android代码优化----ListView中自定义adapter的封装

【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:

android代码优化----ListView中自定义adapter的封装
<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>
android代码优化----ListView中自定义adapter的封装

(2)item_listview.xml:单个item的布局文件

android代码优化----ListView中自定义adapter的封装
 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     <TextView
17         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     <TextView
29         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     <TextView
40         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>
android代码优化----ListView中自定义adapter的封装

其对应的布局效果如下:

android代码优化----ListView中自定义adapter的封装 

(3)Bean.java:ListView的数据集

android代码优化----ListView中自定义adapter的封装
 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 }
android代码优化----ListView中自定义adapter的封装

(4)MyAdapter.java:自定义适配器,继承自BaseAdapter

android代码优化----ListView中自定义adapter的封装
 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     @Override
30     public int getCount() {
31         return mDatas.size();
32     }
33 
34     @Override
35     public Object getItem(int position) {
36         return mDatas.get(position);
37     }
38 
39     @Override
40     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ViewHolder
45     @Override
46     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holder
59             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 }
android代码优化----ListView中自定义adapter的封装

(5)MainActivity.java:

android代码优化----ListView中自定义adapter的封装
 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     @Override
21     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View
31     private void initView() {
32         listView = (ListView) findViewById(R.id.listView);
33     }
34 
35     //方法;初始化Data
36     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 }
android代码优化----ListView中自定义adapter的封装

运行效果如下:

android代码优化----ListView中自定义adapter的封装

【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:

android代码优化----ListView中自定义adapter的封装
<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>
android代码优化----ListView中自定义adapter的封装

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

android代码优化----ListView中自定义adapter的封装
 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     <TextView
17         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     <TextView
29         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     <TextView
40         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>
android代码优化----ListView中自定义adapter的封装

其对应的布局效果如下:

android代码优化----ListView中自定义adapter的封装

(3)Bean.java:数据集

android代码优化----ListView中自定义adapter的封装
 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 }
android代码优化----ListView中自定义adapter的封装

(4)【可复用的代码】ViewHolder.java:

android代码优化----ListView中自定义adapter的封装
 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; //即时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 }
android代码优化----ListView中自定义adapter的封装

(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

android代码优化----ListView中自定义adapter的封装
 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protected
18     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     @Override
31     public int getCount() {
32         return mDatas.size();
33     }
34 
35     @Override
36     public T getItem(int position) {
37         return mDatas.get(position);
38     }
39 
40     @Override
41     public long getItemId(int position) {
42         return position;
43     }
44 
45     @Override
46     public View getView(int position, View convertView, ViewGroup parent) {
47         //初始化ViewHolder,使用通用的ViewHolder,一样代码就搞定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 }
android代码优化----ListView中自定义adapter的封装

(6)ListViewAdapterWithViewHolder.java:继承自ListViewAdapter

android代码优化----ListView中自定义adapter的封装
 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     @Override
23     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 }
android代码优化----ListView中自定义adapter的封装

(7)MainActivity.java:

android代码优化----ListView中自定义adapter的封装
 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     @Override
20     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View
30     private void initView() {
31         listView = (ListView) findViewById(R.id.listView);
32     }
33 
34     //方法;初始化Data
35     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 } 
android代码优化----ListView中自定义adapter的封装

运行效果:

android代码优化----ListView中自定义adapter的封装

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。

 

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