adapter 学习

      在Android应用开发过程中，适配器(Adapter)可是大有可为，尤其是在显示数据、读取数据库用列表显示更是使用频繁。但是今天我们要说的不是读取数据库中的信息，而是自己来添加一行数据让它显示在列表顶层。实现的功能有添加数据和删除数据两项。废话不多说，代码赶紧的！

首先先看下运行效果如下所示：

     

                                 图一                                                                                 图二

   

                                  图三                                                                                   图四

 

以上四张图演示了添加一行数据到列表中的功能，至于删除数据在这里就不演示了，留给童靴们去做。

开始介绍工程项目了，步骤如下：

1、新建项目命名为List

2、编写一个Bean封装其属性，命名为Item.java，代码如下：

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1. package com.wyf.wpf;  
2.   
3. import java.text.SimpleDateFormat;  
4. import java.util.Date;  
5.   
6. public class Item {  
7.       
8.     String task;  
9.     Date created;  
10.   
11.     public String getTask() {  
12.     return task;  
13.     }  
14.   
15.     public Date getCreated() {  
16.     return created;  
17.     }  
18.   
19.     public Item(String _task) {  
20.     this(_task, new Date(java.lang.System.currentTimeMillis()));  
21.     }  
22.   
23.     public Item(String _task, Date _created) {  
24.     task = _task;  
25.     created = _created;  
26.     }  
27.       
28.     @Override  
29.     public String toString() {  
30.     SimpleDateFormat sdf = new SimpleDateFormat("dd/MM/yy");  
31.     String dateString = sdf.format(created);  
32.     return "(" + dateString + ")" + task;  
33.     }  
34. }  

package com.wyf.wpf;import java.text.SimpleDateFormat;import java.util.Date;public class Item {String task;Date created;public String getTask() {return task;}public Date getCreated() {return created;}public Item(String _task) {this(_task, new Date(java.lang.System.currentTimeMillis()));}public Item(String _task, Date _created) {task = _task;created = _created;}@Overridepublic String toString() {SimpleDateFormat sdf = new SimpleDateFormat("dd/MM/yy");String dateString = sdf.format(created);return "(" + dateString + ")" + task;}}

3、编写三个布局

（1）、main.xml：用于主布局

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1. <?xml version="1.0" encoding="utf-8"?>  
2. <LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"  
3.     android:layout_width="fill_parent"  
4.     android:layout_height="fill_parent"  
5.     android:orientation="vertical" >  
6.       
7.     <ListView   
8.         android:id="@+id/myListView"  
9.         android:layout_width="fill_parent"  
10.         android:layout_height="wrap_content"/>  
11.   
12. </LinearLayout>  

<?xml version="1.0" encoding="utf-8"?><LinearLayout xmlns:android="http://schemas.android.com/apk/res/android" android:layout_width="fill_parent" android:layout_height="fill_parent" android:orientation="vertical" > <ListView android:id="@+id/myListView" android:layout_width="fill_parent" android:layout_height="wrap_content"/></LinearLayout>

 

（2）、item.xml：用于显示列表中的每列数据

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1. <?xml version="1.0" encoding="utf-8"?>  
2. <LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"  
3.     android:layout_width="fill_parent"  
4.     android:layout_height="fill_parent"  
5.     android:orientation="horizontal">  
6.     <TextView  
7.         android:id="@+id/row"  
8.         android:layout_width="wrap_content"  
9.         android:layout_height="wrap_content"  
10.         android:layout_weight="1"  
11.         android:padding="5px"  
12.         android:gravity="center"  
13.         />  
14.     <TextView  
15.         android:id="@+id/rowDate"  
16.         android:layout_width="wrap_content"  
17.         android:layout_height="wrap_content"  
18.         android:layout_weight="1"  
19.         android:gravity="center"  
20.         android:padding="5px"  
21.         />  
22. </LinearLayout>  

<?xml version="1.0" encoding="utf-8"?><LinearLayout xmlns:android="http://schemas.android.com/apk/res/android" android:layout_width="fill_parent" android:layout_height="fill_parent" android:orientation="horizontal"> <TextView android:id="@+id/row" android:layout_width="wrap_content" android:layout_height="wrap_content" android:layout_weight="1" android:padding="5px" android:gravity="center" /> <TextView android:id="@+id/rowDate" android:layout_width="wrap_content" android:layout_height="wrap_content" android:layout_weight="1" android:gravity="center" android:padding="5px" /></LinearLayout>

（3）、add.xml：用于弹出对话框提示添加数据的布局

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1. <?xml version="1.0" encoding="utf-8"?>  
2. <LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"  
3.     android:orientation="vertical"   
4.     android:layout_width="fill_parent"  
5.     android:layout_height="fill_parent">  
6.     <EditText   
7.         android:id="@+id/add"  
8.         android:layout_width="fill_parent"  
9.         android:layout_height="wrap_content"  
10.         />  
11.   
12. </LinearLayout>  

<?xml version="1.0" encoding="utf-8"?><LinearLayout xmlns:android="http://schemas.android.com/apk/res/android" android:orientation="vertical" android:layout_width="fill_parent" android:layout_height="fill_parent"> <EditText android:id="@+id/add" android:layout_width="fill_parent" android:layout_height="wrap_content" /></LinearLayout>

4、自定义自己的Adapter,命名为MyAdapter.java,代码如下：

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1. package com.wyf.wpf;  
2.   
3. import java.text.SimpleDateFormat;  
4. import java.util.Date;  
5. import java.util.List;  
6.   
7.   
8. import android.content.Context;  
9. import android.util.Log;  
10. import android.view.LayoutInflater;  
11. import android.view.View;  
12. import android.view.ViewGroup;  
13. import android.widget.BaseAdapter;  
14. import android.widget.TextView;  
15.   
16. public class MyAdapter extends BaseAdapter{  
17.       
18.     private LayoutInflater mInflater;  
19.     private List<Item> items;  
20.       
21.     public MyAdapter(Context context,List<Item> items){  
22.         this.items=items;  
23.         mInflater=(LayoutInflater)context.getSystemService(Context.LAYOUT_INFLATER_SERVICE);  
24.     }  
25.   
26.     @Override  
27.     public int getCount() {  
28.         // TODO Auto-generated method stub  
29.         return items.size();  
30.     }  
31.   
32.     @Override  
33.     public Object getItem(int position) {  
34.         // TODO Auto-generated method stub  
35.         if(items==null)  
36.         {  
37.             return null;  
38.         }  
39.         else  
40.         {  
41.             return items.get(position);  
42.         }  
43.     }  
44.   
45.     @Override  
46.     public long getItemId(int position) {  
47.         // TODO Auto-generated method stub  
48.         return position;  
49.     }  
50.   
51.     @Override  
52.     public View getView(int position, View convertView, ViewGroup parent) {  
53.         // TODO Auto-generated method stub  
54.         Item item=(Item) getItem(position);  
55.         String nameString=item.getTask().toString();  
56.         Date date=item.getCreated();  
57.         SimpleDateFormat sdf = new SimpleDateFormat("dd/MM/yy");  
58.         String dateString = sdf.format(date);  
59.         ViewHolder holder;  
60.         if(convertView==null){  
61.             holder=new ViewHolder();  
62.             convertView=mInflater.inflate(R.layout.item,null);  
63.             holder.nameText=(TextView)convertView.findViewById(R.id.row);  
64.             holder.dateText=(TextView)convertView.findViewById(R.id.rowDate);  
65.             convertView.setTag(holder);  
66.         }  
67.         else{  
68.             holder = (ViewHolder) convertView.getTag();  
69.         }  
70.         holder.nameText.setText(nameString);  
71.         Log.i("TAG","nameString---->"+nameString);  
72.         Log.i("TAG","holder.name---->"+holder.nameText);  
73.         holder.dateText.setText(dateString);  
74.         return convertView;  
75.     }  
76.       
77.     class ViewHolder{  
78.         TextView nameText;  
79.         TextView dateText;  
80.     }  
81.   
82. }  

package com.wyf.wpf;import java.text.SimpleDateFormat;import java.util.Date;import java.util.List;import android.content.Context;import android.util.Log;import android.view.LayoutInflater;import android.view.View;import android.view.ViewGroup;import android.widget.BaseAdapter;import android.widget.TextView;public class MyAdapter extends BaseAdapter{private LayoutInflater mInflater;private List<Item> items;public MyAdapter(Context context,List<Item> items){this.items=items;mInflater=(LayoutInflater)context.getSystemService(Context.LAYOUT_INFLATER_SERVICE);}@Overridepublic int getCount() {// TODO Auto-generated method stubreturn items.size();}@Overridepublic Object getItem(int position) {// TODO Auto-generated method stubif(items==null){return null;}else{return items.get(position);}}@Overridepublic long getItemId(int position) {// TODO Auto-generated method stubreturn position;}@Overridepublic View getView(int position, View convertView, ViewGroup parent) {// TODO Auto-generated method stubItem item=(Item) getItem(position);String nameString=item.getTask().toString();Date date=item.getCreated();SimpleDateFormat sdf = new SimpleDateFormat("dd/MM/yy"); String dateString = sdf.format(date);ViewHolder holder;if(convertView==null){holder=new ViewHolder();convertView=mInflater.inflate(R.layout.item,null);holder.nameText=(TextView)convertView.findViewById(R.id.row);holder.dateText=(TextView)convertView.findViewById(R.id.rowDate);convertView.setTag(holder);}else{ holder = (ViewHolder) convertView.getTag();}holder.nameText.setText(nameString);Log.i("TAG","nameString---->"+nameString);Log.i("TAG","holder.name---->"+holder.nameText);holder.dateText.setText(dateString);return convertView;}class ViewHolder{TextView nameText;TextView dateText;}}

5、编写Activity,这里就不解释了，直接上代码：

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1. package com.wyf.wpf;  
2.   
3. import java.util.ArrayList;  
4.   
5. import android.app.Activity;  
6. import android.app.AlertDialog;  
7. import android.content.Context;  
8. import android.content.DialogInterface;  
9. import android.content.DialogInterface.OnClickListener;  
10. import android.os.Bundle;  
11. import android.view.KeyEvent;  
12. import android.view.LayoutInflater;  
13. import android.view.View;  
14. import android.widget.AdapterView;  
15. import android.widget.AdapterView.OnItemClickListener;  
16. import android.widget.EditText;  
17. import android.widget.ListView;  
18.   
19. public class ListActivity extends Activity{  
20.     private ArrayList<Item> Items;  
21.     private ListView myListView;  
22.     private MyAdapter adapter;  
23.     private String[] str={"添加组","删除组"};  
24.   
25.     /** Called when the activity is first created. */  
26.     @Override  
27.     public void onCreate(Bundle savedInstanceState) {  
28.         super.onCreate(savedInstanceState);  
29.         setContentView(R.layout.main);  
30.         myListView = (ListView)findViewById(R.id.myListView);  
31.         Items = new ArrayList<Item>();  
32.         for(int i=0;i<10;i++){  
33.             Item item=new Item("我是"+i);  
34.             Items.add(item);  
35.         }  
36.         adapter=new MyAdapter(this,Items);  
37.         myListView.setAdapter(adapter);  
38.         myListView.setOnItemClickListener(new OnItemClickListener() {  
39.   
40.             @Override  
41.             public void onItemClick(AdapterView<?> arg0, View arg1, final int position,  
42.                     long arg3) {  
43.                 // TODO Auto-generated method stub  
44.                 new AlertDialog.Builder(ListActivity.this)  
45.                 .setItems(str, new DialogInterface.OnClickListener() {  
46.                       
47.                     @Override  
48.                     public void onClick(DialogInterface dialog, int which) {  
49.                         // TODO Auto-generated method stub  
50.                         switch(which){  
51.                         case 0:  
52.                             LayoutInflater mInflater=(LayoutInflater)getSystemService(Context.LAYOUT_INFLATER_SERVICE);  
53.                             final View view=mInflater.inflate(R.layout.add,null);  
54.                             new AlertDialog.Builder(ListActivity.this)  
55.                             .setView(view)  
56.                             .setTitle("添加")  
57.                             .setPositiveButton("添加",new OnClickListener() {  
58.                                   
59.                                 @Override  
60.                                 public void onClick(DialogInterface dialog, int which) {  
61.                                     // TODO Auto-generated method stub  
62.                                     EditText add=(EditText)view.findViewById(R.id.add);  
63.                                     String str=add.getText().toString();  
64.                                     updateAdapter(str);  
65.                                     dialog.dismiss();  
66.                                 }  
67.                             })  
68.                             .setNegativeButton("取消",new OnClickListener() {  
69.                                   
70.                                 @Override  
71.                                 public void onClick(DialogInterface dialog, int which) {  
72.                                     // TODO Auto-generated method stub  
73.                                     dialog.dismiss();  
74.                                 }  
75.                             }).show();  
76.                             break;  
77.                         case 1:  
78.                             Items.remove(position);  
79.                             adapter.notifyDataSetChanged();  
80.                             dialog.dismiss();  
81.                             break;  
82.                         }  
83.                     }  
84.                 }).show();  
85.             }  
86.         });  
87.    }  
88.     //更新adapter函数  
89.     public void updateAdapter(String str){  
90.         Item newItem;  
91.         newnewItem = new Item(str);  
92.         Items.add(0, newItem);  
93.         adapter.notifyDataSetChanged();  
94.     }  
95. }  

package com.wyf.wpf;import java.util.ArrayList;import android.app.Activity;import android.app.AlertDialog;import android.content.Context;import android.content.DialogInterface;import android.content.DialogInterface.OnClickListener;import android.os.Bundle;import android.view.KeyEvent;import android.view.LayoutInflater;import android.view.View;import android.widget.AdapterView;import android.widget.AdapterView.OnItemClickListener;import android.widget.EditText;import android.widget.ListView;public class ListActivity extends Activity{private ArrayList<Item> Items;private ListView myListView;private MyAdapter adapter;private String[] str={"添加组","删除组"}; /** Called when the activity is first created. */ @Override public void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.main); myListView = (ListView)findViewById(R.id.myListView); Items = new ArrayList<Item>(); for(int i=0;i<10;i++){ Item item=new Item("我是"+i); Items.add(item); } adapter=new MyAdapter(this,Items); myListView.setAdapter(adapter); myListView.setOnItemClickListener(new OnItemClickListener() {@Overridepublic void onItemClick(AdapterView<?> arg0, View arg1, final int position,long arg3) {// TODO Auto-generated method stubnew AlertDialog.Builder(ListActivity.this).setItems(str, new DialogInterface.OnClickListener() {@Overridepublic void onClick(DialogInterface dialog, int which) {// TODO Auto-generated method stubswitch(which){case 0:LayoutInflater mInflater=(LayoutInflater)getSystemService(Context.LAYOUT_INFLATER_SERVICE);final View view=mInflater.inflate(R.layout.add,null);new AlertDialog.Builder(ListActivity.this).setView(view).setTitle("添加").setPositiveButton("添加",new OnClickListener() {@Overridepublic void onClick(DialogInterface dialog, int which) {// TODO Auto-generated method stubEditText add=(EditText)view.findViewById(R.id.add);String str=add.getText().toString();updateAdapter(str);dialog.dismiss();}}).setNegativeButton("取消",new OnClickListener() {@Overridepublic void onClick(DialogInterface dialog, int which) {// TODO Auto-generated method stubdialog.dismiss();}}).show();break;case 1:Items.remove(position);adapter.notifyDataSetChanged();dialog.dismiss();break;}}}).show();}}); } //更新adapter函数public void updateAdapter(String str){Item newItem; newItem = new Item(str); Items.add(0, newItem); adapter.notifyDataSetChanged();}}

上面的代码一般都不难，在这里就没必要详解了，只是需要注意一点，我没要刷新列表数据，就的使用adapter.notifyDataSetChanged();来更新。