder.java:繼承自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需要一個Context，通過Context獲得Layout.inflater，然后通過inflater加載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>(); //將數據裝到集合中去 Bean bean = new Bean("Android新技能1", "Android為ListView和GridView打造萬能適配器", "2015-05-04", "10086"); mDatas.add(bean); bean = new Bean("Android新技能2", "Android為ListView和GridView打造萬能適配器", "2015-05-04", "10086"); mDatas.add(bean); bean = new Bean("Android新技能3", "Android為ListView和GridView打造萬能適配器", "2015-05-04", "10086"); mDatas.add(bean); bean = new Bean("Android新技能4", "Android為ListView和GridView打造萬能適配器", "2015-05-04", "10086"); mDatas.add(bean); //為數據綁定適配器 listViewAdapterWithViewHolder = new ListViewAdapterWithViewHolder(this, mDatas); listView.setAdapter(listViewAdapterWithViewHolder); }}

運行效果：