Android进阶高手（二）适配器（Adapter）那是必须的

       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：

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

<?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

<?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

<?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：

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：

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。

今天就到此了，下班！哈哈！